Master Seminar on Effect Of Salinity and Alkalinity on Physico-chemical Properties of soil Presented by Hemant Kumar M.sc. (previous) Deptt. of Soil Science & Agril. Chemistry College of Agriculture Raipur

Soil Salinity Soils in arid regions commonly have “excessive” concentrations of soluble salts because: Lack of leaching to remove salts Poor Drainage Salts added in irrigation water Evaporation more than rainfall

Soluble Salts Ca2+ Mg2+ Na+ K+ Cl- SO42- HCO3- /CO32- NO3- Common soluble cations found in saline soils: Ca2+ Mg2+ Na+ K+ Common soluble anions found in saline soils: Cl- SO42- HCO3- /CO32- NO3-

Soil Alkalinity Soils are low in soluble salts but relatively high in exchangeable sodium. Mainly caused by the accumulation of CaCO3 and NaCO3 in arid regions or some irrigated land. Commonly, soil alkalinity is found in areas with limited soil weathering.

Categories of Salt Affected soil Saline Soil Sodic /Alkaline soil Saline-Alkaline Soil

Physico-chemical characteristics of salt affected soil Saline soil a) Chemical Characteristics i) EC of the Soil is more than 4 dSm-1(>4) ii) pH of the soil is less than 8.5 (< 8.5) iii) ESP is less than 15 (<15) b) Physical Characteristics i) Soil Structure- Usually good ii) Infiltration rate- High iii) Soil Aeration- Good c) Colour- Usually white

2. Sodic Soil (Black-alkali soil) a) Chemical Characteristics i) EC of the Soil is less than 4 dSm-1 (<4) ii) pH of the soil is more than 8.5 (> 8.5) iii) ESP is higher than 15 (>15) b) Physical Characteristics i) Soil Structure - very poor (soil is in highly dispersed condition ii) Infiltration rate - very poor iii) Soil Aeration - very poor c) Colour- Usually black (Due to O.M dissolves at high pH)

a) Chemical Characteristics 3. Saline-Sodic Soil a) Chemical Characteristics i) EC of soil is higher than 4 dSm-1(>4) ii) pH of the soil is lower than 8.5 (< 8.5) iii) ESP is higher than 15 (>15) b) Physical Characteristics i) Soil Structure - good ii) Infiltration rate - good iii) Soil Aeration - good c) Colour- Usually white

Source: CSSRI, Karnal, Haryana, 2012. Salt Affected Area in India Total Salt affected Area 6.73 million ha Sodic soils 3.77 million ha Saline soils 2.96 million ha Source: CSSRI, Karnal, Haryana, 2012. (http://www.cssri.org/index)

Source: CSSRI, 2012.(http://www.cssri.org/index) S.No. State Saline Soil (ha) Sodic Soil (ha) Total 1 Andhra Pradesh 77598 196609 274207 2 A & N islands 77000 3 Bihar 47301 105852 lowest 153152 4 Gujarat 1680570 highest 541430 2222000 highest 5 Haryana 4915 183399 232556 6 Karnataka 1893 lowest 148136 150029 7 Kerala 20000 20000 lowest 8 Maharashtra 184089 422670 606759 9 Madhya Pradesh 139720 10 Orissa 147138 11 Punjab 151717 12 Rajasthan 195571 179371 374942 13 Tamil Nadu 13231 354784 368015 14 Uttar Pradesh 21989 1346971 highest 1368960 15 West Bengal 441272 2956809 3770659 6727468 Source: CSSRI, 2012.(http://www.cssri.org/index)

Source: CSSRI, 2012.(http://www.cssri.org/index)

Calcium (Ca) +Magnesium (Mg) Saline Stress: Calcium (Ca) +Magnesium (Mg) •Moderately high pH •Drought like conditions •Poor germination and growth •Low nutrient availability •Problem – excess soluble salts, reduce water/nutrient availability, plasmolysis, and osmotic forces

Sodic Stress: Sodium (Na) •Dispersion •High pH >8.4 •No water movement •Erosion •Root limitation •Problem is high pH due to excess sodium, soluble salts are low, dispersion, reduced air and water movement and reduced nutrient availability

Effect of alkalinity and salinity on soil In alkanine condition Soil clay particles can be unattached to one another (dispersed). In saline condition soil particles clumped together (flocculated) in aggregates. Dispersed Particles Flocculated Particles

Dispersed clays plug soil pores and impede water infiltration and soil drainage. In A horizons, where organic matter levels are high and there is a lot of biological activity (earthworms, ants, termites, microbes, etc.) particles tend to be arranged in small, round aggregates or granules. This type of structure is common in the surface horizons of many forest and prairie soils

In flocculated condition water moves mostly in large pores between aggregates. In A horizons, where organic matter levels are high and there is a lot of biological activity (earthworms, ants, termites, microbes, etc.) particles tend to be arranged in small, round aggregates or granules. This type of structure is common in the surface horizons of many forest and prairie soils

Problem in saline soil In saline or Flocculated states of soil the concentration of soluble salts is very high in soil solution. As a result the osmotic pressure of soil solution is also very high. The plant growth and nutrient availability are affected due to osmosis.

Aggregate stability (dispersion and flocculation) depends on the balance (SAR) between (Ca2+ and Mg2+) and Na+ as well as the amount of soluble salts (EC) in the soil. Na+ Ca2+ and Mg2+ + + + ++ ++ ++ + + + + ++ ++ ++ ++ SAR EC Lower EC Higher EC Flocculated soil Dispersed soil

Soil particles will flocculate if concentrations of (Ca2+ + Mg2+) are increased relative to the concentration of Na+ (SAR) is decreased Na+ + Ca2+ and Mg2+ SAR ++ EC Dispersed soil Flocculated soil

Soil particles will flocculate if the amount of soluble salts in the soil is increased (increased EC), even if there is a lot of sodium. Na+ SAR EC Ca2+ and Mg2+ Lower EC Higher EC + ++ Flocculated soil Dispersed soil

Soil particles will disperse if concentrations of (Ca2+ + Mg2+) are decreased relative to the concentration of Na+ (SAR) is increased). Ca2+ and Mg2+ ++ ++ ++ Na+ SAR + + EC + + + Flocculated soil Dispersed soil

Soil particles may disperse if the amount of soluble salts in the soil is decreased (i.e. if EC is decreased). Ca2+ and Mg2+ ++ ++ ++ Na+ SAR EC + + + Lower EC Higher EC Flocculated soil Dispersed soil

Management of Saline Soil Physical Measures Leaching Scraping Flushing Mulching Deep Tillage 2. Chemical Measures: Saline soils cannot be reclaimed by any chemical amendment, conditioner or fertilize

Leaching This is most effective procedure for removing salts from the root zone of soils Scraping: Removing the salts that have accumulated on the soil surface by mechanical means Flushing Washing away the surface accumulated salts by flushing water over the surface is sometimes used to desalinize soils having surface salt crusts .

Mulching Mulching with crop residue, such as straw, reduces evaporation from the soil surface which in turn reduces the upward movement of salts. Deep Tillage Deep tillage would mix the salts present in the surface zone into a much larger volume of soil and hence reduce its concentration and impact. Many soils have an impervious hard pan which hinders in the salt leaching process.

Sugar beet, barley, cotton, date palm, asparagus Crop Rotation : These soils should not be kept fallow but cultivation should be continuously done according to crop rotation. Growing of Salt Bearing crops: Highly tolerant crops Sugar beet, barley, cotton, date palm, asparagus Moderately tolerant crops Rye, sorghum, safflower

Conservation farming practices to control soil salinity Reducing summer fallow Using conservation tillage Adding organic matter to the soil Planting salt-tolerant crops (eg., rapeseed and cabbage)

Management of Sodic soil: Bulky organic manure, green manure, crop residues and other biological materials which produce week organic acids help in creating temporarily in acidic condition and help in reclamation Leaching with good quality water (low SAR) must follow the application of the reclaiming materials A good crop rotation is an excellent insurance agt. Sodicity problem ; rice-dhaincha; Dhaincha-rice-berseem is good Frequent irrigation with small quantities of water is the successful irrigation manangement practices Sometimes, permeabilty of soil can increases by deep ploughing

Amendments Sodic soils are treated by soluble source of calcium to replacing adsorbed sodium on clay surfaces. Acid-forming or acidic amendments include sulfuric acid, elemental sulfur Gypsum (CaSO4.2H2O) Iron Pyrites (FeS2) Iron Sulphate (FeSO4) Lime Sulphure (CaS5) Sulphur Gypsum should be mixed up to 10 or 15 cm. depth. Calcium ion found in gypsum displaces exchangeable sodium ion

Apply gypsum (the amount of gypsum needed can be determined by a soil test). to Replacing sodium with calcium Ca2+ SO42- Ca++ Ca++ - - - - - - - - - Ca++ Ca++ Na+ Na+ Na+ - Here is a schematic representation of sodic soil reclamation. - - - Na+ - - - - - Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+

Gypsum Application

Soil Amendments Sulfuric Acid (H2SO4) sulfuric acid is an effective amendment for correcting or preventing sodium problems: CaCO3 + H2SO4 Ca2+ + SO42- + H2O + CO2 Can be applied to soil or water-run Rates are commonly 1-3 tons/acre

CONCLUSION Soil salinization significantly limits crop production and consequently has negative effects on Food security. And damaging in both socioeconomic and environmental terms. Prevention and reclamation of salt-affected soils require an integrated management approach, Including consideration of socioeconomic aspects, monitoring & maintenance of irrigation schemes and reuse or safe disposal of drainage water.

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