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Clayey Soil degradation is detected via a recent method (introduced by Monier, 1994, in France) for the calculation of a Structure Index using three fluids
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PresentationPresentationbyby
Prof. Dr. Mohamed Fahmy HusseinProf. Dr. Mohamed Fahmy Hussein
The 4The 4thth Conference on Recent Technologies in Agriculture Conference on Recent Technologies in Agriculture
Challenges of Agricultural Modernization Challenges of Agricultural Modernization
Faculty of Agriculture,Faculty of Agriculture,
Cairo UniversityCairo University
Tuesday, 4 November, 2009Tuesday, 4 November, 2009
Mohamed Fahmy Hussein*, , Salah El-AMIR* and Essam RAMADAN**
Application of Structure-Index Technique Application of Structure-Index Technique to Detect Soil Degradation to Detect Soil Degradation
فحص تقنية دليل بناء لرصد تدهور فحص تقنية دليل بناء لرصد تدهور األراضىاألراضى
* Cairo Univ., Fac. of Agric., Soil & Water Dept., Egypt** Ministry of Agriculture, Cairo, Egypt
Location Map, Nile-Delta Apex, Bagour, Monofyah, EgyptLocation Map, Nile-Delta Apex, Bagour, Monofyah, Egypt
Some Experimentral DataSome Experimentral Data
ESP ECaP EMgP EKP CEC Clay% K, cm/hr S.I.MAX 32.21 64.78 40.32 8.33 48.85 54.78 1.470 11.52MIN 3.57 39.50 18.89 0.92 29.11 34.99 0.002 1.68ratio MAX/MIN 9.03 1.64 2.14 9.08 1.68 1.57 735.00 6.86
ESP = Exchangeable Sodium%ECaP = Exchangeable Calcium%,EMgP = Exchangeable Magnesium%EKP = Exchangeable Potassium%CEC = Cation Exchange Capacity, meq/100 gram soilK = Hydraulic Conductivity (Saturated)SI = Structure Index
Structure index = highest (silt+clay) ratio in 3 treatments
mean (stable aggregates+coarse sand) ratio in 3 treatments - (0.9 * C.S. ratio)
Prelude – page-1Prelude – page-1
1) Soil degradation is an environmental problem world-wide.
2) Under irrigated-agriculture, soil degradation is controlled by soil water-regime.
3) A principal change in soil-water regime started in the Nile alluvial-soils of Egypt about 150 years ago, through the replacement of the basin-irrigation by perennial-irrigation.
4) That change has resulted in humid soils with shallow water-table, almost everywhere in the Nile-delta and valley.
5) The over-recharge of the semi-confined (lower) and the unconfined (upper) aquifers was estimated by tritium data-series for GW, and construction of a tritium input-function for Nile water affected by thermo-nuclear bombs of the 1960’s.
Prelude – page-2Prelude – page-2
6) Soil structure is extremely important soil property, expressing the stresses under which the irrigated-soils are cultivated . Unstable aggregates would be formed in clayey-soils under hydraulic and chemical problems (salinity/sodicity development) due to irrigation without field-drainage.
7) Elegant technique has recently been introduced for the evaluation of soil-structure status through estimation of the stable aggregates% under three treatments (1- Alcohol then Water, 2- Benzene then Water, and 3- Water alone.)
8) The Benzene will over-destruct the aggregates, while Alcohol protects the aggregates, and the Water alone treatment is somewhere in-between.
SynopsisSynopsis11
• Fourteen profiles were sampled in the Nile-Delta Apex, Bagour Monofya Govr. for estimation of Structure-Index.
• The samples were also analyzed for salinity level, the exchangeable cations, and the cation-exchange capacity.
• The obtained results are discussed in this work and compared to older results for saline soils at the north of the Nile Delta.
• The increase of the Structure-Index value indicates significant soil-structure degradation (more unstable aggregates.)
• The rise of the piezometric level of the semi-confined aquifer, hydraulically-connected to the unconfined aquifer, during the last 120 years is about 10m (as estimated from tritium model.)
SynopsisSynopsis22
• The chemical change of soil-water chemistry and the rise of the water-table is believed to be behind the observed soil-structure degradation in the study area.
• The value of the Structure-Index, SI, of the studied samples was in the range of about 2-12.
• The linear relationships obtained between the Structure-Index with salinity (EC) and sodicity (ESP) has a high scatter due the contribution of other factors.
• The Structure-Index method seems more sensitive than the classic Structure-Factor method
Tritium Prediction Model for Nile WaterTritium Prediction Model for Nile Water
(425) an excluded value
1
10
100
1000
1950 1960 1970 1980 1990 2000
TU
Years
Reconstructed Tritium Content in Nile water
Fahmy & R.Michel
Old model
measured
precipitation
Stable Aggregates and the Structure-Index ValuesStable Aggregates and the Structure-Index Values
Profile 3
Profile 4
Profile 5
Profile 6
Profile 7
Profile 8
Profile 9
Profile 10
Profile 11
Profile 12
Profile 13
Profile 14
Profile 1
Profile 2
123456789
10111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970
0 10 20 30 40 50 60 70
Ser
ial
nu
mb
er o
f all
sam
ple
s
Stable aggregates, %
(the data-points representing the 5 surfac-layer samplesare shown by triangle, orthogonal and squar symbols)
Alchol
Water
Benzine
Profile 1
Profile 2
Profile 3
Profile 4
Profile 5
Profile 6
Profile 7
Profile 8
Profile 9
Profile 10
Profile 11
Profile 12
Profile 13
Profile 14
123456789
10111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970
0 1 2 3 4 5 6 7 8 9 10 11 12
Ser
ial
nu
mb
er o
f al
l sa
mp
les
Structure index
(low = stable structure, high = poor stucture)
index
lowest
highest
mean
Structure-Index Values in Fourteen ProfilesStructure-Index Values in Fourteen Profiles
Structure-Factor Values in Five ProfilesStructure-Factor Values in Five Profiles
Structure-Index Structure-Index andand Structure-Factor Structure-Factor versusversus ESP ESP
y = 0.124x + 2.696R² = 0.243
0
2
4
6
8
10
12
0 5 10 15 20 25 30 35
Structure index
ESP
y = 0.167x + 0.044R² = 0.401
0
5
10
15
20
0 10 20 30 40 50
(1/SF ) *100
ESP
SI SI versusversus EC, and ln ESP EC, and ln ESP versusversus ln EC ln EC
y = 0.295x + 3.250R² = 0.233
0
2
4
6
8
10
12
0 2 4 6 8 10 12 14 16
Structure index
EC, dS.m-1
y = 0.482x + 1.921R² = 0.579
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
-0.5 0.0 0.5 1.0 1.5 2.0
ln ESP
ln EC, dS.m-1
this work
unpublished data
linear fit
Exchangeable Cations Exchangeable Cations versusversus ESP ESP
0102030405060708090
100
0 20 40 60 80 100
EXP
ESP
X = Ca+Mg
regr. (ECa+MgP)-ESP
X = Ca
regr. ECaP-ESP
X = Mg
regr. EMgP-ESP
X = K
regr. EKP-ESP
Log-transformation of KLog-transformation of Ksatsat, ESP, and Structure-Index, ESP, and Structure-Index
-3.0-2.0-1.00.01.0
0.5 1.0 1.5 2.0
logKsat
log ESP
this work unpublished data all Linear (all)
-3.0
-2.0
-1.0
0.0
1.0
0.0 0.5 1.0
logKsat
log structure index
ملخصملخصأوضحت البيانات وجود تدهور ملحوظ بالبناء األرضى فى نحو نصف –
عدد القطاعات محل الدراسة، حتى بالطبقات العليا ال السفلى يمتاز بسهولته عند structure-index, SI )دليل البناء(فقط . وظهر أن
م=عامل البناء ( مقارنة عدد كبير من العينات ويعطى داللة أوضح منstructure-factor, SF( التقليدى، كما يمكننا ربطه بغيره من المتغيرات -
وهو أمر هام -كتملح وصودية التربة وتوصيلها الهيدروليكى المشبع لما لتلك المتغيرات من عالقة بتدهور بناء التربة بفعل التغيرات
.المائية( ESP( والصودية )EC( بتملح الترية )SIالحظنا ارتباط قيم دليل البناء )–
( عالية SI-ESP( و)SI-ECخطياP، وإن كانت نقاط البيانات فى العالقتبن )التبعثر خصوصاP بالمراحل المتأخرة من تزايد التملح والصودية . وكان
(، مما يعنى أن تدهور SI-ESP( أكبر من ميل الخط )SI-ECميل الخط )التربة يظهر بمجرد بدء تملحها وقبل تحولها لتربة صودية، والحظنا أن
أدى النخفاض رقم الدليل )وهو تحسن وهمى dS/m16تزايد التملح عن سببه تزايد التماسك بفعل التملح المفرط( مما جعل الخط المستقيم
، 12 و 2يلتوى ألسفل . تراوحت قيمة رقم الدليل بين حوالى (، ESP( والصودية )ECوظهرت عالقات خطية موجبة بين التملح )
وانخفض التوصيل الهيدروليكى المشبع بنزايد رقم الدليل . ولحأنا ( ESPلتحويل قيم التوصيل الهيدروليكى ودليل البناء والصودية )
لوغاريتمياP إليضاح االنحدارات الخطية .الحظنا نفع الدليل كمؤشر على حالة بناء التربة، ونعتقد أنه يفيد –
مشروعات صيانة األراضى ثقيلة-القوام، خاصة المتأثرة باألمالح، ألن .التعرف على مدى التدهور هو أولى خطوات تحسين األراضى
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