Reclamation and Management of Saline Soils

Saline soils contain excessive soluble salts, which adversely affect crop growth and soil health. The management of saline soils aims to reduce salt concentration, improve soil structure, and enhance agricultural productivity.

1.1 Identification of Saline Soils

• High electrical conductivity (EC) of soil saturation extract (>4 dS/m).
• Low sodium adsorption ratio (SAR < 13).
• pH is usually less than 8.5.
• Presence of white crusts of salts on the soil surface.

1.2 Causes of Salinity

• Poor drainage leading to water accumulation and salt deposition.
• High evaporation rates leaving salts behind.
• Irrigation with saline water.
• Capillary rise of saline groundwater.

Reclamation of Saline Soils

1. Leaching: Applying excess water to dissolve and flush out salts. Requires good drainage to prevent waterlogging.
2. Improvement of Drainage: Installing subsurface drainage systems. Creating surface drains to remove excess water.
3. Use of Gypsum (CaSO₄.2H₂O): Replaces sodium ions with calcium to prevent soil structure degradation. Improves soil permeability and aeration.
4. Mulching: Reduces evaporation and minimizes salt accumulation on the surface. Organic mulches improve soil organic matter and microbial activity.
5. Crop Selection and Management: Grow salt-tolerant crops like barley, cotton, and sunflower. Use proper irrigation scheduling to maintain a favorable soil-water balance.
6. Agroforestry and Biological Approaches: Planting salt-tolerant trees and grasses like Acacia, Prosopis, and halophytes. Using organic amendments like farmyard manure (FYM) and compost to enhance microbial activity and improve soil fertility.

2. Reclamation and Management of Acid Sulphate Soils

Acid sulphate soils contain iron sulfides, which oxidize upon exposure to air, forming sulfuric acid that leads to extreme acidity and toxicity for plants.

2.1 Identification of Acid Sulphate Soils

• Very low pH (below 4.0).
• Presence of yellowish jarosite deposits.
• High aluminum and iron toxicity affecting plant growth.

2.2 Causes of Acid Sulphate Soils

• Drainage of waterlogged soils exposing sulfide minerals to oxygen.
• Natural oxidation of pyrite (FeS₂) leading to sulfuric acid formation.
• Agricultural activities such as peatland drainage and wetland reclamation.

Reclamation of Acid Sulphate Soils

• Liming: Application of lime (CaCO₃) to neutralize acidity. Rate of application depends on soil pH and acidity level.
• Water Management: Maintaining a waterlogged condition to prevent oxidation of sulfides. Controlled drainage to manage soil acidity.
• Use of Organic Amendments: Application of organic matter (compost, FYM) to improve microbial activity and soil buffering capacity. Use of green manure crops like Sesbania to enhance soil fertility.
• Gypsum Application: Helps in reducing aluminum toxicity and improves soil structure.
• Crop Selection: Growing acid-tolerant crops like rice, pineapple, and legumes. Using proper crop rotation to maintain soil health.
• Subsurface Drainage and Land Reclamation: Improving natural drainage by installing tile drains or open ditches. Land reshaping to facilitate proper water flow and reduce waterlogging.