Research Article Effects of Controlled Irrigation and …downloads.hindawi.com/journals/jchem/2016/2576015.pdfResearch Article Effects of Controlled Irrigation and Drainage on Nitrogen

Research ArticleEffects of Controlled Irrigation and Drainage on Nitrogen andPhosphorus Concentrations in Paddy Water

Shi-kai Gao Shuang-en Yu Guang-cheng Shao Dong-li She Mei WangRong Guo Rui-zhe Cao Shao-feng Yan and Ji-hui Ding

Key Laboratory of Efficient Irrigation-Drainage and Agricultural Soil-Water Environment in Southern China Ministry of EducationCollege of Water Conservancy and Hydropower Engineering Hohai University Nanjing 210098 China

Correspondence should be addressed to Shi-kai Gao igaoshikai163com and Shuang-en Yu seyuhhueducn

Received 14 March 2016 Revised 13 May 2016 Accepted 16 May 2016

Academic Editor Jun Wu

Copyright copy 2016 Shi-kai Gao et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Controlled irrigation and drainage (CID) has received attention for improving water quality Under CID condition water stressis frequently experienced in two contexts first drought and then flooding (FDTF) and first flooding and then drought (FFTD)This study aimed to investigate the effects of FDTF and FFTD on nitrogen (N) and phosphorus (P) dynamics in paddy water atdifferent growth stages The effects of water stress on the migration and transformation of N and P were also investigated Resultsshowed that CID can decrease N and P concentrations in surface water NH

4

+-N was the major form of N in surface drainageand percolation water Mean total phosphorus (TP) NH

4

+-N and NO3

minus-N concentrations were significantly higher than in FFTDduring the growth stage Mean NH

4

+-N NO3

minus-N and TP concentrations were significantly higher in percolation water underflooding stress than those under drought stress at growth stage except for mean TP concentrations at milky stage (stage IV)Meanwhile flooding can sharply increase the NH

4

+-N NO3

minus-N and TP concentrations in percolation water after drought Thuswithout CID the considerably high NH

4

+-N NO3

minus-N and TP concentrations via runoff and leaching can be responsible for theeutrophication of water bodies in the vicinity of paddy fields during the rice growing season when water stress transforms fromdrought into flooding

1 Introduction

Agricultural nonpoint source pollution is a major envi-ronmental issue in many countries with intensive farmingsystems [1 2] Nitrogen (N) and phosphorus (P) loads fromunmanaged agricultural nonpoint sources [2] such as runoffand leaching from paddy fields have been associated withwater body eutrophication of many lakes and streams [34] Paddy rice is one of the most important food crops inSouthern China [5ndash7] The utilization of N is relatively lowin irrigated rice because of rapid N losses through surfacerunoff denitrification leaching and ammonia volatilization[8]Moreover irrational drainage shortens the residence timeof water and accelerates the N and P losses [9] resulting in anincrease in N losses from the paddy fields to adjacent watersHowever P is relatively stable in soils and thus runoff andleaching are the major routes of excessive P losses [10]

Previous research showed that the total drainage outflowwas a primary factor in N and P losses in paddy fields [11]Attempts to reduce the nutrient losses in drainage waterhave led to the promotion of controlled drainage (CD)which has shown the best potential for improving waterquality [12ndash15] Large amounts of water outputs saved canbe obtained in CD systems [11 16] In addition N and Pconcentrations are reduced through crop uptake nitrifica-tion denitrification and sediment deposition [14] Howeverwater conservation has become a basic national policy inChina given the shortage of water resources [17 18]Themostwidely promoted water-saving technology for rice so far isalternate wetting and drying (AWD) [19] The adoption ofwater-saving technologies could alter N and P dynamics andlower nutrient losses [19 20] Peng et al showed that N andP losses were reduced with AWD compared to conventionalirrigation under the same N management [18]

Hindawi Publishing CorporationJournal of ChemistryVolume 2016 Article ID 2576015 9 pageshttpdxdoiorg10115520162576015

2 Journal of Chemistry

Table 1 Controlled thresholds in different stages for controlled irrigation and drainage (CID) in the year 2015

Treatments Tillering stage(stage I)

Jointing-bootingstage (stage II)

Panicle initiationstage (stage III)

Milky stage (stageIV)

Period of watercontrol

FDTF

minus500sim200 minus200sim50sim200 minus200sim50sim200 minus200sim50sim200 Jul 3ndashJul 12minus200sim20sim100 minus500sim250 minus200sim50sim200 minus200sim50sim200 Jul 29ndashAug 6minus200sim20sim100 minus200sim50sim200 minus500sim250 minus200sim50sim200 Aug 24ndashSep 2minus200sim20sim100 minus200sim50sim200 minus200sim50sim200 minus500sim250 Sep 16ndashSep 25

FFTD

200simminus500 minus200sim50sim200 minus200sim50sim200 minus200sim50sim200 Jul 3ndashJul 14minus200sim20sim100 250simminus500 minus200sim50sim200 minus200sim50sim200 Jul 29ndashAug 7minus200sim20sim100 minus200sim50sim200 250simminus500 minus200sim50sim200 Aug 24ndashSep 4minus200sim20sim100 minus200sim50sim200 minus200sim50sim200 250simminus500 Sep 16ndashSep 28

Note minus119868mmsim119869sim119870mm denotes that water depth was kept between ndash119868mm and 119869mm at four stages of rice paddies at normal time the maximum waterheight after rainfall for the control is119870mmWhen water level lowered to minus119868mm irrigation water is added until water level reached 119869mm minus119867mmsim119871mm or119871mmsimminus119867mm indicates the controlled thresholds of water level in different stages The allowable variation of fixed water level was plusmn5mm during the periodof implementation 2mm water leakage per day was adopted when surface water existed FDTF indicates first drought and then flooding FFTD indicates firstflooding and then drought

Although many studies have investigated migration andtransformation of N and P in paddy fields individually underAWD and CD [1 18 19] only a few studies have focused onthe conjunct influences of CD and AWD on the migrationand transformation of N and P Controlled irrigation anddrainage (CID) aims to combine the advantages of CDand AWD The basic feature of CID is to maintain a highdepth of water so that the drainage water is reduced duringrainy days and used when a certain threshold water table isreached (a certain degree of drought stress is produced whensoil moisture content is lower than the saturated moisturecontent and even field capacity) Thus paddy fields mayexperience frequent episodes of alternate drought and flood-ing to various degrees under CID condition The desirableN and P changes and losses may be different from thoseunder drought or flooding stress alone CID practice tends toresult in dramatic changes in the soil physical environmentincluding the aerobic and anaerobic transitions [21] UnderCID condition water stress may be frequently experiencedin two contexts first drought and then flooding (FDTF) andfirst flooding and then drought (FFTD) The current studyattempts to reveal the N and P dynamics in surface andpercolation water from rice paddies under FDTF and FFTDconditions as well as determine the effects of water stress onthe migration and transformation of N and P

2 Materials and Methods

21 Experimental Site and Soil Properties The experimentswere conducted in specially designed experimental tanksat the Key Laboratory of Efficient Irrigation-Drainage andAgricultural Soil-Water Environment in Southern ChinaMinistry of Education (Nanjing latitude 31∘571015840N longitude118∘501015840E 144m above sea level) during the rice growingseason of 2015 (ie May to October) The experimental siteexperiences a subtropical humid climate with an annualmean temperature of 154∘C The mean annual precipitationat Nanjing City (located 20 km northeast of the experimentalsite) is 1047mm with mean annual evaporation of 900mm

The air temperature wind speed and direction relativehumidity total solar radiation and photosynthesis activeradiation were measured at the experimental site using anautomated weather station Precipitation was measured bya tipping bucket rain gauge All meteorological parameterswere stored in a data logger and downloaded weekly via acomputer The frost-free period lasts for 220 days per yearThe soil in the area is a typical permeable paddy soil formedon loess deposits with loamy clay A total of 25 fixed tanksplots were prepared (length times width times depth = 25m times 2m times2m) The irrigation system is an automatic irrigation systemcontrolled by the host electromagnetic valve The soil (0ndash30 cm) in tanks with pH of 697 contained 219 of soilorganic matter 091 gkg of total nitrogen 2765mgkg ofavailable nitrogen 032 gkg of total phosphorus (TP) and125mgkg of available phosphorus

22 Plant Material and Cultivated Practices Nangeng 9108 ahigh-yielding rice variety currently used in local productionwas grown in the paddy tanks Seedlings were raised in aseedbed on May 13 2015 and then transplanted on June 162015 at a hill spacing of 02m times 014m with three seedlingsper hill A week before transplanting the experimental plotswere dry-ploughed and harrowed The soil was soaked a daybefore transplanting and then flooded for about a week with a2-3 cm water layer to promote good crop establishment Thebasal fertilizer was the compound fertilizer (N P

2O5 K2O

15 15 15) and 900 kgha was applied on June 13 2015 Thetillering fertilizerwas urea (with a nitrogen content of 464)and 100 kgha was applied on June 28 2015 The paniclefertilizer was also urea (with a nitrogen content of 464)and 50 kgha was applied on August 18 2015 The weed wascontrolledmanually and pesticides were applied occasionally

23 Experimental Design Eight CID treatments weredesigned for the experiment (Table 1) According to thecharacteristics of rice growth stage we chose tillering stage(stage I) jointing and booting stage (stage II) heading andflowering stage (stage III) and milky stage (stage IV) for

Journal of Chemistry 3

Table 2 Mean TP NH4

+-N and NO3

minus-N concentrations in surface water at different stages

Form of N and P(mgsdotLminus1) Treatments Tillering stage

(stage I)Jointing-bootingstage (stage II)



NH4

+-N FFTD 620a 259a 482a 153a

FDTF 727b 331b 562b 193b

NO3

minus-N FFTD 201a 131a 204a 088a

FDTF 314b 207b 263b 123b

TP FFTD 016a 010a 006a 003a

FDTF 025b 016b 096b 047b

Note mean values in the same row followed by the same letter show nonsignificant difference FDTF indicates first drought and then flooding FFTD indicatesfirst flooding and then drought

the experiments under different irrigation and drainageconditions Treatments were set up in the paddy tanks withclosed bottoms each treatment had three replicates For theFDTF treatments rice experienced drought stress at first andwhen the field water level dropped to the lower limit at thebeginning of growth stage irrigation water was added withan automatic irrigation system until the upper water levellimit was reached the field surface water was then drained tothe maximum water level at normal time after 5 days For theFFTD treatments rice experienced flooding stress at firstand irrigation water was immediately added to the upperwater level limit at the beginning of growth stage the fieldsurface water was then drained until there was no surfacewater after 5 days and when the field water level dropped tothe lower limit at the beginning of growth stage irrigationwater was added until the maximum water level at normaltime was reached The water level management complyingwith the shallow and wetting irrigation requirement wasconducted on other days of each stage

24 Sample Collection and Measurement Field water depthwas observed at nine orsquoclock by a ruler When the minimumlevel was reached the system would irrigate until waterlevel reached maximum level Similarly when water levelexceeded maximum because of rainfall the drainage volumewas subsequently calculated by counting the number ofopened solenoid valves and stored by a data logger Watersamples were collected in polyethylene bottles for threetimes during the submergence period The surface water wascollected using 50mL syringes (without disturbing the soiland selecting the top surface water randomly) all bottleswere rinsed before appropriate amount of water sample wasobtained An underground drainage pipe was installed atthe bottom of the tanks (the distance between undergroundoutlet and field surface is 15m) The collection time ofpercolation water was in accordance with surface water Asthere was no surface water in field the percolation water wascollected when the water level reached 0mm minus250mm andminus500mm Ammonia nitrogen (NH

4

+-N) nitrate nitrogen(NO3

minus-N) and TP in the water samples were analyzed bythe indophenol blue disulfonic acid phenol and ammoniummolybdate methods using a UV-2800 spectrophotometer

25 Statistical Analysis Arandomized complete block designwith three replications was employed Treatment effects were

analyzed using SPSS software version 190 119905-tests at 119875 le 005were used to calculate the difference of mean concentrationsin surface water among different treatments Significance wascalculated based on least significant difference (LSD) test at119875 le 005 except when 119905-tests were used

3 Results

31 Change of NH4+-N Concentration NH

4

+-N concentra-tions over the study period are shown in Figure 1 NH

4

+-Nconcentrations reduced with the time of flooding in FFTDand FDTF surface water at each stage Compared with thefirst day of flooding at each stage theNH

4

+-N concentrationsfor the FFTD surface water were decreased by 509 4225474 and 421 at the end of flooding the NH

4

+-Nconcentrations for the FDTF surface water were decreased by552 531 510 and 325 The mean NH

4

+-N concen-trations in FFTD surface water were significantly higher thanthose in FDTF surface water at each stage (Table 2)

First NH4

+-N concentrations in the FFTD percolationwater were reduced with time during the study period andthen stabilized at each stage The NH

4

+-N concentrationsin FDTF percolation water reached the maximum on thefirst day of flooding at each stage Moreover the maximumof NH

4

+-N concentrations in FDTF percolation water wassignificantly higher than that at the water level of minus500mmCompared with the first day of flooding at each stage theNH4

+-N concentrations for the FFTD percolation waterwere decreased by 229 498 657 and 211 at theend of flooding the NH

4

+-N concentrations for the FDTFpercolation water were decreased by 374 556 618and 363 During the time of flooding the mean NH

4

+-Nconcentrations in FDTF percolation water were significantlyhigher than those in FFTD percolation water at each stage(Table 3) For the FFTD and FDTF treatments the meanNH4

+-N concentrations in percolation water under floodingcondition were significantly higher than those under droughtcondition at each stage (Table 3)

32 Change of NO3minus-N Concentration The dynamics of

change of NO3

minus-N concentrations in water at the four stagesis shown in Figure 2 In addition to FDTF surface waterat stage IV the NO

3

minus-N concentrations reduced with thetime of flooding in surface water at each stage In stage IVthe maximum of NO

3

minus-N concentrations in FDTF surface


NH

4

+-N

(mg

L)N

H4

+-N

(mg

L)

NH

4

+-N

(mg

L)N

H4

+-N

(mg

L)

FDTF surfaceFDTF percolation

FFTD surfaceFFTD percolation



1st 4th 5th 6th3rd2ndTillering stage (stage I)

1st 4th 5th 6th3rd2ndJointing-booting stage (stage II)

1st 4th 5th 6th3rd2ndPanicle initiation stage (stage III)

1st 4th 5th 6th3rd2ndMilky stage (stage IV)

0

2

4

6

8

10

12

0

2

4

6

8

10

12

0

1

2

3

4

0

2

4

6

8

10

Figure 1 Change of NH4

+-N concentration at each stage FDTF indicates first drought and then flooding FFTD indicates first flooding andthen drought 1st 2nd and 3rd indicate the concentration on the first third and fifth day of flooding for the FFTD treatments and at thewater level of 0mm minus250mm and minus500mm for the FDTF treatments 4th 5th and 6th indicate the concentration on the first third andfifth day of flooding for the FDTF treatments and at the water level of 0mm minus250mm and minus500mm for the FFTD treatments Vertical barsrepresent standard error of the mean

Table 3 Mean TP NH4

+-N and NO3

minus-N concentrations in percolation water at different stages during the time of flooding and drought

Form of N and P(mgsdotLminus1) Treatments

TimeTillering stage (stage

I)Jointing-booting stage

(stage II)Panicle initiationstage (stage III) Milky stage (stage IV)

Flooding Drought Flooding Drought Flooding Drought Flooding Drought

NH4

+-N FFTD 517b 401c 124b 083c 234b 088d 092b 077c

FDTF 618a 383c 169a 107c 301a 160c 110a 061c

NO3

minus-N FFTD 172b 117c 083b 039c 133b 079c 051a 034b

FDTF 243a 153c 110a 086b 178a 135b 057a 026b

TP FFTD 0088b 0056c 0055b 0038c 0046b 0036c 0032a 0035a

FDTF 0106a 0066c 0101a 0034c 0064a 0034c 0039a 0040a











NO

3

minus-N

(mg

L)

NO

3

minus-N

(mg

L)N

O3

minus-N

(mg

L)

NO

3

minus-N

(mg

L)

0

1

2

3

4

5

0

1

2

3

4

0

1

2

3

4

5

00

05

10

15

20

Figure 2 Change of NO3

minus-N concentration at each stage FDTF indicates first drought and then flooding FFTD indicates first flooding andthen drought 1st 2nd and 3rd indicate the concentration on the first third and fifth day of flooding for the FFTD treatments and at thewater level of 0mm minus250mm and minus500mm for the FDTF treatments 4th 5th and 6th indicate the concentration on the first third andfifth day of flooding for the FDTF treatments and at the water level of 0mm minus250mm and minus500mm for the FFTD treatments Vertical barsrepresent standard error of the mean

waterwas observed on the third day after flooding Comparedwith the first day of flooding at each stage the NO

3

minus-Nconcentrations for the FFTD surface water were decreasedby 351 622 621 and 164 at the end of floodingthe NO

3

minus-N concentrations for the FDTF surface waterwere decreased by 388 522 404 and 269 Themean NO

3

minus-N concentrations in FDTF surface water weresignificantly higher than those in FFTD surface water at eachstage (Table 2)

The NO3

minus-N concentrations reached the peak value onthe third day of flooding in FFTD percolation water at stageI The NO

3

minus-N concentrations showed a declining trend andthen fluctuated slightly in FFTD percolation water duringthe growth stage except at stage I For the FDTF treatmentsthe NO

3

minus-N concentrations in percolation water showeda rising trend at first and then a decrease at stage I theNO3

minus-N concentrations fluctuated in other stages Moreoverthe NO

3

minus-N concentrations on the first day of floodingin FDTF percolation water at each stage were significantly

higher than that at the water level of minus500mm Comparedwith the first day of flooding at each stage the NO

3

minus-N con-centrations for the FFTD percolation water were decreasedby 387 378 328 and 178 at the end of floodingthe NO

3

minus-N concentrations for the FDTF percolation waterwere decreased by 253 674 634 and 230 Duringthe time of flooding the mean NO

3

minus-N concentrations inFDTF percolation water were significantly higher than that inFFTD percolation water at each stage (Table 3) For the FFTDand FDTF treatments the mean NO

3

minus-N concentrations inpercolationwater under flooding conditionwere significantlyhigher than that under drought condition during the growthstage except at stage IV (Table 3)

33 The Change of TP Concentrations The dynamics ofchange of TP concentrations in water at the four stages isshown in Figure 3 TP concentrations in FFTD and FDTFsurface water reduced with the time of flooding at each stageCompared with the first day of flooding at each stage the TP










TP (m

gL)

TP (m

gL)

TP (m

gL)

TP (m

gL)

00

01

02

03

04

00

01

02

03

000

005

010

015

020

000

005

010

015

020

Figure 3 Change of TP concentration at each stage FDTF indicates first drought and then flooding FFTD indicates first flooding and thendrought 1st 2nd and 3rd indicate the concentration on the first third and fifth day of flooding for the FFTD treatments and at the waterlevel of 0mm minus250mm and minus500mm for the FDTF treatments 4th 5th and 6th indicate the concentration on the first third and fifth dayof flooding for the FDTF treatments and at the water level of 0mm minus250mm and minus500mm for the FFTD treatments Vertical bars representstandard error of the mean

concentrations for the FFTD surface water were decreasedby 318 550 629 and 499 at the end of floodingthe TP concentrations for the FDTF surface water weredecreased by 326 546 665 and 484 The meanTP concentrations in FDTF surface water were significantlyhigher than those in FFTD surface water at each stage exceptat stage IV (Table 2)

The TP concentrations fluctuated widely in percolationwater at each stage In FDTF percolation water the TPconcentrations reached the maximum on the third day offlooding and then declined at stages II and III The TP con-centrations in percolation water decreased with time in theother stages Compared with the first day of flooding at eachstage the TP concentrations for the FFTD percolation waterwere decreased by 448 284 277 and 303 at the endof flooding the TP concentrations for the FDTF percolationwater were decreased by 594 67 133 and 332During the time of flooding the mean TP concentrationsin FDTF percolation water were significantly higher thanthat in FFTD percolation water at each stage except at stage

IV (Table 3) Moreover mean TP concentrations in FDTFand FFTD percolation waters under flooding condition weresignificantly higher than that under drought condition at eachstage except at stage IV (Table 3)

4 Discussion

41 Impact of CID on NH4+-N and NO3

minus-N Concentrationsin Surface Water The NH

4

+-N and NO3

minus-N concentrationswere clearly affected by the duration of flooding (Figures1 and 2) NH

4

+-N and NO3

minus-N concentrations changecontinuously according to biochemical reactions involvedand the rates of these reactions correlate with the waterdepth [22] With the microbial interactions soil particlessedimentation and plant uptake implementation of CID cansignificantly decrease NH

4

+-N and NO3

minus-N concentrationsin surface water in this study Shao et al reported that CIDcould decrease water flow [23] Thus the decrease in lossesof NH

4

+-N and NO3

minus-N by CID implementation is not only


associated with runoff volume but also related to NH4

+-Nand NO

3

minus-N concentrations During prolonged floodingbiological denitrification is strengthened and nitrificationis suppressed in low-oxygen environments [24] NH

4

+-Nis the stable component of N in paddy water [1 7] andthus NH

4

+-N is the dominant form of N runoff Similarresults were also found in paddy soil in Southern China[5 25] Low water availability can inhibit microbial activ-ity by lowering intracellular water potential and reducinghydration and activity of enzymes in soil [26] resulting inthe accumulation of inorganic N under drought conditionsMeanwhile reflooding a dry soil promotes N mineralization[27] The amount of N tied up in bacterial osmolytes maybe metabolized on reflooding initially producing a pulseof dissolved organic N that may then be mineralized andnitrified [28] Therefore CID may be a useful strategy tocontrol N runoff when paddy fields are flooded after droughtCareful consideration must be given to the NH

4

+-N andNO3

minus-N runoff concentration when water stress transformsfrom drought to flooding


minus-N Concentrations inPercolationWater N leachingmay be affected by soil proper-ties watermanagement and crop growth Surface subsidenceand cracks formed in soil because of drought influence soilstructure and quality Water is quickly percolated when thesoil is reflooded after drought and nutrients through thecracks preferentially migrate into the subsoil [29 30] Asa result flooding can sharply increase the NH

4

+-N andNO3

minus-N concentrations in leachates after droughtMoreoverthe mean NH

4

+-N and NO3

minus-N concentrations were sig-nificantly higher in percolation water under flooding stressthan those under drought stress during the growth stageIn general NO

3

minus-N leaching is more likely to occur thanNH4

+-N leaching because of soil adsorption of NH4

+-Nand the migration distance of NH

4

+-N in soil is very short[18 31 32] However the current study found significantlyhigher NH

4

+-N than NO3

minus-N concentrations in percolationwater This finding may be due to long-term floodingconfined process of nitrification and intense denitrificationIn addition the soil was maintained in a reduced statebecause of the outlet below shallow groundwater table in theexperimental field during the time of drought [10] resultingin lack of oxygen Moreover a majority of NH

4

+-N in thepercolation water from paddy fields also may come from theslow mineralization and decomposition of organic N in thesubsoil [18]

43 Impact of CID on TP Concentrations The mobility andtransfer of P in paddy soil-water can be affected by floodingresulting in changes of P concentrations in the field surfacewater Moreover the particles in topsoil are disturbed byirrigation thereby inducing release and suspension of PIn this experiment we observed that TP concentrationsin surface water followed a decreasing trend during thetime of flooding which was consistent with the research ofZhang et al [33] In addition the mean TP concentrationsin FDTF surface water were significantly higher than that

in FDTF (Table 2) because the environment of FDTF hasobviously improved the effectiveness of soil P and promotedthe transformation of insoluble P into available P [34]

Soils generally have a strong adsorption capacity of P inpaddy fields [35] and thus P leaching can be ignored [36]However several studies have reported that P leaching is amain reason for water eutrophication [10 18] Water is themedium of P leaching which is closely related to field watertable management in paddy soil Certain amount of P inpercolation water directly comes from downward migrationof P in surface water and is positively correlated with Pconcentrations in surface water Changes in P concentrationsare often attributed to high water tables resulting fromflooding which promotes anaerobic conditions Anaerobicsoil conditions can increase the solubility and mobility ofP [13] Moreover anaerobic conditions created by floodingwater may increase the release of P to the soil solutionbecause of the reduction of Fe3+ to Fe2+ [37] As a resultthe mean TP concentrations were significantly higher inpercolation water under flooding stress than under droughtstress during the growth stage except at stage IV Similarresults in paddy soil in Southern China were also reported[38] In early period of flooding after drought high TPconcentrations favor eutrophication because of the presenceof cracks in the soil thereby allowing TP to leach moreeasily through preferential flow For paddy fields flooded afterdrought soils become reduced because of the decrease inoxygen and TP concentrations are increased continuouslyin the early period of flooding As a result P solubilityand extractability in FDTF condition were relatively higherthan those in FFTD thereby increasing the risk of TPleaching

5 Conclusions

Field experiments conducted in Southern China indicatedthat CID implementation increased the N and P use efficien-cies via the reduction of N and P concentrations in surfaceand percolation water NH

4

+-N and NO3

minus-N concentrationsdecreased with the duration of flooding in the four stages butdiffered considerably among the treatments NH

4

+-Nwas themajor form of N in surface drainage and percolation waterThe TP concentration in surface water followed a decreasingtrend during the time of flooding Compared with FFTD themean NH

4

+-N NO3

minus-N and TP concentrations were signif-icantly higher in FDTF surface water at each stage Moreoverthe mean NH

4

+-N NO3

minus-N and TP concentrations weresignificantly higher in percolationwater under flooding stressthan those under drought stress during the growth stageexcept for the mean TP concentration at stage IV Floodingafter drought can sharply increase theNH

4

+-NNO3

minus-N andTP concentrations in leachates High NH

4

+-N NO3

minus-N andTP concentrations via runoff and leaching were an importantcause of water eutrophication in paddy fields during therice growing season Thus CID should be implementedto control the high concentrations of NH

4

+-N NO3

minus-Nand TP when water stress transforms from drought toflooding


Abbreviations

CID Controlled irrigation and drainageCD Controlled drainageAWD Alternate wetting and dryingFDTF First drought and then floodingFFTD First flooding and then droughtN NitrogenP PhosphorusNH4

+-N Ammonium nitrogenNO3

minus-N Nitrate nitrogenTP Total phosphorusStage I Tillering stageStage II Jointing and booting stageStage III Heading and flowering stageStage IV Milky stage

Competing Interests

The authors declare that there are no competing interestsregarding the publication of this paper

Acknowledgments

This work was funded by the Key Program granted bythe National Nature amp Science Foundation of China (nos51479063 and 41401628) and supported by the FundamentalResearch Funds for the Central Universities (nos 2015B34614and 2015B14714) and the Priority Academic Program Devel-opment of Jiangsu Higher Education Institutions

References

[1] M-H Xiao S-E Yu D She X-J Hu and L-L Chu ldquoNitrogenand phosphorus loss and optimal drainage time of paddyfield under controlled drainage conditionrdquo Arabian Journal ofGeosciences vol 8 no 7 pp 4411ndash4420 2015

[2] H J Sun H L Zhang Z M Yu et al ldquoCombination systemof full-scale constructed wetlands and wetland paddy fields toremove nitrogen and phosphorus from rural unregulated non-point sourcesrdquo Environmental Geochemistry and Health vol 35no 6 pp 801ndash809 2013

[3] H Nakasone M A Abbas andH Kuroda ldquoNitrogen transportand transformation in packed soil columns from paddy fieldsrdquoPaddy and Water Environment vol 2 no 3 pp 115ndash124 2004

[4] L Van Chinh K Hiramatsu M Harada and M Mori ldquoNitro-gen and phosphorus runoff modeling in a flat low-lying paddycultivated areardquo Paddy andWater Environment vol 6 no 4 pp405ndash414 2008

[5] X Hu X Shao Y Li J He S Lu and Y Qiu ldquoEffects ofcontrolled and mid-gathering irrigation mode of paddy rice onthe pollutants emission and reductionrdquo Energy Procedia vol 16pp 907ndash914 2012

[6] M-H Xiao S-E Yu G Cheng and D-L Shao ldquoTechnicalstandards of irrigation and drainage management in paddyfield of water-saving and pollution-reduction with high yieldrdquoJournal of Food Agriculture and Environment vol 10 no 2 pp1005ndash1011 2012

[7] X Zhao Y Zhou J Min S QWangWM Shi and G X XingldquoNitrogen runoff dominates water nitrogen pollution from rice-wheat rotation in the Taihu Lake region of Chinardquo AgricultureEcosystems amp Environment vol 156 pp 1ndash11 2012

[8] J Z Xu S Z Peng S H Yang and W G Wang ldquoAmmoniavolatilization losses from a rice paddy with different irrigationand nitrogen managementsrdquo Agricultural Water Managementvol 104 pp 184ndash192 2012

[9] R Kroger S C Pierce K A Littlejohn M T Moore andJ L Farris ldquoDecreasing nitrate-N loads to coastal ecosystemswith innovative drainage management strategies in agriculturallandscapes an experimental approachrdquo Agricultural WaterManagement vol 103 pp 162ndash166 2012

[10] J Wang D J Wang G Zhang et al ldquoNitrogen and phosphorusleaching losses from intensively managed paddy fields withstraw retentionrdquo Agricultural Water Management vol 141 pp66ndash73 2014

[11] R O Evans R W Skaggs and J W Giiliam ldquoControlledversus conventional drainage effects on water qualityrdquo Journalof Irrigation and Drainage Engineering vol 121 no 4 pp 271ndash276 1995

[12] B Bohne I J Storchenegger and P Widmoser ldquoAn easy to usecalculation method for weir operations in controlled drainagesystemsrdquo Agricultural Water Management vol 109 pp 46ndash532012

[13] M R Williams K W King and N R Fausey ldquoDrainage watermanagement effects on tile discharge and water qualityrdquo Agri-cultural Water Management vol 148 pp 43ndash51 2015

[14] G Bonaiti and M Borin ldquoEfficiency of controlled drainageand subirrigation in reducing nitrogen losses from agriculturalfieldsrdquo Agricultural Water Management vol 98 no 2 pp 343ndash352 2010

[15] M D Dukes R O Evans J W Gilliam and S H KunickisldquoInteractive effects of controlled drainage and riparian bufferson shallow groundwater qualityrdquo Journal of Irrigation andDrainage Engineering vol 129 no 2 pp 82ndash92 2003

[16] I Wesstrom I Messing H Linner and J Lindstrom ldquoCon-trolled drainagemdasheffects on drain outflow and water qualityrdquoAgricultural Water Management vol 47 no 2 pp 85ndash100 2001

[17] B A M Bouman L Feng T P Tuong G Lu H Wang andY Feng ldquoExploring options to grow rice using less water innorthern China using a modelling approach II Quantifyingyield water balance components and water productivityrdquoAgricultural Water Management vol 88 no 1ndash3 pp 23ndash332007

[18] S-Z Peng S-H Yang J-Z Xu Y-F Luo and H-J HouldquoNitrogen and phosphorus leaching losses from paddy fieldswith different water and nitrogen managementsrdquo Paddy andWater Environment vol 9 no 3 pp 333ndash342 2011

[19] X Z Tan D G Shao H H Liu F S Yang C Xiao and HD Yang ldquoEffects of alternate wetting and drying irrigation onpercolation and nitrogen leaching in paddy fieldsrdquo Paddy andWater Environment vol 11 no 1ndash4 pp 381ndash395 2013

[20] N Pirmoradian A R Sepaskhah and M Maftoun ldquoEffects ofwater-saving irrigation and nitrogen fertilization on yield andyield components of rice (Oryza sativa L)rdquo Plant ProductionScience vol 7 no 3 pp 337ndash346 2004

[21] G Shao J Cui S Yu et al ldquoImpacts of controlled irrigationand drainage on the yield and physiological attributes of ricerdquoAgricultural Water Management vol 149 pp 156ndash165 2015

[22] I Yoshinaga A Miura T Hitomi K Hamada and E ShiratanildquoRunoff nitrogen from a large sized paddy field during a crop


periodrdquo Agricultural Water Management vol 87 no 2 pp 217ndash222 2007

[23] G-C Shao S Deng N Liu S-E Yu M-H Wang and D-LShe ldquoEffects of controlled irrigation and drainage on growthgrain yield and water use in paddy ricerdquo European Journal ofAgronomy vol 53 pp 1ndash9 2014

[24] A A Elmi C Madramootoo and C Hamel ldquoInfluence ofwater table and nitrogenmanagement on residual soil NOminus

3and

denitrification rate under corn production in sandy loam soilin Quebecrdquo Agriculture Ecosystems amp Environment vol 79 no2-3 pp 187ndash197 2000

[25] G-C Shao M-H Wang S-E Yu N Liu M-H Xiao andM Yuan ldquoPotential of controlled irrigation and drainage forreducing nitrogen emission from rice paddies in SouthernChinardquo Journal of Chemistry vol 2015 Article ID 913470 9pages 2015

[26] J M Stark and M K Firestone ldquoMechanisms for soil moistureeffects on activity of nitrifying bacteriardquo Applied and Environ-mental Microbiology vol 61 no 1 pp 218ndash221 1995

[27] R Seneviratne and A Wild ldquoEffect of mild drying on themineralization of soil nitrogenrdquo Plant and Soil vol 84 no 2pp 175ndash179 1985

[28] S-R Xiang A Doyle P A Holden and J P Schimel ldquoDryingand rewetting effects on C and N mineralization and microbialactivity in surface and subsurface California grassland soilsrdquoSoil Biology andBiochemistry vol 40 no 9 pp 2281ndash2289 2008

[29] G Crescimanno and G Provenzano ldquoSoil shrinkage charac-teristic curve in clay soils measurement and predictionrdquo SoilScience Society of America Journal vol 63 no 1 pp 25ndash32 1999

[30] T Sander and H H Gerke ldquoPreferential flow patterns in paddyfields using a dye tracerrdquo Vadose Zone Journal vol 6 no 1 pp105ndash115 2007

[31] Y-H Tian B Yin L-Z Yang S-X Yin and Z-L Zhu ldquoNitro-gen runoff and leaching Losses during rice-wheat Rotations inTaihu Lake region Chinardquo Pedosphere vol 17 no 4 pp 445ndash456 2007

[32] V Aparicio J L Costa and M Zamora ldquoNitrate leachingassessment in a long-term experiment under supplementaryirrigation in humid Argentinardquo Agricultural Water Manage-ment vol 95 no 12 pp 1361ndash1372 2008

[33] Z J Zhang J Y Zhang R He Z D Wang and Y M ZhuldquoPhosphorus interception in floodwater of paddy field duringthe rice-growing season in TaiHu Lake Basinrdquo EnvironmentalPollution vol 145 no 2 pp 425ndash433 2007

[34] S K Sanyal and S K De Datta ldquoChemistry of phosphorustransformations in soilrdquo in Advances in Soil Science vol 16 pp1ndash120 Springer 1991

[35] X J XieW Ran Q R Shen C Y Yang J J Yang and ZH CaoldquoField studies on 32P movement and P leaching from floodedpaddy soils in the region of Taihu Lake Chinardquo EnvironmentalGeochemistry and Health vol 26 no 2 pp 237ndash243 2004

[36] A N Sharpley R W Mcdowell and P J A KleinmanldquoPhosphorus loss from land to water integrating agriculturaland environmental managementrdquo Plant and Soil vol 237 no 2pp 287ndash307 2001

[37] I Wesstrom and I Messing ldquoEffects of controlled drainage onN and P losses and N dynamics in a loamy sand with springcropsrdquo Agricultural Water Management vol 87 no 3 pp 229ndash240 2007

[38] Y-H Shan L-Z Yang T-M Yan and J-G Wang ldquoDownwardmovement of phosphorus in paddy soil installed in large-scale

monolith lysimetersrdquo Agriculture Ecosystems amp Environmentvol 111 no 1ndash4 pp 270ndash278 2005

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Carbohydrate Chemistry

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Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


Chromatography Research International


Applied ChemistryJournal of



Theoretical ChemistryJournal of


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Spectroscopy

Analytical ChemistryInternational Journal of


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ElectrochemistryInternational Journal of



CatalystsJournal of


Table 1 Controlled thresholds in different stages for controlled irrigation and drainage (CID) in the year 2015

Treatments Tillering stage(stage I)

Jointing-bootingstage (stage II)



Period of watercontrol

FDTF

minus500sim200 minus200sim50sim200 minus200sim50sim200 minus200sim50sim200 Jul 3ndashJul 12minus200sim20sim100 minus500sim250 minus200sim50sim200 minus200sim50sim200 Jul 29ndashAug 6minus200sim20sim100 minus200sim50sim200 minus500sim250 minus200sim50sim200 Aug 24ndashSep 2minus200sim20sim100 minus200sim50sim200 minus200sim50sim200 minus500sim250 Sep 16ndashSep 25

FFTD

200simminus500 minus200sim50sim200 minus200sim50sim200 minus200sim50sim200 Jul 3ndashJul 14minus200sim20sim100 250simminus500 minus200sim50sim200 minus200sim50sim200 Jul 29ndashAug 7minus200sim20sim100 minus200sim50sim200 250simminus500 minus200sim50sim200 Aug 24ndashSep 4minus200sim20sim100 minus200sim50sim200 minus200sim50sim200 250simminus500 Sep 16ndashSep 28

Note minus119868mmsim119869sim119870mm denotes that water depth was kept between ndash119868mm and 119869mm at four stages of rice paddies at normal time the maximum waterheight after rainfall for the control is119870mmWhen water level lowered to minus119868mm irrigation water is added until water level reached 119869mm minus119867mmsim119871mm or119871mmsimminus119867mm indicates the controlled thresholds of water level in different stages The allowable variation of fixed water level was plusmn5mm during the periodof implementation 2mm water leakage per day was adopted when surface water existed FDTF indicates first drought and then flooding FFTD indicates firstflooding and then drought

Although many studies have investigated migration andtransformation of N and P in paddy fields individually underAWD and CD [1 18 19] only a few studies have focused onthe conjunct influences of CD and AWD on the migrationand transformation of N and P Controlled irrigation anddrainage (CID) aims to combine the advantages of CDand AWD The basic feature of CID is to maintain a highdepth of water so that the drainage water is reduced duringrainy days and used when a certain threshold water table isreached (a certain degree of drought stress is produced whensoil moisture content is lower than the saturated moisturecontent and even field capacity) Thus paddy fields mayexperience frequent episodes of alternate drought and flood-ing to various degrees under CID condition The desirableN and P changes and losses may be different from thoseunder drought or flooding stress alone CID practice tends toresult in dramatic changes in the soil physical environmentincluding the aerobic and anaerobic transitions [21] UnderCID condition water stress may be frequently experiencedin two contexts first drought and then flooding (FDTF) andfirst flooding and then drought (FFTD) The current studyattempts to reveal the N and P dynamics in surface andpercolation water from rice paddies under FDTF and FFTDconditions as well as determine the effects of water stress onthe migration and transformation of N and P

2 Materials and Methods

21 Experimental Site and Soil Properties The experimentswere conducted in specially designed experimental tanksat the Key Laboratory of Efficient Irrigation-Drainage andAgricultural Soil-Water Environment in Southern ChinaMinistry of Education (Nanjing latitude 31∘571015840N longitude118∘501015840E 144m above sea level) during the rice growingseason of 2015 (ie May to October) The experimental siteexperiences a subtropical humid climate with an annualmean temperature of 154∘C The mean annual precipitationat Nanjing City (located 20 km northeast of the experimentalsite) is 1047mm with mean annual evaporation of 900mm

The air temperature wind speed and direction relativehumidity total solar radiation and photosynthesis activeradiation were measured at the experimental site using anautomated weather station Precipitation was measured bya tipping bucket rain gauge All meteorological parameterswere stored in a data logger and downloaded weekly via acomputer The frost-free period lasts for 220 days per yearThe soil in the area is a typical permeable paddy soil formedon loess deposits with loamy clay A total of 25 fixed tanksplots were prepared (length times width times depth = 25m times 2m times2m) The irrigation system is an automatic irrigation systemcontrolled by the host electromagnetic valve The soil (0ndash30 cm) in tanks with pH of 697 contained 219 of soilorganic matter 091 gkg of total nitrogen 2765mgkg ofavailable nitrogen 032 gkg of total phosphorus (TP) and125mgkg of available phosphorus

22 Plant Material and Cultivated Practices Nangeng 9108 ahigh-yielding rice variety currently used in local productionwas grown in the paddy tanks Seedlings were raised in aseedbed on May 13 2015 and then transplanted on June 162015 at a hill spacing of 02m times 014m with three seedlingsper hill A week before transplanting the experimental plotswere dry-ploughed and harrowed The soil was soaked a daybefore transplanting and then flooded for about a week with a2-3 cm water layer to promote good crop establishment Thebasal fertilizer was the compound fertilizer (N P

2O5 K2O

15 15 15) and 900 kgha was applied on June 13 2015 Thetillering fertilizerwas urea (with a nitrogen content of 464)and 100 kgha was applied on June 28 2015 The paniclefertilizer was also urea (with a nitrogen content of 464)and 50 kgha was applied on August 18 2015 The weed wascontrolledmanually and pesticides were applied occasionally

23 Experimental Design Eight CID treatments weredesigned for the experiment (Table 1) According to thecharacteristics of rice growth stage we chose tillering stage(stage I) jointing and booting stage (stage II) heading andflowering stage (stage III) and milky stage (stage IV) for


Table 2 Mean TP NH4

+-N and NO3






NH4

+-N FFTD 620a 259a 482a 153a

FDTF 727b 331b 562b 193b

NO3


FDTF 314b 207b 263b 123b

TP FFTD 016a 010a 006a 003a

FDTF 025b 016b 096b 047b




4





3 Results


4


4


4


4


4


First NH4


4


4



4


4




change of NO3


3


3



NH

4

+-N

(mg

L)N

H4

+-N

(mg

L)

NH

4

+-N

(mg

L)N

H4

+-N

(mg

L)









0

2

4

6

8

10

12

0

2

4

6

8

10

12

0

1

2

3

4

0

2

4

6

8

10



Table 3 Mean TP NH4

+-N and NO3







NH4

+-N FFTD 517b 401c 124b 083c 234b 088d 092b 077c

FDTF 618a 383c 169a 107c 301a 160c 110a 061c

NO3


FDTF 243a 153c 110a 086b 178a 135b 057a 026b

TP FFTD 0088b 0056c 0055b 0038c 0046b 0036c 0032a 0035a

FDTF 0106a 0066c 0101a 0034c 0064a 0034c 0039a 0040a











NO

3

minus-N

(mg

L)

NO

3

minus-N

(mg

L)N

O3

minus-N

(mg

L)

NO

3

minus-N

(mg

L)

0

1

2

3

4

5

0

1

2

3

4

0

1

2

3

4

5

00

05

10

15

20




3


3


3


The NO3


3


3



3



3


3


3


3












TP (m

gL)

TP (m

gL)

TP (m

gL)

TP (m

gL)

00

01

02

03

04

00

01

02

03

000

005

010

015

020

000

005

010

015

020





4 Discussion



4

+-N and NO3


4

+-N and NO3


4

+-N and NO3


4

+-N and NO3




+-Nand NO

3


4


4


4

+-N andNO3




4

+-N andNO3


4

+-N and NO3


3




4


4

+-N than NO3


4





5 Conclusions


4

+-N and NO3


4


4

+-N NO3


4

+-N NO3


4

+-NNO3


4

+-N NO3


4

+-N NO3



Abbreviations




Competing Interests


Acknowledgments


References



























3and


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Table 2 Mean TP NH4

+-N and NO3






NH4

+-N FFTD 620a 259a 482a 153a

FDTF 727b 331b 562b 193b

NO3


FDTF 314b 207b 263b 123b

TP FFTD 016a 010a 006a 003a

FDTF 025b 016b 096b 047b




4





3 Results


4


4


4


4


4


First NH4


4


4



4


4




change of NO3


3


3



NH

4

+-N

(mg

L)N

H4

+-N

(mg

L)

NH

4

+-N

(mg

L)N

H4

+-N

(mg

L)









0

2

4

6

8

10

12

0

2

4

6

8

10

12

0

1

2

3

4

0

2

4

6

8

10



Table 3 Mean TP NH4

+-N and NO3







NH4

+-N FFTD 517b 401c 124b 083c 234b 088d 092b 077c

FDTF 618a 383c 169a 107c 301a 160c 110a 061c

NO3


FDTF 243a 153c 110a 086b 178a 135b 057a 026b

TP FFTD 0088b 0056c 0055b 0038c 0046b 0036c 0032a 0035a

FDTF 0106a 0066c 0101a 0034c 0064a 0034c 0039a 0040a











NO

3

minus-N

(mg

L)

NO

3

minus-N

(mg

L)N

O3

minus-N

(mg

L)

NO

3

minus-N

(mg

L)

0

1

2

3

4

5

0

1

2

3

4

0

1

2

3

4

5

00

05

10

15

20




3


3


3


The NO3


3


3



3



3


3


3


3












TP (m

gL)

TP (m

gL)

TP (m

gL)

TP (m

gL)

00

01

02

03

04

00

01

02

03

000

005

010

015

020

000

005

010

015

020





4 Discussion



4

+-N and NO3


4

+-N and NO3


4

+-N and NO3


4

+-N and NO3




+-Nand NO

3


4


4


4

+-N andNO3




4

+-N andNO3


4

+-N and NO3


3




4


4

+-N than NO3


4





5 Conclusions


4

+-N and NO3


4


4

+-N NO3


4

+-N NO3


4

+-NNO3


4

+-N NO3


4

+-N NO3



Abbreviations




Competing Interests


Acknowledgments


References



























3and


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


NH

4

+-N

(mg

L)N

H4

+-N

(mg

L)

NH

4

+-N

(mg

L)N

H4

+-N

(mg

L)









0

2

4

6

8

10

12

0

2

4

6

8

10

12

0

1

2

3

4

0

2

4

6

8

10



Table 3 Mean TP NH4

+-N and NO3







NH4

+-N FFTD 517b 401c 124b 083c 234b 088d 092b 077c

FDTF 618a 383c 169a 107c 301a 160c 110a 061c

NO3


FDTF 243a 153c 110a 086b 178a 135b 057a 026b

TP FFTD 0088b 0056c 0055b 0038c 0046b 0036c 0032a 0035a

FDTF 0106a 0066c 0101a 0034c 0064a 0034c 0039a 0040a











NO

3

minus-N

(mg

L)

NO

3

minus-N

(mg

L)N

O3

minus-N

(mg

L)

NO

3

minus-N

(mg

L)

0

1

2

3

4

5

0

1

2

3

4

0

1

2

3

4

5

00

05

10

15

20




3


3


3


The NO3


3


3



3



3


3


3


3












TP (m

gL)

TP (m

gL)

TP (m

gL)

TP (m

gL)

00

01

02

03

04

00

01

02

03

000

005

010

015

020

000

005

010

015

020





4 Discussion



4

+-N and NO3


4

+-N and NO3


4

+-N and NO3


4

+-N and NO3




+-Nand NO

3


4


4


4

+-N andNO3




4

+-N andNO3


4

+-N and NO3


3




4


4

+-N than NO3


4





5 Conclusions


4

+-N and NO3


4


4

+-N NO3


4

+-N NO3


4

+-NNO3


4

+-N NO3


4

+-N NO3



Abbreviations




Competing Interests


Acknowledgments


References



























3and


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










NO

3

minus-N

(mg

L)

NO

3

minus-N

(mg

L)N

O3

minus-N

(mg

L)

NO

3

minus-N

(mg

L)

0

1

2

3

4

5

0

1

2

3

4

0

1

2

3

4

5

00

05

10

15

20




3


3


3


The NO3


3


3



3



3


3


3


3












TP (m

gL)

TP (m

gL)

TP (m

gL)

TP (m

gL)

00

01

02

03

04

00

01

02

03

000

005

010

015

020

000

005

010

015

020





4 Discussion



4

+-N and NO3


4

+-N and NO3


4

+-N and NO3


4

+-N and NO3




+-Nand NO

3


4


4


4

+-N andNO3




4

+-N andNO3


4

+-N and NO3


3




4


4

+-N than NO3


4





5 Conclusions


4

+-N and NO3


4


4

+-N NO3


4

+-N NO3


4

+-NNO3


4

+-N NO3


4

+-N NO3



Abbreviations




Competing Interests


Acknowledgments


References



























3and


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










TP (m

gL)

TP (m

gL)

TP (m

gL)

TP (m

gL)

00

01

02

03

04

00

01

02

03

000

005

010

015

020

000

005

010

015

020





4 Discussion



4

+-N and NO3


4

+-N and NO3


4

+-N and NO3


4

+-N and NO3




+-Nand NO

3


4


4


4

+-N andNO3




4

+-N andNO3


4

+-N and NO3


3




4


4

+-N than NO3


4





5 Conclusions


4

+-N and NO3


4


4

+-N NO3


4

+-N NO3


4

+-NNO3


4

+-N NO3


4

+-N NO3



Abbreviations




Competing Interests


Acknowledgments


References



























3and


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



+-Nand NO

3


4


4


4

+-N andNO3




4

+-N andNO3


4

+-N and NO3


3




4


4

+-N than NO3


4





5 Conclusions


4

+-N and NO3


4


4

+-N NO3


4

+-N NO3


4

+-NNO3


4

+-N NO3


4

+-N NO3



Abbreviations




Competing Interests


Acknowledgments


References



























3and


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Abbreviations




Competing Interests


Acknowledgments


References



























3and


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of





3and


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

Documents

Research Article Effects of Controlled Irrigation and …downloads.hindawi.com/journals/jchem/2016/2576015.pdfResearch Article Effects of Controlled Irrigation and Drainage on Nitrogen