Eroded and Compacted Soils: Reclamation and Management

Eroded Soils

Definition:

Soil erosion refers to the detachment, transportation, and deposition of soil particles from one place to another due to water, wind, gravity, or human activities. It reduces soil fertility and depletes essential nutrients required for plant growth.

Formation of Eroded Soils:

• Natural factors: Heavy rainfall, strong winds, floods, and droughts.
• Anthropogenic factors: Deforestation, overgrazing, poor agricultural practices, mining, and construction activities.

Characteristics of Eroded Soils:

• Loss of topsoil, leading to decreased fertility.
• Shallow soil depth, making it difficult for plant roots to anchor.
• Increased runoff, causing water scarcity and nutrient leaching.
• Presence of gullies, rills, and sheet erosion patterns.
• Reduced organic matter and microbial activity.

Effects of Soil Erosion on Plant Growth:

1. Loss of nutrients: Reduced soil fertility affects crop yields.
2. Loss of water-holding capacity: Plants experience moisture stress.
3. Poor root penetration: Shallow and compacted soils limit root development.
4. Exposure of subsoil layers: Hard, unproductive layers limit plant growth.

Reclamation and Management of Eroded Soils

A) Biological Methods:

1. Crop Management: Use of deep-rooted and erosion-resistant crops.
2. Crop Rotation: Alternating crops to maintain soil fertility and prevent erosion.
3. Cover Cropping: Growing vegetation to protect soil from wind and water erosion.
4. Strip Planting: Alternating strips of erosion-prone and erosion-resistant crops.
5. Mulching: Adding crop residues or organic matter to reduce soil erosion.
6. Windbreaks: Trees and hedges act as barriers against wind erosion.

B) Cultivation Practices:

1. Contour Ploughing: Ploughing across slopes to slow water runoff.
2. Graded Furrows: Creating channels to direct water flow and prevent erosion.
3. Minimum Tillage: Reducing soil disturbance to maintain natural structure.

C) Mechanical Protection:

1. Graded Channels: Constructed waterways to control surface runoff.
2. Absorption Terraces: Designed to store rainwater and prevent soil loss.
3. Bench Terraces: Horizontal steps cut into slopes for cultivation.
4. Irrigation Terraces: Reduce surface water runoff in hilly areas.

Compacted Soils

Definition:

Soil compaction occurs when soil particles are pressed together, reducing pore space and increasing bulk density. This results in poor water infiltration, root penetration, and aeration.

Formation of Compacted Soils:

• Heavy machinery use: Tractors and harvesters exert pressure on soil.
• Overgrazing: Livestock trampling compacts the surface layer.
• Poor tillage practices: Repeated tillage at the same depth creates hardpans.
• Raindrop impact: Water hitting bare soil creates a compacted crust.

Characteristics of Compacted Soils:

• High bulk density (1.6 g/cm³ or more).
• Low porosity, reducing oxygen and water movement.
• Formation of hardpans, restricting root growth.
• Poor water infiltration, leading to surface runoff.
• Crusting on the surface, preventing seedling emergence.

Effects of Soil Compaction on Plant Growth:

1. Reduced root growth: Hardpans limit root penetration.
2. Waterlogging: Poor drainage causes oxygen deficiency.
3. Nutrient deficiency: Roots struggle to access nutrients in compacted soils.
4. Increased runoff and erosion: Lack of water absorption leads to topsoil loss.

Reclamation and Management of Compacted Soils

Cultivation Practices:

• Deep Tillage: Breaks up compacted layers and improves aeration.
• Subsoiling: Loosens the hardpan without disturbing surface layers.
• Use of Organic Amendments: Adding compost and manure enhances soil structure.

Biological Management:

• Cover Crops: Legumes and deep-rooted plants help loosen compacted soils.
• Green Manuring: Incorporating green crops improves soil texture.
• Earthworm Introduction: Worms help aerate and mix the soil.

Mechanical Methods:

• Aeration Techniques: Using spiked rollers or aeration tools to create pores.
• Gypsum Application: Improves soil aggregation in sodic compacted soils.
• Controlled Traffic Farming: Limiting machinery movement to designated lanes.

Soil Cracking and Soil Crusting

Soil Cracking:

Soil cracking is a result of shrinkage and expansion due to changes in moisture content. It occurs mainly in clay-rich soils and affects plant growth by:

• Exposing roots to air and causing desiccation.
• Breaking root systems, reducing nutrient uptake.
• Promoting soil erosion through water infiltration into cracks.

Soil Crusting:

Soil crusting is the deterioration of soil structure, where soil aggregates break and disperse due to rainfall, compaction, or excessive tillage. It leads to:

1. Seedling emergence failure.
2. Reduced water infiltration and increased runoff.
3. Loss of soil aeration.
4. Enhanced erosion risk.

Control of Soil Crusting:

1. Surface Mulching: Applying straw or crop residues to protect soil.
2. Addition of Organic Matter: Improves aggregate stability and soil structure.
3. Use of Soil Conditioners:
   • HPAN (Hydrolyzed polyacrylonitrile)
   • VAMA (Vinyl acetate maleic acid copolymer)
   • PVA (Polyvinyl alcohol)
4. Chemical Amendments: Application of gypsum or pyrite in sodic soils to lower exchangeable sodium percentage (ESP).
5. Light Tillage: Breaking the crust before it hardens to enhance seed germination.