In-situ Moisture Conservation Techniques to Reduce Evapotranspiration (ET)

1. Mulching

• Definition: Covering the soil surface with crop residues, straw, leaves, stones, or synthetic materials.
• Mechanism: Prevents direct exposure of soil to sun and wind → reduces soil temperature. Slows down evaporation from soil surface. Conserves moisture and moderates microclimate.
• Benefits: Reduces ET losses by 20–50%. Improves infiltration and soil organic matter.
• Examples: Paddy straw mulch in vegetables, polyethylene mulch in tomato, groundnut.

2. Crop Residue Management (Stubble Mulching)

• Method: Leaving residues of previous crops (wheat/paddy stubbles) on the field.
• Effect: Forms a protective layer, reducing direct evaporation. Protects against hot winds and suppresses weeds (which otherwise transpire water).

3. Shelterbelts and Windbreaks

• Definition: Rows of trees or tall crops planted on field boundaries.
• Function: Reduce wind velocity → lower evaporative demand. Provide shade → reduced soil temperature.
• Examples:
  • Shelterbelt species: Casuarina, Eucalyptus, Acacia.
  • Windbreak crops: Sorghum, Pearl millet (taller crops planted around shorter ones).

4. Shading / Intercropping with Tall Crops

• Principle: Growing tall crops with short crops to reduce radiation load on soil surface.
• Examples: Maize + Cowpea. Pigeon pea + Groundnut
• Effect: Reduces soil exposure to sunlight → less evaporation. Improves microclimate for intercrops.

5. Antitranspirants

• Definition: Chemicals sprayed on crop foliage to reduce transpiration.
• Types & Examples:
  • Stomatal closing type: PMA (Phenylmercuric acetate), ABA (Abscisic acid).
  • Film forming type: Kaolin, Wax, Silicon oils.
  • Reflectant type: Kaolin, CaCO₃ (increase leaf albedo).
  • Growth retardants: Cycocel (CCC).
• Limitations: Costly, temporary effect.
• Benefit: Reduce transpiration losses, especially under drought stress.

6. Plastic / Polythene Mulches

• Effect: Create barrier to evaporation. Conserve >70% soil moisture. Also reduce weed growth (which otherwise waste water).
• Use: Vegetables, fruit orchards, flower crops.

7. Dust Mulching

• Definition: Repeated shallow hoeing of soil surface to create a fine soil mulch.
• Effect: Breaks soil capillaries → prevents upward movement of water → reduces evaporation.
• Limitation: Effective only in low-rainfall areas; repeated hoeing may harm soil structure.

8. Proper Planting Geometry & Canopy Management

• Close spacing: Faster canopy closure → reduces sunlight hitting the soil → lower evaporation.
• Planting density: Optimum plant population maintains balance between water conservation and yield.
• Canopy management: Training/pruning in orchards to maintain shade and reduce ET losses.

9. Use of Drought-Tolerant / Short-Duration Varieties

• Mechanism: Lower transpiration rate per unit biomass. Reduced leaf area index, waxy coating on leaves, sunken stomata → less water loss.
• Examples: Short-duration sorghum, pearl millet, chickpea.

10. Weed Control

• Reason: Weeds compete with crops for water and increase transpiration losses.
• Techniques: Manual weeding, herbicides, intercultivation.
• Benefit: Saves 30–40% soil moisture that would otherwise be lost to weeds.