🌱 Land Resources and Soil Conservation

This lesson builds core elective concepts in BSc Agriculture with practical applications and exam-oriented clarity.

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Land Resources and Soil Conservation

Land Use Statistics in India

India's total geographical area is 328.7 million hectares (Mha). The land use pattern (latest estimates) is:

Land Use Category	Area (Mha)	% of Total
Net sown area (cultivated)	141.4	43.0%
Forest	71.4	21.7%
Fallow lands	26.0	7.9%
Pastures and grazing	10.2	3.1%
Land under misc. trees/groves	3.5	1.1%
Barren/unculturable wasteland	17.8	5.4%
Land put to non-agricultural use	28.0	8.5%
Culturable wasteland	14.1	4.3%

Key concern: ~120 Mha (36.7% of total) is degraded to varying degrees, reducing productive potential.

Land Capability Classification

Developed by the USDA Soil Conservation Service, the land capability classification groups land into 8 classes (I–VIII) based on the degree of limitation for agricultural use:

Class	Description	Suitable For
I	No significant limitations	All crops, no special management
II	Minor limitations	Most crops, simple conservation needed
III	Moderate limitations	Limited crops, intensive conservation
IV	Severe limitations	Occasional cropping, mainly pasture/hay
V	Not cultivable (wetness/stoniness)	Pasture, range, forestry
VI	Severe, non-arable	Pasture, range, forestry
VII	Very severe limitations	Only range, wildlife, watershed
VIII	No agricultural use	Recreation, wildlife, watershed only

Classes I–IV are suitable for cultivation; V–VIII are not recommended for cropping.

Soil Erosion: Types and Causes

Soil erosion is the detachment and transportation of soil particles by water or wind. India loses an estimated 28.28 tonnes/ha/year of soil on average (ICAR estimate), totalling ~5.3 billion tonnes annually.

Water-Induced Erosion

1. Splash/Raindrop erosion: Impact of raindrops detaches soil particles; first stage of erosion; dislodges fine particles.

2. Sheet erosion: Thin uniform layer of soil removed over large area by overland flow; difficult to detect early; most damaging in aggregate.

3. Rill erosion: Small channels (rills, < 30 cm deep) formed by concentrated flow; common on slopes; can be obliterated by tillage.

4. Gully erosion: Large channels (> 30 cm deep) cut by concentrated water flow; most visible form; permanently removes land from cultivation; common in Chambal ravines (MP, UP, Rajasthan), Chhota Nagpur (Jharkhand).

5. Stream bank erosion: Lateral erosion of river banks by flowing water; causes loss of agricultural land along rivers.

6. Landslides/Mass movement: On steep slopes; common in Western Ghats, Himalayan foothills.

Wind Erosion

Common in arid and semi-arid zones — Rajasthan (Thar Desert), Gujarat, Haryana, Punjab. Operates through:

• Saltation: Particles bounce along the surface (50–80% of wind erosion)
• Suspension: Fine particles carried aloft over long distances
• Surface creep: Coarse particles roll along surface

Vulnerable soils: Sandy, loose, low organic matter, dry soils lacking vegetation cover.

Universal Soil Loss Equation (USLE)

The USLE (Wischmeier & Smith, 1978) predicts average annual soil loss:

$A = R \times K \times L \times S \times C \times P$

Where:

Factor	Full Name	Description
A	Average annual soil loss	Tonnes/ha/year
R	Rainfall-runoff erosivity index	Energy × intensity of rainfall
K	Soil erodibility factor	Susceptibility of soil to erosion
L	Slope length factor	Effect of slope length
S	Slope steepness factor	Effect of slope gradient
C	Cover and management factor	Influence of vegetation/cropping
P	Support practice factor	Effect of conservation practices

Higher A = greater erosion. Conservation practices aim to reduce C and P values. R and K are site-specific; L and S are topographic.

REVISED USLE (RUSLE): Updated version with improved factor equations, widely used in India.

Land Degradation: Causes and Types

Land degradation is the decline in land quality from its potential productive state.

Causes

• Deforestation — removal of protective cover accelerates erosion
• Overgrazing — destroys ground cover, compacts soil, accelerates erosion
• Improper tillage — deep ploughing along slopes, stubble burning
• Waterlogging — poor drainage, over-irrigation; ~3.3 Mha affected in India
• Soil salinity/alkalinity — secondary salinization from irrigation; ~6.73 Mha salt-affected soils
• Mining and quarrying — physical disturbance, acid mine drainage
• Industrial effluents — heavy metal contamination of soils
• Shifting cultivation (jhum) — if rotation period too short

Soil Conservation Practices

Agronomic Measures

• Contour farming: Ploughing/planting along contour lines; reduces runoff velocity
• Strip cropping: Alternating strips of erosion-prone and erosion-resistant crops along contours
• Cover crops: Legumes like cowpea, groundnut protect soil between main crops
• Mulching: Surface covering with straw, crop residue; reduces splash, improves moisture

Engineering/Mechanical Measures

• Contour bunding: Earth embankments along contours; impound runoff; suitable for < 6% slopes
• Graded bunding: Bunds with slight gradient to safely divert runoff; for 6–10% slopes
• Terracing (bench terracing): Cut-and-fill terraces on steep slopes (> 10%); very effective but costly
• Gully plugging: Brushwood, rockfill, gabion check dams to stop gully advance
• Windbreaks and shelterbelts: Rows of trees/shrubs perpendicular to prevailing wind; reduce wind speed, protect crops and soil

Vegetative Measures

• Contour hedges: Vetiver grass, Napier grass along contours — bioengineering approach
• Grassed waterways: Vegetation-lined channels to safely carry concentrated runoff
• Afforestation: Plantation on barren/wasteland slopes

Wasteland Development

National Wasteland Development Board (NWDB) established 1985; restructured as National Land Resources Management Council. India has ~14 Mha culturable wastelands. Approaches:

• Watershed development programmes (PMKSY, IWMP)
• Afforestation and pasture development
• Joint Forest Management for degraded forest areas

Reclamation of Problem Soils

Salt-Affected Soils (Usar/Saline-Alkaline)

• ~6.73 Mha in India; concentrated in UP (usar), Punjab, Haryana, Rajasthan
• Saline soils: EC > 4 dS/m; flushed with good water + drainage
• Sodic/Alkaline soils (usar): High ESP, pH > 8.5; treated with gypsum (calcium displaces sodium) + rice-wheat rotation + green manure

Acid Soils

• ~49 Mha in India; NE states, West Bengal, Odisha, Kerala
• Treated with liming (agricultural lime/dolomite); raises pH, improves nutrient availability

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Summary Cheat Sheet

Topic	Key takeaway
Main focus	Land use statistics, soil erosion types, USLE formula, land capability classification, and conservation practices for ELEC 13 Natural Resources Management.
Section context	Revise this lesson with the rest of Land and Water Resources for stronger conceptual continuity.