Study on evaluation of mulching effect and establishment ofirrigation threshold for water田 savingproduction

節水のためのマルチンダ効果と濯滋時期の評価に関する研究

ZHANG QINGTAO

2009

Study on evaluation of mulching effect and establishment of irrigation threshold for water-saving production

節水のためのマルチング効果と濯滋時期の評価に関する研究

ZHANG QING TAO

Doctoral Dissertation

The U nited Graduate School of Agriculture Sciences， Tottori University

2009

Contents

Contents............ ...... ...... ... ...... ......... '" '" ............ .，. .，. ... ..........・…...・H ・ 1

List of figures ......…・・・・・・・・・・・・・・・……・・・一.............................……ー・・・・・・…… IV

List of tables............…..........一一・…・・・・・・一..........…・・・・・・・・・・・…一..…......一一 VIII

List of symbols ・一.............................一......…・・・…....・・・・・・……・・…一.....一..， VII

Summaη……...............……・・・一-…・・・・・・・・・…・・・・・・…・・・・・・…一............・・・・・・・・ IX

Acknowledgements.・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ー・・・・…...........一..................・H ・. XIII

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1.1.1 Drought and salinization in the 'world and ameliorative ejjects of mulching..… 1

1.1.2 Swiss chard and grapevines in drylands and semi-arid regions ・・・・・……・・・・・…・ 5

1.1.3 Sub-suゆceirri抑制一…・…一…一一…・・……一……一一……一…一…… 6

1.1.4 Inセαtionscheduling for grapevines based on soil water potential threshold ... 7

1.2 Objectives ...........一'"一......…….，.一...................…・・・・…・・・・・・…・・・・・・・・・・・・ 8

Chapter2

Ameliorative effect of mulching on water use efficiency of Swiss chard and salt

accumulation under saline irrigation ................................…・・・ー・・・・・・・一...... 10

2.1. Introduction ..................................................................…・・・・・・・… 10

2.2. Materials and methods ...…・一...…….......一..................…・・・・・・・・・・ーυ …・ 10

2.3. Results and discussion ….......一..........一一.............一-…一................... 12

2.4. Conclusions.一一..............一................一............…......……・・・…・・・・…… 22

Chapter3

Effects of mulching on evapotranspiration， yield and water use efficiency of Swiss

chard (Beta vulgαris L. var.sαvescens) irrigated with diluted seawater......…… 24

3.1. Introduction …...............................一....一.....一一........一一・・・…-一-一…・・ 24

3.2. Materials and methods …......一.......…・・・…・・・・・・・ー・・・……・・・・・・・・・・・・・・・・・・… 24

I

3.3. Results and discussion . . . . . . . . . . . . ... . .. . . . . . . . . . . . . . . . . . .. . . .. . . . . .. . . . . . . . . . . . . . . .. . . . 25

3.4. Conclusions... ...... ......... ... ............ ... ......... ... .........…....一・・・・・・・・・・・….， 32

Chapter 4

Effects of mulching and sub-surface irrigation on soil moisture and temperature，

growth， yield， and berry quality of‘Gros Colman' grapevines....・H ・-……H ・H ・-…. 33

4.1. Introduction ...... .....・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・…・・・・・・・… 33

4.2. Materials and methods ...... ......... ..... .... ... ... ... ... ............ ... .....・・・・・・・… 36

4.2.1 Plant and soil materials and experimentallの!out.............................・H ・・・ 36

4.2.2 Experimental measurements .....................................・・・・・・・・・・・・・・・・・・・… 37

4.2.3 Statisticα1 analysis .................................…...........................…・・… 38

4.3. Results .ー・・・・・・・・・ー・一........................................................…............ 39

4.3.1 Evapotran伊 iration，soil moisture and soil temperature ...…..............…・・・・・・ 39

4.3.2 Shoot length， leqfαrea， photoのmthesisand berry diameter.....…・・・・・・・・・・・・・・・・・ 43

4.3.3 Fresh yield， lj!ater use々がciencyand befηsugar content ....................・・・… 47

4.4. Discussion..... . . . . . . .…・・・・・・・・・・一.........….......................................一… 53

4.4.1 Ejjをctson soil .…ー……-一………………………・……………・・・………'" 53

4.4.2 E.，砕ctson the vegetative stalus of plants .…ー…・…ー…....・H ・-・…一一-…・・・・… 53

4.4.3 E.，酔ctson the productive status (yield and quality) and WUE ofplants・…・・…. 54

4.4.4. General discussion... . . .…一.........................…・・・・・・・・・・・・・・・・・・・・・・・・・・・・・… 56

4.5. ConcIusions .......・・・・・一........................................................…・・…… 58

Chapter 5

Determination of soil wate剖rpotential threshold for i廿nγr匂a剖tinggrapev吋ine儲si泊nthe last

phase of Stage 1 0ぱfbe町nηγgrowthbased on phot初ogramme抗tr吋icmeasurement of berry

size .，. ......... ... .....・・・・・・・・・・・・・・・・・・・・・・・・・・・・ー・・・・・・・・・・・・・・・・・・・・・・・・・ー・・・・・・・・・・・ー・…・ 59

5.1. Introduction ............................................................................... 59

5.2. Materials and methods ...・・・・・・・・・ー・ー・…・・・・・・・・・・・・ー・・・・・・・・・・・・・・・・….......….. 63

5.2.1 Plant and soil materials ..・ー・・ー・・・・・・・・・・ぃ・・・・・………・・・・・・・・・ー・・・・・・・・・…...... 64

5.2.2 Experimental details…・・・・・・・・・・・・・・・・・・・・・・…・・・・・・・・・・・…・・一...................… 64

5.2.3 Time series ana加isof berry diameter data . . . .……...…..…一……………. 66

II

5.2.4 Statistical analysis ……………………………………………………………・・ 69

5.3. Results . .. . . .…・・・…一........…一・・・・一.......................……・・・…・・・ー・・・・・・.... 69

5.3.1 Daily vαriation o.f soil water potential .........…......一......…・・・・・・・・・…一....... 69

5.3.2 Daily variation o.f berηdiameter ....一一・・・・・・・・・・・・・….........……'"一・・…・・・… 69

5.3.3 Relationshがbetweenbeny size αnd!jf .........一-…-一.........……......一・・・・・… 72

5.3.4 Relationship among !jf， photosynthesis and transpiration rate.・・・・・…・・・ー・・・・・・… 72

5.4. Discussion .. .. .. . .. '" .. .. .. .... .. . ..一.....一.........................一・・・・・・・・・・・・・・・・… 74

5.5. Conclusions . . .…….........…...一........................................….......・H ・.77

Cbapter6

Establishment of soil water potential threshold for irrigating grapevines during

berry ripening based on leaf photosynthesis and photogrammetry technology ... 78

6.1. lntroduction ................一一・・・・…............一.......…一・・・・・・・・・・・・……・・・….. 78

6ムMaterialsand methods ............................一...............…・・・・・・…・・・…… 80

6.2.1 Plantαnd soil materials ..............・・・・…・・・・一一...….......ー・・一........…...... 80

6.2.2 Experimental details.一…・・・一-一..........…・・・・・・…・・・・・・…・・・・・・・・・・・・・・・・・・・…・ 81

丘2.3Time series analysis o.f berry diameter data・…・……・………………………. 82

6.2.4 Statistical anαかsis…………………………………………………………….. 84

6.3. Results......................................................……・・・・ー・ー・・・・・・・一....一… 84

6.3.1 E.砕cto.f soil water potential (!jf) on the trend value o.fberηdiameter.…..…... 84

6.3.2 Daily variation o.f soil water potential， photosynthesis， stomatal conductance and

tranぞpiration............... ... ...... .......... ........ ...... '" ........…・・・・・・・・・…・・・・・ 84

6.3.3 Relatわns均 仰wng!jf， belη diameter and lea.f physiological pαrameters.....…87

6.4. Discussion......…・・・・・・・・・・一一...................................一.......…・・・・・・・・……..91

6.5. Conclusions.・・ー・・・・…....................................................................・H ・96

Cbapter7

Genel対 conclusions.……・・・…ー…・……・・…・ー………………………….....・H ・98

References..・・・・・ー・・・・・・…一・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・….........一..・…・・・・ 103

Su酷踊aryin Japanese...…………-一………………・…-一-……・・………… 119

List of related publications...………・・…-…………………………・………“ 121

List of related conferences papers...……………………………………… 122

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Fig. 1-1 Water melon fields covered by gravel mulch in Gaolan in the northwest of

China ............ ......................一...............................…..................2

Fig. 1-2 Salt-affected soils in the worId ..................一...........................…υ..4

Fig. 2-1 Cumulative evapotranspiration (mm) as affected by saline water and

mulching treatments. Alphabets above the bar indicate difference among treatments at p

valueく 0.05 ........... .... .，. ... '" ...・・・・・・…........ ... .，. ....... ........ .... ..... ... ...... 13

Fig. 2-2 Average soil salinity (dS m-I) as affected by saline water and mulching

treatments. The average soil salinity indicates the average of 4 soil layers and 3 replications for each

treatment. Alphabets above the bar indicate difference among treatments at p value < 0.05 ............ 14

Fig. 2-3 Averaged soil temperature COC) in 2 soil depths (5 cm and 10 cm) as affected

by different mulching treatments. The average soil tempera印reindicates the average of soil

temperature measured during 3 days in 15 minutes interval .......................................... 19

Fig. 2-4 Dry biomass as affected by mulching and saline water treatments. Alphabets

above the bar indicate difference among treatments at p valueく 0.05・・・・・・・・・・・・・・・・・・・・・・・・…・・・・・・ 20

Fig. 2-5 Water use efficiency (WUE) as affected by mulching and saline water

treatments. Alphabets above the bar indicate difTerence among treatments at p valueく 0.05...........22

Fig. 3-1 Cumulative evapotranspiration of Swiss chard measured in winter and spring

as affected by mulching treatment ..................................................... .26

Fig. 3-2 E百ectsof mulching on hourIy change in cumulative ET of Swiss chard during

each day on 3 consecutive days in winter and spring seasons ............……....28

Fig. 3-3 Salt distribution at the end of experiment under different mulching treatments

as reflected by electrical conductivity of 1 :5 soil extract .............・・….........29

Fig. 4-1 lrrigation amount (kg) and evapotranspiration (kg) of grapevine for di百erent

mulching and irrigation treatments from June 5 to September 21. MSS: mulching

combined with sub-surface seeper hose irrigation; SS: no幽ll1ulchcombin巳dwith sub-surface seeper hose

irrigation; MS: ll1ulching combined with surtace seeper hose irrigation; S: no-mulch combined with surface

seeper hose irrigation............................................................................ 40

Fig.ι2 Effects of mulching and irrigation method on volumetric soil water content at

three soil depthsラ where(A): 7 cm; (B): 17 cm; (C): 27 cm; (D): average values of

three depths. ・・・・・・・・…・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・…・・・…・・・・・・・・・・・・・・・・・・・・.41

IV

Fig. 4-3 E官ectsof mulching on mean， maximum (Max) and minimum (Min) soil

temperatures at 7 cm soil depth from June 5 to September 21 (A) and daily

variation of soil temperature at 7 cm soil depth on June 27 (B). Each symbol in

Fig. 4-3 (A) represents th己average土standa付加01'(SE) (n=3). . .・・・・・・・・・…......................…42

Fig.ι4 Effects of mu1ching and irrigation method on shoot length for prima1'Y shoot

(A) and lateral shoot (B) of grapevine. …………………・・……………………・・ 44

Fig. 4-5 Effects of mulching and i1'rigation method on leaf a1'ea fo1' p1'imary leaf (A)

and late1'alleaf (B) of grapevine …一....一...…....一・・・・・・…・ー・・・・・・・・….......・...45

Fig.ι6 Daily va1'iation of photosynthesis (AN) fo1' p1'ima1'Y leaf (A) and lateral leaf

(B)， stomatal conductance (gs) (C) and int1'insic WUE (AN gs-l asμmol CO2 mol

H20ぺ)(D) fo1' prima1'Y leaf of grapevine unde1' diffe1'ent mu1ching and i1'rigation

methods on 2 Augustラ2008.…......・・・・・・・・・・・・・・・・・・・・・…・・…・・・・・・…・・・・・・・・・・・….46

Fig. 4-7 E託ectsof mu1ching and i1'rigation method on ber1'Y diamete1' of g1'apevine.

Each symbol 1'ep1'esents the ave1'age土 standa1'de汀01'(SE) (n口 10)・・・…・・・・・・・・… 48

Fig. 4-8 Effects of mulching and irrigation method on f1'esh yield (pe1' t1'ee) of

g1'apevine. ..……一・・・・・…一......................…-一-一一.........................….50

Fig.ι9 E首ectsof mulching and i1'1'igation method on wate1' use efficiency (Y ET1)

of g1'apevine， whe1'e Y is f1'esh yield (g). ........................…・・・・・・・・・・・・ー・・… 51

Fig. 4-10 E妊ectsof mu1ching and irrigation method on berry sugar content of

g1'apevine. ..................…一..........…......................................一......52

Fig. 5-1 Schematic diag1'am oftwo cameras and the marked berries ..，……・・・……...67

Fig. 5-2 Diurnal va1'iations in a time series of diamete1' fo1' Berry No. 2 from 29 June

to 1 July. The solid line represents measured berry diameter， and the dashed line represents the trend

line................................................................................... .…・・・・・ 68

Fig. 5-3 S011 water potential (lf1) of the 1'oot zone (10 cm and 20 cm soil depths) after

i1'rigation (shown by arrow) fo1' potted 2-year old Pione g1'apevine企om28 June to

1 July. Means土 SE(n = 6)・一......…・・・・一.........…・・・・・・…・・・…・一............… 70

Fig. 5-4 Daily variation of berry size in a 2-yea1' old Pione grapevine in be1'ry-growth

stage from 27 June to 28 June (A) and from 29 June to 1 July (B). Means土 SE

(n=3)...................................................…....................................71

Fig. 5-5 Effect of soil water potential (lf1) (10 cm soil depth) on the trend value of berry

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diameter. Means 二七 SE(n = 6) …日 ・・・・一一・・・・・・・・……..........…・・・・・・・・…・・・・・…73

Fig. 6-1 Schematic illustration of experimental setup ……・....・.............一…一・82

Fig. 6-2 Diumal variations in a time series of diameter for Berry No. 2 from Aug.

17 to Aug. 19. The solid line represents measured b己rrydiameter.、 andthe dashed line represents the

trend line....................................一一......一-一・・・…・・・・一一・・・・・・・・・・・・・・・・…・・・・ 83

Fig. 6-3 Effect of soil water potential (If/) (10 cm soil depth， n=6) on the trend value of

berry diameter. dD1/dlfl担 ddD2/dlfl represent differential of trend value of berry diameter No.l and

No.2 on soi1 water potential. . . . . . . . . . . . . . . . . . . . . . . . . . • . . . • . .…・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・… 85

Fig. 6-4 Daily variation of soil water potential (If/)， photosynthesisラ stomataI

conductance なs)and transpiration (ηof grapevine from 13 to 19 August， 2008.

Each symbol represents the average土standarderror (SE) . ・・・・・・・・・・・・・・・・・…・・・・・・・・・・・・・・・・・・・・・・ 86

Fig. 6-5 Relationship among soil water potential (at 10 cm soil depth) (n=6)，

photosynthesis (AN) (n=3)， intrinsic WUE (AN gs-1 as !lmol C02 mol H20-1) and

extrinsic WUE (AN T1 as mmol CO2 mol H20勺 (n=3)of primary leaf of

grapevine in the moming from 13 to 19 August， 2008...…一・・・・・・・・・・…・一一.....88

Fig. 6-6 Relationship between trend value of berry (No. 2) diameter and leaf

photosynthesis (AN)， stomatal conductance (gふtranspiration(η， leaf temperature，

intrinsic WUE (AN gs-1 asμmol C02 mol H20・1)and extrinsic WUE (AN T1 as

mmol CO2 moI H20-1) of primary leaf of grapevine in the moming from 13 to 19

Augustラ2008.Values are vine means (n=3)・・・・・・一..….................…・・・・・・…-一...... 89

Fig.ι7 Relationship between leaf stomatal conductance and leaf photosynthesis (ん)ラ

intrinsic WUE (AN gs-1 asμmol CO2 mol H20-1)， extrinsic WUE (AN T

1 as mmol

C02 mol H20-1) and sub-stomatal C02 concentration (Ci) of primary leaf of

grapevine in the moming from 13 to 19 August， 2008. Values are vine me叩 s(n=3)…90

VI

List of tables

Table 2-1 Chemical characteristics of seawater (AトBusaidiet al.， 2007)…............. 11

Table 2-2 Soil salinity (dS m-1) as atlected by mulching under low and high saline water

ilTigation .........................・・・・・・・・・・・・・・・・・・いい・・・・・・・・・…・・・・・・・…・・・・・・・・・・・…15

Table 2-3 Soil water content (g gぺ)as a能 ctedby mulching and saline water

treatments................................................................................ ...17

Table 2-4 Soil temperature (oC) as affected by mulching and saline water .…・・・・・ ・・・…18

Table 3-1 Average soil temperature at different layers measured during the entire winter

and spring seasons of the experimental period .......一・・・……..........一"…...30

Table 3-2 Evapotranspiration (Eη， fresh yield， dry yield and water use efficiency

(WUめofSwiss chard as a能 ctedby mulching treatment ...・・・一-一..............31

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List of symboIs

ADR: amplitude domain reflectometry

AN: net photosynthesis (μmol CO2 m-2 S-I)

CCD: optical coupler

CI: cool night index

Ci: sub-stomatal CO2 concentration (J!mol CO2 / mol air)

D: berry diameter (mm)

T: tr溜 lspiration(mmol H20 m-2 S-l)

EC: electrical conductivity (dS m-I)

Es: soil evaporation (mm)

ET: Evapotranspiration (mm)

ETR: electron transport rate

extrinsic WUE: photosynthesis / transpiration

fc: focal length

G: gravel mulch

gs: stomatal conductance (mol H20 m-2 S-l)

intrinsic WUE: photosynthesis / stomatal conductance

LSD: least significant difference

M: mulch

MS: mulching combined with surface Seeper Hose seepage irrigation

MSS: mulching combined with sub-surface Seeper Hose seepage irrigation

N: no-mulch

R: rice-straw mulch

S: no-mulch combined with surface Seeper Hose seepage irrigation

SDI: sub-surface drip irrigation

SS:れかmulchcombined with sub-surface Seeper Hose seepage irrigation

Ts: soil temperature (oC)

WUE: water use efficiency (kg m-3)

θ: soil water content (cm3 cm-3)

平f:soil water potential (kPa)

vrn

Summary

Given the current demographic trends and global warming， as much as 60% of the

global population may suffer serious water scarcity by the year 2025. Agriculture is likely

to suffer the most unless more efficient water management is practiced， particularly in

drylands.恥1ulchingis an efficient method controlling evaporation. Reducing evaporation

loss helps to conserve soil moisture and control salt accumulation. Since saline water

resources are more abundant than fresh waterラthecareful use of saline or diluted seawater

is important for agriculture. Irrigation scheduling also plays an important role in

developing water-saving agriculture. Determination of threshold value at which irrigation

should be scheduled is necessary for water-use-efficient production. This study was

carried out from 2005 to 2008 at the Arid Land Research Center， to evaluate mulching

e百ectfor sustainable agriculture and establish irrigation threshold for water剛 saving

production.

ln the first part， ameliorative e百ectof mu1ching on water use e百iciency(WUめ of

Swiss chard and salt accumulation under saline irrigation was investigated in order to

conserve soil water and maintain lower level of salts in the topsoil. A pot exper咽imentwas

conducted in a greenhouse to evaluate the effects of three mulching types together with

diluted seawater irrigation. Seawater was diluted to achieve the electrical conductivity of

irrigated water as 4.8 and 7.4 dS m-I. Pots were mulched in the form of gravel， pine-

needles and rice-straw， respectively. Mu1ches sign出cantlyreduced evapotranspiration

(Eηin all the treatments and reduced salt accumulation under high saline irrigation. High

diluted seawater irrigation could be used under mulch condition without serious salinity-

damage to Swiss chard. Averaged soil temperature (Ts) among mu1ches di百eredas gravel

> rice-straw > pine-needles > no-inulch during winter season， regardless of soi1 depth.

Mu1ching improved plant biomass as well as WUE. Under high saline water， rnt叫1

were d副itJ釘fe叙redfor t出hedry mat従te釘rproduction and WUE i加nthe order of gravel > p戸ineか醐

needles > rice-straw > no-mu1ch.τhe experiment indicated that mulching practice can be

also used favorably for crop production under saline IlTigation.

ln the second part， the effect of gravel mulch (G) and rice輪 strawmu1ch (R) on the soil

salinity， ET，

IX

allow the water table to keep between 50 crn and 80 crn depth. At the end of the

experirnent， the electrical conductivity of 1:5 soil extract was rneasured in four soil

depths (5， 10， 15， 25crn). The curnulative ET was higher with no柵 rnulch(292 rnrn) than

under R (254.7 rnrn) and G (216.6 rnrn). The fresh and dry yields of Swiss chard were，

respectively， 76% and 113% higher under R and 49% and 64% higher under G than under

no-rnulch. The electrical conductivity of 1:5 soil extract in the top 25 crn soil layer was

lower under rnulching than under no-rnulch. MuIching increased the soil ternperature

slightly. These contributed to the increase of yield under rnulching as cornpared to under

no-rnulch treatments. RM treatment increased WUE by 143% and 10% as cornpared to

no-mulch and G treatrnent， respectively. Thus rnulching using R is recomrnended for

reducing salinity effect under shallow water table of saline water and irnproving WUE.

In the third part， effects of mulching and sub-surface seepage irrigation on soil water，

soiI ternperature， growth， berry quality and yield of grapevines (Vitis vinifera L.) were

investigated. This experirnent was conducted in a greenhouse using 4 weighing

lysirneters from 5 June to 21 Sep.， 2008. Four treatrnents: mulching cornbined with sub-

surface Seeper Hose seepage irrigation (MSS); no-mulch cornbined with subωsurface

Seeper Hose seepage irrigation (SS); rnulching cornbined with surface Seeper・Hose

seepage irrigation (MS); no-rnulch combined with surface Seeper Hose seepage irrigation

(S)， were used. Growing investigation was included of shoot length， leaf areaラ

photosynthesis (A)サ， berry diameter， berry sugar content and fresh yield of grapevines.

MS gave the highest fresh yield while SS gave the lowest value due to higher θ(upper

soil)， A必 Tsand diarneter fOl・ MSas compared with SS. MS gave the higher WUE than

MSS due to the higher water content at top soil and higher yield for MS. These

cornbination of rnulch and seepage irrigation were di古eredfOl・ WUEin the order of MS >

MSS > SS > S. Compared with SS， the berry diarneter，ラ freshyieldラ WUE，and berry sugar

content for MS were enhanced by 2.8 mrn， 271.5 g/tree， 33% and 15%ラrespectively.MSS

gave higher berry sugar content than MS， which could be attributed to the higher Ts and

lower soil w慌 erat the top soil layer under the condition of sub-surface irrigation. Ts

should become an irnportant index for the berry quality of grapevine.

In the

X

measurement of berry size. After irrigation， grapevine was allowed to experience

decreasing ljf monitored by tensiometers. The instantaneous variations in the berry

diameter were measured by photogrammetry simultaneously. Photosynthesis was also

measured. Berry diameter increased at night and decreased in the day， and showed

sensitivity to developing so11 moisture stress. Berry diameter increased rapidly after

irrigation till ljf became二3kPa. In the ¥jf range of二3kPa to ;;;:5.4 kPa， the growth rate

decreasedラ andas ljf decreased beyond二5.4kPa， the berry started shrinking and the

shrinkage showed a strong linear relationship with decreasing ljf. In contrastラ

photosynthesis and transpiration remained unaffected by decreasing ljf until it became -

9.3 kPa beyond which photosynthesis decreased significantly. Thus， berry diameter was a

better indicator of developing moisture stress than photosynthesis and transpiration and -

5.4 kPa should be considered as the threshold ljf for scheduling irrigation in the last phase

of Stage 1 ofberry development in grapevines.

In the fifth part， the criticalvalue of soil water potential was discussed for irrigation

scheduling during berry ripening stage (Stage 3) of grapevines. When soil water potential

decreased from -13.2 kPa to 雌 14.7 kPa， photosynthesisラ stomatal conductance，

transpiration， extI恒sicWUE (= photosynthesis / transpiration) and intrinsic WUE (=

photosynthesis / stomatal conductance) decreased rapidly and did not recovery thereafter.

In contrast， the berry size remained almost unaffected by decreasing soil water potential

until it became -16.2 kPa beyond which the berry shrunk significantly. Thus，

photosynthesis response was more sensitive to water stress than berry size during the

berry ripening stage. When stomatal conductance < 0.03 mol H20 m糊2S-l (corresponding

to -14.7 kPa)， photosynthesisラ intrinsicWUE and extrinsic WUE decreased rapidly，

whereas substomatal C02 concentration increased steeply， indicating that norトstomatal

1imitations to photosynthesis become dormant. A more sensitive response of

photosynthesis to water limitation compared to stomatal conductance at this last stage of

soil drying led to a decrease in photosynthesis/stomatal conductance. When stomatal

conductance> 0.03 mol H20 m-2 s七photosynthesisand substomatal CO2 concentration

decreased， whereas extrinsic WUE and in

XI

be同悦n-13.2 and -14.7 kPa (corresponding to stomataI conductance range of 0.09 -0.03

-2 ぺmoI H20 m-'" S-1). After irrigation， soiI water potential should be kept Iower than -6.9 kPa

because the highest intrinsic WUE occurred in the soiI water potentiaI range企om・6.9to欄

14.6 kPa. ln hyper arid and arid areasラ thesoiI water potentiaI threshold for irrigation

scheduling should be considered as -16.2 kPa (corresponding to stomataI conductance

value ofO.02 mol H20 m-2 s勺inthis important stage of economic yield development and

fruit quality in grapevines.

ln conclusion， rice欄 strawmulch was a better option than graveI mulch for improving

crop yield and water use efficiency in the long run. The rice-straw mulch combined with

surface irrigation exceeded no mulch combined wIth sub-surface irrigation for enhancing

the berry diameter， fresh yield， WUE and berry sugar content. Mulching combined with

surface irrigation outbalanced mulching combined with sub-surface irrigation in

improving yield and WUE. Hence when the s況u巾b.引 lrfi白ac印eirrigation is used foαr咽 vineyards，

the placement depth of sub-surface irrigation hose should be shaIlower than 15 cm.

Mulching combined with sub-surface irrigation gave higher berry sugar content than

mulching combined with surface irrigation due to higher average soiI temperature and

lower soil moisture at the top soil layer under sub-surface irr詰ation.Besides the effective

mulching cultivation and irrigation methods， the appropriate irrigation scheduling is also

very important for saving water. A new photogrammetry system is suitable for measuring

berry diameter for irrigation scheduling， therefore photogrammetry could be used for

determining the critical point at which the belTy contracted under stressful condition. The

berry diameter was a better indicator of sensing water stress than photosynthesis in the

last phase of Stage 1 of berry growth since the berry contracted under the moderate water

stress. Nevertheless， in the ripening stage， the leaf photosynthesis was more sensitive to

water stress than berry size， so Ieaf photosynthesis measurement and photogrammetry

technology could be used together to establish irrigatiol1 threshold to get cost四 effective

use of water resources， especially for fruit trees. Sil1ce the water demand for vines in

various growth stages is 110t uniforrn and drought has different e

XII

Acknowledgements

At the outset， 1 want to thank God for being so merciful during my studies and

inspiring me by providence in my life.

This thesis would never be completed without the contribution of many people to

whom 1 would like to express my appreciation.

1 want to express my grateful thanks to The Japanese government for granting me a

scholarship and Global Center of Excellence (GCOE) program for providing research

budget.

1 would like to express my deepest appreciation to my supervisor Prof. Inoue

加1itsuhirofor his thoughtful supervisionラ valuableguidance， intellectual encouragement，

good advices and critical and constructive comments. 1 have learned a lot 合omhim in

these five years because he has dedicated himself to instruct me and help me in my

experiments and during my studies at the Arid Land Research Center. Prof. Inoue also

provided me much attention and care which helped my life. It's generous of him to give

me so much of his time and show me so much consideration. 1 want to express my

maximum respect to him.

1 am also deeply indebted to my associate明 supervisorProf. Koji Inosako and Prof.

Kenji Suzuki， whose comments， advice and support were of great value to me. Their

intellectual encouragement during the thesis writing is unforgettable.

1 am grateお1to Dr. Ahmed and Dr. Andry of the GCOE program for their valuable

and critical comments during the development of my thesis proposa1. Their comments

were very beneficial for my study. 1 do appreciate their help.

1 would like to extend my appreciation to the entire Land Conservation division staff

for the knowledge they have given me during the period of studies at the Arid Land

Research Center. Their advice and help made even the smallest incident important and

charming. It is gene1'ous of them to take so much interest in my study. 1 also appreciate

their eve1'-willing attitude to help me solve my personal problems.

Last but not least， 1 have app1'eciated the endeavor， adviceラ helpand courage of my

wife Li Liラ andmy daughter Zhang Shi Ran， in coping with me while 1 was busy fo1' a

long time with my experiments and studiesラ andgiving me impetus in my study. 1 also

want to thank my parents for their patience and long-waiting fo1' me in my hometown.

xrn

Chapter 1

1.1 Introduction

1.1.1 Drought and salinization in the world and ameliorative句fJects01

mulching

Drought and salinization represent serious threats to the sustainability of irrigated

agriculture in many arid and semI-arid regions (Konukcu et al.， 2005). The water-use

efficiency techniques used with conventional resources have been improved. Howeverラ

the shortage of water resources of good quality is becoming an important Issue in water-

scarce countriesラ whichwilJ have to rely more on the use of non-conventional water

resources to partly alleviate water scarcity. At the same time， a rapid increase in the

population ofthese areas during the past two decades has significantly increased the need

for water.ラ foodand fibre. Hence， land and water resources have been put under severe

stress (Ghadiri et al.， 2005).

Direct evaporation from soil is a rr悶jorway of water loss because it is not directly

related with biomass production. Apparently， there are three main advantages of reducing

soil evaporation (Es). First， preventing Es can help conserve soil moisture and save water.

Second， PI

preventing Es can also benefit environment此tsince it can reduce leacl副1吋ingof nitrate

f免er此凶t討ilize匂rsand t出hu山sreduce polh叫i式凶t討ion(Romi比ce抗tal.吋， 2003勾).

Application of mulch is known to be effective in reducing Es (Cadavid et al吋 1998).

Trees with organic mulch and tree-shelter treatments had a greater survival than trees

with plastic mulch and no mulch， particularly when salinity was higher (Sun et al.， 1994).

ln northwest China， use of gravel mulch has been an indigenous farming technique for

crop production for over 300 years (Li， 2003)ラ especiallyin watermelon fields (see Fig.

1-1). The farmers usually use 10 mm gravel to mulch the fields and the interval of

changing mulch is several decades， so the work of mulching and removing gravel is not

an obstacle for the farmers. lncreasing water-use efficiency (WUE) should be a key issue

for research (AI-Kaisi and Yin， 2003) and it is currently a priority for the United Nations

policy.ラ whatis called the 'Blue Revolution' and summarized as ‘more crop per dropラ

1

(Annan， 2000).

Fig. 1-1 Water melon fields covered by gravel mulch in Gaolan in the northwest of China

(by Wang Jie Min)

More than 50% of all the existing irrigation systems of the world are more or less

affected by soil salinization and alkalinization (Szabolcs， 1989). ln the future， one ofthe

consequences of extension of irrigation in arid and non-arid areas would be increasing

hazard of secondary salinization， caused by irrigation. The yearly loss of arable land by

secondary salinization and alkalinization is more than 10 million hectares and this area is

distributed in different developed and developing countries in all the continents. In soils

where salinity and alkalinity is a result of improper method of irrigation the amelioration

is rather expensive， therefore the prediction and prevention of salinization before

construction and exploitation of irrigation systems is necessary (Szabolcs， 1989).

lrrigation-induced salinization is one of the most important reasons of reduced

agricultural productivity in many arid and semi-arid regions (Fujimaki et al.， 2003).

Freshwater resources of these areas， both surface and ground water， have been over-

exploited， often at the expense of deteriorating water and land quality. As supplies of

2

good-quality irrigation water are expected to decrease in several regions due to increased

municipal industrial agricultural competition， available freshwater supplies need to be

used more efficiently (Qadir and Oster， 2004). With limited room for expanding irrigated

agricuIture due to the lack of extra capacity in freshwater resources， the possible use of

saline or sea water has some appeal， especially in coastal areas， such as in Iran (Ghadiri et

al.， 2005) and Italy (Baccio et al.， 2004 and D' Amico et al吋 2004).

Saline water was previously considered unusable for irrigation， but new research

during the past two decades has helped bringing into practice some large irrigation

schemes， which depend on saline water (Beltran， 1999 and Qadir et al吋 2001).Ir吋gation

with saline water could provide an interesting opportunity to meet increasing food

demands without competing with other pressing needs for 合eshwater such as domestIC

and industrial water use in water scarce regions (Karlberg and Vries， 2004). The

availability of water resources of marginal quality such as drainage water， saline

groundwaterラ treatedwastewater and diluted sea water has therefore become an important

consideration. As a consequence of the use of the marginal quality water， howeve乙saIts

may accumulate in the root zone， damaging the following crops if the rainfal1 is

insufficient to leach them out. 1n the experiment on use of diluted sea water， soil analysis

after harvest showed that the electrical conductivity of the saturation extract had

increased significantly in diluted sea water treatments (Ghadiri et al.ラ 2005).This may

suggest that the mixing of sea and σround waters at the rates used in these experiments

may not be sustainable over a long period of time and soil salinization may occur unless

soils are of light texture and sufficient good quality fresh water or winter rain is available

to lower the salinity of soil between successive crops (Ghadiri et al.， 2005).

Thus， the use of these waters in irrigated lands requires the control of soil salinity by

means of leaching and drainage of excess water and saIt. An extra quantity of water in

excess of that needed for evapotranspiration must be applied as a long幽 termstrategy and

the extra quantity of irrigation water must be able to pass through the root zone (Qadir et

al.， 2003). However， the leaching of saltsラ soilmicroelements and agrochemicals can

i

3

groundwater. Therefore， irrigation with saline water requires a comprehensive analysis

(Be1tran， 1999).

Salinity generally affects the growth of plants by either producing an ion excess or a

water deficits in the expanded leaves (Ghadiri et al.， 2005). Water uptake is restricted by

salinity due to the high osmotic potential in the soil and high concentrations of specific

ions that may cause physiological disorders in the plant tissues (Feigin， 1985) and reduce

yields (Verma and Neue， 1984). However， some crops such as wheat and barley can be

salt tolerant (Ghadiri et al.， 2005). Research suggests that irrigation of barley with up to

two-thirds sea water is feasible and may result in economically significant yields.

Saline soil

397.1

million ha

Sodic soil

434.3

million ha

Based on the FAO/Unesco soil Map ofthe World

77 million ha of cultivated area is on salt-affected soils

Fig.l・2Salt鍋 affectedsoils in the world

Salinity is a widespread environmental stress for crop plants. It is common in arid，

semiaridヲ andcoastal regions (see Fig. 1・2).In those environments， seawater infiltrations

can occur (Milnes and Renard， 2004) or the sea provides the only source of water for

irrigation (Baccio et a1.， 2004). The use of diluted sea waterラ salineand/or sodic drainage

water and groundwater for agriculture is expected to increase. This warrants

modifications in the existing soil， irrigation， and crop management practices used， in

4

order to cope with the increases in salinity and sodicity that will occur (Qadir et al.， 2007).

Salts in the soil solution are left behind as soil water evaporates. Therefore， salt

accumulation can be reduced by preventing Es. Mulching the soil surface with

bituminous emulsion up to 75 g m司2decreased the mean salt concentration in the root

zone (10% level) (Wahba et al.， 1990). Only a few studies have been made about the

effects of preventing salt accumulation using mulch (Wahba et al.ヲ 1990).Furthermore，

there is lack of research on comparing effects of different kinds of mulch on salt

accumulation. Residues of wheat and barley have been found to be more effective in

decreasing Es than those of sorghum or cotton. This is attributed to the thinner stems of

wheat and barley than sorghum or cotton (Jalota and Prihar， 1998). Pine-needles are

thInner than rIce-straw令 however，there Is lack of research on comparing effects of pine-

needle and rice-straw on preventing evapotranspiration (E1) and salt accumulation.

1.1.2 Swiss chard and grapevines in d，η;/ands and semi-arid regions

Beet (Beta vulgaris L.) is an important crop within many arable rotations in the world

and it is commonly grown in rotation with wheat (Triticum spp.) and barley (Hordeum

spp.) and sometimes with potato (Solanum spp.) (Smith et al.， 2001). It is a valuable

break crop， preventing the build up of disease and reducing the need for pesticides in the

following crops (Tzilivakis et al吋 2005).Drought is the most serious cause of yield loss

in the UK beet crop (Jaggard et al.， 1998). For this reason the availability of water

resources of marginal quality such as drainage wateζsaline groundwater and treated

wastewater has become an important consideration. Sugar beet yield was higher in the

field irrigated with moderately saline water (5.9-7.0 dS m -1) than in the field irrigated

with fresh water (Moreno et al.， 2001). Glycine betaine accumulation increased under

salinity and this accumulation correlated with higher tissue levels of Na in red帽 beet

(Subbarao et al.， 2001). Swiss chard (Beta vulgaris L. var. jlavescens) is a kind of beet.

However， there are few studies on e茸ectsof mulch and diluted sea water irrigation on

Swiss chard (Louvigny et al吋 2002).

The grapevine plays a very important role in the economic， social and cultural sectors

of many regions; however vineyards are often grown in regions under stressful conditions

and thus they are vulnerable to climate change (Santos et al.， 2007). 1n a vineyard， one

5

mulching material of a sewage sludge and bark compost improved water retention

capacity of the soilラ reducedevaporation and soil temperature fluctuations (Pinamonti，

1998). Neverthelessラ thewavelength-selective polyethylene mulch had no detectable

effects on vine development， yield components and fruit quality (Bowen etal.， 2004).

Rice-straw mulching increased WUE of Swiss chard by 143 and 10% as compared to no-

mulch control and gravel mulching treatrnent， respectively (Zhang et al吋 2009).

Unfortunately， there is lack of inteIτmtional literature evaluating effects of the rice-straw

mulch on grapevines growth.

Grapevine is a traditionally non-irrigated crop that occupies quite an extensive

agricu1tural area in drylands and semi-arid regions. Recently， irrigation was introduced to

increase the low land yield (Escalona et al.， 2003)ラbuta good cornpromise between grape

quality and yield is of rnajor importance for the achievement of high-quality products as

wine (Cifre et al.ラ 2005).

1.1.3 Sub問 S町向ceirrigation

Soon after the conventional surface irrigation， the soil is very wet， resulting in lack of

air. Later， this soil becomes dry and hard， causing a degree of sa1tsラ andis a continuous

cycle. Sub-surface irrigation， in which water is applied below the soil surfaceラ canhelp

conserve water by reducing evaporative water losses in agricu1tural systems (Siyal and

Skaggs， 2009). Sub-surface irrigation has been practiced in various forms， including

pitcher or pot irrigation (Bainbridge， 2001; S iyal and Skaggsラ 2009)，perforated or porous

clay pipe irrigation (Ashrafi et al吋 2002;Shu et al.ラ 2007)and drip IlTigation (Patel and

Rajput， 2008). However， reports on the response of grapevines to suトsurfaceirrigation

have not been found.

Sub側 surfacedrip irrigation (SD1) is the most advanced method of irrigation， which

enables the application of the smal1 amounts of water to the soil (ASAE Std.， 1999) while

maintaining a relatively dry soil surface (Patel and Rajput， 2008). Nevertheless， one

technological problem is the formation of cavity at the soil surface above the water

emission points (Patel and Rajputラ 2008).Another problem is spatially dependent

reductions in dr旬perdischarge (Ben-Gal et al.ラ 2004).1n additionラinmany parts of the

world， plastic drip tubing and emitters are cost-prohibitive (Siyal and Skaggsラ 2009)ラ so

6

some cheap materials for simple microωirrigation technique should be developed.

Seeper Hose is an absolutely new environmental soil control system which consists of

a f1exible rubber tubing that contains many micro pores and is laid sub-surface or

underground to supply water， air， or fertilizer directly to plants. However，ラ noresearch has

been conducted using sub-surface Seeper Hose irrigation for grapevines. A combination

of mulching and sub司 surfaceSeeper Hose irrigation techniques has not been tested on

grapevines， and could probably yield even more promising results.

1.1.41rrigation schedulingfor grapev初esbased on soil water potential

threshold

Improving the efficiency of irrigation is essential for long-term sustainability of grape

production and the wine industry. Deficit irr討i

increasing fruit quality by raising dry matter and sugar content (Cha討1mηlerset al.ラ 1981).

Several studies have shown that appropriate and moderate water stress is beneficial for

berry growth in grapevines， whereas severe water deficit or saline irrigation decreases the

production of assimilates， reduces transpiration， shoot growth， and yield and quality of

fruit (Shani et al.， 1993; Delgado et al吋 1995;Pellegrino et al.ラ 2005;Lovisolo and

Schubertラ 2006;Lovisolo et al吋 2008).The potential for water saving by deficit irrigation

in orchard crops has remained unexplored so far (Fereres et al.， 2003). It is， therefore，

important to determine the critical timing for starting irrigation， especially in drylands

where drought represents a serious threat to the sustainability of agriculture (Konukcu et

al.ラ 2005).

McCarthy (2000) reported that grape berry size was most sensitive to water stress

during the post司f10weringperiod， whereas moisture deficit after veraison had only a

minor effect on berry weight at maturity and berries were insensitive to water deficit in

the month before harvest (McCarthy， 1997a). lmai et al. (l991b) further reported that

daily variation in berry diameter might be a useful index for soil moisture control in

grape production. The upper limit of I.jf in the ripening stage was regarded as lfI = -12.6

kPa since the berry swelling was conspicuously affected by soil drying (Imai et al.，

1991 b). τheir study， however・ラ did not indicate the threshold value of lfI at which

7

irrigation should be scheduled during the berry deve10pment stages as only two levels of

lfI were tested.

lmai et al. (1991 b) concluded that in the ripening stageラ berrysize is affected

conspicuously by decreasing 1fI. However， McCarthy (2000) reported that moisture deficit

after veraison had only a minor effect on grape berry weight at maturity and belTies we1'e

insensitive to wate1' deficit in the month before ha1'vest (MCCatihyラ 1997a).The

maturation stage is c1'itica1 for grape be1'1'Y quality. In the maturation stageラ isthe berry

size sensitive to dec1'easing 1fI? Cifre et al. (2005) reported that stomatal conductance (gs)，

sap flow and trunk growth variations could be used as indicators of water stress for

grapevine. During the maturation stage of grapevine， which kind of physiological

pa1'amete1' is useful and suitable for ir1'igation management? Further studies should be

done to clear these questions for scheduling irrigation in the maturation stage of

grapevme.

There a1'e many studies on the effects of various irrigation regimes on vine growth

(B1'avdo et al.， 1985; Poni et al.， 1994; Esteban et al.， 2001; Pellegrino et al吋 2004;

Reynolds et al.， 2005). However， what is the threshold lfI at which the grapevine must be

irrigated during different berry deve10pment stages is not known. We hypothesized that

this value could be established by measuring diurnal variations in berry diameter， leaf

photosynthesis and stomatal conductance of grapevine experiencing increasing soil

moisture stress. It isラ however，necessary that the measurements of berry diameter are

made with great precision because the changes a1'e rather small.

A new system equipped with automated photogrammetry was developed by Moritani

et al. (2006; 2007) to measure soil erosion (Pyle and Richards， 1997). This system

consists of two high-precision digital cameras， attached to a computer with an image-

analysis program of three側 dimensionalalgor対1m.This system can also be applied fo1'

measu1'ing合uitsize with th1'ee major advantages. First， the measurement precision is high.

Second， the ber1'Y diameter can be monitored automatically. Thirdラ thedetermination is

nondestructive. However.ラ thereis lack of information about measuring berry size using

the new photog1'ammet1'Y system.

1.2 Objectives

8

The objectives of this study were to evaluate mulching effects for Swiss chard and

grapevines p1'oduction and estab1ish ir1'igation threshold fo1' waterωsaving management of

grapevines. Mo1'e specifically， the following objectives we1'e add1'essed in the study:

1) Compa1'ison of the three m此 hingmaterials effects (i.e.， rice-straw， pine-needles and

gravel) under diluted seawater ir1'igation condition on evapotranspiration， water use

efficiency of Swiss chard， soil water content， soil temperature and salt accumulation

2) Evaluation of the rice-straw mulch (M) and sub-surface Seepe1' Hose i1'rigation (SS)

e首ectson ET， WUE， soil water content (8) and tempe1'atureラ groVv也 (shootlength， leaf

area， photosynthesis and ber1'Y diameter)， berry quality (suga1' content) and yield of 'G1'os

Colman' grapevines (向的 viniferaL.)

3) Establishment of the c1'itical soil wate1' potential value fo1' starting irrigation in

grapevines during the berry“growth stage and 1'ipening stage， based on photog1'ammet1'Y

of berries， photosynthesis of leaf and a tensiometer measurement system of soil wate1'

potential， as the water deficit developed in the soil.

9

Chapまel・2Ameliorative effect of mulching on water use

efficiency of Swiss chard and salt accumulation under saline

irrigation

2.1 Introduction

ln several areas in many countries， irrigation is causing a rapid decIine of the

groundwater table (Zhang et al.， 2003). Application of mulch is known to be effective in

reducing evaporation and thus preventing nonゐeneficialloss of water (Cadavid et al吋

1998) because mulch provides resistance to vapor f10w from the soil surface to the

atmosphere. There are many kinds of mulch material.

ln many arid and s臼emlト岨a訂ri同da創re悶as，ラ f合旨尚e白shwa剖terresources 働ゐbo叫thsurfお注おceand ground

1玖W司iVa椛terト-have been oveぽr-幽必.

coas針tala釘reas(Ghadiri et al吋 2005).But as a consequence， sa1ts may accumulate in the

root zone. Thus， the use of these waters in irrigated lands requires the control of soil

salinity by means of leaching and drainage of excess water and salt. It is possible that the

leaching water requirement might be decreased if mulch was used. However， there is lack

of research on effect of application of mulch combined with diluted sea water irr怯ation

on crop performance and salt accumulation in the soil. Hence， this study was conducted

using Swiss cha1'd.

2.2 Materials and Methods

A greenhouse expe1'iment was conducted at Arid Land Research Center， Tottori

Unive1'sity from Nov. 3ラ 2005to Feb. 8ラ 2006.Clay soil brought from Tohaku Totto1'i

p1'efecture was used fo1' the experiment. Soil was air dried and sieved via 4 mm sieve. The

sand， silt， and cIay pe1'centages ofthe soil were 17.8，28.3 and 53.9， respectively. The pH

and electrical conductivity (ECl;5) ofthe soil we1'e 5.5 and 0.04 dS m-1 respectively. The

bulk density of the soil was 1.1 g cm づ. Seawater was diluted with tap water to achieve

the electrical conductivity (ECw) as 4.8 and 7.4 dS m-1• The chemical composition of

seawater is shown in Table 2-1. The soil surface in Wagne1' pot (29 cm depth and 25 cm

10

diameter with the closed outlet) was mulched up to 3 cm thickness either with gravel，

pme凶 needlesor rice-straw. The soillayer depth was 26 cm. There was also an unmulched

control soil. The densities of gravelラ pine-needlesand rice-straw were measured as 1.54 g

cm三0.052g cm-3 and 0.027 g cm-3， respectively. The diameter of gravel was 0.5 ~ 1.5

cm. The length of pine-needles and rice-straw was about 5 cm. The pots were arranged

in randomized complete block design and replicated 3 times. After 15 days two seedlings

of Swiss chard (Beta vulgaris L. subspp. cycla) were transplanted in every pot. A

compound NPK fertilizer (12・12-12)was applied at the rate of 1.8 t ha-1 which is equal

to 216 kg ha-I ofN， P and K respectively. lnitially the pots were irrigated with tap water.

The dilllted seawater irrigation was started after 48 days oft1百 lsplantationto avoid early

shocking effects on plants. The pots were weighed everyday by an electronic balance and

the difference in weight was considered as evapotranspiration (ET). An equal amount of

water to an average value of ET across all mulch treatments was applied at 5 days

intervals. For no-mlllch treatment the pots were irrigated according to their ET. Water llse

efficiency (WUE) was calclllated by the equation: WUE = Plant biomass yield / ET.

Table 2-1. Chemical characteristics of seawater (AI-Bllsaidi et al.， 2007).

pH ECw

dS m-1

7.5 38.5

Na十

mgL-1

cr ω十

K

11211 18834 377

Ca2+

266

Mg:2+ U D

1976

NO'>- P

0.2 2.1

During the growth periodラ theplants were harvested twice. ln the first harvesting 2-3

largest leaves from the base of plants were sampled. The plants were grown for 3 months.

The shoots (leaves plus stem) were harvested above the soil sllrface for fresh biomass

yield. Dry biomass was determined a設erdrying the shoots in an oven at 65 Oc for 48 h. The post嶋 harvestsoils were sampled in 4 layers (0-5 cm， 5“10 cm， 10-15 cm and 15-20

cm) from 36 pots to measure the soil water content and electrical conductivity (EC) on

Feb.8ラ 2006.There were 144 soil samples with 3 replications for each trea加lentand

11

layer. The soil water content was determined by drying soil samples in an oven at 105 oC.

The EC of soil water suspension (1: 5) was measured with an EC meter (B-173 Horiba

CoふThesoil temperature was measured afternoon on daily basis at the depth of 2， 5， 10

and 15 cm by a mercury-in柚 glassthermometer. The average soil temperature was

calculated across the measured data.

An additional experiment was conducted to confirm the effect of mulching on soil

temperature using the same pots filled with moist Tohaku clay soil. The soil surface in

the pots was mulched up to 3 cm thickness either with gravel， pine-needles or rice‘straw.

There was also an unmulched control soil. This time the soil temperature was recorded at

15 minutes interval within the soil depth of 5 cm and 10 cm for three days using eight

Onset TidbiT v2 Temperature Data Loggers with an accuracy of 0.2 oc.

Data were generally subjected to statistical analysis using SPSS (Version 11.5)

sofhvare and means were separated by the least significant difference (LSD) method at

probability level of 5%.

2.3 Results and Discussion

Evapotranspiration: Evapotranspiration (E乃 wassignificantly affected by mulching

treatments. Compared with no-mulchラ mulchtreatments substantially prevel託edET(Fig.

2-1). Among the mulches the magnitude of ET was differed in the order of pine-needles

:::; rice-straw > gravel under low saline irrigation. Compared with the treatment of no欄

mulch in conjunction with tap water irrigation， the ET for the treatment of gravel mulch

under high saline irrigation was reduced by 56%. The significance of reducing ET is to

save water whereas crop yield does not decline. Generally transpiration losses from the

crops are difficult to control since directly related to the crop growth parameters， whereas

the soil evaporation can easily be reduced or modified. Rasiah et al. (2001) reported that

gravel mulching was effective in reducing the evaporation losses from the sand dune soil

and considerable saving in the irrigation inputs was associated with gravel mulching.

12

140

吉田ll ロNo-mu1ch 間 Gravel 日PII1e-needles 菌 Rice-straw

120

a

汁1 b b

80

Icdムcd

官ζ韮C。E ZJ 6 Z

40

20

O

Tap water Low saline High saline

Fig. 2-1. Cumulative evapotranspiration (mm) as affected by saline water and mulching

treatments. Alphabets above the bar indicate difference among treatments at p valueく 0.05.

The ET was lowered in saline irrigation under nか mulchtreatment. In other words， the

increasing water salinity was negatively associated with the ET for no-・mulchtreatment.

The application of water with salts reduced cumulative level of ET possibly due to the

formation of salt crust on the soil surface from unmulched soils. This phenomenon could

be related to the enhanced water densityラ viscosityand chemical bonds in the soiI錨 salt

system. F AO (1998) reported that density， temperature and salinity affected several water

characteristics e.g.ラ evaporationand so on. Newson and Fahey (2003) also reported a

reduced rate of evaporation due to the developrnent of salt crust on the soil surface. It is

also reported elsewhere that soil salinity condition affected crop development and

evapotranspiration (F AOラ 1998).The ET value was insignificantly differed between tap

water and saline water among the three mulching materials (Fig. 2-1)ラ whichcould

probably be related to the lower evaporation as welI as lower accumulation of salts under

mulches (Table 2-2).

Soil salinity: Salts accurnulation in the soiI was highly affected by the application of

saline irrigation water (Fig. 2-2). The EC values ofthe soil reflected the accumulation of

13

salts. As expected the average EC of soi1 increased with the concentration of irrigation

water. Blanco and Folegatti (2002) also found a linear association between salinity and

application of saline water in the soil profile. Under high saline water various mulching

types reduced the average salt accumulation (Fig. 2-2). However， there was no effect of

mulching on the average soil EC under tap water and low saline water conditions， which

could be attributed to lower level of salts accumulation.

2.5 図間伶蜘~ロPine-needles 盟GravelロNo“mulch

a 2.0

b

r'g∞開岳会主芯沼田】きどき芸言問ω匙苦言〈

ハυnυ

cde 1.5

1.0

0.5

High saline Low saline Tap water

Fig. 2-2. A verage soil salinity (dS m勺asaffected by saline water and mulching

treatments.ηle average soil salinity indicates the average of 4 soil layers and 3 replications for each treatment.

Alphabets above the bar indicate differ拍 ceamong trea加 entsat p valueく 0.05.

14

Table 2-2. Soil salinity (dS m-1) as affected by mulching under low and high saline water

irrigation.

Saline water Mulching 0-5 cm 5-10 10-15 15-20

Low saline water No-mulch 2.31 b 0.50 c 0.40c 1.08 bc

Gravel 0.97 c 0.97 ab 0.45 bc 0.96 bc

Pine輔 needles 1.13 c 0.92 b 0.65 bc 0.92 c

Rice-straw 1.05 c 0.86 b 0.54 bc 1.15 bc

High saline water No・mulch 3.90 a 1.18 ab 0.59 bc 1.00 bc

Gravel 1.50 bc 1.26a 0.59 bc 1.47 bc

Pine-needles 1.47 bc 1.18 ab 0.47 bc 1.45 bc

Rice-straw 1.83 bc 1.29 a 0.86 b 1.55 b

Alphabets in a column indicate difference among t陀 atmentsin the same column at p < 0.05.

The mulch treatments significantly reduced salt accumulation in the upper soil (0-5 cm)

whereas unmulched pots accumulated higher salts in the upper soil (Table 2-2). In the

upper soil (0-5 cm)， the EC for mulch treatments under high saline water irrigation was

no more than that for no-mulch treatment under low saline water irrigation (Table 2-2).

This suggested that high saline water irrigation could be used under mulch condition

without serious salinity-damage for crop. Under high saline water mulchi泊ngwith gr悶.ヨavelラ

pl加neか剛剛剛剛削-n刷刷網

i加nthe soil layer 0ぱfO開-5cmη1. In the middle horizon ofthe soils (5凶 10cm and 10-15 cm)， the

15

salt accumulation was lowered as compared to the upper or Iower zone of the soil (Table

2-2). This could suggest that mulching could affect the movement of salts in the soils. In

1987 Yamamoto found that NaCl distribution in soil profiles depended on evaporation

rate and soil texture etc. During our experiment higher salinization of soils occurred due

to the continuous application of saline water. Water uptake by plants and evaporation

合omthe soil surface were reported the main factors governing salt accumulation in the

topsoillaye1' (BerトHuret al.， 2001). Salts deposition also depended on the soil moisture

depletion and 1'oot development due to the plant growth.

Soil water cOlltellt: Compa1'ed with nかmulchtreatment， mulch t1'eatment significantly

enhanced soil wate1' content in the upper soil (0・5cm) ac1'oss all irrigation waters (Table

2-3). Under high saline water the soil water contentsおrgravel and pine-needles we1'e

higher than those for nか mulch，regardless of soil depth. The average values of soil water

content fo1' gravel mulch were higher than those of rice綱 strawmulch except tap wate1'

irrigation. Irrespective of irrigation water， the average values of soil water contents were

improved with the application of gravelラ pine-needlesand rIce-straw by 27%， 18% and

15%， respectively as compared to nかmulch.Several researchers reported mulching as a

common practice to conserve soil water in small fa1'ms (日開Asswadand Groenevelt， 1985;

Groenevelt et al.， 1989).

Soil tmψerature: When compared to the nか mulchtreatment the mulching condition

enhanced averaged soil tempe倒 的 (Table2-4 and Fig. 2-3). These temper仰1'e

va1'Iations of soils could be directly associated to the manipulation of the thermal

conditions of soil surface by mulching residues. In addition， greater average tempe1'ature

was 1'ecorded in the soil with gravel treatment under saline condition as compared to rice-

straw and pine-needles. A veraged soil temperature among mulches differed as gravel >

rice-straw > pine-needles > no-mulch， regardless of soil depth (Fig. 2-3). The averaged

soil temperature at the depth of 5 cm under gravel mulch was enhanced by 1.2 oC as

compared to no・mulchwhereas the temperature value increased by 0.5 oC in gravel

mulched soil within the soil depth of 10 cm. The differences of soil temperature among

mulches in 5 cm soil

16

Table 2-3. Soil water content (g g-l) as affected by mulching and saline water treatments.

Saline water Mulching 0-5 cm 5-10 10嶋 15 15-20 Average

Tap water No側 mulch 0.27 c 0.32 cd 0.36 bc 0.38 c 0.33 d

Gravel 0.37 ab 0.38 bcd 0.40 abc 0.41 abc 0.39 bc

Pine-needles 0.36 b 0.35 bcd 0.39 abc 0.41 abc 0.38 bc

Rice-straw 0.37 ab 0.38 bcd 0.39 abc 0.41 abc 0.39 bc

Low saline water No“mulch 0.29c 0.32d 0.36 bc 0.38 c 0.34d

Gravel 0.43a 0.44 a 0.45a 0.45a 0.44 a

Pine-needles 0.41 ab 0.40 abc 0.40 abc 0.44 a 0.41 ab

Rice-straw 0.35 b 0.36 bcd 0.37 bc 0.38 c 0.37 cd

High saline water Nか mulch 0.27c 0.32 d 0.35c 0.37 c 0.33 d

Gravel 0.43a 0.44 a 0.44 a 0.44 ab 0.44 a

Pine剛・needles 0.40 ab 0.41 ab 0.41 ab 0.44 ab 0.42 ab

Rice-straw 0.38 ab 0.39 ab 0.39 abc 0.39 bc 0.39 bc

Alphabets in a column indicate di偽 renceamong treatments in the same column at p < 0.05.

17

Table 2-4. Soil temperature (OC) as affected by mulching and saline water.

Irrigation

water

Mulch type Soil depth (cm) I

2 5

Tap water No-mulch 13.4 13.1

Gravel 13.8 13.8

Pine-needles 14.0 14.4

Rice幽 straw 14.0 13.4

Mean 13.8 13.7

High saline No-mulch 12.3 13.3

可vater

Gravel 14.1 15.2

Pine-needles 13.2 13.7

Rice-町straw 14.0 14.3

Mean 13.4 14.1

10 15

14.2 14.3

14.2 14.4

14.1 14.3

14.1 14.6

14.2 14.4

13.7 14.1

14.3 14.6

14.1 14.2

14.3 14.3

14.1 14.3

1 The average soil temperature was calculated across the measured data.

Mean 2 Max 2 Min 2

13.7 18.3 1.3

14.1 18.4 2.4

14.2 18.0 3.5

14.0 18.4 2.3

14.0 18.3 2.4

13.4 18.1 2.5

14.6 18.5 3.2

13.8 18.7 3.6

14.2 18.4 3.1

14.0 18.4 3.1

2 Mean， ma;ximum and minimum va¥ues of soil temperature show the average values across 4 soillayers out

ofwhole measured data.

18

depth were more pronounced than temperature differences observed in 10 cm soil depth

(Fig. 2-3). These results showed that effect of mulches on heat retention in top soil layer

(5 cm) was higher. Li (2003) reported higher soi1 temperature with a mulch as compared

to no-mulch treatment. It is also reported that gravel-mulch had a smaller heat storage

capacity than the bare soil (Li， 2003). The higher soil temperature under gravel-mulch

could be related to the less evapotranspiration than rice-straw and pine-needles. Warmer

soi1s in the winter season could contribute to an improved plant growth as well.

，-、

u o 、・4

~ 』

2 吋..

19

芝 18~ 仏

語。喝国

伺圃圃

・静酬。副

司:::1 17 ω t)JJ 号事』

~ -〈16

i盟 5cmDI0cml

No-mulch Pine-needles Rice-straw Gravel

Fig. 2-3. Averaged soil temperature (OC) in 2 soil depths (5 cm and 10 cm) as affected by

different mulching treatments. The average soil temperature indicates the average of soil temperature

measured during 3 days in 15 minutes interval.

The mulching condition also enhanced the minimum soil tempera印re，when compared

to the no-mulch treatment (Table 2-4). Under tap water irrigation， the minimum soil

temperatures under gravel， pine-needles and rice-straw mulches were enhanced by 1.8、

2.7 and 1.7 times、respectivelyas compared to no-mulch. Mulching condition also

increased the maximum soil temperature under high saline irrigation. It is also reported

that the mulch layer retained heat， protected plants from frost damage in the early spring

and the fall seasons (Li， 2003). It was mentioned elsewhere that strawωmulch reduced soil

temperature and delayed crop development under low ambient temperature (Zhang et al.ラ

19

2005b).Irrespective of mulching types， high saline irrigation increased the minimum soil

temper抵ureas compared to ordinary tap water (Table 2-4). However， high saline water

could not enhance mean soil temperature as compared with ordinary tap water irrigation

during the experiment.

Crψ biomα~S: Crop growth was significantly affected by mulching conditions. The

application of mulches improved dry biomass yield of Swiss chard irrespective of

irrigation treatments (Fig. 2-4). Since mulch reduced ET and improved soil water content

as well as soil temperature in winter season， crop growth may positively be affected. Li

(2003) attributed better plant response to gravel-sand mulch due to greater water

availability and higher temperature regime. Huang et aI. (2005) also repOlted that straw

mulch significantly decreased ET and increased yield during both dry and wet seasons.

Among the mulches gravel produced the highest crop biomass under saline irrigation

(Fig. 2-4). The higher biomass under gravel mulch could be related to the lower ET，

higher soil water content and improved soil temperature during winter.

12

ロNo-mulch 盟 Gravel 困 Pine-needles 図 Rice-straw

nu 'ei -.

ω4

判。aMW〉∞sassb凸

ab a b g C C

d

g

f 6 U

b

4

2

O

Tap water Low saline High saline

Fig. 2-4. Dry biomass as affected by mulching and saline water treatments. Alphabets above

the bar indicate di汀erenceamong treatments at p valueく 0.05.

20

The crop biomass of Swiss chard could not decrease with diluted seawater. This could

be attributed to the higher tolerance of Swiss chard towards salts and the presence of

essential plant nutrients in the seawater. Since the experiment was conducted durセ19the

winter season， the amount of saline water consumed for irrigation was less due to low

evapotranspiration rate. 1n general the crop response to the salinity depends on the plant

species， soil textureラ waterholding capacity and composition of the salts. The inhibitory

effects of salinity on growth were also reported to be related to the nutritional status of

the plants (Bernstein et al.， 1974). Pal et al. (1984) concluded that salt tolerant crop like

barley could be grown economically with irrigation water up to the EC value of 16 dS m-

1. Ghulam et al. (1997) obtained a reasonable bar1ey yield with irrigation water (ECw) up

to 9.3 dS m-I under・15%excess water as leaching requirement. The depressing effects of

salinity on other crops have been reported by some researchers (Abdul et al.， 1988;

Heakal et al.ヲ 1990;Koszanski and Karczmarczyk， 1985).

Water use efficiellのl:Application of mulches had significant effects on water use of Swiss

chard (Fig. 2-5). The mulch material gave higher WUE regardless to the irrigation

treatments. This could be attributed to the higher plant biomass and low ET under

mulching conditions. For WUE the types ofthe mulches differed as gravel > pine-needles

> rice四 straw> no-mulch unde1' high saline water whereas under tap water， the mulches

remained statistically similar for WUE. The WUE was increased by mo1'e than 100% fo1'

g1'avel mulch as compared to no-mulch unde1' saline water irrigation. The higher plant

biomass， lower ET and higher conservation of soil water unde1' gravel mulch could be the

factors responsibJe for higher WUE when compared with other mulching materials in

saline irrigation.

Diluted seawater irrigation maximized WUE than ordinary tap water. Higher biomass

production and less evaporation from the soil surface under mulching and / or saline

i1'1'igation could be the possible 1'easons fo1' highe1' efficiency of wate1' use by plants. The

increasing level of evapotranspi1'ation has 1'educed the water use efficiency of plants

unde1' no-mulch treatment. Soil management practices like mulching improve soil wate1'

and thus increase the availability of water to the c1'op. These changes would affect

evapot1'anspi1'ation rates and potentially increase crop biomass. The ability of mulch to

21

enhance WUE in a soil-plant system could encourage mulching practice for the

enhancement of crop production.

6

回Pine-needles 国 Rice-strawロNo-・.mulch 麗 Gravel〈悶

agMX)旨

g宮、語。。苦言詰注

5

a 4

C C 3 C

2

O

Tap water Low saline

Fig. 2-5. Water use efficiency (WUE) as affected by mulching and sa1ine water

High saline

a

treatments. A¥phabets above the bar indicate difference among treatments at p va¥ueく 0.05.

2.4 Conclusions

The findings of the experiment indicated that soil water content， salt level of soilラplant

biomass. and water use efficiency of Swiss chard were profoundly inf1uenced by

mulching and sa1ine water. Mulching of soils significantly reduced the ET and

accumulation of salts in the topsoil of the pots. The mulching practice improved soil

water content， crop biomass yield and WUE. The soil temperature was slightly increased

with the application of mulches during the winter season. The averaged soil temperature

at the depth of 5 cm under gravel mulch was enhanced by 1.2 oC as compared to no-

mulch. The enhancement of soil temperature by mu1ch in 5 cm depth was more than 10

cm depth. Among the mulches gravel mu1ch followed by pine輔 needlesmulch proved to

be effective especially under high saline conditions. Ultimately the crop performance was

ameliorated under saline conditions. The mulch induced higher plant growth may provide

22

an opportunity for the safe use of saline water. However， these conclusions were only

based on a short-te1'm experiment during winter season when the soil evapo1'ation was

1'elatively low and the c1'op g1'ew slowly. Hence， the long-term expe1'iments， field and/or

laboratory， a1'e needed to assess the impact of saline water use under mulching on

evaporation and salinity interrelation fo1' the sustainability of agriculture. The

comprehensive understanding also necessitates that we continue to strive for systems that

are efficient in their use of wate1' and nutrients in arid and semi-arid areas.

23

Cbapter 3 Effects of mulcbing on evapotranspiration， yield

a詮dwater use efficiency of Swiss cbard (Beta vulgarおしval二

flavescens) irrigated witb diluted seawater

3.11ntroduction

Some research on sea water irrigation show that a 1: 1 mixture of Caspian Sea and wel1

water can be used for irrigation without a significant reduction in the growth and yield of

barleyラ providedthat it is not applied earlier than the time of ear formation (Ghadiri et al.，

2005). This would promise a significant1y reduced demand on the limited ground water

resources in many countries for agricu1tural use.

Comparison of effects of different kinds of mu1ch on ET， salt accumulation， soil

temperatureラ yieldand WUE in one experiment is very scarce. A long-term experiment

(more than half year) using large weighing lysimeters was conducted to further evaluate

the conjunctive effects of mulching and saline irrigation. In order to study the effect of

different kinds of mulch in detailラthisexperiment was conducted in three lysimeters in a

greenhouse to monitor dynamic variation of ET and soil temperature under mu1ch and no幅

mulch conditions.

3.2真萱aterialsand 1¥査ethods

The experiment was carried out in a greenhouse at the Arid Land Research Center，

Tottori University， Japan， using three weighing lysimeters. Each lysimeter was 1.2 m high

and had a diameter of 0.798 m (surface area 0.5 m2). The top 40 cm of lysimeter column

was filled with the Tohaku c1ay soil (sand : silt : c1ay = 17.8% : 28.3% : 53.9%) to

achieve a bulk density of 1.1 g cmてandthe rest of column was filled with a sandy soil

with a bulk density 1.58 g cm-3• The ETwas estimated by measuring the weight changes

of the lysimeter with an electronic balance， with a resolution of 50 g， which corresponds

to 0.1 mm depth of water. Detai!ed description of the lysimeter is given by Inoue and

Shimizu (1998). Soil temperature was monitored by 4喝 letrodesensors at six depths (7，

17，27ラ 47，67and 97 cm) in each column. A computer continuously recorded the weight

24

of1ysimeter and soil temperature data at 15 min time interval.

Swiss chard (Beta vulgaris L. var.jlavescens) seeds were sown on October 01，2005

in plastic tray containing potting soil to produce seedlings for the experiment. Fourteen

seedlings were transplanted in each lysimeter on November 03， 2005. Just before

transplanting， a compound NPK fertilizer (12-12-12) was applied at the rate of

1800 kg ha -1. An irrigation tubeラ 70cm in height with a small hole in the bottom， was

inserted into the center of each lysimeter and used for sub-irrigation. The plants were

irrigated with tap water in the fir説 20days after transplanting. From November 23， 2005，

they were irrigated with saline water (ECw of 6.86 dS m-I) prepared by diluting seawater

with tap water. The ground water level was kept between 50 and 80 cm below the soil

surface.

Three mulching treatments， no柵 mulch(control)， rice-straw mulch (R) and gravel mulch

(G) were compared. Based on the study of Sharma et al. (1985)， the thickness of mu1ch

was kept 3 cm. During the whole experimental period， which lasted from November 2005

to June 2006 and covered the winter (November to February) and the spring (March to

early June) seasonsラtheSwiss chard was harvested two times. First harvest was done at

the end of the winter seasonラ onMarch 1，2006， when only the largest four leaves of each

plant were cut at their base. Second harvest was done in spring， at the end of the

experiment， when all of the above ground material (leaves and stem) were harvested and

their企eshand oven-dry weights were determined.

Soil samples were taken from four layers (5， 10， 15 and 25 cm soil depth) at the end of

experiment to measure electrical conductivity (1:5 soil extract， EC1:5) using a

conductivity meter B-173 (Horiba Coふ

Statistical analysis: The statistical analysis software SPSS v 11.5 (SPSS Inc， ChicagoラIL，

USA) was used to analyze data. Means were compared by the LSD (least significant

difference) at p < 0.05 level of significance.

3.3 Results and Discussion

Evapotranspiration: Fig. 3-1 shows the cumulative ET during the winter and spring

25

-， -.6.- no-mulch

明Tinterseason 100 -1

80イ

60イ

40イ

20イ

120

O

11-Feb 22-Jan 2-Jan 13-Dec 23-Nov 3-Nov

200 一 企 no-mulch

Spring season

一・-Rice mulch

(自国)同日吉お【同∞ロ

Eち

Q50容認ω吉田口Q

(自国)同836Ha∞口語ぢ向gvωω昌吉吉田口U

9-Jun 20・恥i[ay30・Apr10-Apr 21-恥1ar

O

1-恥1ar

Fig. 3-1. Cumulative evapotranspiration ofSwiss chard measured in winter and spring as

26

a百ectedby mulching treatment

parts of the total growth period. The ET was higher in spring than in winter under a11

treatments. This difference can be attributed to low evaporative demand of the

atmosphere and sma11er growth of the plants in winter than in spring. During winter both

the mulching treatments reduced ET more or less equally as compared to no-mulch. In

contrast， during spring the reduction in ET due to mulching was higher under G than

under R. The R gave higher ET compared to G in spring because the crop grew better

under R and would have transpired more water than under the G treatment. These results

showing reduction in ET because of mulching are consistent with the observations of

several other workers (Mao 1998; Rahman et al.， 2005; Yang et al吋 2006).

E宜ectsof mUlching on the hourly change in the cumulative ET during each day on

three days in both winter (Feb. 27 to 29) and spring (May 20 to 22) are shown in Fig. 3-2.

There was no irrigation given on these days， hence the hourly change in ET ref1ected the

water balance (.d.w) in the lysimeter as the system interacted with the ambient atmosphere.

Results showed that for the nかmulchtreatment， the .d.w increased rapidly before 14:00，

then the rate of increase slowed down. We attribute this to higher solar radiation before

14:00. For gravel mulch treatment， the .d.w showed nearly the same trend as for the no欄

mulch. Under RM， however， the .d.w value became negative during earぢmorningon the

first two days in spring and during a食ernoonon all the three days in winter， i.e.， the

weight of the ly引meterincreased. The maximum weight increase for R 1'a溜angedf1'om O.ユ2

tぬo1.4 mm dat繍六帽

du1'ing ea包1'1砂ymoming i泊nsp戸n泊Iね19and during af註!errね∞1冶oonin winte1'， when humidity is high， we

think that this 1'e丑ectsthe capability of R to adso1'b wate1' vapor f1'om the air. This was

also confirrned by visual observation of the rice straw mulch. As a result， R not only

prevented soi1 evaporation， but also could“catch" water f1'om the air， which would be of

benefit for crop growth in drylands. The ability of straw mulch to adsorb water vapor

from the air has also been reported earlier (Kosmas et al.， 1998; Kosmas et al吋 2001).

Electrical conductivity (ECZ:5): The electrical conductivity (EC1:5) of soi1 at diffe1'ent

depths for three treatments at the end ofthe experiment is shown in Fig. 3-3. There we1'e

significant differences between no-mulch and the two mulch treatments and the

differences were particularぢconspicuousin the top 10 cm soil layer， where most of the

roots ofthe

27

W inter season 一+ーGravelmulch --0-Rice mulch ーか no・mulch

2.0 〆-、

℃

ε g

ト匂I:;:J

v 〉

..... 主 0.0F“ ロコζJ ・0.5

1.5

1.0

0.5

v刷鞠刷圃T

Feb 29

，...蜘剛附句・園圃醐守

Feb 28

-1.0

Feb 27

Spring season 3.0 ，....、、

句3

~ 2.0

』I:;:J

g: 1.0 国

20.0 仁J

時

e

Mい町

四

・

哨

Mm

-;・l

-

T

a

F

6

F

口付一

聞

Vd

圃

a

F

8

M

4 O 24

T

20

r-ー圃T岡田"'"T

8 12 16

May 21

4 24 0 20 8 12 16

お1ay20

4

-1.0 0

Fig.3一2.E百ect給sofmu1chi加ngon hourly change i泊ncumu叫lla剖ti討veET of Swiss cha創rddl出II汀r泊g

each day on 3 consecutive days in winter and spring seasons

28

(dSrr .1) ECJ.5

10.0 8.0 6.0 4.0 2.0 0.0

0

-+-G

!一←R

l竺 no・mu1ch

5

10

15

(gQ)戸一

Eo凸

20

25

30

Fig.3ー-3.Salt distribution at the end of experiment under difterent mulching treatments

as reflected by electrical conductivity of 1:5 soil extract.

29

plant are located. This could be attributed to higher evaporation of water from the soil

surface under noィnulch，which would have allowed greater upward movement of salt

from the sub-irrigation with saline water. There were no differences in the EC I:5 values

between the RM and GM treatments.

Soil temperature: The average soil temperature (Table 3-1) at every depth was higher

under G and R than under no-mulch but the difference did not generally reach the level of

significance. Only at 17 and 47 cm depths the average temperatures during winter were

significantly higher under G than under no-mu1ch. During spring again， significantly

higher average temperatures were recorded for 17 cm depth under mulching treatments

than under・no-mu1ch.Mao (1998)， Li (2003) and Rahman et al. (2005) also reported

increase in soil temperature due to mu1ching in winter cropping season.

Table 3-1. Average soil temperature at di荘erentlayers measured during the entire winter and spring seasons of the experimental period

Depth (cm) 7 17 27 47 67 97

Winter season (oC)

no-mu1ch 8.30a 8.05b 8.61a 8.97b 7.51a 7.23a

G 9.98a 10.25a 8.82a 9.67a 7.89a 7.82a

R 9.59a 9.87ab 8.23a 9.54ab 8.03a 7.82a

Spring season (OC)

no-mu1ch 22.80a 19.53b 19.26a 18.03a 18.03a 18.06a

G 23.18a 23.11a 20.04a 19.74a 18.74a 18.47a

R 23.14a 23.14a 20.01a 18.92a 18.24a 18.73a

Different letters in a column denote significant di百erencesbetween treatments at pく 0.05.

Yield and water use宅伊ciency:The e在ectof mu1ching on total ET， fresh and dry matter

yield， and WUE of Swiss chard， for winter， spring and the whole crop dur割 ionis shown

in Table 3-2. The total seasonal fresh matter yield under R was 76% higher as compared

30

to no-mulch and under G it was 49% higher than nか mulch.The Dry matter yield results

showed similar trends. This imp伊1

mu1ch can be attributed to the reduction in sali泊ni包za従tiOlη1of the surface layer of soil (Fig.

3-3) and improved moisture availability to the plants because of lesser ET (Fig. 3-1).

Table 3-2. Evapotranspiration (Eη， fresh yieldラ dryyield and water use efficiency (WUE) of Swiss chard as a首ectedby mulching treatment.

Treatment ET Fresh matter yield Dry matter yield WUE

(mm) (g plant- (g plant (kgm・3)

Winter season

no・mulch 110.8 14.8土3.1 1.6土0.9 0.23

G 77.9 16.6土2.5 1.9土0.5 0.39

R 81.6 19.2土2.1 2.3土0.9 0.45

Spring season

no-mulch 181.2 33.6土6.3 9.5土2.5 0.84

G 138.7 55.5土5.6 16.3ま1.8 1.88

R 173.1 66.1土5.9 21.3土4.1 1.97

Total

noィnu1ch 292 48.4土11.3 11.1土3.6 0.61

G 216.6 72.1土14 18.2土2.9 1.34

R 254.7 85.3土13 23.6土4.2 1.48

The relative increases in the yield because of mulching were higher in the spring part

of the growing season than in the winter. This can be attributed to higher evaporative

demand of the atmosphere in spring， which would have subjected the plants under no-

mulch to more stress than the mulched plants. As already indicated， the total seasonal ET

31

was highest under nかmulchand it was reduced by 26 and 13% by G and R treatments，

respectively. Thus， G was more effective in reducing ET as compared to R. As both G and

R would have provided nearly the same ground cover to prevent evaporation， the higher

ET under R should have been because of more transpiration under this treatment， which

should have improved photosynthesis and ultimately benefited crop growth and yield

(Table 3-2).

WUE was improved by mulching treatment (Table 3-2) because of reduced ET and

higher yield than under no・mulchand the highest value was recorded under R. WUE

increased by 143% under R treatment over no珊 mulchand by 10% over G treatment.

Although both ET and yield were higher under R than G， the relative increase in yield

under R was higher than in G. Therefore the WUE was the highest under R.

3.4 Conclusions

Both gravel mulch (G) and rice-straw mulch (R) could reduce salt accumulation when

diluted seawater irrigation was used for irrigation. Compared wIth no-mulch、theEC1・50f

soil under mulches was nearly 38% lesser. The ET was 26% lesser under G and 13%

lesser under R than under no-mulch. On the other hand， the fresh and dry yields were，

respectively， 76% and 113% higher under R and 49% and 64% higher under G than

under no-mulch. Therefore， the WUE increased by 143% under R and 120% under G as

compared with nか mulchtreatment. Monitoring of hou山I及1r匂 changeof cumulative ET over

three days period when no irrigation was given， indicated that there was smal1 adsorption

ofwater 合omthe atmosphere by the R during the relatively cooler hours ofthe dayラ and

this could be very useful for crop growth in the arid and semi-arid regions. It can be

concluded from this study that mulching was a good strategy for getting good yield and

water use efficiency for Swiss chard when grown with saline shallow ground water.

Compared with the gravel mulch， the rice straw mulch showed a measure of superiority

during this long-term experiment period (about 6-7 months)， and given the additional

advantage of convenience in managing the material used， thereforeラ ricestraw mu1ch was

a better option than gravel mulch. Further experiments should be conducted to assess the

impact of rice-straw mu1ching on growth of other crops， like grapevines.

32

ChapteI・4Effects of mulching and sub-surface irrigation on

soil moisture and temperature， growth， yield， and beI・E・y

quali匂Tof 'Gros Colman' grapevines

4.1. Introduction

Water is the most limiting resource in drylands. Given current demographic trends

and future grO¥椛hprojectionsラ asmuch as 60% of the global population may su百erwater

scarcity by the year 2025 (Qadi1' et al.， 2007). Improvements in water use efficiency

(WUE) of crops are essential under the scenarios ofwater scarciりに Applicationof mulch

is known to be effective in reducing soil evaporation and saving water (Cadavid et al吋

1998; Li， 2003). Several mulching materials improved plant biomass as well as WUE of

Swiss chard (Zhang et al吋 2008).Riceωstraw mulching increased WUE of Swiss chard by

143 and 10% as compa1'ed to no削 mulchcontrol and gravel mulching treatmentラ

respectively (Zhang et al吋 2009).Besides Swiss chard，σrapevines are often grown in arid

and semi-arid areas.

The grapevine plays a very important role in the economicラ socialand cultural sectors

of many regions; however vineyards are often grown in regions under stressful conditions

and thus they are vulnerabJe to c1imate change (Santos et al.， 2007). To facilitate

adaptation to conditions of limited rainfall and less irrigation water， mulching could

provide an alternative means to control grapevine response to irrigation with maximum

WUE. Compared with the control， soil moistures and nutrient were enhanced and the

severity of Bo的ノtiscinerea (a saprophytic fungus causes bot1'戸isbunch rot in grapes)

infections were reduced fo1' shredded paper and grape marc mulches (Jacometti et al.ラ

2007a). In a vineyard， one mulching material of a sewage sludge and bark compost

improved water retention capacity of the soil， reduced evaporation and soil temperature

f1uctuations (Pinamontiラ 1998).In additionラ theuse of 1'ye mulch could be applied as an

effective weed control technique in conventionalラ aswell as organic deciduous tree

orchards (Ormenio“Nunez et al.， 2008). Nevertheless， the wavelength欄 selective

polyethylene mulch had no detectable effects on vine developmentラyieldcomponents and

33

fr・uitquality (Bowen et al吋 2004).Rice (or Paddy) straw is normally burnt on mechanized

farms with air pollution and used as fodder by small farmers having no other alternative

feed (Tripathi and Katiyar， 1984). Unfortunately， there is lack of international literature

evaluating effects ofthe rice舗 strawmulch on grapevines growth.

Grapevine is a traditionally norトirrigatedcrop that occupies quite an extensive

agricultural area in drylands and semi-arid regions. Recently， irrigation was introduced to

increase the low land yield (Escalona et al.， 2003)， but a good compromise between grape

quality and yield is of major importance for the achievement of high暢 qualityproducts as

wine (Cifre et al.ラ 2005).Excessive amount of irrigation water not only results in a waste

of water， but also causes nutrient loss and promotes excessive vegetative growth at the

expense of fruits. lrrigation would give more benefits if schedules and dosages were

oriented to maximize WUE of grapevines (Fereres et al.， 2003). Deficit IlTigation in fruit

crops can be of value in increasing fruit quality by raising dry matter and sugar content

(Chalmers et al.， 1981). Several studies have shown that appropriate and moderate water

stress is beneficial for berry growth in grapevinesラwhereassevere water deficit or saline

irrigation decreases the production of assimilates， reduces transpiration， shoot growth，

and yield and quality of fruit (Shani et al.ラ 1993;Delgado et al.， 1995; Pellegrino et al吋

2005; Lovisolo and Schubert， 2006; Lovisolo et al吋 2008).McCarthy (2000) reported that

grape berry size was most sensitive to water stress during the post-f1owering periodラ

whereas moisture deficit a註erveraison had only a minor effect on berry weight at

maturity and berries were insensitive to water deficit in the month before harvest

(McCarthy， 1997a). The potential for water saving by deficit irrigation in orchard crops

has remained unexplored so far (Fereres et al.， 2003). The grape cultivar 'Gros Colman'

(Vitis vinifera) is the later-maturing variety with a handsome grape and large round

berries (Hogg， 2007) mainly cultivated in greenhouses (Okamoto et al吋 1999).Water-

saving research on this variety is surprisingly lacking although nothing is known about

the adaptation to water stress of this variety. Similarly like muIching effects， sub酬 surface

irrigation (SS) can also save wate

34

conserve water by reducing evaporative water losses in agricultural systems (Siyal and

Skaggs， 2009)， similarly like mulching e町ects.Sub-surface irrigation has been practiced

in various formsヲ includingpitcher or pot irrigation (Bainbridge， 2001; Siyal and Skaggsラ

2009)， perforated or porous clay pipe irrigation (Ashrafi et al吋 2002;Shu et al吋 2007)and

drip irrigation(Patel and R司put，2008). However， reports on the response of grapevines

to sub.耐surfaceirrigation have not been found.

Sub-surface drip irrigation (SDI) is the most advanced method of irrigation， which

enables the application ofthe small amounts ofwater to the soil (ASAE Std吋 1999)while

maintaining a relatively dry soil surface (patel and Rajput， 2008). Today， SDI is used

throughout the world to irrigate field crops， vegetables， and合uits(Patel and Rajput，

2008; Camp， 1998). Nevertheless， successful use of SDI system depends on appropriate

solutions to a number of technological and economic obstacles. One technological

problem is the formation of cavity at the soil surface above the wate1' emission points

(Patel and Rajput， 2008). Another problem is spatially dependent reductions in drippe1'

discharge (Ben-Gal et al.， 2004). Factors that affect SDI uniformity are emitter clogging，

root intrusion， root pinching， mechanical and pest damage， soil ove1'burden and

compaction， soil hydraulic parametersラ and，possibly， system age (Lamm and Camp，

2007). In addition， in many parts of the wor1d， plastic drip tubing and emitte1's are cost-

prohibitive (Siyal and Skaggs， 2009)ラsosome cheap materials for simple micro-irrigation

technique should be developed.

Seeper hose is an absolutely new environmental soil control system which consists of

a f1exible rubber tubing that contains many micro pores and is laid suかsurfaceor

unde1'g1'ound to supply water， ai1'， 01' fertilizer dir・ectlyto plants. The seeper hose is made

by new materials (special rubbe1') with outstanding durabi1ity. Water seeps out from small

holes very slowly， making water control precise and e宜ective.The soil wetness is

maintained， wiII not dry out， avoids unnecessa1'y overf1ow and conserve wate1'

considerably. With a burying machine， the seepe1' hose can be used in various pr吋ects，

such as golf coursesラ nurseryplants and soccer fields (Uh uni hose co吋 LTD).However，

no research has been conducted using sub綱 surfaceseepe1' hose i1'rigation fo

35

objectives ofthis study were therefore to:

(a) provide an initial body of knowledge about the soil conditions， growth response and

performance of 'Gros Colman' grapevines (巧的vin{舟raL.) to water stress; and

(b) evaluate the e百ectsof rice鍋 strawmulch (M) and sub-surface seeper hose irrigation

(SS) on ET， WUE， soil water content (8) and temperatureラ growth(shoot length， leaf

area， photosynthesis and berry diameter)， berry quality (sugar content) and yield.

4.2. Materials and methods

4.2.1. PIαnt and soil materi，αls and experimental layout

The experiment was carried out in 2008 in a greenhouse at the Arid Land Research

Center， Tottori University， Japan， using three-year情。ld'Gros Colman' grapevines (日tis

vinifera L.) grown in large weighing lysimeters. On 25 February 2008， 'Gros Colman'

grapevines (目的 vinifera)were transplanted into 4 lysimeters (with 3 vines for each) in

the greenhouse under natural conditions of temperature， light and humidi句'.The amount

of water applied was controlled by a time clock-solenoid valve assembly connected with

a compressive pump. The grapevines were irrigated according to water requirement till

the experiment started. The plants were provided liquid fe1'tilize1' containing all essential

mine1'al nutrients (Wang et al.， 2001; Thippaya1'ugs et al.， 2002) once every week. The

experiment started from June 5ラ 2008.There were four treatments: mulching combined

with sub欄 surfaceSeeper Hose seepage irrigation (MSS); no-mu1ch combined with sub-

surface Seeper Hose seepage irrigation (SS); mu1ching combined with surface Seeper

Hose seepage i1'rigation (MS); no-mulch combined with su1'face Seeper Hose seepage

i1'rigation (S). Based on the study of Sha1'ma et al. (1985)， the thickness of mulch was

kept 3 cm. Two concent1'ic circles， la1'ge circle (outer ring) and small circle (inner ring)，

were made by the Seepe1' Hose tube and placed in each lysimeter fo1' irrigation， with the

large circle outside three vine t1'unks and the small circle inside three vine trunks. For

sub-surface irrigation， the Seeper Hose rings were placed at 15 cm soil depth. Pumping

was used to pump water from a big tank into the Seeper Hose for irrigation. The irrigation

amount was determined based on the mean values of actual ET in the former week (ETf).

For the co的・01treatment Sラ vineswere irrigated slightly more water than their ETfi

36

whereas the irrigation amounts for other treatments were only equal to around 90% of

their ET.J; respectively.

Each lysimeter was 1.2 m high and had a diameter of 0.798 m (surface area 0.5 m2).

The top 40 cm of lysimeter column was filled with a mixture of sandy soil (sieved

through a 2-mm sieve)ラ peatmoss， humic allophone soil and lime in a volumetric ratio of

1200 : 600 : 200 : 1， respectively. The mixture had a pH of 6.2 and field capacity ofthe

substrate， which was measured using drying method in an oven， was 0.467 (by volume).

A nonwovenes sheet was spread on the bottom of the mixture and ar・oundthe inner wall

of each lysimeter. Root depth was therefore clearly limited in the upper 37 cm. The rest

of column was filled with a sandy soil. lmai et al. (1987) and Okamoto and lmai (1989)

reported that when the rooting zone of Kyoho and Pione grapevines was restricted in a

defined volume by a raised bed or container， shoot grO¥椛hwas reduced and berry set and

maturation were improved. In addition， Kyoho vines grown under restriction of rooting

zone also showed improvement in accumulation of skin color， juice total soluble solids，

favorable vine growth and berry characteristics when rooting-zone depth was 20 cm

(Wang et al.， 2001).

τo encourage uniform vegetative growthラ vineswere pruned to retain 12 nodes per

vine; only two or three shoots per vine were le註 andwere trained horizontally. Eight

shoots for each treatments were left and trimmed twice between bloom and the veraison

stage of the berries. Lateral shoots were cut back to the first node. At flowering， one

cluster was left on each of the two shoots. Each cluster was trimmed to retain only 80-

100 florets and once berry-set occurred， further trimming was done to retain only 40-50

berries per cluster. At fruit growth stageラ thec1uster was protected with a white cover

合omdirect solar radiation. Integrated pest management procedures were usedラ inc1uding

manual control and spraying with non-toxic sprays. Ripe grapes are harvested on Sep. 22

by hand. Growing investigation inc1uded shoot length， leaf area， photosynthesis， berry

diameterラberrysugar concentration， f民shyield of grapevines.

4.2.2. Experimentα1 measurements

The ET was estimated by measuring the weight changes of the lysimeter with an

electronic balance， with a resolution of 50 g， which corresponds to 0.1 mm depth of water.

Detailed descr旬tionof the lysimeter is given by Inoue and Shimizu (1998). Soil

37

temperature was monitored by 4-eletrode sensors at the soil depth of 7 cm in each column

with three replications. A computer continuously recorded the weight of lysimeter and

soil temperature data at one hour time interval. Volumetric soil water content (θ~ was

monitored every 15 minutes by amplitude domain reflectometry (ADR) soi1 moisture

sensors installed at three depths (7， 17 and 27 cm) in each column with three replications.

A CRl OX data logger and control module (CampbelI Scientific Inc.， Utah， USA) is used

for system programming and automated data storage of ADR sensors.

The shoot length was measured inおurdays from June 2 to July 7 because shoot

growth ofvines tends to stop at the end of June or early July in Japan (Wang et al吋 2001).

Midrib length and leaf width were measured， and leaf area equations were calculated.

Therea立er，the midrib length of three vines from each treatment was measured in three

days， and the total leaf area was ca1culated. Twenty days a註erfull bloom， 20 berries per

treatment were marked， and the transverse diameter was measured at different intervals.

Net photosynthesis (AN) and stomatal conductance (gs) of three healthy primary and

lateral leaves of the σrapevine for each treatment were measured at 2 hours interval

during daytime on August 2 by a portable photosynthesis system (Lト6400，Li-Cor Inc.，

Lincoln， NE， USA). Measurements were conducted on 2 cm x 3 cm Ieaf portion in the

middle part of a leafblade confined in the leaf chamber ofthe system.

Twelve to twenty berries for each treatment were sampled at 7-10 days interval for

measuring fresh yield and sugar concentration from July 31 to Sep. 12. These berries

were pooled and squeezed by hand in new polythene bags. Samples of juice were taken

企omthese bags and sugar concentration CBrix) was measured through a digital

refractometer (Atago PR-I01， 0-45% oBrix土 0.1% at 5-40 oC; Atago Company Ltd吋

Japan). At harηvest on Sep. 22， 2008， after仕eshyield for each treatment was measur・ed，

ten berries per treatment were sampled randomly and placed in new polythene bags，

squeezed by hand and samples assessed as above.

4.2.3. Statistical analysis

Analysis ofvariance (ANOVA) was performed on data using “the average土 standard

error (SE)" analysis based on excel program.

38

4.3 Results

4.3.1. Evapotran伊 iration，soil moisture and soil temperature

Maximum irrigation amount (not shown) and ET were recorded for surface irrigation

without mu1ch (Fig. 4-1) because S tends to consume more water (including intensive

soil evaporation) than mu1ching or sub-surface irrigation. MSS gave the lowest value of

ET in the three treatments (Fig. 4-1)ラ whichcould be related to the lowest irrigation

amount (not shown) and lower soil evaporation under mu1ching and sub-surface

irrigation. The ETwas reduced by 1.3， 0.7 and 0.1 mmlday under MSSラ comparedwith Sラ

SS and MS treatments. MS and SS also reduced ETby 30.5% and 16.4%， compared with

S. The ET for SS was higher than that for MSラ a1thoughirrigation amount for SS was a

little lower than that for MS (not shown). This can be attributed to low evaporative

demand under the mu1ching condition.

The highest e occurred for S at the soil layer of 0-40 cm except a few days (Fig. 4-2

A， B， C and D) due to the highest irrigation amount (not shown). The differences of θ

between S and other treatments became greater in August and September than in June and

July. The volumetric soil water contents at the soil depth of7 cm for mulching treatments

(MS and MSS) were higher than that for SS except a few days (Fig. 4-2 A) due to the

lower ETunder mu1ching conditions (Fig. 4-1). The evalues at 7 cm depth for MSう MSS

and SS on June 15 were 0.207， 0.143 and 0.079ラ respectively.MS gave higherθat the top

layer than MSS (Fig. 4-2 A)， which could be attributed to two factors. The first point was

that the irrigation pipe was placed at 15 cm soil depth for MSS， whereas on the soil

surface for MS， which caused the lower e at the top layer for MSS. The second point was the lower irrigation amount for MSSラ comparedwith MS. Before Aug. 11， the e at 17 cm depth for MS was lower than MSS and SS except some days (Fig. 4-2 B) because sub-

surface irrigation for MSS and SS led to higher soil moistures at the depth just below the

irrigation pipes. SS gave higher e at 17 cm depth than MSS in most of days (Fig. 4-2 B)

due to the higher irrigation amount for SS. At the depth of 27 cmラ formost of daysラ the

lowest θoccurred under SS treatment whereas the θfor MSS was a little higher than that

for MS (Fig. 4-2 C). This can be a位 ibutedto lower ET under mulching regime and sub-

surface irrigation treatments (Fig. 4-1). The average θwas higher for MS and MSS than

39

for SS in most of days (Fig. 4-2 D).

三 5C百'てz

i 4

53 +J ロ3

52 a f唱何

ぢ 1p.. 6

高 O

自S0 MS &'1 SS器MSS

Fig. 4-1. Average evapotranspiration (mmJday) of grapevine for different mu1ching and

irrigation treatments from June 5 to September 21. MSS: mulching combined with sub-surface seeper

hose irrなation;sS: no・mulchcombined with sub齢 surfa∞seeperhose irrigation: MS: mulching combined with surface

seeper hose irrigation; S: nか mulchcombined with surface seeper hose irrigation.

MSS gave the highest average soil temperature at 7 cm soil depth (Fig. 4-3 A) due to

the lowest ET (Fig. 4-1) led to the smallest consumed heat energy. There were no

significant di能 rencesof average soil tempera加reamong other treatments (Fig.ι.3 A).

Except S， SS gave the highest maximum soil temperature at 7 cm soil depth， with MS the

lowest (Fig. 4-3 A). The average soil temperature for MSS was 5.10C higher than SS，

while the maximum soil tempera印refor MS was 3.20C lower than SS. ln addition，

compared with MS， MSS enhanced the average soi1 temperature by 4.60C (Fig. 4-3 A)，

which could be attributed to the less ET under sub・引lffaceirrigation (Fig. 4-1). There

were no significant di荘、erencesof minimum soil temperature among different treatments

(Fig. 4-3 A). On June 27， the mulching regimes enhanced soil temperature from 0:00 to

7:00， whereas reduced it from 11 :00 to 20:00， compared with no醐・mu1chingtreatment (Fig.

4-3 B). The highest soil temperature during one day occurred at 14:00 for S， whereas

17:00 for MS and SS (Fig. 4-3 B).

40

@ S .“ -0-司圃お1S 一 -6--MSS ふ SS

0.30 「 宍 (A)

0.25

0.20

0.15

0.10 -

0.05 -

0.00

0.40

0.35

乱含 島 (B)

44g① ロ0 0 」J コ0.25

0.20

0.15 ~

2 炉C診J 百4

F・。∞ F・吋4

〉言。日ロ。(C)

0.50

0.40

0.30

0.20

0.10

0.00

0.401

(D)

よ% 品門0.25

0.20

0.15

0.10

0.05

0.00

2-Jun 22-Jun 12伺 Jul トAug 21-.占¥.ug 10-Sep

Day

Fig.4ー2.E汀ectsof mulching and irrigation method on volumetric soil water content at three soil depths， where (A): 7 cm; (B): 17 cm; (C): 27 cm; (D): average values of three depths.

41

ElMSS口SSb3MS ~ S 40

34

22

16 (Q。)2550仏

gg明。∞

28

10

Min

--f:，.--MSS一寸「ーSS・・・0・.-MS--・一一S30

28

Max Mean

24

26

22

20

20:00 16:00 12:00 8:00 4:00 0:00

Time (hourう

Fig. 4-3. Effects of mulching on mean， maximum (Max) and minimum (Min) soiI

temperatures at 7 cm soil depth from June 5 to September 21 (A) and daiIy variation of

soil temperature at 7 cm soil depth on June 27 (B). Each symbol in Fig_ 4-3 (A) represents the average

42

土standarderror (SE) (n=3).

4.3.2. Shoot length， leaf area， photosynthesis and beny diameter

The primary shoot for S was the lowest on June 2 (Fig.ι4 A). Mulching enhanced

primary shoot length than nか mulchingon July 7. MS enhanced the primary-shoot length

by 7.9， 15.6 and 29.7 cm/mm irri. on July 7， compared with MSS， SS and S (Fig. 4-4 A)，

although the water stress for MS was more severe than S. This could be related to the

higher soil temperature during night and improved soil organic matter under MS than

under S (Fig. 4-3 B) and the higherθat 7 cm soil depth for MS than for SS and MSS

(Fig. 4-2 A). Mulching and sub叩 rfaceirrigation gave longer Iateral shoot than S (Fig.

4-4 B). The lateral shoot Iength for SS was enhanced by 56% on July 7， compared with S

(Fig. 4-4 B)， which indicated that SS enhanced the irrigation efficiency based on the

shoot length Ievel.

For primary and lateral leaf areaラ MSgave higher values than S (Fig. 4-5 A and B)

due to the higher soiI temperature during night under MS (Fig. 4-3 A) led to well-growth

of grapevine Ieaves under mulching and the shorter shoot length under S (Fig. 4-4). On

June 30， MS enhanced the primary and lateral leaf area by 69 and 99%， compared with S

(Fig. 4-5 A and B). There were no significant differences of leaf area among other

treatments (Fig. 4-5).

Under sub-surface irrigation， mulching enhanced the photosynthesis (Fig. 4-6) due to

the higher e (Fig. 4-2 A， C and D)， Ts at the upper soil layer (Fig.ι3) and shoot length

(for primary Ieaf) (Fig. 4-4 A) than no叩 ulching.Under surface irrigation， mulching aIso

enhanced AN for primary Ieaf (Fig. 4-6)， which could be contributed to the higher soil

temperature during night under MS (Fig. 4-3 A) Ied to higher leaf area under mulching

(Fig. 4-5) and the shorter shoot length under S (Fig. 4-4). MSS enhanced AN by 83% at

16:00 as compared with S (Fig. 4-6). Sub-surface irrigation treatments gave higher AN

than surおceirrigation (Fig.牛6).Two peak values of AN occurred for MSS (瓜 10:00and

14:00)， while only one peak value occurred for MSラ SSand S (Fig. 4-6). There were no

significant differences of gs among different treatments. MS gave the highest intrinsic

WUE in the morning， whereas S gave the lowest value (Fig. 4-6) due to lower AN， higher

ET and Ts fluctuation under S. The intrinsic WUE at 10:00 for MS was 3.5 times oft註at

for S.

43

一ー 企 ・-MSS一一企一一SS・・・0---MS一一争一一S

(A) Primary shoot 80 1

60 -1

40イ

20 ~

(B) Lateral shoot

100寸

80イ

60 ~

40 -1

20 ~

O

(【

'E回目。)阿古切Rwコ。。岡山∞

O

July 7 June 29 June 23 June 2

Fig.ι4. Effects of mu1ching and irrigation method on shoot length for primary shoot

(A) and lateral shoot (B) of grapevine. The Y-ordinate represents the shoot length divided by iπigation

arnoWlt. Each symbol represents the average (per shoot)土 standarderror (SE) (n=3)_

44

一・企・-MSS一一昔「一-SS.ー・0・..MS • S

(A) Primary shoot

J ・ー-三'1(， :ァ. 三"';"" ~.一ーー・ーーー

(B) Lateral shoot

， ， ， ， .

， ' 一'

， ・ rt ，

， ，

' 一'， -， . ， --.，.r' .

，-

・--'" ， ， ，

10001

800 ~

600J

400 ~

200 -!

(Hag日刊日

υ)g詰官。J

O

June 30 June 23 June 6

Fig. 4-5. Effects of muJching and irrigation method on leaf area for primary Jeaf (A)

and Jateral leaf (B) of grapevine. Each symbol represents the average (per shoot)土 standarderror

45

(SE) (n=3).

--ft--MSSー-.-SS・・・0・・・ MS-+一一S

、¥ 、 .、、、

p、 、~

」一一一一「

A N

WUE，

，J ぎ奮。

101

81 61 4J

llI「i1111寸

jil--」ili--4B

nununu

7

'

R

U

内

J

0.00

(-・55一切円

'gNou-。E1)

回一凶

ω』判何回

λ的。一ち戸山内向

(7557∞NEFCONE-

。g)

(?自国

7dZ3

ωωロSυ

同岡田

uロOQ

志村回ロSH∞

同h戸怪2FQZロ羽パ甘口][

18:00 16:00 12:00 14:00

Time (h) 10:00 8:00

10

Fig. ~. Daily variation of photosynthesis (AN)， stomatal conductance (gs) and intrinsic WUE (AN gs-l asμmol CO2 mol H20-

1) for primary leaf of grapevine under different

muIching and irrigation methods on 2 August， 2008. Each symbol represents the average土 standard

error (SE) (n=3).

Mulching and/or sub-surface irrigation regimes also enhanced the berry diameter in

most of days (Fig. 4-7) due to the improved soil and growth conditions. The berry for

46

MS was larger than that for S due to higher shoot length， leaf area， AN and intrinsic WUE

under mulching. MSS gave larger berry size than SS， which can be contributed to the

higher θ， AN， and average soil temperature for MSS. The higher vallles of berry size were

recorded for SS than S (Fig. 4-7)， which can be related to higher shoot length， AN and

intrinsic WUE of primary leaf for SS. On Sep. 5， compared with MS， S and SS， MSS

enhanced the berry diameter by 0.1， 3.5 and 2.3 mm mm-1 irri.， respectively.

4.3.3. Fresh yield， water use efficiency and berry sugar content

MS gave the highest企eshyield while SS gave the lowest value in four treatments

(Fig. 4-8). Compared with SS， the fresh yield for MS and MSS increased 271.5 g tree-1

and 73.2 g tree-1， respectively， which can be related to the higher θ(at the upper soil

layer)， AN， intrinsic WUE， the longer shoot and the larger berry diameter for mulching.

Under both mulching and no-mu1ching conditions， the sub-surface irrigation reduced the

合eshyield compared with sllrface irrigation due to the lower θ(at the upper soil layer)

under sub-surface irrigation.

• S

ru F

-zv

/

，

g

zv

eoeil--「1

J

i

l

l

-

J

g

i

t

i

i

t

-

-

e

I

4

1

n

H

U

7

t

R

U

• SS ・・・0・・・ MS 一ー 企 ・-MSS(ア司自国国)む古田宮}UKCH@悶

Sep.5 Aug.22 Aug.4 June 30 June 25

3

Fig. 4-7. Effects of mulching and irrigation method on berry diameter of grapevine. Each

symbol represents the average土standardeηor (SE) (n=lO).

MS gave the highest WUE， followed by MSS and SS， while S gave the lowest value

in four treatments (Fig. 4-9). Compared with S， MS enhanced WUE by 42%， which can

be contributed to the improved soil condition (higher soil temperature during night and

47

soil nutrient)， the higher AN， the longer shoot， the larger leaf area， la1'ger berry sizeラ high

intrinsic WUE， higher yield and lower ET under MS led to well-g1'owth of g1'apevine

under mulching. Compared with SS， MSS enhanced WUE by 11% due to the higher e， AN，

average soil temperature， lower ET and highe1' yield under MSS. Compa1'ed with MSS，

MS enhanced WUE by 20% owing to the higher e (at the uppe1' soil laye1') and higher

yield unde1' MS. Compared with S， SS enhanced WUE by 7%， which can be related to

highe1' shoot length， AN， intrinsic WUE of primary leaf and ber1'Y size fo1' SS. Compa1'ed

with SS， MS enhanced WUE by 33% due to the higher e， AN and yield， higher soil

temperature during night， larger berry size and intrinsic WUE， and lower ETunder MS.

The highest be1'ry sugar content occurred under MSS fo1' most of days (Fig. 4-10). At

ha1'vest on Sep. 22ラ theberry suga1' contents for mulching conditions were significantly

higher than that fo1' SS， which can be related to the ameliorative environmental factors

(such as soil temperature and moisture) and plant growth conditions (such as AN， leaf area，

be1'1'Y diameter， yield and WUE) fo1' mulching. Compared with SS， the mulching

treatments enhanced berry sugar content by 15% at the ha1'vest time. Higher berry sugar

contents were recorded for S than SS in most of days (Fig. 4-10)， which can be related to

fa1' lowe1' e and soil tempe1'ature during night in the upper soil layer under SS. MSS gave

highe1' be1'ry sugar content than MS for some days， which could be att1'ibuted to the lowe1'

soil moisture at the top soil laye1' and higher Ts under the condition of sub-su1'face

lrngatlOn.

Although grape σrowing 1'equires less water per value of crop than most plants， the

p1'edicted cIimatic change (i.e. reduced rainfall and increased evapot1'aspiration rates) will

intensify water stress on vines， especially in wate1'-limited regions， a旺ectingthe ability of

existing varieties to ripen fruit (Jones et al吋 2005)ラthequality of grapes/wine and thus the

overall economics of grape production (Santos et a1.， 2007). Therefore， mulching and /or

sub-surface irrigation should be 1'ecommended for water-saving production of grapevines.

48

マゐ 1100 +d4』必J 占

L4J 4 900 0.

'戸・万・Gp〉・・44 3

700 』∞ h 4h J

500

SS MSS S MS

Fig. 4-8. E狂ectsof mulching and irrigation method on fresh yield (per tree) of grapevine.

Each symbol represents the average土standarderror (SE) (n=3).

毘SロSSE:l MSS臨 MS会 8J

3議E7 6

4∞ ロ 5

s S4 3

Fig. 4-9. E百ectsof mulching and irrigation method on water use efficiency (Y ET1) of

grapevinゑ whereY is fresh yield (g).

49

--t，.--MSS -叶-， SS ・・・0・・・ MS--4--S 20

14

11

17

〈引か)詰

ggou』dMW

ロ∞h'ao伺

8

Sep_ 12 Sep. 22 Sep. 5 Aug. 16 Aug.22

Day

Aug.8 July 31

5

Fig. 4-10. E能 ctsof mulching and irrigation method on berry sugar content of grapevine.

Each symbol represents the average土standぽderror (SE) (n=3).

4.4 Discussion

4.4.1. Effects on soil

MS decreased ET slightly as compared with SS， although irrigation amount for MS

was a li抗lehigher than that for SS (Fig. 4-1). This can be attributed to low soil

evaporative demand under the mulching condition， which is consistent with the finding of

Pinamonti (1998) who reported that the compost mulching improved permeability of

wateれwaterstorage and reduced evaporation.

Under sub剛 surfaceirrigation， rice-straw mulching increased e (Fig. 4-2)ラ aneffect

50

partially attributed to insulation and lower soi1 temperね resin the afternoon (Fig. 4-3)，

but also to the high water-holding capacity of the mulches because of their high organic

matter content (Li et al.， 2004) and low bulk densities (Jacometti et aL， 2007b). An

increase in soil moisture of 34% was also found under straw， another low bulk density

organic mulch， in South Australia (Buckerfield and Webster， 1996).

The mulching regimes increased soil temperature at nightラ whereasreduced it in the

afternoon， compared with no-mulching treatment (Fig. 4-3 B). Tripathi and Katiyar

(1984) reported that paddy straw enhanced the minimum soil temperature by 3 oc，

whereas reduced the maximum value by 7.4 oC as compared with bare soil. Organic

mulching reduced soil temperature f1uctuations (Pinamontiラ 1998;Jacometti et al.， 2007a).

MS and MSS lowered the maximum soil temperature as compared with SS (Fig. 4-3 A)，

which indicated that mulching could prevent the possible plant damage due to high

temperature. Pinamonti (1998) showed that laying the plastic film may turn out to be

counterproductive due to the excessive heat which hinders the plants growth (r・educed

vegetative development along with an increase in dead vines)， whereas the compost

mulch regulated soil temperatures by reducing seasonal f1uctuation and protecting the soil

against extremes oftemperature.

4.4.2. sfj告ctson the vegetative status ofplants

Rice-straw mulching enhanced pr加 aryshoot length than no・mulching(Fig.ι4 A)，

whereas Jacometti et aL (2007a) observed that the mulched paper lowered vine canopy

density by up to 1.4 times that of the other treatments. This di百erencemay be related to

the higher nutr匂ntsunder rice-straw mulching led to stronger growth vigor. Mulching

tends to enhance the leaf area as compared with S (Fig. 4-5). Pinamonti (1998) also

reported that the compost mulch improved the general performance and the growth of

grapevines during the first year: the pruning weight was 120-140% higher than in the

control plots.

The mulching treatments enhanced the photosynthesis (Fig. 4-6) due to improved soi1

condition under mulching. Sub-surface irrigation tends to improve irrigation efficiency

based on photosynthesis level (Fig. 4-6). Poni et al. (2009) showed that photosynthesis

was already limited after 2 days of water stress and this limitation steadily increased for

51

Lambrusco grapevines which have higher stomatal sensitivity under water stress.

However， the gs for the 'Gros Colman' grapevine seems to be insensitive for water deficit

based on our present experiment (Fig. 4-6). MS gave the higher intrinsic WUE than S in

the morning (Fig. 4-6) although the soil water content for MS was far lower than that for

S. Water deficit treatment was indeed able to consistently increase intrinsic and extrinsic

WUE as compared to unstressed vines (Poni et al.， 2009; Dry and Loveys， 1999;

Koundouras et al.， 2008). One of the first vine responses to drought is the reduction of

leaf stomatal conductance associated with an optimization of intrinsic WUE， an indicator

oflong蝋termregulation of carbon assimilation under drought (Bota et al.， 2001; Ci合eet

al.，2005).

Under sub欄 surfaceirrigation， mulching regimes also enhanced the berry diameter (Fig.

4-7)， which can be partly contributed to the higher e under mulching. Wang et al. (2003)

also found that berry size and bunch weight are positively correlated with soil moisture，

predominantly during the early stages of berry development when they grow rapidly

(Wang et al.ラ 2003).

4.4.3. Effects on the productive status (yield and quαlity) and WUE ofplants

Mulching elevated the fresh yield of grapevines regardless the irrigation method (Fig.

4-8). The use of straw and mulched cover crops has been also shown to increase yield in

grapes by 46..-....-60% and this increase was linked to elevated soil moisture， earthworm

presence and additional nutrient sources released slowly (Buckerfield and Webster， 1996;

]acometti et al吋 2007a).

The fresh yield of grapevines for MS was higher than that for MSS (Fig. 4-8)， which

can probably be related to the lower e (at the upper soil layer) for MSS due to the deep

placement depth (15 cm below the soil surface) of sub-surface irrigation hose. The

placement depth of sub-surface drip laterals has an impact on crop yield and the

maximum onion yield was recorded at 10 cm depth of drip lateral in all treatments with 6

depths of placement of drip lateral (Patel and Rajputラ 2008).ln deeper placement of drip

lateral (20 and 30 cm below surface)ラadequatesoil water was found at 30， 45 and 60 cm

soil depth (Patel and Rajputラ 2008).Our data showed that the e at 17 and 27 cm depths for MSS was higher than MS except some days (Fig. 4-2 B and C) because suトsurface

52

irrigation for MSS led to higher soil moistures at the depth just below and near the

irrigation pipes. Sub-surface irrigation system should be designed such that the wetted

soil volume matches as closely as possible to the crop rooting pa託ern.Generally， root

density was higher in the upper soillayer (0 to 20 cm) than in the deeper soillayers for

grapevines (Morlat and Jacquet， 2003)， regardless soil types (Soar and Loveys， 2007).

Mulches increased grapevine root densities in the upper 20 cm (Smart et al.， 2006).

The berry sugar concentrations for mulching conditions were significantly higher than

that for SS (Fig. 4-10). Marc and paper treatments can also increase grape skin strength

by up to 10% in the paper treatment and sugar concentrations by 1.2-1.4 oBrix (Jacometti

et al.， 2007a). MSS gave higher berry sugar concentration than MS， which could be

attributed to the higher Ts and lower soil moisture at the top soillayer under the condition

of suかsurfaceirrigation. Pinamonti (1998) showed that the nutrients uptake was more

inf1l1enced by the physical conditions of the soil (temperatllreラ moisture)than by the

availability of nutrients in the soil. Improved wine quality was also uSllally due to

moderate water stress which induced higher concentration of anthocyanins and phenolics

in the berries (Zsofi et a上、 2009).Organic mulching elevates vine yield and sugar content

(Jacometti et al.， 2007a)， which is inf1uenced by environmental conditions at f1owering，

fruit set and the early stages of grape expansion (Wang et al.ラ 2003).

The WUE for MS was higher than that for S (Fig. 4-9) due to lower ET and higher

yield under MS. Water deficit strategies would increase WUE as compared to full

irr詰ation(Dry et al.ラ 1996).In this connection， data reported by Willliams et al. (1994)

show that WUE (g of dry weight per kg of water transpired) decreased from 5.85 for a

treatment irrigated at 20% vine ET to 1.84 for plants receiving 140% of vine ET.

Compared with S， SS redllced yield (Fig. 4-8) whi1e enhanced WUE by 7% (Fig. 4-9)

due to the lower ET for SS. To give priority to high waterべlseefficiency over maximum

yieldラ irrigationshould be applied only when the indicator parameter drops below a

certain threshold vallle in drylands (Cifre et al.， 2005).

4.4.4. General discussion

Although grape growing requires less water per vallle of crop than most plants， the

predicted climatic change (i.e. reduced rainfall and increased evapotraspiration rates) wilI

53

intensify water stress on vines， especially in water-limited regionsラaffectingthe ability of

existing varieties to ripen fruit (Jones et al.， 2005)， the quality of grapes/wine and thus the

overall economics of grape production (Santos et al.， 2007). Effective water management

in vineyards may attempt to maintain the plants at a limit between water stress and excess

water consumption， thus making a rational use of irrigation water. This kind of irrigation

may save water with respect to empirical irrigation， improving yield as compared with

rainfed grapevines， and maintaining the high fruit quality (Cifre et al.， 2005).

Mulching tends to improve the physical conditions of the soil (temper説 ureand

moisture) leads to a balance growth performance， higher yield and quality of grapevines.

MSS increased the berry sugar concentration on most dates， although the water stress for

MSS was far more severe than S. MS gave the higher fresh yield than S， although the

water stress for S was far less than MS. SS reduced the fresh yield as compared with S

due to the severe water stress under SS. MS should be given a priority for saving water

due to its high WUE. It is currently a priority for the United Nations policy， what is called

thピBlueRevolution' and summarized as‘more crop per drop' (Annan， 2000).

Different soil water content affects grape quality and ref1ects in wine quality

(Conradie et al.， 2002). Jackson and Cherry (1988) show that in regions with a high

rainfall the ripening capacity of grapes is lower to that predicted by the c1imatic thermal

indices. A certain lack of water during the ripening period is favorable to the organoleptic

wine quality in temperate regions which do not generally suffer droughts (Tonietto and

Carbonneau， 2004). Water deficit can also improve fruit and wine quality at a moderate

level of stress (Bravdo and Hepner， 1987)ヲ whichresults in larger relative skin mass in

the berries (Roby and Matthews 2004) and thus higher concentration of phenolics and

anthocyanins (Kennedy et al. 2002b， Ojeda et al. 2002， Sivilotti et al. 2005).

Interestinglyラ MSSimproved berry sugar concentration while decreased the yield as

compared with MS， which could be explained that in grapevines， highest crop load is

usually linked to low grape quality. Thus， in factラ limitationsto grape yield are a common

practice (if not compulsory) for a market standard wine production and premium wines

(Cifre et a1.

54

higher tolerance of grapevine to water deficit imposed after veraIson (Poni et al.， 1993;

Behboudian and Singh， 2001) as compared to preveraison stressラ especiallyas reduced

sensitivity of berry growth (Keller et al吋 2006).Poni et al. (2009) also showed that water

stress did not significantly alter yield or its components while achieving an improvement

in must soluble solids and total anthocyanins. Poni et al. (2009) believe that the primary

factor that determined the excellent vine performance of the water stress treatment is

linked to vine balance. Based on our dataラthe'Gros Colman' grapevine is a stress-tolerant

variety for severe water deficit. Being an important and extensive crop in drought-prone

areas， the variety of grapevine with a high tolerance for water stress is very useful for

grapevine production.

Weed growth was also reduced by mu1ching treatments as compared with control

(data not shown). Therefore， the mu1ch allowed a reduction of herbicide applications

(Pinamonti， 1998).

An interesting highlight in this study concerns that the highest average soil

temperature led to the highest sugar concentr百ionfor MSS. The quality and the typeness

of wines depend on natural factors and human factors. 1n fact， air temperature inf1uences

composition and quality of grapes (Coombeラ 1987).Tonietto and Carbonneau (2004)

developed cool night index (Cl) as a viticultural climatic indice based on an indicator of

night air temperature conditions during maturation. During the ripening period， the air

temperature plays a determinant role for grape maturation， including the aroma and the

coloration， having an important effect on the characteristics of the wines (Jackson and

Lombard， 1993). The day air temperatures inf1uence the coloration (Tonietto and

Carbonneau， 2004). The duration of the phenological stages was dependent on vintage

temperature characteristics rather than on vineyard site (Zsofi et al.ラ 2009).Therefore， it

could be concluded that the average soil tempera如reshould be recommended as an

important index for the quality of grapevines， similarぢlikeair temperature.

When the suかsurfaceirrigation is used for vineyards， the placement depth of sub-

surface irrigation hose for 'Gros Colman' grapevine should be shallower than 15 cm since

the placement depth of 15 cm decreased yield and WUE as compared with surface

irrigatio

55

grapevmes.

The response of soil and grape to different mu1ching and irrigation treatments could

give a useful basis for vine growers for variety selection and choice of viticultural

practices， especially in drylands.

4.5 Conclusions

MS gave the highest fresh yield while SS gave the lowest value due to higher e

(upper soil)， AN， Ts and diameter for MS as compared with SS. MS gave the higher WUE

than MSS due to the higher water content at top soil and higher yield for MS. These

combination of mulch and seepage irrigation were dほeredfor WUE in the order of MS >

MSS > SS > S. Compared with SS， the berry diameter， f1'esh yield， WUE， and berry sugar

content fo1' MS we1'e enhanced by 2.8 mm， 271.5 g tree-1， 33% and 15%ラ1'espectively.

MSS gave highe1' ber1'Y suga1' content than MS， which could be attributed to the highe1' Ts

and 10we1' soil water at the top soil laye1' unde1' the condition of sub四 surfaceir1'igation. Ts

should become an important index fo1' the berry quality ofσrapevine.

56

Chapter 5 Deter腕 inationof soil water potential threshold for

irrigating grapevines in the last phase of Stage 1 of berry

growth based on photogrammetric measurement of berry size

5.1 Introduction

Because of increasing population， land and water resources have been put under

severe stress (Ghadiri et al.， 2005). Given current demographic trends and future growth

projections， as much as 60% of the global population may suffer water scarcity by the

year 2025 (Qadir et al.ラ 2007).As the agriculture sector is one of the largest consumers of

water， it is likely to suffer the most unless more efficient water management is practiced，

particularly in semi-arid and arid areas. Grapevine (Vitis vinifera L.) is an impo出口tfruit

crop grown in semi-arid and arid environments. 1n the drylands of northwest China grape

production is common but its sustainability is threatened by unreliable water resources

(Du et al.， 2005). The problem of water scarcity is going to get further aggravated with

climate change， which is also likely to affect the quality of grapes/wine and thus the

overall economics of grape production (Santos et al.ラ 2007).Therefore， improving the

efficiency of irrigation is essential for long-term sustainability of grape production and

the wine industry.

Irrigation management plays an important role in determining water use efficiency in

agriculture (Dukes and Scholberg， 2005). Under arid and semiarid conditions， water

availability plays the main role in regulation of berry growth and sugar accumulation for

vines and， therefore， the highest attention should be paid in these areas to irrigation

management， seeking the degree of stress that allows optimizing the combination of yield

and berry quality in each situation (Santesteban and Royo， 2006). Horticultural produce is

sold by weight， and since water is the major component of most fresh horticultural

commodities there is often a marked premium in ensuring that water content is

maximised， whilst ensuring that produce quality does not su汀er(Jones and Tardieu，

57

1998).

Traditionally， grape producers tend to use excessive amount of irrigation water

during the berry development stage to maximize berry size. This not only results in a

waste of water， but also causes nutrient loss and promotes excessive vegetative growth at

the expense of fruits. Deficit irrigation in fruit crops can be of value in increasing fruit

quality by raising dry matter and sugar content (Chalmers et al吋 1981).Several studies

have shown that appropriate and moderate water stress is beneficial for ben'y growth in

grapevines， whereas severe water deficit or saline irrigation decreases the production of

assimilatesラ andreduces t1'anspi1'ation， shoot growth， and yield and quality of合uit(Shani

et al.， 1993; Delgado et al吋 1995;Pel1egrino et al.， 2005; Lovisolo and Schubert， 2006;

Lovisolo et al吋 2008).In deficit irrigation water application is withheld unti1 the vine has

experienced a certain level of wate1' stress， after which a specific volume of water is

applied to allow continued sugar accumulation and the maintenance of canopy cover.

This practice prevents excessive vegetable growth allowing light to diffuse into the

fruiting area improving fruit color and quality while minimizing yield 1'eductions

(P1'ichard et al.， 2004). The potential fo1' water saving by deficit irrigation in many

orchard crops has remained unexplored so far (Fereres et al吋 2003).It is， therefore，

important to determine the critical timing for starting irrigation， especially in drylands

where drought represents a serious th1'eat to the sustainability of agriculture (Konukcu et

al.，2005).

It is well known that the 1'ates of many physiological processes， such as

photosynthesis， are more c10sely 1'elated to cell turgor pressure or to cell volume， than to

absolute Ijf (Sinc1air and Ludlowラ 1985;Jones， 1992). Wate1' plays a key role in cell

expansion and growth. Nume1'ous studies (Bravdo et al.， 1985; Poni et al.， 1994; Esteban

et al.， 2001; Reynolds et al.ラ 2005)have focused on ir1'igation management based on soil

wate1' content. However， a local measurement of soil wate1' content may not 1'epresent the

true picture， especial1y fo1' drip irrigation. Therefo1'e， the use of physiological indicators

of plant wate1' status would be a mo1'e app1'opriate criteria. Besides soil and envi1'onment

factors， plant physiological pa1'ameters would be important indexes fo1' determining when

to begin irrigation. During last de

58

physiological information has value in estimating the degree ofwater stress to which fruit

trees are subjectラ usingreadily accessible measurements. Many growers of various fruit

trees have reported substantial savings in water coupled with good yields and quality

through fine-tuning irrigation scheduling based on physiological indicators (Ton et alラ

2004a). Many of them are based on continuous monitoring of stem diameter (Selles and

Berger， 1990; Fereres et al.， 1999; Goldharner and Fereres， 2004) and/or fruit diameter

(Gratacos and Gurovich， 2003; Ton et al.， 2004a; Avidan et al. 2005). Some ofthe studies

were carried out on grapevines (Myburghヲ 1996;Ton and Kopyt， 2004; Ton et al吋 2004b;

Kopyt et al.， 2005)， although published information about practical implementation of

fruit size measurernent results in irrigation control of industrial vineyards is limited. Most

of above-mentioned studies about physiological indicators were conducted using

phytomonitoring methodology. Nevertheless， Intrigliolo and Castel (2007) reported that

trunk diameter was able to detect vine water stress only during a short period of time

before veraison.

Severe water stresses due to water deficits rnay cause retardation of ben'y growth

(Hardie et al吋 1981)and damage of plant by reducing photosynthesis through both

stomatal and nonstomatal e官ects(Ennahli and Ear1ラ 2005).Ferreyra et al. (2006) reported

that when plants maintained stem water potential (measured at midday) greater than -

0.75 MPa， between berry set and veraison， yield and berry size were high. A continuous

recording of the micro variations of berry diameter is being considered as a new tool for

estimating water stress of grapevines. This seems to be a substantial step ahead to

precision viticulture (Ton and Kopyt， 2004). lmai et al. (1991a) reported that the berry

diameter of grapevines shrunk in the day time and swelled at night because of the deficit

of water content in the day time. ln the early stage of berry development， cane and berry

diameter shrinkages for grapevines occurred because of the water stress (Imai et al.ラ

1991 b). Thereforeラ berrydiarneter can become a useful indicator for irrigation

management ofvineyards when water is lirnited.

Overall， the berry development of grapevine follows a double sigmoidal shape with a

strong increase in diameter ear1y (Stage 1)， a slower lag phase (Stage 2)ラ anda rapid

gr

59

bloom to approximately 50-60 days thereafter (Coombe and McCarthyラ 2000).During

this period， the berry is formed and the seed embryos are produced. Gr，問eens叩pa釦ne抗ta剖1..

(1994) have shown t白ha拭txylem s泊apis the main source of wa低te町rfおorberries during their first

gr

division occurs t出hroughStage 1ラ andby the end of this period， the total number of cells

within the berry are established (Coombe， 1987). Thus， the extent of cell division has

some bearing on the eventual size of the berry. Alsoラ duringthe first growth period， the

berry expands in volume as solutes such as tartaric and malic acid， tannins and other

compounds accumulate. The accumulation reaches an apparent maximum around

veraison (Possner and Kliewer，ラ 1985).These solutes are critically important to wine

quality. The berry diameter increased 3.5-fold between 12 and 120 days a丘eranthesis

(Chatelet et a1.， 2008). The berry development is the most critical for economic yield as

fruit size at harvest is an important aspect of the quality of the fruit (Zhang et al.ラ 2005).

孔1cCarthy(2000) reported that water stress during the post-flowering period had most

significant effect on berry size， whereas moisture deficit after veraison had only a minor

effect on berry weight at maturity and berries were insensitive to water deficit in the

month before harvest (McCarthy， 1997a). lmai et al. (1991b) showed that grape berry

diameter tends to increase during night and decrease in daytime and the range of diurnal

variation increases with decreases in soil water potential (lfl). These authors concluded

that berry growth is closely related to lfl.

Water deficits during Stage 1 offruit growth are thought to reduce potential berry size

by reducing the number of cel1s per berry. The reduction of cell number causes smaller

berries and almost always causes a reduced yield (Prichard et al吋 2004).A vidan et al.

(2005) used daily diameter increment ofberry as one ofthe main indications of grapevine

water status for adjusting irrigation and concluded that the direct monitoring of ber匂

growth may help to optimize irrigation rate. Therefore， the use ofberry diameter as a key

and main plant parameter for reflecting and defining the water potential thresholds for

irrigation was considered important. There are many studies on the effects of various

irrigation regimes on vine growth (Bravdo et al吋 1985;Poni et al吋 1994;Esteba

60

not known. This information is critical to optimize water us久 pr・eventnutrient loss and

improve yield and quality of grapes. lmai et al. (1991 b) already reported that daily

variation in berry diameter might be a useful index for soil moisture control in grape

production. The upper limit of lf.I in the ripening stage was regarded as lf.I = -12.6 kPa

since the berry swelling was conspicuously affected by soil drying (Imai et al吋 1991b).

Vines watered at lf.I = -15.8 kPa歩合ombud burst to seed-hardening， showed slower

primary shoot growthラ weakerlateral shoot growth， smaller leaf area and slower berry-

size increase than those watered at lf.I = -3.2 kPa (Imai et al吋 1991a).Their study，

howeverラ didnot indicate the threshold value of¥jf at which irrigation should be scheduled

during the berry development stage as only two levels of lf.I were tested. We hypothesize

that the threshold value could be established by measuring diurnal variations in berry

diameter of grapevine experiencing increasing soil moisture stress. It isラ however，

necessary that the measurements are made with great precision because the changes are

rather small.

A new system of automated photogrammetry has been developed by Moritani et al.

(2006; 2007) for continuous measurement of soil erosion (Pyle and Richards， 1997). This

system， which consists of two high胴 precisiondigital cameras， attached to a computer with

an image縄 analysisprogram of th1'・ee-dimensionalalgorithm， can also be applied for

measuring fruit size with three major advantages. First， the measurement precision is high.

Second， the berry diameter can be monitored automatically. Third， the determination is

nondestructive. There is lack of published information about measuring berry size using

photogrammetry.

The goal of this study was to establish the critical soil water potentiaI value for

starting irrigation of grapevines in the last phase of Stage 1 of berry growth， based on

photogrammetry of berries and a tensiometer system for measuring soil water potential.

This was done by examining instantaneous variations in berry diameter， soil water

potential and photosynthesisラasthe water deficit developed in the soil.

5.2 Materials and methods

The study was conducted in 2008 at the Arid Land Research Center， Tottori (35015' Nラ

133047' E)， Japan.

61

5.2.1. Plant and soil materials

On 25 February 2008ラ 2-year幽 oldPione grapevines (均isvinifera L.， cv. V. labrasca)

were transplanted into 34閏 litercapacity horticultural pots in a greenhouse under natural

conditions of temperature， light and humidity. Each pot (39 cm surface diameter， 32 cm

depth) contained 28 kg of a mixture of sandy soil (sieved through a 2-mm sieve)， peat

moss， humic allophone soil and lime in a volumetric ratio of 1200 600: 200 1，

respectively. The mixture was placed on a 2 cm thick layer of microvesicular pumice to

allow企eedrainage. The mixture had a pH of 6ユThepots were irrigated with an

alltomatically timed drヤ in'igationsystem to ensure optimum moisture regime for the

vines. Four emitters per vine were located approximately 10 cm from the trunk. The

amount of water applied was controlled by a time clock-solenoid valve assembly. The

irrigation amounts for March， April， May and JlIne were 2.4， 3ム4.5and 6.0 L per pot

per week， respectively.τhe plants were provided liquid fertilizer containing all essential

mineralωtrients (Wang et a1.， 2001; Thippayarugs et al.， 2002) once every week.

To encollrage uniform vegetative growth， vines were pruned to retain 12 nodes per

vine; only two shoots per vine were left and were trained horizontally. The anthesis

started from May 17， 2008. Shoots were trimmedれ材cebetween bloom and the veraison

stage of the berries. Lateral shoots were cut back to the first node. At flowering， one

cluster was left on each of the two shoots. Each cluster was trimmed to retain only 200-

250 florets and once berry-set occurred， further trimming was done to retain only 40-50

berries per cluster.

5.2.2. Experimental detai!s

On 26 June (40 days a食erflowering)， when the berries were in the last phase (the last

week) of Stage 1， a pot containing the grapevine was placed in an environmental1y

controlled growth chamber (type GC-A， FlIji Electric Co. Ltd.， Tokyo， Japan) in which

temperatllre was set to 12112 h (day/night) cycles of 35/20 oC with 12 hours iI1umination.

The relative hllmidity， air flow and dillrnalluminous intensity were set at 50%， 0.3 m S-1

and 5000トlmolm-2 S-1 ， 1・espectively.After placement in the growth chamber， the vine was

62

irrigated to saturated condition. From then on till 15:00 h on 28 June the vine experienced

deceasing !f/. At 15:00 h on 28 June it was irrigated again to saturation. Thereafterラ the

plant again faced a deceasing !f/.

Soil water potential was measured every two hours by a pressure transducer system

(Marthaler et al吋 1983)for field-installed tensiometers with a short section of clear plastic

tubing at the upper end. The system consists of a pressure transducer with attached

syringe needle， tensiometers and digital read-out. The needle is inserted through the

septum stopper which closes the upper end of the tensiometer. A spring guarantees

smooth insertion of the needle into the septum as it is forced down. The pressure in the

air below the septum stopper， in equilibrium with the water press出‘e，is read on the digital

read-out， which is calibrated in millibars. Upon withdrawal of the needle from the

tensiometer， the septum stopper seals the tensiometer. The tr溜 lsducerconsists of a steel

enclosure with a t1官 lsducermembrane separating the enclosure in an upper chamber an

in a lower chamber. The upper chamber is at atmospheric pressure (Marthaler et al吋

1983). The soil water pot胞ent託ialwas cal比Cl叫lla低tedby subtracti加ngthe stem length of the

tensiometer fi企romthe reading on the resistivity meter (calibrated i加nmilliba紅r吟.Twelve

tensiometers (filled with deaerated water) were put in the pot， six at a depth of 10 cm and

other six at a depth of 20 cm.

Berry diameter was monitored every hom・bya new photogrammetry-system that

consists of two digital cameras (Nikon D2H， 16，000 pixels) attached to a computer

having an image analysis program of three剛 dimensionalalgorithm. The measurement

precision ofthe system was 0.2 mm. Details ofthis system are described by Moritani et al.

(2006).

A rectangular analytical合amewith scale was fixed vertically on the grapevine and

the grape cluster was placed inside the frame. Three marked berries and two digital

cameras were oriented as shown in Fig. 5-1 and these positions were fixed. The distance

between two cameras was 1.2 m. The distance between the camera and the target berries

was 1.8 m. Pictures taken by the pair of digital cameras were collected on a compute工

The focal length (fc) and resolution of CCD (t5ccd) of the digital cameras were 50 mm

and 0.0094 mm， respectively. The inner orientation factors of the di

63

were adjusted to minimize parallax to obtain a rectified photograph. Through rectification

and elimination of longitudinal parallax， the y-coordinate of a point in the left rectified

image was the same as that in the right one. The same point in the paired images could

easily be searched by scrolling the point in the x-axis direction.

Net photosynthesis and transpiration rate of two healthy spur leaves of the grapevine

were measured at various intervals by a portable photosynthesis system (Lト6400、LトCor

lnc.， Lincoln， NE， USA). Measurements were conducted on 2 cm x 3 cm leaf portion in

the middle part of a leaf blade confined in the leaf chamber of the system. The

measurements were repeated three times on each leaf.

5.2.3. Time series analysis ofbelηI diameter data

As the berry diameter showed diurnal variations over the study period， it was

necessary to remove the periodic f1uctuations by time series analysis (Box et al.， 1994;

加loranet al吋 2009).Periodic f1uctuation of berry diameter was filtered by cubic

polynomial trend line， and the main secular growth trend part was thus obtained. It was

then possible to establish the relationship between the tendency part of berry diameter

and soil water potential in the root zone. An example of determining the trend line of the

time serIes of diameter of Berry No. 2 from 29 June to 1 July is given in Fig. 5-2. Time働

series berry diameter measurements were available for 47 hours. The trend line in this

figure can helps in removing the short-term f1uctuations in the time series of berry size.

The trend values of berry diameter were computed as

yi = 22.831-0.0629 Xi十 0.0066x/ -0.0001 x/， ，-2 = 0.67， N = 47

where Xi is the berry diameter measurement time (ith hour)， yi is the trend value of berry

diameter (mm) at ith hourラ andN is the total hours of measurement in this figure.

64

Camera

4 p

，F F

d d' d

，

・'，F ，F

.. 〆

Fig. 5-1. Schematic diagram of two cameras and the marked berries.

65

般金縁還

ミよ予

ミ.. 1.0

さ誌予ぞむ

切

と・ 23β '-必co

寺下宍a・-宅鹸

22.0

一骨-B制作長弘之

Iミ:00 O:C地

L一一一一一、〆一一一一/

Juれを

1よる00

30

。:制 iよ:紛 0:制

。fdさy(h)

Fig.5ー2.Diurnal variations in a time series of diameter for Berry No. 2 from 29 June to 1

July. The solid line represents measured berry diameter‘おldthe dashed line represents the trend line.

66

5.2.4. Statistical anαlysis

Analysis of variance (ANOVA) was performed on data of photosynthesis and

transpiration rate using the statistical analysis software SPSS vl1.5 (SPSS Inc， Chicago，

ILラ USA).The data means were compared for any significant differences using Duncan's

multiple range tests at a significance level of PO.05・

5.3 Results

5.3.1. Daiかvariationof soil wαter potential

After irrigation in the a食emoonof 28 June， the Ijf decreased slowly during the first 2

days (Fig. 5-3)， but started decreasing rapidly in the afternoon on 1 July when it

decreased to -6.2 kPa in the 10 cm soil depth. The rate of decrease of Ijf in the daytime

was faster than during the night. The trend for the change in Ijf at the 10 cm and 20 cm

soil depths was similar， although Ijf in the 10 cm soil depth was lower than that in the 20

cm soil depth because of evaporative losses from the soil surface.

5.3.2. Daiかvariationofberry diameter

The diameter of grape berry (average ofthree berries) tended to increase during night

and decrease during daytime (Fig. 5-4). During the predawn period on 28 June， the

average diameter of grape berries significantly increased by 13% over measurements

taken three hours before (Fig.ι4A). The average increase in diameter of the berries

from 03:00 h to 06:00 h on 28 June was 2.9 mm. In contrastラ theincrease during the night

between 30 June and 1 July was only 1.6 mm (Fig. 5-4B). This di偽記ncecan be

attributed to the lower soil water potential (-13.6 kPa at 10 cm depth) in the aftemoon of

28 June (Fig. 5-3). Although the grapevine was irrigated to saturated condition

afterwards， the berry on 30 June could not retain the previous rapid growth rate. The

maximum average berry diameter on 30 June was less than that before the water stress，

which also indicated that the exposure to water stress of -13.6 kPa could confine the

subsequent natural growth of grape berries even when the soil water potential was

improved.

67

Time of day (11)

28 June 29 June 30 June ~ー-... r一一一人一一一『、

1 J~.lly

0:00 12:0

'ee 0 包

--+cFc .q ・a4 J

3。94 ・6

4E包診.司a 四 9

ー12同E・。戸C吋4

ー15

0:00 12:00 0:00 12:00 0:00

hdm

p

p

d

d

m

m

Fig.5ー3.Soil water potential (1fI) of the root zone (10 cm and 20 cm soil depths) after

irrigation (shown by a汀ow)for potted 2同 yearold Pione grapevine from 28 June to 1 July.

Means土 SE(n = 6).

68

よi.5".、.、ε よ6.ラE 、、.-'-

)" " 。GG酬d〉〉

E eo 2....5

てコ よ3.5と

∞ 。〉 ))号

21.5

〉号号

，戸・、、ε E 2-1.タ、、.-

+Lφ φ B

E qa 2j.5

てコと、 n" Q)

∞ 21.5

6:00 12:00 18:00 0:∞ 、h

一一一一二当=---一一守

27 June

(a)

6:00 12:00 18:00

三￥竺

28 June

(b)

..，

11:00 0:00 12:00 0:0012:00 0:00

Z芯Zi 語読7守 巳 T JIly l，

Time of day (h)

Fig. 5-4. Daily variation ofbe町 sizein a 2-year old Pione grapevine in be町ー

growth stage仕om27 June to 28 June (A) and合om29 June to 1 July (B).

Means士SE(n = 3)

69

The diurnal changes in berry size (Fig. 5-4) reflected changes in radiation and

temperature since the grapevine was placed in the grm九rthchamber where temperature

was set to 35 oC in the day of 12 h with the luminous intensity of5000μmol m-2 S-l while

the night cycle of 12 h had temperature set to 20oC.

5.3.3. Relationsh伊betweenberry size and Ifl

The diurnal fluctuations in berry diameter time series data (合om29 June to 1 July)

were removed by time series analysis， and the relation between the Ifl at 10 cm soil depth

and the trend value of berry diameter is shown in Fig. 5-・5.After irrigation， the berry

grew fast till the Ifl at 10 cm depth reached -3 kPa. When Ifl further decreased from -3

kPa to -5.4 kPa， the belTy grew at a slower rate. When lfI decreased beyond -5.4 kPa， the

berry started to contract. The absolute value of the slope for Ifl-diameter relation curve

during 29 June was higher than that during 30 June (Fig. 5--5)， which indicates that the

berry grew faster under the condition of high 平人 When Ifl decreased beyond -5.4 kPa，

there was a sharp linear decrease in berry size on 1 July (Fig. 5--5).

5.3.4. RelationshがamongIfl， photo伊 lthesisand tran平 irationrate

Photosynthesis and transpir誕ionrate were not much affected by changes in Ifl as long

as it did not decrease beyond -9.3 kPa (Table 5--1). When Ifl reached -9.3 kPa， a

significant decrease occurred in photosynthesis. When手Idecreased further (企om-10.2

kPa to -13.6 kPa)， there was a further significant decrease in photosynthesis. When Ifl

reached -10.2 kPa， a significant decrease occurred in tr溜 1spiration.

70

(gg)む芯

gc屯λ

ーロω心

刷。mu

ロ【CK〆甘口ωhr円

23.ヲ

23.4

22.9

22.4

-2 -4 間 14暢 6 -8 -10 剛 12

~'--.，r"""" J 刷

用ー、、/戸

29 June 30 June 1 July

Soil water potential (kPa)

Fig. 5-5. Effect of soil water potential (ψ) (10 cm soil depth) on the trend value of

berry diameter. Means土 SE(n = 6).

71

5.4 Discussion

The diameter of grape berry tended to increase during night and decrease during

daytime (Fig. 5-4)ぉ alsoreported by Coombe and Bishop (1980)， Imai et al. (1991b)

and Greenspan et al. (1994)， Greenspan et al. (1994) reported that under growth chamber

conditions in the Stage 1 of berry development， virtually all berry growth occurred during

the night; day periods were characterized by either contraction or absence of expansion.

Irrigation in vineyards is generally scheduled based on either an arbitrarily fixed soil

moisture potential as measured by tensiometers or the estimated cumulative crop

evapotranspiration (Ar羽 ljOet al吋 1995).The central importance of !fI in irrigation

management arises from the fact that di百erencesin water potential between soil and plant

provide the driving force for water movement and therefore determine the direction of

water flow (Jones and Tardielん1998).Applying water at higher ljf value would result in

wasteful use (Bowen and Frey， 2002). Under arid and semiarid conditions， water

availability plays a main role in regulation of berry growth and sugar accumulation in

vines. As shown by Poni et al. (2009)， vines subjected to stress by allowing soi1植drying

for half of the root system improved the composition of grapes in terms of soluble solids

and anthocyanin content， without significant change in yield， and this was attributed to

ear1ier shoot growth cessation， enhanced maturity and a leaf to fruit r混 iothat mitigated

the effect of post-veraison stress. However， if!fl is too low， the fresh and dry matter yield

of grape would also decrease because of a decrease in the supply of photosynthates due to

decreased photosynthesis. Ennahli and Earl (2005) also demonstrated that water stress

reduced berry growth and photosynthesisラ andResco et al. (2009) reported that excess

water stress even constrained photosynthetic recovery after re働 watering.McCarthy

(1997b) showed that withholding irrigation for about three weeks after anthesis resulted

in a 30% reduction in berry weight compared to fully irrigated grapevines. During most

of the contraction of pre回 veraisonberries， xylem vascular inf10w was nil， while water was

lost via berry transpiration and backflow合omxylem since xylem conduction could be in

both directions (Greenspan et al.ラ 1994).It is therefore， necessary to establish only that

degree of soil moisture stress which would allow opti

72

moisture potential for ir1'igation， as attempted in our studies， becomes important.

1mai et a1. (1991 a) indicated that the increase in be1'1'Y size was more 1'apid in vines

wate1'ed at !fJ = -3.1 kPa than in those wate1'ed at !fJ = -15.8 kPa until seed-ha1'dening.

Because they only tested two levels of soil wate1' potential， they could not point out the

threshold !fJ after which the ber1'Y would begin contraction. Imai et a1. (l991b) sought the

relation between !fJ and grape berry growth measured by a displacement senso1' with

rubber string. Howeve1'， the critical !fJ again could not be determined in their study

because they measured the !fJ sta口ingfrom about -6 kPa going to -50 kPa. Continuous

monitoring of !fJ and berry size would provide the early detection of water stress that

would be useful for on-line fine-tuning of irrigation 1'egime. 1n our expe1'iment， we

measured instantaneous changes in !fJ and berry diameter continuously a立ersaturated

irrigation (Fig. 5-3 and 5-5)， so it was possible to establish this critical !fJ for scheduling

irrigation. The ber1'Y growth continued at fast rate when !fJ was above -3 kPa. When !fJ

further decreased from -3 kPa to -5.4 kPa， the ber1'Y grew at a slower rate. When '11

dec1'eased beyond -5.4 kPa， the berry started to contract. It is clear企omthese results that

for scheduling irrigation in grapevines the critical !fJ in the active root zone in the last

phase of ber1'Y development Stage 1 should therefore be -5.4 kPa (Fig. 5-5).

It is interesting that decrease in !fJ up to -9.3 kPa had no significant effect on the

photosynthesis in g1'apevine while the berry size started showing a shrinkage as the !fJ

became -5.4 kPa. A significant reduction in the photosynthesis only occurred when !fJ

reached a value of -9.3 kPa， whe1'eas the be1'ry size showed a linear reduction when !fJ

dec1'eased f1'om -5.4 kPa to -13 kPa. The1'efore， berηsize was more sensitive to moistu1'e

st1'ess than photosynthesis in g1'apevine， and thus a better indicator of the soil moisture

stress fo1' i1'rigation scheduling pu1'pose. Bota et a1. (2004) showed that limitation to

photosynthesis in five C3 speciesヲ includingVitis vintfera， by decreased Rubisco activity

and RuBP content did not occur until drought was very severe. Primary events of

photosynthesis such as the electron t1'ansport capacity are very resilient to drought

(Cornic et a1.ラ 1989;Epron and D1'eyer， 1992). Sousa et a1. (2005) indicated that sap flow，

leaf water potential and leaf transpiration 1'ate i

73

and this could be related to the fact that water deficits during Stage 1 of fruit growth

reduced berry size by reducing cell division (Prichard et al.， 2004). Continuous

monitoring of berry size provided the early detection of water would be useful for・on皿 line

fine-tuning of irrigation regime by growers.

Although some growers may prefer a high berry yieldラ othersprefer a high quality

product that might require introducing some water stress by partial root zone drying and

deficit irrigation. Based on our results on the relationship between ¥If at 10 cm soil depth

and berry growth， the following suggestions are made for appropriate irrigation under

various scenarios in the last phase ofberry development Stage 1:

(1) In areas where water availability is low or moderate， the critical point for

scheduling irrigation during berry-growth phase should be approximately -5.4 kPa， as

this will permit substantial water saving than irrigation scheduled at higher lfI. Because

the grape be町 contractedin size when the !jf decreased beyond -5.4 kPa (Fig. 5-5)， the

upper limit of soi1 drying is regarded as approximately -5.4 kPa.

(2) ln hyper剛 aridand arid areas， irrigation water is very scarce and should be used

even more economically. In this case， it is possible to set the critical irrigation point lower

than -5.4 kPa， because photosynthesis did not decrease rapidly when !jf decreased up to-

9.3 kPa (Table ι1).註owever，permitting deveIopment of severe moisture stress might

affect the yield， as shown by Hardie and Considine (1976) and Hardie et al. (1981).

Thereforeラ furtherstudies should be done to determine the proper !jf to ensure that any

reduction in the economic yield is acceptable in light of the improvement in water use

efficiency under drylands.

(3) In the humid and semi-humid areas， a full irrigation strategy with no water stress

for vines can be carried out. The critical soil water potential for scheduling irrigation

should be -3 kPa (Fig. 5-5)， as this would permit maximization of berry yield. Some

farmers indeed prefer to produce high quantities of berries， such as those who plant

grapevines for table grapes sold by weight. There is often a marked premium in ensuring

that water content is maximized， whilst ensuring that produce quality does not su百er

(Jones and Tardieu， 1998). Howeverラ toomuch water may cause excess growth of shoot

and leaf at the expense of economic yield.

Since the water demand fc

74

has different effect on 企uitdevelopment at different stagesラ furtherexperiments should be

conducted to establish critical irrigation values in various growth stages. ln addition，

further test should be done under open-field conditions.

5.5 Conclusions

Establishing a critical value of soil water potential for scheduling irrigation is

essential for grapevine p1'oduction in arid and semiarid areas. This critical value fo1'

irrigation in the last phase (last week) of berηdevelopment Stage 1 was dete1'mined by

instantaneous measurement of ber1'Y size by photogrammetry and soil water potential by

tensiomete1's simultaneously during a drying cycle after irrigation， and establishment of

the relationship between these two factors. BetTy diameter tended to increase at night and

decrease in the day， and the trend value demonstrated sensitivity to developing soil

moisture stress in the root zone. Berry diameter increased 1'apidly after irrigation tilI 1fJ

became -3 kPa. In the 1fJ range of -3 kPa to -5.4 kPa， the rate of g1'owth started decreasing，

and as 1fJ decreased beyond -5.4 kPa， berry diameter started shrinking and the shrinkage

showed a strong linear relationship with decreasing 平人 ln contrast， photosynthesis and

transpiration rate remained unaffected by decreasing 1fJ until it became -9.3 kPa beyond

which photosynthesis decreased significantly. Thus， benγdiameter was a better indicator

than photosynthesis of developing moisture stress in grapevines in the last phase (1ast

week) of berry development Stage 1 and based on this attribute -5.4 kPa should be

considered as the threshold Ijf for scheduling irrigation in this important stage of economic

yield development in grapevines to get cost欄 effectiveuse of water resources. Howeverラ

this threshold 1fJ should not be recommended directly in othe1' stages (including the

ripening stage) of grapevines growth because the growth characteristics and water demand

are quite different in various growth stages. Therefore， further expe1'iments a1'e needed to

establish the soil wate1' potential threshold during the ripening stage fo1' g1'apevines.

75

Chapter 6 Establishment of soil water potential threshold for

irrigating grapevines during berry ripening based on leaf

photosynthesis and photogrammetry technology

6.1 Introduction

The problem ofwater scarcity is going to get further aggravated with climate change，

which is also likely to affect the quality of grapes/wine and thus the overall economics of

grape production (Santos et al吋 2007).In the drylands of northwest China， grape

production is vital for local farmer's life and economic development， but its sustainability

is threatened by lInreliable water resources (Du et al.， 2005). Therefore， improving the

efficiency of irrigation is essential for long欄 termsustainability of grape production and

the wine industry.

Deficit irrigation in fruit crops can be of value in increasing合uitquality by raising

dry matter and sugar content (Chalmers et al.， 1981). The potential for water saving by

water-use開 efficientirrigation and deficit irrigation in orchard crops has remained

unexplored so far (Fereres et al.ラ 2003).It is， thereforeラimportantto determine the critical

timing for starting irrigation， especial1y in drylands where drollght represents a seriolls

threat to the sllstainabili守ofagriculture (Konukcu et al吋 2005).

Overall， the berry development of grapevine fol1ows a double sigmoidal shape with a

strong increase in diameter early (Stage 1)， a slower lag phase (Stage 2)， and a rapid

growth from veraison (Stage 3) which then gradually slows down (Coombe and

孔1cCarthyラ 2000;Chatelet et al咋 2008).The third period of growth (Stage 3) lasts from

veraison to harvest (Kennedy， 2002a). Fruit ripening is characterized by so註eningand

coloring of the berry. Overallラ theberry approximately doubles in size between the

beginning of the third growth period and harvest. The phloem becomes the primary

source of ingress after veraison (Kennedyラ 2002a).The berry development is the most

critical for economic yield as fruit size at harvest is an important aspect of the qllality of

the合uit(Zhang et al.， 2005).

76

The growth characteristics and water demand are quite different in various growth

stages‘ 1mai et al. (1991 b) showed that the grape berry diameter contracted when Ijf

decreased from -12.6 to -63.1 kPa during the maturation stage. They further reported that

daily variation in berry diameter might be a useful index for soil moisture control in

grape production. However， the critical Ijf beyond which the berry contracted most

obviously during maturation stage could not be determined c1early and sufficiently in

their study because they did not measure any other data of Ijf between -12.6 kPa and -

63.1 kPa. These authors conc1uded that in the ripening stage， berry size is affected

conspicuously by decreasing Ijf. However，恥1cCarthy(2000) reported that moisture deficit

after veraison had only a minor effect on grape berry weight at maturity and berries were

insensitive to water deficit in the month before harvest (恥1cCarthyラ 1997a).The

maturation stage is cr悩calfor grape berry quality. 1n the maturation stageラ isthe berry

size sensitive to decreasing Ijf? Cifre et al. (2005) reported that stomatal conductance (gs)ラ

sap f10w and trunk growth variations could be used as indicators of water stress for

grapevine. During the maturation stage of grapevine， which kind of physiological

parameter is useful and suitable for irrigation management? Further studies should be

done to c1ear these questions for scheduling irrigation in the maturation stage of

grapevll1e.

There are many studies on the effects of various irrigation regimes on vine growth

(Poni et al.， 1994; Esteban et al.， 2001; Reynolds et al.， 2005). However， what is the

threshold Ijf at which the grapevine must be irrigated during the maturation stage is not

c1ear. This information is critical to optimize water useラpreventnutrient loss and improve

yield and quality of grapes.

We hypothesize that this value could be established by measuring diurnal variations

in berry size and a few physiological parameters of grapevine expeI允IIcingincl-easing

soil moisture stress. It is， however， necessary that the measurement of belTy size is made

with great precisionおrberry diameter because the changes are rather small.

A new system equipped with automated photogrammetry was developed by Moritani

et al. (2006; 2007) to measure soil erosion (Pyle and Richardsラ 1997).This system

consists of two high-precision digital cameras， attached to a computer wit

77

measuring fruit size with three major advantages. First， the measurement precision is high.

Second， the berry diameter can be monitored automatically. Third， the determination is

nondestructive.

The goal of this study was to establish the critical soil water potential value for

starting irrigation of grapevines during the maturation stage by examining instantaneous

variations in photosynthesis (AN)， stomatal conductance， berry diameter， and soil water

potential， as the water deficit developed in the soi1.

6.2 Materials and methods

6.2.1. Plant and soil materials

On 25 February 2008， 2-year-old Pione grapevines (Vitis vinifera L.ラ cv.V labrasca)

were transplanted into 34司 litercapacity horticultural pots in a greenhouse unde1' natural

conditions of temperature， light and humidity. Each pot (39 cm su1'face diamete1'， 32 cm

depth) contained 28 kg of a mixture of sandy soil (sieved th1'ough a 2-mm sieve)， peat

moss， humic allophone soil and lime in a volumetric ratio of 1200 600 200 1，

respectively. The mixture was placed on a 2 cm thick layer of microvesicular pumice to

allow free drainage. The mixture had a pH of 6.2. The pots we1'e irrigated with an

automatically timed drip irrigation system to ensure optimum moisture regime for the

vines. Four emitters per vine were located app1'oximately 10 cm from the trunk. The

amount of water applied was controlled by a time clock-solenoid valve assembly. The

irrigation amounts fo1' March， Ap1'il， May， June， July and August were 2.4， 3.2， 4.5， 6.0，

7.5 and 8.5 L per pot pe1' weekラ respectively.The plants were provided liquid fertilizer

containing all essential mineral nutrients (羽langet al.， 2001; Thippayarugs et al吋 2002)

once everv week.

To encourage uniform vegetative growthラ vineswere pruned to retain 12 nodes per

vine; only two shoots per vine were left and were trained ho1'izontally. Shoots were

trimmed twice between bloom and the veraison stage of the berries. Late1'al shoots we1'e

cut back to the fi1'st node. At f10weringヲ onecluster was left on each of the two shoots.

Each cluster was trimmed to retain only 200-250 florets and once berry-set occurredラ

further trimming was done to 1'etain only 40-50 berries pe1' cluster.

78

6.2.2. Experimental detai/s

On 13 August (88 days after f1owering)， when the berries were in the maturation stage，

a pot containing the grapevine was placed in a wind tunnel with a twか layersglass

chambe1' (schematically illust1'ated in Fig. 6-1) in a glass dome building (called“A1'id

Domeづofthe A1'id Land Resea1'ch Center.ラ TottoriUnive1'sityラ To託o1'i(35015' N， 133047'

E)， Japan. Natural solar 1'adiation can pass th1'ough the glass dome. An a1'tificial light

source was set 50 cm highe1' than the top ofthe grapevine fo1' supplying enough radiation

ene1'gy. The diurnal artificial luminous intensity， relative humidity and air f10w we1'e set at

3000 Ilmo1 m酬2s-¥ 50% and 0.3 m S-l 1'espectively. The tempe1'ature was set to 12112 h

(day/night) cycles of35120 oC. These conditions are controlled.

A丘町 placementin the wind tunnelラ thevine was i1'1'igated to satu1'ated condition.

From then on till the end of this expe1'iment no i1'rigation was applied and the vine

expe1'ienced deceasing 'V fo1' seven days. Soil wate1' potential was measured every two

hours by a pressure transduce1' system (Ma1'thale1' et al吋 1983).The system consIsts of a

pressure transduce1' with attached sY1'inge needle， tensiomete1's and digital 1'ead-out.

Twelve tensiomete1's we1'e put in the pot， six at a depth of 10 cm and othe1' six at a depth

of20 cm.

Ber1'Y diameter was monitored every hour by a new photog1'ammetry-system that

consists of two digital came1'as (Nikon D2H， 16，000 pixels) attached to a computer

having an image analysis program of th1'ee田 dimensionalalgorithm. The measurement

precision ofthe system was 0.2 mm. Details ofthis system are described by Mo1'itani et al.

(2006).

A 1'ectangula1' analytical frame with scale was fixed ve1'tically on the grapevine and

the grape cluste1' was placed inside the frame. Two marked be1'1'ies and two digital

cameras we1'e oriented as shown in Fig. 6-1 and these positions were fixed. Pictures

taken by the pai1' of digital cameras we1'e collected on a computer. The focal length (fc)

and resolution of CCD (bccd) of the digital cameras were 50 mm and 0.0094 mm宅

respectively. The inner orientation facto1's of the digital cameras are given by Moritani et

al. (2006). The relative o1'ientation and gradient of the pai1' pictu1'es were adjusted to

minimize parallax to obtain a 1'ectified photograph. Th1'ough 1'ectification and elimination

79

of longitudinal parallax， the y-coordinate of a point in the left rectified image was the

same as that in the right one. The same point in the paired images could easily be

searched by scrolling the point in the x-axis direction.

Two-Iayers glass chamber

Wind blower &

Artificial light

Air conditioner I source

江、Solar radiation

Fig. 6-1. Schematic illustration of experimental setup.

Net photosynthesis (AN)， stomatal conductance (gs)， transpiration (η， sub-stomatal

CO2 concentration (Ci) and leaf temperature of two healthy spur leaves of the grapevine

were measured every two hours (from 7:00 to 23:00) per day， simultaneously with ¥jf

measurements， using a portable photosynthesis system (LI-6400， LI-Cor Inc.， Lincoln，

NE， USA). Measurements were conducted on 2 cm x 3 cm leaf portion in the middle part

of a leaf blade confined in the leaf chamber of the system. The measurements were

repeated three times on each primary and lateral leaf.

6.2.3. Time series analysis ofberηdiameter data

As the berry diameter showed diumal variations over the study period， it was

80

necessary to remove the periodic f1uctuations by time series analysis (Box et al.， 1994;

Moran et al.， 2009). Periodic f1uctuation of berry diameter was filtered by quartic

polynomial trend line， and the main secular growth trend part was thus obtained. It was

then possible to establish the relationship between the tendency part of berry diameter

and soil water potential in the root zone. An example of deter溜 iningthe trend line of the

time series of diameter of Berry No. 2 from 17 August to 19 August is given in Fig. 6-2.

Time齢 seriesberry diameter measurements were available for 48 hours. The trend line in

this figure can help us to remove short-term f1uctuations in the time series of berry size.

The trend values of berry diameter were computed as

Y2232.267-0.0546xg-00032xf÷0.0003d-0.000006xf，F・，2= 0.41， N = 48

where Xi is the berry diameter measurement time (ith hour)， Yi is the trend value of berry

diameter (mm) at ith hour，ラ andN is the total hours of measurement in this figure.

35 ' Berry No. 2

司u

(EE) 231 E E百

ち 29e:'

畠 27→

25

12:00 0:00 12:00 0:00 12:00 0:00 」ー~'-…一~一--./ '-ーー一一γ一-.-/17 Aug. 18Aug. 19Aug.

Time of day (h)

Fig.6ー2.Diurnal variations in a time series of diameter for Berry No. 2 from Aug. 17 to

Aug. 19. The solid line represents measured berry diameter， and the dashed line represents the trend line.

81

-m s

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Values of Ijf， AN， gs and T for each replicate were averaged for daily variation of these

parameters before the mean and the standard error were calculated.

6.3 Results

6.3.1. Effect of soil water potential (Ijf) on the trend value ofber.ηdiameter

The diurnal f1uctuations in berry diameter time series data (17 August to 19 August)

were removed by time series analysis， and the relation between the Ijf at 10 cm soil depth

and the trend value of berry diameter is shown in Fig. 6-3. The berry contracted very

slowly when the Ijf at 10 cm depth decreased ftom -9.6 kPa to -16.2 kPa. When Ijf further

decreased from -16.2 kPa to -16.4 kPa， the berry shrunk rapidly.京市enIjf decreased

beyond -16.4 kPa， the berry also shrunk rapidly， but the rate was lower than that when Ijf

decreased from -16.2 kPa to -16.4 kPa. The differential of trend value of berry diameter

on soil water potential (dD/dljf) was highest when Ijf decreased from -16.2 kPa to -16.4

kPa (Fig. 6ー3)，which also indicated that the berry shrunk fastest during that stage.

6.3.2. Daily variation of soil water potential， photosynthesis， stomatal conductance and

transpiration

After irrigation in the morning of 13 Augustラthe¥jf decreased slowly during the first 3

days (Fig. 6-4)， but started decreasing a li伐 fasterwhen it decreased to -6.2 kPa in the

10 cm soil depth. The trend for the change in Ijf at the 10 cm and 20 cm soil depths was

similar， although Ijf in the 10 cm soil depth was lower than that in the 20 cm soil depth

because of evaporative losses from the soil surface.

In the first five days， the highest values of photosynthesis and stomatal conductance

occurred during da戸imeand the lowest values occurred during night (Fig. 6-4). Before Ijf

decreased to -13.2 kPa， AN， gs and T f1uctuated in a normal range. However， when Ijf

decreased from -13.2 kPa to -14.7 kPa， AN decreased from 7.1 to 0.38 Ilmo1 CO2 m-2 S-1

for primary leaf. ln addition， in the following 33 hours， AN f1uctuated in a low幽 value

82

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Soil water potential (kPa)

Fig.6ー3.Effect of soil water potential (1fI) (lO cm soil depth， n=6) on the trend value of berry diameter. dD]/dlfl and dD2/dlfl represent differential oftrend value ofberry diameter NO.l釦 dNO.2 on soil water potential.

83

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Fig. 6-4. Daily variation of soil water potential (lf/)， photosynthesisラ stomatal

conductance (gs) and transpiration (乃 ofgrapevine from 13 to 19 August， 2008. Each symbol represents the av巴rage土 standarderror (SE). There were six replicates of measurements for soil wat巴rpotential， while three replications were measured for photosynthesis， 5tomata1 conductance and tran5piration.

84

range and did not recovery the high value as before. AN for lateral leaf， gs and T for

primary and lateral leaf showed the similar trend.

6.3.3. Relationship among 1jI， berη diameter and leaf physiological parameters

When ljI decreased from -6.9 to -14.6 kPa， the highest values of intrinsic WUE (AN

gsぺasμmolCO2 mol H20-1) of primary leaf of grapevine (in the morning) occurred (Fig.

6-5 C). Before ljI decreased to -14.6 kPa， AN (in the morning) f1uctuated in a range of

3.06 to 8.16)..lmol CO2 m-2s-1 for primary leaf(Fig. 6-5A). ¥¥市enljI decreased beyond -

14.6 kPa， AN decreased from 5.1 to 0.38μmol CO2 m-2

S-l for primary leaf， and

furthermoreラ AN，extrinsic WUE (AN T1 as mmol C02 mol H20-

1) and intrinsic WUE

(n寸)of primary leaf of grapevine (in the moming) decreased fast and could not recover

the high value as before (Fig. 6-5A， B and C). When ljI reached -17.1 kPa， A怜 extrinsic

and intrinsic WUE became near zero.

Relationship between leaf physiological parameters and berry growth of grapevine

was shown in Fig. 6-6. When leaftranspiration (in the morning) decreased from 1.38 to

0.69 mmol H20 m-2 S-l， the trend value of berry diameter did not decrease significantly

and keep a value of higher than 31 mm. However， the trend value of berry diameter

decreased fast (lower than 30 mm) when T decreased beyond 0.69 mmol H20 m・2S-l (Fig.

6-4).

The relationship among berry diameter and Aぬ gs，Ieaf temperature， intrinsic and

extrinsic WUE of primary leaf of grapevine in the morning from 13 to 19 Augustラ 2008

also showed the similar trend. When leaf temperature was too high， or AN， T， gs， intrinsic

and extrinsic WUE were too low， the berry contracted obviously (Fig. 6-6).

ん decreasedwith gs (Fig. 6--7 A) and their relation could be illustrated as

y = 2.36 Ln (x) + 10.8， / = 0.66，

where y is AN， X is gs of primary leaf of grapevine in the morning企om13 to 19

August， 2008. A significant decrease occurred inん (Fig.6--7 A) when gs (in the

morning) decreased from 0.03 to 0.02 mol H20 m-2 S-l， during which ljI reached -14.7 kPa

(Fig.6-4).

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86

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87

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1)， extrinsic WUE (AN r1 as mmol CO2 mol

H20ぺ)and sub-stomatal C02 concentration (Ci) of primary leaf of grapevine in the morning from 13 to 19 August， 2008. Values are vine means (n=3).

88

When gs (in the moming) decreased from 0.26 to 0.03 (or 0.04) mol H20 m-2 S-I， the

intrinsic and extrinsic WUE increased (Fig. 6-7 B and C). Thereafter a signi五cant

decrease occurred in the intrinsic and extrinsic WUE (Fig. 6-7 B and C) when gs (in the

moming) decreased from 0.03 to 0.02 mol H20 m・2s-¥ during which lfI reached -14.7 kPa

(Fig. 6-4). When gs decreased to 0.017 mol H20 m-2 S-I， Aぬ intrinsicand extrinsic WUE

became almost zero (Fig. 6-7 A， B and C). Ci decreased for decreasing ranges of gs (in

the morning) from 0.26 to 0.15 mol H20 m抱2S-I and from 0.15 to 0.03 mol H20 m舗2d，

whereas increased steeply when gs decreased beyond 0.03 mol H20 m輔2S-I (Fig.6-7D).

6.4 Discussion

The production of a good quality wine with a sufficient level of yield is dependent on

the management of soil water in vineyards. Irrigation in vineyards is general1y scheduled

based on either soil moisture potential as measured by tensiometers or the accumulation

of certain amount of estimated crop evapotranspiration (Araujo et al.， 1995). The central

importance of lfI in irrigation management arises from the fact that di百erencesin water

potential between soil and plant provide the driving force for water movement and

therefore determine the direction of water flow (Jones and Tardieu， 1998). Applying

water at higher lfI value would result in wasteful use (Bowen and Frey， 2002). Under arid

and semiarid conditions， water availabi1i守 playsa main role in regulation ofberry growth

and sugar accumulation in vines. As shown by Poni et al. (2009)， vines subjected to stress

by al10wing soil-drying for half of the root system improved the composition of grapes in

terms of soluble solids and anthocyanin content， without significant change in yield， and

this was attributed tωoe儲ar出i五le釘rshoot gr

ratio t出ha祇tmitigated the ef汀fecはtof pos幻t.幽→.べver限aisonstress. However， if lfI is too low， the fresh

and dry matter yield of grape would also decrease because of a decrease in the supply of

photosynthates due to decreased photosynthesis (Fig. 6-4 and Fig. 6-5). Ennahli and Earl

(2005) also demonstrated that water stress reduced berry grov.th and photosynthesis， and

Resco et al. (2009) reported that excess water stress even constrained photosynthetic

recovery after re-watering. It is thereforeラ necessaryto establish a degree of soil moisture

stress that would allow optimizing the combination of yield and berry quality in each

89

situation whilst enhancing the productivity of irrigation water (Santesteban and Royo，

2006). It is in this context that the determination of threshold soil moisture potential for

irrigation， as attempted in our studies， becomes important.

Physiologically based irrigation tools may attempt to maintain the plants at a limit

between water stress and excess water consumption， thus making a rational use of

irrigation water. This kind of irrigation may save water with respect to empirical

irrigation， improving yield as compared with rainfed grapevinesラ andmaintaining the

high fruit quality (Ci合eet al.ラ 2005).

lmai et al. (1991a) indicated that the increase in berry size was more rapid in vines

watered at lJf口 -3.11♂a than in those water吋 atlJf = -15.8 kPa until seed-hardening.

Because they only tested two levels of soil water potential， they could not point out the

critical Ijf after which the berry would begin contraction. lmai et al. (1991 b) sought the

relation between lJf and grape berry growth measured by a displacement sensor with

rubber string. They found that the berry diameter contracted when Ijf decreased from -

12.6 kPa to -63.1 kPa during the maturation stage. However， the critical lJf during

maturation stage could not be determined clearly and su伍cientlyin their study because

they did not measure any other data of lJf between -12.6 kPa and -63.1 kPa， so they did

not state the accurate value of lJf beyond which the berry contracted most obviously. In

our experiment， we measured instantaneous changes in lJf and belTy diameter

continuouslyラ soit was possible to find this critical lJf for scheduling irrigation. The berry

contracted very slowly when the lJf at 10 cm depth decreased from -9.6 kPa to -16.2 kPa

(Fig. 6-3). When lJf further decreased from -16.2 kPa to -16.4 kPa， the berry shrunk fast.

When lJf decreased beyond -16.4 kPa， the berry also shrunk fastラ butthe rate was lower

than that when lJf decreased from -16.2 kPa to -16.4 kPa. The di百erentialof trend value

of berry diameter on soil water potential (dD/dlJf) was highest when lJf decreased from -

16.2 kPa to -16.4 kPa (Fig. 6-3). Therefore， irrigation should be arranged no later than -

16.2 kPa.

It is interesting that decrease in lJf up to -16.2 kPa had no significant effect on the

berry size (Fig. 6-3) in grapevine while ん， gs and T started showing an obvious decline

as the lJf decreased beyond -13.2 kPa (Fig. 6-4). In addition， in the following 33 hours，

AN， gs an

90

(Fig. 6-4). Therefore， ANヲgsand T are more sensitive to moisture stress than berry size in

grapevine during the maturation stageラ thiscould be related to the fact that in maturation

stageラ theberry enlargement may correspond to the berry growth which is due mainly to

the photosynthates accumulation and transformation (from leaf to fruit)， and the berry

grow1h probably does not caused by the swelIing of fresh pulp that depends on the water

status. Therefore， photosynthesis parameters (AN， gs andηare thus better indicators of

the soil moisture stress than berry size during the maturation stage of grapevine. Zsofi et

al. (2009) and Cifre et al. (2005) also believed that gs is a reliable tool for determining the

degree of water stress. Schultz (2003) and Cifre et al. (2005) showed that tight stomatal

c10sure occurred at relatively low soil water deficit in many grapevine cu1tivars， leading

to a rapid reduction of gs・

AN is usual1y higher in the morning than in the a立ernoon.明尽lenlfI decreased beyond

-14.6 kPa， AN， extrinsic and intrinsic WUE (in the morning) decreased rapidly and could

not recover the high value as beおre(Fig. 6-5 A， B and C). In additionラ theseparameters

became near zero when lfI reached -17.1 kPa. Flexas et al. (2002) and Cifre et al. (2005)

also reported that AN and intrinsic WUE decreased steeply in the phase of severe water

stress. ANラ T，gs， intrinsic and extrinsic WUE had only slight effects on berry growth when

they were relative highラ whereasberry contracted steeply when these values were too

low， during which lfI reac1凶-]4.7kPa (Fig. 6-4 and 6-6).

The drought-induced， curvilinear correlation between gs and AN (Fig. 6-7 A) is

consistent with Koundouras et al. (2008). AN decreased rapidly (Fig. 6-7 A) when gs

decreased beyond 0.03 mol H20 m-2 S-I， during which lfI reached -14.7 kPa (Fig. 6-4).

Based on Fig. 6-7， three phases of photosynthesis response can be differentiated

along a water sむ~ess gradient:

(1) A phase of severe water stress takes place when gs is very low (< 0.03 mol H20 1ぜ2d

1). During this stress phase， AN， intrinsic WUE (AN gs-I) and extrinsic WUE decreased

rapidly (Fig. 6-7 A， B and C)， whereas Ci increased steeply (Fig. 6-7 D)， indicating

that non-stomatal limitations to photosynthesis become dominant. A similar response

was found by Flexas et al. (2002) and Cifre et al. (2005) who reported this character

when gs < 0.05 mol H20 m-2 sぺThisvalue is a little higher than our data， which

91

could be related to different grapevine cultivars. Bota et al. (2004) showed that

limitation to photosynthesis in five C3 species， including巧出 vin砕ra，by decreased

Rubisco activity and RuBP content did not occur until drought was very severe.

Primary events of photosynthesis such as the electron transport capacity are very

resilient to drought (Cornic et al.， 1989; Epron and Dreyer， 1992). When gs < 0.05

mol H20 m-2 S-I， a general decline in the activity and amount of photosynthetic

enzymes is observed (Maroco et al.， 2002) and AN did not recover after irrigation

(Quick et al.， 1992)， indicating that norトstomatalinhibition (metabolic and/or

restricted internal CO2 diffusion) occurred. ln addition， our data showed that when gs

decreased beyond 0.03 mol H20 m-2 S-1 (corresponding to -14.7 kPa， as shown in Fig.

6-4)， T also decreased rapidly and could not recover. Besides the decrease of T， the

ratio of AN T1 also decreased (Fig. 6-7 C)， maintaining the thylakoid electron

transport rate (ETR) high relative to AN (Flexas et al吋 2002).The curvilinear‘

relationship between gs and AN (Fig. 6-7A) implies a more sensitive response of AN

to water limitation compared to gs at the last stage of soil drying， leading to a decrease

in AN gs-1 (Fig. 6-7 B)ラi.e.a decline of carbon assimilation in relation to water supply.

(2) A phase of moderate water stress is defined for a decreasing range of gs from 0.15 to

0.03 mol H20 m九-1.1n this phase，ん andCi decreased (Fig. 6-7 A and D)， while

extrinsic and intrinsic WUE usually increased (Fig. 6-7 B and C). Flexas et al. (2002)

and Cifre et al. (2005) showed the similar phenomenon during intermediate gs values

(0.15 > gs > 0.05 mol H20 m-2 S-I). Zsofi et al. (2009) reported th剖 improvedwine

quality of grapevine was due to moderate water stress which induced higher

concentration of anthocyanins and phenolics in the berries. During this phase， the

activity of photosynthetic enzymes， such as Rubisco， is mostly unaffected (Cifre et al.

2005; but see Maroco et al.， 2002). Therefore， in this phase， stomatallimitations seem

dominant and photosynthesis is rapidly reversed upon rewatering (Flexas et al吋 1999)ラ

but norトstomatallimitations are already developing (Maroco et al吋 2002;Cifre et al.

2005).

(3) A mild water stress phase is characterized by relative high values of gs (> 0.15 mol

H20 m・2Sぺ)・ Duringthis phase， AN decreased slight1y， which results in small increases

of intrinsi

92

(Fig. 6-7 D). These characters are consistent with Flexas et al. (2002). At this stage，

stomatal closure is probably the only limitation to photosynthesis (Cifre et al. 2005).

During phase (2) and phase (3)， i.e. gs is higher than 0.03 mol H20 m-2 S-1， or lJf is

larger than -14.7 kPa， the curvilinear relationship between gs and AN (Fig. 6-7 A) implies

a less sensitive response of AN to water limitation compared to gs at the first stages of soil

drying， leading to an increase in AN gs-1 (Fig. 6-7 B)， i.e. a near optimization of carbon

assimilation in relation to water supply (Chaves et al.， 2002; Koundouras et al. 2008).

Although some growers may p児島ra high berry yield， others prefer a high quality

product that might require introducing some water stress by partial root zone drying and

deficit irrigation. Based on our results， the following suggestions are made for

appropriate irrigation during the ripening stage of grapevines:

(1) ln areas where water availability is low or moderateラ thecritical soil water potential

range for scheduling irrigation should be between -13.2 and -14.7 kPa

(corresponding to gs range of 0.09 ~ 0.03 mol H20 m之 S-l)，because AN， gs， T，

extrinsic and intrinsic WUE decreased steeply in the phase of severe water stress

(when lJf decreased beyond this range). Furthermore， this will permit substantial water

saving than irrigation scheduled at higher 1Jf. A立erirrigation， lJf should be kept lower

than -6.9 kPa because the highest values of intrinsic WUE occurred when lJf

decreased from -6.9 to -14.6 kPa. A higher intrinsic WUE is in agreement with a

higher biomass production for grapevines (Stamatiadis et al.， 2007). Some farmers

indeed prefer to produce high quantities of ben.ies， such as those who plant

grapevines for table grapes sold by weight.

(2) ln hyper可 ridand arid areasラ irrigationwate1' is ve1'y sca1'ce and should be used even

more economically. The critical point for scheduling i1'1'igation should be

approximately -16.2 kPa (corresponding to gs value of 0.02 mol H20 m-2 S-I)， because

the grape be1'ry cont1'acted in size steeply when the lJf dec1'eased beyond -16.2 kPaラthe

uppe1' limit of soil d1'ying is rega1'ded as -16.2 kPa. Although permitting development

of severe moisture stress in this case might a百ectthe yield， as shown by Ha1'die et al.

(1981)ラ thelimitations to grape yield are a common practice (if not compulso1'Y) fo1' a

93

ma1'ket standa1'd wine p1'oduction and p1'emium wines (Ci合eet al. 2005).

Since the wate1' demand fo1' vines in va1'ious growth stages is not uniformラ furthe1'

expe1'iments should be conducted to establish critical irrigation values in va1'ious growth

stages. Our 1'esults p1'ovide useful info1'mation fo1' i1'1'igation management of vines during

the matur前ionstage that could be adopted by g1'owers unde1' different wate1' 1'esou1'ce

availability scena1'ios.

6.5 Conclusions

Establishing a c1'itical value of soil wate1' potential fo1' scheduling i1'rigation is

essential for g1'apevine production in drylands. This critical value for i1'rigation during the

ripening stage was dete1'mined by instantaneous measurement of berηsize by

photogrammetry， photosynthesis by photosynthesis system and soil water potential by

tensiometers simultaneously during a drying cycle afte1' IlTigation， and establishment of

the relationship among these facto1's. When lJf dec1'eased from -13.2 kPa to -14.7 kPa， Aぬ

gs， T， ext1'insic and intrinsic WUE decreased 1'apidly and did not 1'ecove1'y thereafter. In

contrast， the be1'ry size remained almost unaffected by dec1'easing lJf until it became -16.2

kPa beyond which the berry shrunk significantly. Thus， photosynthesis response was

mo1'e sensitive to water st1'ess than be1'ry size during the maturation stage of grapevine.

When gs < 0.03 mol H20 m♂ピ(correspondingto -14.7 kPa)， AN， intrinsic and extrinsic

WUE dec1'eased 1'apidly， whe1'eas Ci increased steeply， indicating that non-stomatal

limitations to photosynthesis become dominant. A more sensitive 1'esponse of AN to wate1'

limitation compared to gs at the last stage of soil drying led to a dec1'ease in AN gs・1.When

gs> 0.03 mol H20 m-2 s・iラANand Cj decreased， while extrinsic and intrinsic WUE usually

increased. Therefore， stomatal limitations seem dominant in this stage. A less sensitive

response of AN to water limitation compa1'ed to gs at the first stages of soil d1'ying led to

an increase in AN gs-l.

Based on these resu Its， theお1l0wingsuggestions are made for appropriate irr包ation

during the ripening stage of grapevines. In a1'eas where water availability is low 01'

moderate、thecritical soil wate1' potential 1'ange for scheduling irrigation should be

94

between -13.2 and -14.7 kPa (corresponding to gs range of 0.09 ~ 0.03 mol H20 m-2 S-I).

A長官 irrigation，lJf should be kept lower than -6.9 kPa because the highest values of

intrinsic WUE occurred when lJf decreased from --6.9 to -14.6 kPa. 1n hyper-arid and arid

areasラ thethreshold lJf for scheduling irrigation should be considered as -16.2 kPa

(corresponding to gs value of 0.02 mol H20 m-2 S-I) in this important stage of economic

yield development and fruit quality in grapevines to get cost圃 effectiveuse of water

resources. However， it should be mentioned that this threshold lJf could not be

recommended directly in other stages of grapevines growth because the growth

characteristics and water demand are quite different in various growth stages. Therefore，

further experiments are needed to establish the soil water potential threshold during other

growth stages of grapevines.

95

Chapter 7 General conclusions

Water is the most limiting resource in drylands. Improvements in water use efficiency

(WUE) of crops are essential under the scenarios of water scarcity. Application of mu1ch，

sub田 surfaceirrigation and irrigation scheduling are effective in reducing soil evaporation

and saving water.

Soil water content， salt level of soil， plant biomass and water use efficiency of Swiss

chard were profoundly influenced by mulching and saline water. Mulching of soils

significantly reduced the ET and accumulation of salts in the topsoil of the pots. The

mu1ching practice improved soil water content， crop biomass yield and WUE. The soil

temperature was slightly increased with the application of mulches during the winter

season. The averaged soil temperature at the depth of 5 cm under gravel mulch was

enhanced by 1.2 oC as compared to no-mulch. The enhancement of soil temperature by

mu1ch in 5 cm depth was more than 10 cm depth. Among the mulches gravel mulch

followed by pine-needles mulch proved to be effective especially under high saline

conditions during this short-term experiment (about 3 months). Ultimately the crop

performance was ameliorated under saline conditions. The mulch induced higher plant

growth may provide an opportunity for the safe use of saline water. The long-term

experiments， field and/or laboratory， are needed to assess the impact of saline water use

under mulching on evaporation and salinity interrelation for the sustainabi1ity of

agriculture. The comprehensive understanding also necessitates that we continue to strive

for systems that are efficient in their use of water and nutrients in arid and semi輔 aridareas.

A long-te町rmexperiment (more than half year) u山1隠Sl也ng1拘ar培geweighing ly戸F喝simete町rswas

conducted to further evaluate the cor吋1甘uunctivee在ecはtsof ml叫1

Both gravel mulch (G) and rIce-straw mulch (R) could reduce salt accumulation when

diluted seawater irrigation was used for irrigation. Compared with control， the EC1:5 of

soil under mulches was nearly 38% lesser. The ET was 26% lesser under G and 13%

lesser under R than under control. On the other handラ thefresh and dry yields wereラ

respectivelyラ 76%and 113% higher under R and 49% and 64% higher under G than under

control. ThereforeラtheWUE increased by 143% under R and 120% under G as compared

with control treatment. Monitoring of hourly change of

96

period when no irrigation was given， indicated that there was small adsorption of water

from the atmosphere by the R during the relatively cooler hours ofthe day， and this could

be very useful for crop growth in the arid and semi-arid regions. It can be concluded from

this study that mulching was a good strategy for getting good yield and water use

efficiency for Swiss chard when grown with saline shallow ground water. Compared with

the gravel mulch， the rice straw mulch showed a measure of superiority during this long-

term experiment period (about 6-7 months)ラ andgiven the additional advantage of

convenience in managing the material used， therefore， rice straw mulch was a better

option t註angravel mulch.

Besides Swiss chardラgrapevinesare often grown in regions under stressful conditions.

Similar1y like mulching (M) effectsラ sub-surfaceirrigation (SS) can also help conserve

water by reducing evaporative water losses in agricultural systems.

MS gave the highest fresh yield while SS gave the lowest value due to higherθ

(upper soil)‘AM Ts and diameter for MS as compared with SS. MS gave the higher WUE

than MSS due to the higher water content at top soil and higher yield for MS. These

combination of mulch and seepage irrigation were di能 l吋 forWUE in the order of MS >

MSS > SS > S. Compared with SS， the berry diameter，合eshyield， WUE， and berry sugar

content for MS were enhanced by 2.8 mm， 271.5 g tree-I， 33% and 15%， respectively.

MSS gave higher berry sugar content than MS， which could be attributed to the higher・Ts

and lower soil water at the top soil layer under the condition of suかsurfaceirrigation. Ts

should become an important index for the berry quality of grapevine.

Besides the irrigation method， the appropriate irrigation scheduling is also very

important for saving water. Determining a critical value of soil water potential for

scheduling irrigation is essential for grapevine production in arid and semiarid areas. This

critical value for irr‘igation during the berrγ“growth stage was determined by

Instantaneous measurement of berry size by photogrammetry and soil water potential by

tensiometers simultaneously during a drying cycle a食erirrigation， and establishment of

the relationship between these two factors.BeIηdiameter tended to increase at night and

decrease in the day， and the trend value demonstrated sensitivity to developing soil

moisture stress in the root zone.

97

decreasing， and as lfI decreased beyond -5.4 kPa， berry diameter started shrinking and the

shrinkage showed a strong linear relationship with decreasing 1fI. 1n contrast，

photosynthesis and transpiration rate remained unaffected by decreasing lfI until it became

-9.3 kPa beyond which photosynthesis decreased significantly. Thus， berry diameter was

a better indicator than photosynthesis of developing moisture stress in grapevines during

the berry-growth stage and based on this attribute -5.4 kPa should be considered as the

threshold lfI for scheduling irrigation in this important stage of economic yield

development in grapevines to get cost-effective use of water resources. However， this

threshold lfI should not be recommended directly in other stages (incIuding the ripening

stage) of grapevines growth because the growth character匂ticsand water demand are

quite different in various growth stages. Therefore， further experiments a1'e needed to

establish the soil water potential threshold during the ripening stage fo1' grapevines.

During the berry ripening stage， a c1'itical value of soi1 water potential for scheduling

irrigation is established for grapevine production in drylands. This critical value for

ir1'igation was determined by instantaneolls measurement of berηsize by

photogrammetryラ photosynthesisby photosynthesis system and soil water potential by

tensiometers simultaneously during a d1'ying cycle a丘町 irrigation，and establishment of

the relationship among these factors. When lfI dec1'eased from -13.2 kPa to -14.7 kPa， AN，

gs， T， extrinsic and intrinsic WUE decreased 1'apidly and did not recovery thereafter. 1n

contrastラtheberry size remained almost una百ectedby decreasing lfI until it became -16.2

kPa beyond which the berry shrunk significantly. Thus， photosynthesis response was

more sensitive to water stress than berry size during the maturation stage of grapevine.

When gs < 0.03 mol H20 m-2 S-1 (corresponding to -14.7 kPa)， AN， intrinsic and extrinsic

WUE decreased rapidly， whereas Ci increased steeply， indicating that non暢 stomatal

limitations to photosynthesis become dominant. A more sensitive response of AN to water

limitation compared to gs at the last stage of soil drying led to a decrease in AN gs-l. When

gs> 0.03 mol H20 m-2 S-I， AN and C decreased， whi1e extrinsic and intrinsic WUE usually

increased. Therefore， stomatal limitations seem d

98

Based on these results， the following suggestions are made for appropriate irrigation

during the ripening stage of grapevines. In areas where water availability is low or

moderate， the critical soil water potential range for scheduling irrigation should be

between -13.2 and -14.7 kPa (corresponding to gs range ofO.09 ~ 0.03 mol H20 m・2ぎ1).

After irrigation， !jf should be kept lower than -6.9 kPa because the highest values of

intrinsic WUE occurred when !jf decreased from -6.9 to -14.6 kPa. In hyper-arid and arid

areas， the threshold !jf for scheduling irrigation should be considered as -16.2 kPa

(corresponding to gs value of 0.02 mol H20 m-2 S-I) in this important stage of economic

yield development and企uitquality in grapevines to get cost-effective use of water

resources. Howeverラ itshould be mentioned that this threshold !jf could not be

recommended directly in other stages of grapevines growth because the growth

characteristics and water demand are quite different in various growth stages.

Based on our study， it can be concluded that photosynthesis response was more

sensitive to water stress than berry size during the berry ripening stage ofσrapevine， this

could be related to the fact that in ripening stage， the berry enlargement may correspond

to the berry growth which is due mainly to the photosynthates accumulation and

transformation (合omleaf to合uit)，instead of the swelling of 合eshpulp that depends on

the so11 water status. However， in berry growth stage， the increase of berry size mainly

depended on cell division and swelling that would be strongly related to soil water status.

In conclusion， rice-straw mulch was a better option than gravel mulch for improving

crop yield and water use efficiency in the long run. The rice肩 strawmu1ch combined with

surface irrigation exceeded no mulch combined with sub-surface irrigation for enhancing

the berry diameterラ freshyield， WUE and berry sugar content. Mu1ching combined with

surface irrigation outbalanced mulching combined with SUb-SUI台ce irrigation in

improving yield and WUE. Hence when the sub-surface irrigation is used for vineyardsラ

the placement depth of sub“surface irrigation hose should be shallower than 15 cm.

Ml凶I辻1chingcombined with s叩ub-s且§剖s乱釦uぽ1げr白C印eirη凶T吋riga抗矧tiぬongave hi泡gh碍erberry s叩uga創rcontent than

mη1U1chi治1η19c∞omτηlbi加ne吋dw礼;yi江t

99

diameter for irrigation scheduling， therefore photogrammetry could be used for

determining the critical point at which the berry contracted under stressful condition. The

berry diameter was a better indicator of sensing water stress than photosynthesis in the

last phase of Stage 1 of berry growth since the berry contracted under the moderate water

stress. Neverthelessラ inthe ripening stage， the leaf photosynthesis was more sensitive to

water stress than berry size， so leaf photosynthesis measurement and photogrammet1'Y

technology could be used together to establish irrigation th1'eshold to get cost-e官ective

use of water 1'esourcesラ especiallyfor fruit trees. Since the wate1' demand fo1' vines in

va1'ious growth stages is 110t uniform， further experiments should be conducted to

establish critical irriσation values in other σrowth sta!les. とD

100

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副首eringin maturation date. Ann. Bot. 95， 685--693.

Zhang Q.T.， Ahmed O.A.B吋 InoueM.， Saxena M.C.， Inosako K吋 KondoK.， and Suzuki

K吋 2009.Effects ofmulching on evapotranspiration， yield and water use efficiency of

Swiss chard (Beta vulgaris L. var. flavescens) irrigated with diluted seawater. Journal

ofFood， Agriculture & Environment‘7 (3&4)， October. (Accepted)

Zhang Q.T.， Inoue M.， Inosako K吋 lrshadM吋 KondoK吋 QiuG.Y. and Wang S. P.ラ 2008.

Ameliorative effect of mu1ching on water use efficiency of Swiss chard and salt

accumulation under saline irrigation. Journal of Food， Agriculture & Environmentラ 6ラ

480 -485

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115

mulch intensity and cropping density on soil evaporationラ evapotranspiration，water-

use efficiency and soil water content - case study of winter wheat in the North China

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116

SummaηT in Japanese

要旨

本研究では、持続的な節水農業のために、種々のマルチング効果を評価し、濯説時期開始

点(護班閤{直)を評価することを目的とした。

乾操地では良質の水が少なく節水が重要である。そこで、希釈海水を謹瀧に技用し、さら

に、濯蹴後の土壌面蒸発を軽減するためにマノレチングを行い 供試作物には耐塩性のあるフ

ダンソウを用いた。1I2000aのワグネノレポット内に東伯土壌(粘土 54%)を充填し、いずれも

厚さ 3cmの砂利マルチ、松葉マノレチ、稲ワラマルチとマルチなしの条件で、冬期にポット

栽培試験を行ったc 電気伝導度 (EC)が 4.8dS 舷 1と7.4dS m-1の希釈携水を用いた塩水

濯蹴条件下で、砂利による保温効果もあり、砂利マルチが水利用効率、乾物量ともに高く、

マルチング、効果が認められた。

地下水位を初期に 50cmに保ち、希釈海水 (EC= 6.9 dS m-1) による地下濯瓶条件下で、

東伯土壌にいずれも厚さ 3cmの砂利マルチ、稲ワラマルチを施し、 11月から 2月の冬、 3

月から 6月の春にウェイイングライシメータを用いたフダンソウの栽培試験を行った。いず

れの時期でも、マルチなしは積算蒸発散最と土壌中の塩分濃度が高いこと、マルチなしと比

較して乾物重は穏ワラマルチが 113%、砂利マルチが 64%高いこと、稲ワラマルチはマルチ

なしと比較して水利用効率が 143%高く、砂利マノレチと比較しでも水利用効率が 10%高いこ

とがわかった。以上の結果から、稲ワラマルチを用いたマノレチング、は塩を含んだ、浅い地下水

面の条件下で、塩類集積を軽減し水利用効率の向上に貢献することが認められた。

乾燥地ではブドウは高収入が期待される果樹であるが不適切な濯瓶による水資源の枯渇が

問題となり節水栽培が急務である。上述の実験で効果が認められた稲ワラマルチを用いて、

東信土壌に浸潤型多孔質チューブを地上と地中深さ 15cmに設置し、 6月から 9月にウェイ

イングライシメータを用いたブドウ(lii"ti汐凶dθ'l"aL.)栽培試験を行った。マルチなしと

比較して穏ワラマルチは水科用効率が高いこと、揺ワラマルチと多孔質チューブ、を地上に設

置した場合が水利用効率、新鮮重、果粒径、果粒糖度ともに高いことから、節水と品質向上

が期待できた。

さらに節水を考える場合、濯概時期の判定が重要となる。温湿度を制御したグロースチャ

ンパー内に鉢植えのブドウを置いて、 2台の高性能デ、ジタノレカメラを用いた画像解析で果粒

径とテンシオメータで根群域の土壌水分ポテンシャルを測定した。ブドウの成長期において、

果粒は昼に縮小し夜に肥大する日変化を示し、濯獄後に果粒は徐々に肥大し、さらに、土壌

水分ポテンシャルがある間値を過ぎると水分ストレスによって果粒が縮小することが明らか

になった。ブドウの果粒径と土壌水分ポテンシヤノレの関係が、濯説開始時期を評価する判断

材料になることがわかった。

同様lこ，グロースチャンパー内で、葉の光合成と気孔抵抗の変化を誕定して、ブドウの成

熟期の栽培試験を狩った。深さ 10cmの土壌水分ポテンシヤノレが-13.2kPaから-14.7kPaに

117

減少したときから、光合成と気孔コンダクタンスが著しく減少し、回復しなかった。その後、

土壌水分ポテンシヤノレが-16.2kPaに減少したときに果粒径が減少した。このように、ブド

ウの成熟期の場合、光合成などの反応が果粒径の変北よりも水分ストレスに敏感であること

を明らかにした。

本研究は、いくつかのマルチ資材の中から、塩を含む水で濯概した場合の稲ワラマルチに

よる節水効果と塩類集積軽減効果を示したこと、稲ワラマルチと濯蹴強度の低い浸潤型多孔

質チューブを用いた栽培実験でブドウの収量と品震に対するマノレチング、効果を示したこと、

濯蹴開始時期を判定する方法に新たにデジタノレカメラを用いた面鏡解析を採用し、その有効

性を示したことなどの新しい知見は、乾燥地農学に貴重な情報を提供したものであり、乾操

地の持続的農業に貢献するものと期待される。

118

Abstract in English

This study was carried out to evaluate mulching e挽 ctfor sustainable agriculture and establish

in'igation threshold (based on a new photogrammetry system) for '"頃er幽 savingproduction.

Water-saving is important since freshwater resources have been over-exploited in many areas.

Therefore a pot experiment was conducted to evaluate the e提出 ofthree mulching types (gravel，

pine-needles and rice-straw with 3 cm thickness) together with diluted seawater irrigation during

winter season. Seawater was diluted to achieve the electrical conductivity of irrigated water as 4.8 and

7.4 dS 1ぜ1.High diluted seawater irrigation could be used under mulch condition without serious

salinity-damage to Swiss chard. Gravel mulching enhanced soil temperature， biomass and water use

e百iciency(WUE) under saline irrigation.

F肝rom立mNo仰vem町mτηIb加eぽrt加oJ如une杭e久ラ t批hee任能ect0ぱfg伊rav刈elm制 ulc凶Cぬh(G町)and ric切e令阿刊4引哨哨s鈎柑tむ汀rawmu叫1u叫ul凶clぬh(∞R町)(ο3cm thickness)

on Swiss chard we段reinvestigated. Three weighing Iysimeters were irrigated with di1uted seawateI・(6.9

dS m'l) from beIow.官lecumulative ET and soiI salinity were higher with no・mulchthan mulches.

The dry yield was 113% higher under R and 64% higher under G than under no-mulch. R increased

WUE by 143% and 10% as compared to no-mulch and G， respectively. Thus mulching using R is

recommended for reducing salinity under shaIlow water table of saline water and improving WUE.

The grapevine plays an important role in enhancing income in drylands with the problems of

water scarcity and improper irrigation， hence water-saving production is on urgent business. Based on

the resuIts of above酬 mentionedexperiment， effects of rice-straw mulching and sub-surface seepage

irrigation (at 15 cm soil depth) on growth of grapevines (Vitis vinij針。L.)in weighing Iysimeters were

investigated from June to September. Mulching combined with surface irrigation gave the highest

be汀ysize， fresh yield and WUE， while mulching combined with sub-surface irrigation gave the

highest sugar content.

It is also essential to detennine the critical timing for starting irrigation in drγlands.、市enthe

berries were in the last phase of Stage 1， a potted grapevine w部 placedin an environmentaIly

controlled growth chamber. Benγdiameter was monitored by a new photogrammetry崎 system

119

ln the similar way， when the berries were in the ripening stage (Stage 3)， leafphotosynthesis and

stomatal conductance were monitored合oma potted grapevine in a growth chamber. When soil water

potential (at 10 cm soil depth) decreased from幽 13.2kPa to幽 14.7kPa， photosynthesis， stomatal

conductance and transpiration decreased rapidly and did not recoverγthereafter. Afterwards the berry

shrunk significantly as soil water potential became -16.2 kPa. Thus， photosynthesis was more sensitive

to water stress than berry size during the ripening stage.

ln conclusion， rice岨 strawmulch was a good option in several mulching materials for preventing

soil salinity and improving WUE. Furthermore， the rice-straw mulch combined with seepage irrigation

could influence yield and quality of grapevines. A new photogrammetry system is suitable for

measuring berry diameter for irrigation timing scheduling， therefore this effective method could be

used to get cost-effective use of water resources， especially for fruit trees under stressful conditions.

The valuable informatIon provided here will benefit the sustainable agricultu問、 especiallyin arid and

semi糊 aridareas.

120

List of related publication

Ameliorative effect of mulching on water use efficiency of Swiss chard and salt

accumulation under saline irrigation

Authors: Qing Tao ZHANG，恥1itsuhiro払JOUEラ KojiINOSAKO， Muhammad

IRSHAD， Kensuke KONDO， Guo Yu QIU and Shi Ping WANG

Publication: Joul11al ofFood， Agriculture & Environment

Date， Volume， Pages: 2008. 6， pp. 480“ 485

This paper covers the chapter 2.

Effects of mulching on evapotranspiration， yield and water use efficiency of Swiss

chard (Beta vulgaris L. var.jlavescens) irrigated with diluted seawater

Authors: Qing Tao ZHANG， Bouya Ahmed OULD AHMED， Mitsuhiro INOUE，

五tIohanChandra SAXENA， Koji INOSAKO， Kensuke KONDO and Kenji

SUZUKI

Purぅlication:Joul11al ofFood， Agriculture & Environment

Dateラ Volumeラ Pages:2009. 7 (3&4)， October， 2009. Accepted (This manuscript wil1

be published in this upcomingjoul11al issue)

This paper covers the chapter 3.

121

List of related conferences papers

l.ZHANG QingtaQ， W ANG ShipingラMORITANI Shigeokiラ骨~OUE 加litsuhiro， XIE

Qiang， TSUJI Wataru， TANABE Kenji， 2008. Establishment of irrigation critical

value in berry growth stage of grapevines based on photogrammetry. Proceedings of

the 63rd meeting ofthe JSIDRE (The Japanese society of irrigation， drainage and rural

engineering) annual branch meeting in Hiroshima， Chugoku and Shikoku， Japan. pp.

32-133

2. ZHANG Qingtaoラ INOUEMitsuhiro， KONDO Kensuke and Y AMAMOTO Tahei，

2006. Effects of various mulching materials on salt accumulation and water use

efficiency of Swiss chard irrigated with diluted sea water. Proceedings of the 2006

meeting of the JSIDRE (The Japanese society of irrigation， drainage and rural

engineering) annual meeting in Utsunomiya， Japan. pp. 728-729

3. WANG Shiping， INOUE Mitsuhiro， Z.HANG QingtaQ， MORIT ANI Shigeokiラ TSUJI

Wataru， TANABE Kenji， T AMURA Fumio， 2009. Establishment of irrigation critical

value in berry maturity stage of grapevine based on photosynthesis and its

transformation. Hort. Res (Japan). 8 (suppl.1): 91 pp (in Japanese)

4. WANGラ S.P.，Z.HANG‘O.T.ラINOUE，M吋 ZHANGラ C.X.ラ2009.A New Self“Watering

Technique for Container-Grown Grapevine…Capillary Wicking Water Cultivation

(CWWC)， American Society for Horticultural Science， St. Louis， USA

122