Reclamation of alkaline (IGKV RAIPUR C.G)

Reclamation of alkaline (IGKV RAIPUR C.G)

1. RECLAMATION OF ALKALINE SOIL INDIRA GANDHI KRISHI VISHWAVIDYALAYA RAIPUR (C.G)

2. RECLAMATION OF ALKALINE SOIL ALKALINE SOIL – Alkali soils are formed due to concentration of exchangeable sodium and high Ph. because of high alkalinity resulting from sodium carbonate the surface soil is discolored to black, hence the term black is used . REASON FOR ALKALINITY - The excessive irrigation of uplands containing Na salts results in the accumulation of salts in the valleys. In arid and semi arid areas salt formed during weathering are not fully leached. Irrigation soils with poor drainage.

3. RECLAMATION OF SOIL METHODS- There are three general ways by which saline and alkali soils can be ameliorated in order to avoid injurious effect to plants . ERADICATION - The most common methods generally used to free the excess salts of saline soils are- 1. Under Drainage 2. Leaching Or Flushing A combination of the two ,flooding after tile drains is the most effective .leaching method is very much effective in ameliorating saline soil whose soluble salts are largely neutral and high in ca2+ and mg2+ and very little exchangeable Na+ leaching saline –alkali or sodic soils with water high in soluble salt but low in exchangeable Na+ may be effective

4. CONTROL - The retardation of evaporation is an important features of control of salty soil this will not only save moisture but will also retard the upward translocation of soluble salts into the root zone .salt free irrigation water should be used .the use of salt resistant crop is an another important feature of the successful management of saline and alkali soils. Highly salt resistant crops –barley ,sugarbeat cotton. Moderatey salt resistant crop-wheat ,rice ,maize Low salt resistant crops-beans reddish

5. CONVERSION- In this conversion method different chemical amendments are used for changing part of the caustic alkali carbonates into sulphates and ultimately lost by leaching .All chemical amendments are not suitable for all soil conditions. The amendments are not suitable for all soil condition .the amendments suitable for different soil condition are indicated below .

6. AMENDMENTS SOIL CONDITION Gypsum saline and alkali soil having Ph range up to 9.0 . Sulphur Alkaline and Saline –alkali soil . Iron sulphate having Ph range 8.0-9.0 . Iron pyrite . Limestone saline soil having Ph less than 8.0

7. CHEMICAL REACTION INVOLVING RECLAMATION OF SALT AFFECTED SOILS GYPSUM (CaSo₄.2H₂O)- when gypsum is applied to ameliorate salt affected soils .the following reaction will take place and loss of exchangeable sodium (Na⁺) occurs and calcium will take place of sodium on the exchange complex. Gypsum reacts with both Na₂CO₃ and the adsorbed sodium as follows- Na₂CO₃ +CaSO₄ → CaCO₃ +Na₂SO₄ ↓ Leachable

8. Clay ]Na + CaSo ₄ →Ca [ Clay +Na₂SO₄ ↓ Leachable SULPHUR – when sulphur is applied to salt affected soils the following reaction takes place. 2S +3O₂ = 2SO₃ SO₃ +H₂O = H₂SO₄ H₂SO₄ + Na₂CO₃ →Co₂ +H₂O +Na₂SO₄↓ leachable The production of H₂SO₄ is common for all soil as mentioned above

9. A. H₂SO₄ + CaCO₃ → CO₂+H₂O +CaSO₄ CaSO₄ +Na[clay →Ca [clay +Na₂SO₄ ↓ B. H₂SO₄ +2CaCO₃ → CaSO₄ + Ca (HCO₃)₂ CaSO₄ + Na[clay →Ca [clay +Na₂SO₄ ↓ Ca (HCO₃)₂+Na[clay →Ca [clay +H₂SO₄ FeSO₄ +2H₂O →H₂SO₄ +Fe(OH)₂ H₂SO₄+ CaCO₃ →CaSO₄ +H₂O+CO₂ CaSO₄+ Na [ clay →Ca[clay +Na₂SO₄ ↓ IRON SULPHATE [FeSO₄] - when iron sulphate is applied to the soil following chemical reaction will Occur.

10. FeSO₄ + H₂O →H₂SO₄ +Feo Ferrous oxide In calcareous soil –H₂SO₄ +CaCO₃ → CaSO₄ +CO₂ + H₂O CaSO₄ +Na[clay →Ca [clay +Na₂SO₄ ↓ leachable In non-calcareous soil H₂SO₄ +Na [clay →H [clay +Na₂SO₄ ↓ leachable LIME SULPHUR ( CaS₂ ) when lime sulphur is applied to soils the following reaction takes place –

11. CaS₅ + 8O₂+4H₂O →CaSO₄ + H₂SO₄ If the soil is calcareous then the production of gypsum will take place from H₂SO₄ as follow – H₂SO₄+ CaCO₃ →CaSO₄ +CO₂+H₂O CaSO₄ + Na [clay →Ca [clay +Na₂SO₄↓ If the soil is non-calcareous then the following reaction will take place. 10 Na-clay +4H₂SO₄+CaSO₄ →8H-clay +Ca-clay +5Na₂SO₄ ↓ leachable

12. OTHER METHODS (SALT PRECIPITATION THEORY) Soil precipitation theory is employed satisfactory for the reclamation of sodic soils. the elimination of salts and exchangeable sodium from soils by leaching is presently practicing but the leached salts have been washed into ground waters or streams making those water more salty and again that too much salty water is used for irrigation purpose .a new concept in managing salty soils has been developed and that is known as precipitation of salts . This idea suggests that instead of leaching salts completely .

13. They can be leached to only 0.9 -1.8 m deep where much of the salt would from slightly soluble gypsum or carbonates during dry periods and not react any longer as soluble salts. The amount of salt precipitating out will vary with the cation and anion composition of those salts .the ions precipitating will be mostly those of calcium ,magnesium ,carbonate bicarbonate and sulphate . The management technique is simply to apply less water ,but to do it more carefully to ensure uniform depth of wetting .

14. GYPSUM REQUIREMENT- The main principle for the reclamation of sodic or alkali soils is to replace exchangeable Na by another cation calcium .of all calcium compounds , gypsum is considered the best and cheapest for the reclamation purpose .calcium solublized from gypsum replaces sodium leaving soluble sodium sulphate is the water ,which is then leached out. gypsum requirement is expressed as of Ca 2+ per 100 gm soil . The gypsum requirement is determined from the formula gypsum requirement (GR) me of Ca2++/ 100g soil =

15. THANK YOU