Soil and Land Degradation

Land/Soil Degradation

Definition

Land/soil degradation is a process that leads to the decline in the quality and productivity of the land due to natural or human-induced factors. It results in reduced agricultural potential, loss of biodiversity, and negative impacts on ecosystem functions.

Degraded Soil

Degraded soils have poor physical, chemical, and biological properties, making them unsuitable for agricultural and environmental sustainability. These soils require significant reclamation efforts to restore fertility and productivity.

2. Types of Land Degradation

Land degradation is broadly classified into six major categories:

2.1 Water Erosion

• Sheet Erosion: The uniform removal of the topsoil layer due to raindrop impact and surface runoff.
• Rill Erosion: The formation of small channels on the soil surface caused by concentrated water flow.
• Gully/Ravine Erosion: Advanced stage of rill erosion, forming deep gullies, leading to severe land degradation.
• Landslides: Movement of soil and rock downslope due to water saturation and deforestation.

2.2 Wind Erosion

• Deflation: Lifting and removal of loose soil particles by the wind.
• Abrasion: Sand particles carried by the wind strike and erode rocks and soil surfaces.
• Deposition: Accumulation of wind-transported soil particles in different locations, leading to sand dunes.

2.3 Soil Fertility Decline

• Reduction in essential nutrients (N, P, K) due to continuous cropping and poor management.
• Loss of organic matter, reducing soil structure and water-holding capacity.

2.4 Waterlogging

• Occurs when excess water accumulates in the root zone, restricting oxygen supply.
• Reduces microbial activity and leads to root suffocation and plant death.

2.5 Salinization

• Accumulation of soluble salts in the soil, affecting plant growth.
• Common in poorly drained irrigation systems.

2.6 Lowering of the Water Table

• Over-extraction of groundwater for irrigation leads to depletion of aquifers.
• Causes reduced availability of water for agriculture and drinking purposes.

3. Causes of Soil Degradation

3.1 Natural Causes

• Climate variations (drought, heavy rainfall, floods).
• Soil erosion by wind and water.

3.2 Human-Induced Causes

1. Deforestation: Removal of vegetation exposes soil to erosion and nutrient loss.
2. Overgrazing: Leads to soil compaction and destruction of plant cover.
3. Intensive Agriculture: Excessive use of fertilizers and pesticides deteriorates soil health.
4. Overexploitation of Vegetation: Unsustainable harvesting of plants depletes soil nutrients.
5. Industrial Activities: Release of pollutants degrades soil quality.

4. Processes of Soil Degradation

4.1 Degradation of Soil Physical Properties

• Soil Compaction: Reduction in soil pore space due to heavy machinery and overgrazing.
• Surface Crusting: Formation of a hard crust that reduces water infiltration.
• Loss of Soil Structure: Breakdown of soil aggregates, leading to erosion.

4.2 Degradation of Soil Hydrological Properties

• Waterlogging: Excessive water accumulation leads to poor root aeration.
• Aridification: Loss of soil moisture due to high evaporation and low rainfall.

4.3 Degradation of Soil Chemical Properties

• Loss of Soil Nutrients: Decline in essential nutrients due to leaching and continuous cropping.
• Salinization and Alkalization: Accumulation of salts and increased soil pH.
• Chemical Pollution: Excessive use of agrochemicals leads to toxicity.

4.4 Degradation of Soil Biological Properties

• Reduction in Beneficial Microorganisms: Decrease in soil bacteria, fungi, and earthworms.
• Increase in Harmful Organisms: Growth of parasitic weeds and soil-borne pathogens.

5. Soil Quality and Soil Health

5.1 Soil Quality

Soil quality refers to the soil’s ability to function effectively in its natural and managed ecosystem roles, including:

• Supporting plant growth.
• Regulating water flow.
• Filtering pollutants.

5.2 Soil Health

Soil health focuses on the soil’s biological properties and its ability to sustain agricultural productivity over time.

6. Importance of Soil Quality Concept

• Sustainability: Ensures long-term agricultural productivity.
• Environmental Protection: Prevents soil erosion and pollution.
• Ecosystem Balance: Supports biodiversity and natural cycles.
• Water Conservation: Improves water retention and reduces runoff.

7. Soil Health Assessment and Indicators

7.1 Ideal Indicators of Soil Health

An ideal soil health indicator should:

• Be easily measurable and interpretable.
• Reflect changes in soil functions.
• Respond to soil management practices.

7.2 Categories of Soil Indicators

7.3 Specific Soil Quality Indicators

Chemical Indicators

• pH Level: Measures soil acidity or alkalinity.
• Electrical Conductivity: Assesses soil salinity.
• Organic Matter Content: Indicates soil fertility.

Physical Indicators

• Bulk Density: Measures soil compaction.
• Water Infiltration Rate: Determines soil drainage capacity.
• Aggregate Stability: Evaluates soil structure and erosion resistance.

Biological Indicators

• Microbial Biomass: Reflects soil microbial activity.
• Earthworm Population: Indicates soil aeration and fertility.
• Soil Respiration: Measures biological activity and decomposition.

Characteristics of Healthy Soil

• Good Soil Tilth: Loose and well-structured soil for root growth.
• Sufficient Nutrients: Balanced levels of essential elements.
• Minimal Pest and Disease Pressure: Low incidence of harmful organisms.
• High Beneficial Microbial Activity: Presence of nitrogen-fixing bacteria and mycorrhizae.
• Efficient Water Holding Capacity: Retains moisture while allowing excess drainage.