Presentation on Salt-Affected soils and Acidic soils

The presentation is about soil affected soils and acid soils

1. PROBLEMATIC SOILS (SALT-AFFECTED SOILS AND ACIDIC SOILS) Name – Shubhashree Sahu ID – 21401 Subject – Forest Soil Management

2. SALT AFFECTED SOILS The higher concentration of soluble salts in soil, which affects crop growth and yield of most of the crops. Such soils are considered salt affected. In 1954, The US Salinity Laboratory grouped salt affected soils into:- Saline soil Alkali soil Saline-Alkali

3. Salt Affected Soil Occur when rainfall is not sufficient for adequate leaching of salts Common in arid condition Can ruin soils for agriculture Common salt ions :- Chlorides and sulphates of Na + , Ca 2+ ,Mg 2+

4. Classification EC ( dS / Mol ) pH ESP Saline Soil > 4 < 8.5 < 15 Alkali Soil < 4 > 8.5 > 15 Saline soil/ Solanchak Alkali Soil/ Sodic/ Solontez

5. Salt affected soils in India The salt affected soils account for 6.727 Mha equivalent to 2.1% of the geographical area of the country. Out of total 6.727 Mha of salt-affected soils, 2.956 Mha are saline 3.771 Mha are sodic

6. SALINE SOIL – Characterization Chemical Characteristics i ) EC of saturated soil extract is more than 4 dSm -1 ii) pH of the soil is less than 8.5 iii) ESP is less than 15 b) Physical Characteristics i ) Soil structure – Usually good ii) Infiltration rate – High iii) Soil aeration – Good iv) Colour – Usually white

7. SALINE SOIL – “White Alkali ” soils Concentration of neutral salts ( Cl - , SO 4 2- ) is higher than alkali salts (HCO 3 - ,CO 3 2- ) Characterized by saline efflorescence, white encrustation of salts at the surface. Salts raise the osmotic potential of the soil solution and thus reduces available soil water. Plants have to use more energy to get the water they need.

8. Saline Soil – Formation The process by which saline soil is formed is called Salinization. Saline soils occur mostly in arid or semi-arid regions. In arid regions – Due to less rainfall and high evaporation rate the soluble salts tends to move to surface in dissolved state and then accumulates on soil surface.

9. Effects of saline soil on plants Stunted growth Wilting Blueish-green colour Necrosis of leaf tips Drought stress symptoms Specific toxicity Plant species vary in salt tolerance Salt injury – High salt levels when high rates of fertilizers or manures applied.

10. Alkali Soil – Characterization Chemical Characteristics i ) EC of the saturation soil extract is less than 4dSm-1. ii) pH of the soil is more than 8.5 iii) ESP is higher than 15 Physical Characteristics i ) Soil Structure – Very poor ( Soil in dispersed/ deflocculated state) ii) Infiltration rate – Very low iii) Soil aeration – Very poor iv) Colour – Usually black

11. Alkali Soil – “Black Alkali Soils” Concentration of alkali salts(HCO3-, CO32- ) is higher than neutral salts(Cl-,SO42-). Major problem is the effect of sodium on flocculation and aggregation of soil particles. Sodium causes soil particles to disperse No aggregation of soil particles Individual soil particles clog soil pores Poor soil physical properties

12. Effect of Alkali soil on plants

13. Management of Salt affected soil

14. Physical Measures Leaching When soil elements after dissolving with water go down from upper parts to the lower level, it is called leaching. In this method saline elements of the soil are transferred to lower levels after dissolving with water. This water, along with the supply of water to crops, takes away salts after dissolving them. That is why more water is required in this method.

15. 2.Scratching Many times salts are collected in large quantity and it looks like heap. Then it has to be scratched out from the field to reduce salinity of the soil. This method is not practicable on large scale. 3.Drainage With drainage of additional water, concentration of salts does not take place. Drains may be constructed in the field so that excess water keeps on discharging

16. Chemical Measures Reclamation of alkali/ sodic soils requires neutralization of alkalinity and replacement of the most of the sodium ions from the soil – exchange complex by the more favourable c alcium ions. Solvent calcium Salt : Gypsum and Phospho Gypsum Little Soluble Calcium Salt : Lime Stone Acid and Acid Producing : Sulphur, Acid of Sulphur, Pyrites Gypsum is the most commonly used chemical amendment.

17. Soil management measures Preparation of the Field Fields should be kept leveled. Water distribution during irrigation is balanced in leveled field which prevents concentration of salts . Preparation of Basin and Sowing Sowing of crop should be done on the slope following furrow and basin method. In basin irrigation, the salt collects near the basin, the adverse effect of which is visible on plants. Special attention should be given to irrigation. Reduction in Evaporation Growing of Crops bearing Salts and Alkali condition.

18. ACIDIC SOILS Soil having pH < 7.0 is called acidic soil. They contains excessive amount of dissolved ions of Al, Fe, Mn and Cu. Acidic soils are deficient in Ca and Mg. Acid sulphate soils are rich in pyrite which on oxidation forms sulphuric acid. These soils have pH < 3.5. Crops on these soils suffer mainly due to Al, Fe and other micronutrients( except Mo) toxicity.

19. Reclamation of Acidic soils Liming Application of lime is recommended for reclaiming acidic soils. Burnt lime – CaO , Hydrated lime – Ca(OH) 2 , Basic slag – CaSiO 2 , Limestone – CaCO 3 , Dolomite – CaCO 3 .MgCO 3 . It improves the base saturation, inactivates iron, manganese and aluminium in soil solutions. Lime should be applied once in five years depending on soil pH.

20. THANK YOU