Problem Soils & Water Quality Management - Issues Dr. M. Dhakshinamoorthy Professor of Soil Science & Agricultural Chemistry

Introduction and scope Geographical area 329 m.ha Problematic : more than 50 %(175 m.ha) Wind and water erosion Water logging Acidity Alkalinity Salinity % degraded every year Water erosion-56% Wind erosion-28% Chemical degradation-12% Physical degradation-4%

Classification of Salt affected soils Classific ation pHEC (dSm -1 ) ESPDominantProblemSolution Cations Anions Saline<8.2>4.0<15Ca, MgCl,SO 4 Less HCO 3 No CO 3 High O.P.Drainage apply sand to clayey soil Org. manure chessel plough Saline alkali <8.5>4.0>15Ca,Mg, Na CO 3 & HCO 3 Poor drainage Gypsum and drain Alkali (sodic) >8.5<4.00>15NaCO 3 & HCO 3 Poor drainage and aeration suface and subsurface hardening poor fertility Gypsum and drain

S.NoVisual characters NormalSalineAlkali 1.Climatic zone Every zoneArid & semi arid zone Semi arid and sub humid zone 2.Rain/ irrigation water Absorbed quickly Stagnates for long time 3.Standing water quality (soil surface) Clear, No salt efflorescence Clear, white, salt efflorescence Ash colour, dark brown, salt efflorescence 4.Ground water quality Good or poor both Generally poor 5.CrustMay / may not be there;, usually thin not very hard May / may not be there; usually thin ;or not very hard Usually present; thick and hard Visual Characters in Saline, alkali and normal soils

Sodic soil Reclamation Basic principle Replace Na + by H +, Ca 2+, Mg 2+ Gypsum+Organic matter+ Drainage

Genesis of problem soils for command areas Excessive application of water Excessive application of water Seepage of canal water Seepage of canal water Irrigation with salt water Irrigation with salt water Poor drainage capacity of soil Poor drainage capacity of soil Erratic use of irrigation water Erratic use of irrigation water Concave relief Concave relief Intrusion of sea water Intrusion of sea water Digging of deep borewells in coastal areas Digging of deep borewells in coastal areas Slopy lands Slopy lands Use of drainage water Use of drainage water High salt content in soil High salt content in soil

Problem soils other than salt affected soils Hard pan soils – clay pan, CaCO 3 pan, silica pan. Calcareous soils Salt marshy soil – sea water intrusion, pH 3.0 acid sulphate soils. Water logged soils: a.Poorly drained and b.imperfectly drained

Acid soils Genesis and occurrence The leaching of bases is the pre requisite for the formation of acid soils. The major process involved in the formation of acid soils is laterization and podzolisation. Acid soils are mostly peaty and marshy soils. Very low pH is an indication of the presence of Sulphuric acid as the ‘cat clays’ ( Kari or Pokkali soils) which occurs mostly in kerala.

Characteristics Low pH high proportion of exchangeable H + and Al 3+ Kaolinite and illitic low CEC’s high base unsaturation aluminium, managanese and Iron - toxic conc. deficiency of Ca 2+ and Mg 2+ nutrient imbalance microbial imbalances low in available Phosphorus high Phosphate fixation

Management growing crops suitable for a particular soil pH. ameliorating the soils - amendments CaCO 3 + H 2 O + CO 2 Ca (HCO 3 ) 2 Ca (HCO 3 ) 2 Ca HCO 3 - H - soil + Ca 2+ Ca – soil + 2H + H + + HCO3H 2 CO 3 H 2 O + CO 2

Managing poor quality water.

Major soluble constituents of irrigation water are - Cations - Ca 2+ Ca 2+ Mg 2+ Mg 2+ Na + Na + K + K + Anions – SO 4 2- SO 4 2- HCO 3 - HCO 3 - CO 3 2- CO 3 2- Other elements viz., Li,Si,Cu,I,Ni,Co,F,B,Ba,Ar, Sb,Bi,Cr,Mn,Pb,Mo,Se,PO 4 and other org. materials.

Factors affecting soluble salts in ground water 1. Physico chemical char. of the rocks with which water is coming into contact. 2. Geological history of the area. 3. Climate of the area including during and frequency of rain, humidity, intensity and duration of sunshine, wind velocity etc., 4. Micro organism present in the area. 5. Chemical., physical and minerological charactistics of the soil 6. Topography of the sea. 7. Vegetative cover. 8. Human interference.

STANDARDS OF GROUND WATER WITH RESPECT TO SOILS SL. NO. NATURE OF SOIL EC dS/m. for crops semitolerant tolerant 1234 Deep black soil and alluvial soil Clay>30% Clay>30% (fair to moderate drainage) (fair to moderate drainage) Heavy textured soil Clay 20-30% Clay 20-30% (good drainage) (good drainage) Medium textured soils Clay 10-20% Clay 10-20% ( good drainage) ( good drainage) Light textured soils Clay <10% Clay <10% (excellent drainage) (excellent drainage)

Factors affecting the suitability of ground water for irrigation 1. Chemical composition of water 2. Soil characteristics 3. Plant characteristics 4. Climate 5. Management aspects

Chemical composition of water Total soluble salts Total soluble salts pH pH CO 3 CO 3 HCO 3 HCO 3 Cl Cl SO4 SO4 Ca Ca Mg Mg Na Na B SAR SAR ESP ESP

Soil characteristics Structure Structure Texture Texture Organic matter Organic matter Nature of clay minerals Nature of clay minerals Topography Topography

 Plant Characteristics: Varies with the different stages of crop growth. Varies with the different stages of crop growth. Germinating and seedling stages are more sensitive to salinity. Germinating and seedling stages are more sensitive to salinity.  Climatic Characteristics: Crops tolerate to salinity more during winter than summer. Crops tolerate to salinity more during winter than summer. Rainfall leaches salts from root zone. Rainfall leaches salts from root zone. Temperature. Temperature.

Management aspects Application of FYM etc., improves permeability and structure. Application of FYM etc., improves permeability and structure. Keeping gypsum gunny bags in the channel increases calcium content. Keeping gypsum gunny bags in the channel increases calcium content. Conjunctive use of poor quality water with good quality water. Conjunctive use of poor quality water with good quality water. Incorporating green manure crops. Incorporating green manure crops. Irrigating small quantity of water at frequent intervals. Irrigating small quantity of water at frequent intervals. Application of increased fertilizer dose N-as AmSO 4,P- as Super PO 4 and DAP. Application of increased fertilizer dose N-as AmSO 4,P- as Super PO 4 and DAP. Improve drainage. Improve drainage. Raising salt tolerant crops – cotton, ragi, sugar beet, paddy, ground nut, sorghum, maize, sunflower, chillies, tobacco, onion, tomato, garden beans, amaranthus and lucerne. Raising salt tolerant crops – cotton, ragi, sugar beet, paddy, ground nut, sorghum, maize, sunflower, chillies, tobacco, onion, tomato, garden beans, amaranthus and lucerne.

Classification of irrigation water quality Quality of water water EC dS/m. pH Na (%) Cl (me/l) SAR ExcellentGoodFairPoor Very poor Unsuitabl e > > > > >15

Special considerations while using poor quality of water Saline water having SAR > 20 and Saline water having SAR > 20 and Mg/Ca > 3 leads to water stagnation - Apply gypsum. Mg/Ca > 3 leads to water stagnation - Apply gypsum. Leave the field fallow during rainy season. Leave the field fallow during rainy season. Cl/SO 4 > 2.0 addition of P. Cl/SO 4 > 2.0 addition of P. Use canal water in conjunction with saline water during early crop stage. Use canal water in conjunction with saline water during early crop stage. Addition of 20% extra seed rate. Addition of 20% extra seed rate. When EC iw < EC e – irrigate before on set of monsoon When EC iw < EC e – irrigate before on set of monsoon

Special considerations while using poor quality of water Addition of organic manures enhances crop yields. Addition of organic manures enhances crop yields. Accumulation of B,NO 3,Fe,Si,Se,F and heavy metals beyond critical limits – toxic. Accumulation of B,NO 3,Fe,Si,Se,F and heavy metals beyond critical limits – toxic. Soils with shallow water table (1.5m)and hard sub soil apply next lower EC iw / canal water. Soils with shallow water table (1.5m)and hard sub soil apply next lower EC iw / canal water. Irrigation with alkali water apply gypsum every year / season. Irrigation with alkali water apply gypsum every year / season. Adopt pressure irrigation for saline / alkali waters. Adopt pressure irrigation for saline / alkali waters.

Salt tolerance of crops TolerantSemi TolerantSensitive Field crops: Barley, sugar beet, cotton, sugarcane Rice, sorghum, maize, red gram. Field beans, grams, peas. Vegetables: Turnip, beet root. Tomato, cabbage, cauliflower, potato, carrot, onion. Green beans Fruits: Date palm, coconut. Grapes, guava, mango, apple -