1. You have learnt from the lessons in the earlier Modules that soil properties influence soil health. These soil properties in turn are affected by the agricultural practices followed by a farmer. Good agricultural practices not only help in managing the soil but also improve soil health. What are these good agricultural practices? Virtual Academy for the Semi Arid Tropics Course on Soil and Soil Health Module III: Soil Health Management

2. The good agricultural practices that help in improving and managing soil health focus on: Improving and maintaining organic matter in the soil; Avoiding tillage practices that harm the soil structure; Conserving the soil from erosion and other soil degrading effects; Adopting integrated nutrient and pest management practices, Rectifying soil problems like acidity and alkalinity. Virtual Academy for the Semi Arid Tropics Course on Soil and Soil Health Module III: Soil Health Management

3. Virtual Academy for the Semi Arid Tropics Lesson 5: Rectifying problem soils Course on Soil and Soil Health Module III: Soil Health Management After successful completion of this Lesson, you will be able to answer: 1.How problem soils result? 2.Why problem soils need attention? 3.How soils become saline? 4.How plant growth is affected in saline soils? 5.What practices are used to reclaim saline soils? 6.What is soil alkalinity? 7.How alkaline soils are formed? 8.How alkaline soils are reclaimed?

4. Virtual Academy for the Semi Arid Tropics Lesson 5: Rectifying problem soils Course on Soil and Soil Health Module III: Soil Health Management After successful completion of this Lesson, you will be able to answer: 9. What is soil acidity? 10. How soil acidity is identified? 11. How crop growth is affected in acid soils? 12. What are the materials used for rectifying soil acidity? 13. How acid soils are reclaimed?

5. Virtual Academy for the Semi Arid Tropics Lesson 5: Rectifying problem soils Course on Soil and Soil Health Module III: Soil Health Management Soil health is affected when soils acquire certain characteristics due to nature or from interventions by human beings. Such problem soils are not economical to cultivate crops unless the problems are rectified.

6. Virtual Academy for the Semi Arid Tropics Lesson 5: Rectifying problem soils Course on Soil and Soil Health Module III: Soil Health Management Soil salinity occurs due to concentration of salts, like chlorides of calcium, magnesium and sodium, at the root zone. Water availability to the plants is affected in such soils and consequently the plant growth is retarded.

7. Virtual Academy for the Semi Arid Tropics Lesson 5: Rectifying problem soils Course on Soil and Soil Health Module III: Soil Health Management A very saline soil may form a white crust on it surface, which is commonly referred to as “white alkali”

8. Virtual Academy for the Semi Arid Tropics Lesson 5: Rectifying problem soils Course on Soil and Soil Health Module III: Soil Health Management Soil salinity is corrected by leaching the salts out of root zone. For this: The field is divided into smaller plots and bunds are formed around the plots to impound water. Drains are constructed around the field for proper drainage of water from the field. The plots are flooded with good quality irrigation water up to 15 to 20 cm.

9. Virtual Academy for the Semi Arid Tropics Lesson 5: Rectifying problem soils Course on Soil and Soil Health Module III: Soil Health Management Soil salinity is corrected by leaching the salts out of root zone. For this: The water is impounded for 2 to 3 days to dissolve the salts and then the water is drained out of the field. Flooding and drainage are to be repeated 5 or 6 times till the soluble salts are leached from the soil to a safer limit.

10. Virtual Academy for the Semi Arid Tropics Lesson 5: Rectifying problem soils Course on Soil and Soil Health Module III: Soil Health Management Soil alkalinity results due to the accumulation of sodium salts of chlorides and bicarbonates in the soil. Excess sodium salts affects: soil structure resulting in hard surface soils with poor drainage. decreased availability many plant nutrients. The poor crop growth in these soils is due to restricted root system nutritional imbalances.

11. Virtual Academy for the Semi Arid Tropics Lesson 5: Rectifying problem soils Course on Soil and Soil Health Module III: Soil Health Management Alkaline soil with hard surface and poor drainage

12. Virtual Academy for the Semi Arid Tropics Lesson 5: Rectifying problem soils Course on Soil and Soil Health Module III: Soil Health Management Soil alkalinity can be overcome by converting exchangeable sodium into water soluble salts and then leaching these soluble salts out of the field. Gypsum (Calcium sulfate) a byproduct from fertilizer factories is used to rectify soil alkalinity. The required quantity of gypsum depends on the amount of exchangeable sodium. A soil test will reveal the amount of exchangeable sodium in the soil.

13. Virtual Academy for the Semi Arid Tropics Lesson 5: Rectifying problem soils Course on Soil and Soil Health Module III: Soil Health Management For every 1 m.e of exchangeable sodium per 100 gm of soil, 4 tons of gypsum per ha is to be added into the soil. Small quantities of gypsum up to 3 tons could be applied in one dose. Larger quantities are applied in 2 or 3 split doses. After incorporating gypsum into the soil, the field is impounded with irrigation water for 2 or 3 days. Later the excess water is drained out. This gypsum application is to be done well in advance of the sowing season.

14. Virtual Academy for the Semi Arid Tropics Lesson 5: Rectifying problem soils Course on Soil and Soil Health Module III: Soil Health Management Soil acidity occurs due to : washing out of the soluble salts in heavy rainfall areas; frequent use of large quantities of acid forming fertilizers like ammonium sulfate and ammonium chloride. Soil acidity is identified from soil pH lower than 6.5 low content of soluble salts of calcium and magnesium.

15. Virtual Academy for the Semi Arid Tropics Lesson 5: Rectifying problem soils Course on Soil and Soil Health Module III: Soil Health Management Crop growth is very poor in the acid soils due to: poor root system; adversely affected microorganisms’ activities; low availability of nutrients like nitrogen, phosphorus, calcium, magnesium, and molybdenum.

16. Virtual Academy for the Semi Arid Tropics Lesson 5: Rectifying problem soils Course on Soil and Soil Health Module III: Soil Health Management Root system affected Poor maize crop by acidity in an acid field

17. Virtual Academy for the Semi Arid Tropics Lesson 5: Rectifying problem soils Course on Soil and Soil Health Module III: Soil Health Management Soil acidity can be rectified by the application of lime products like: limestone, burnt lime, chalk, basic slag, a byproduct from fertilizer factories, pressmud cake from sugar factories.

18. Virtual Academy for the Semi Arid Tropics Lesson 5: Rectifying problem soils Course on Soil and Soil Health Module III: Soil Health Management The amount of lime required depends on: the soil type and its pH. lower the soil pH, higher the amount of lime fine textured soils like clay soils require higher amount of lime compared to coarse structured soils like sandy soil for the same soil pH level. Usually 2 to 3 tons of lime is applied on unplowed land and then disked to mix with the soil. This application is to be done 10 to 15 days before sowing.

19. This concludes the Lesson 5 on Rectifying problem soils in this Module. This course on Soil and Soil Health also concludes with this Module on Soil Health Management To learn more about this subject, you may review the Internet links given in the Modules. To review, select any Module from the Course contents Virtual Academy for the Semi Arid Tropics Course on Soil and Soil Health Module III: Soil Health Management