Last reviewed 1 Oct 2026 · 7 min read
Meaning and role
Agronomic (agronomical) measures use crops, vegetation, tillage and cultural practices — rather than engineering structures — to control runoff and soil loss. They are:
- Cheap and simple for farmers to adopt.
- Effective on gentle slopes (usually up to about 7 %), where erosion is mainly sheet and rill.
- Complementary to mechanical measures (terraces, bunds, waterways) on steeper slopes.
They work by (1) protecting the soil surface from raindrop impact, (2) reducing runoff velocity, (3) increasing infiltration and organic matter, and (4) improving soil structure.
Link with USLE. In the Universal Soil Loss Equation (A = R·K·LS·C·P), agronomic measures lower the cover-management factor C and the support-practice factor P.
1. Contour farming
- Ploughing, planting and cultivating along the contour (across the slope) instead of up and down the slope.
- Each ridge and furrow acts as a small barrier that holds water and slows runoff, so soil loss falls by about 50 % or more on gentle slopes.
- Limits: works for gentle slopes (about 2–7 %) and short slope lengths; during intense storms ridges may break and cause gullies, so it is often combined with graded bunds or terraces.
- Contour lines are laid out with a level (A-frame, line level or dumpy level); because natural slopes vary, the contour rows are usually adjusted into smooth curves.
- Benefits: higher moisture storage, lower fuel use, better yields in dry years.
2. Strip cropping
Growing different crops in alternate strips across the slope, so that erosion-resistant strips trap the soil washed from erosion-prone strips.
| Type | Description |
|---|---|
| Contour strip cropping | Strips of an erosion-permitting crop (row crops like maize, cotton) alternate with erosion-resisting crops (grass, legumes, small grains); strips follow the contour |
| Field strip cropping | Strips of uniform width laid across the general slope (not exactly on contours) in fields with regular slopes |
| Buffer strip cropping | Strips of permanent grass or legumes placed in critical positions (e.g., steep parts, narrow bands) between cultivated areas |
| Wind strip cropping | Strips perpendicular to the prevailing wind direction (see wind erosion) |
- Strip width depends on slope, soil, rainfall and implements; a steeper slope needs narrower strips.
- A rotation of the strips is practised each year.
3. Cover crops and close-growing crops
- Close-growing crops (grasses, legumes like cowpea, green gram, groundnut, berseem) cover the soil densely and give high protection (low C factor).
- Cover crops are grown between main crops or in orchards to protect the soil and add organic matter and nitrogen (green manuring with dhaincha or sunn hemp).
- Intercropping (growing two or more crops together in a definite pattern) and mixed cropping increase ground cover and spread risk.
- Crops are ranked by their protective effect: forest/grass > legumes and pulses > cereals > row crops (maize, cotton, sorghum) > fallow.
4. Mulching
Mulch is a protective layer of material spread on the soil surface.
| Type | Examples | Benefits |
|---|---|---|
| Organic mulch | Straw, crop residues, dry leaves, grass, sawdust, coir | Reduces evaporation, controls weeds, cools soil, adds organic matter on decomposition |
| Stubble mulch | Crop stubble left on the surface with sub-surface tillage (sweeps, blades) | Reduces wind and water erosion; conserves moisture in dryland |
| Plastic mulch | Black or transparent polythene film | Conserves moisture, controls weeds, warms soil; used with drip in high-value crops |
| Dust (soil) mulch | A shallow-tilled loose layer | Breaks capillary rise and reduces evaporation |
| Live mulch | A low-growing legume under a crop | — |
- Usual rate of straw mulch is about 4–6 t/ha (more in erosion-prone slopes).
- Mulching can cut runoff by 50–70 % and soil loss by a large factor in field studies; results vary with slope and rainfall.
- Cautions: possible pests/diseases, nitrogen immobilisation by wide C:N residues (add nitrogen), and the cost and availability of material.