In-situ Moisture Conservation Techniques

(To Reduce Runoff & Increase Infiltration in Dryland Agriculture)

In-situ moisture conservation means conserving rainwater at the place where it falls by reducing its loss through runoff and increasing infiltration into the soil profile for crop use.

1. Contour Farming

• Principle: Tillage and sowing are done across the slope along contour lines instead of up and down.
• Mechanism: Each contour furrow or ridge acts as a barrier, reducing the velocity of surface water.
• Benefits:
  • Reduces runoff by 20–30%
  • Increases water infiltration
  • Reduces soil erosion
• Example crops: Millets, pulses, groundnut in hilly/undulating regions.

2. Contour Bunding

• Structure: Small earthen embankments constructed along contour lines.
• Purpose: Breaks slope length, prevents fast runoff, and holds water temporarily.
• Benefits:
  • Improves water storage in upper soil layers
  • Reduces soil erosion significantly
  • Useful for rainfall areas of 600–750 mm.

3. Graded Bunds

• Structure: Similar to contour bunds, but built with a gentle gradient (0.2–0.4%).
• Purpose: Allows safe removal of excess water while conserving soil moisture.
• Suitable for: High rainfall (>750 mm) and soils prone to waterlogging.

4. Compartmental Bunding

• Method: Large fields are divided into small squares/rectangles (10×10 m or 20×20 m) with low bunds.
• Mechanism: Each compartment holds water like a mini-basin, reducing runoff.
• Benefits:
  • High infiltration
  • Uniform moisture distribution
  • Ideal for black soils in central India.

5. Broad-Bed and Furrow (BBF) System

• Design: Alternate raised beds (1–1.5 m) and sunken furrows.
• Mechanism: Crops sown on beds remain safe from excess water; furrows collect rainwater and enhance infiltration.
• Benefits:
  • Improves root aeration
  • Reduces erosion and runoff
  • Maintains optimum moisture for longer periods
• Best for: Vertisols (cotton, soybean, pigeon pea).

6. Tied Ridges and Furrows

• Method: Ridges and furrows are constructed across the slope; cross-bunds (“ties”) are added at intervals to form small basins.
• Benefits:
  • Water stagnates in furrows → more time for infiltration
  • Enhances soil moisture for deep-rooted crops like maize and sorghum.

7. Vegetative Barriers / Contour Strips

• Practice: Planting grasses (vetiver, napier, marvel grass) or shrubs along contour lines.
• Role:
  • Acts as a live barrier to slow runoff
  • Enhances percolation
  • Prevents soil erosion.
• Additional Benefit: Provides fodder/fuelwood.

8. Mulching

• Types: Organic (straw, leaves, crop residues), Inorganic (plastic sheets, stones).
• Functions:
  • Reduces runoff by protecting soil surface from raindrop impact
  • Prevents crust formation
  • Improves infiltration and reduces evaporation simultaneously.

9. Conservation Tillage (Minimum/Zero Tillage)

• Method: Minimum disturbance of soil and retention of crop residues.
• Effect:
  • Crop residues act as mulch
  • Reduces runoff velocity
  • Enhances water infiltration.
• Examples: Zero tillage wheat in rice–wheat system.

10. Deep Ploughing / Subsoiling

• Mechanism: Breaking compact hardpan layers in soil by using subsoiler or deep plough.
• Benefits:
  • Improves soil porosity
  • Facilitates deeper water penetration
  • Enhances root growth and moisture use efficiency.

11. Farm Ponds and Water Harvesting Trenches (On-farm Storage)

• Construction: Small ponds or trenches at the lower end of field.
• Benefits:
  • Traps excess runoff water
  • Allows gradual infiltration into soil
  • Stored water can be reused for supplemental irrigation.

Summary

• To reduce runoff: Contour farming, contour bunds, compartmental bunds, tied ridges, vegetative barriers.
• To increase infiltration: BBF, mulching, conservation tillage, deep ploughing, farm ponds.
• These techniques increase water use efficiency, crop yields, and sustainability in dryland areas.

Facts

To Reduce Runoff & Increase Infiltration

• Contour Farming – reduces runoff by 20–30% and erosion on slopes.
• Contour Bunding – suitable for rainfall of 600–750 mm; reduces soil loss by ~50%.
• Graded Bunds – slight slope (0.2–0.4%) allows safe disposal of excess water.
• Compartmental Bunding – most effective in black soils (Vertisols); conserves water in mini compartments.
• Broad Bed and Furrow (BBF) – improves crop yield in Vertisols by 20–30%; best for cotton, soybean, pigeon pea.
• Tied Ridges – create micro-basins; enhance infiltration and conserve water for maize, sorghum.
• Vegetative Barriers (Vetiver, Napier) – reduce soil loss by 60–70% and slow runoff.
• Farm Ponds – store excess runoff; provide water for supplemental irrigation in dry spells.

To Reduce Evapotranspiration (ET)

• Mulching (straw, residues, plastic) – reduces evaporation by 20–50%.
• Plastic Mulches – conserve up to 70% soil moisture; widely used in vegetables.
• Dust Mulch (hoe tillage) – breaks capillaries, reducing evaporation.
• Crop Residue Mulching – reduces ET and suppresses weeds.
• Shelterbelts/Windbreaks – reduce wind speed by 30–50%, lowering ET.
• Shading/Intercropping – tall crops (maize, pigeon pea) reduce soil exposure and evaporation.
• Antitranspirants – Kaolin, PMA, CCC reduce transpiration by 10–30%.
• Weed Control – prevents weeds that may use 2–3× more water than crops.
• Drought-Tolerant Varieties – have lower transpiration due to leaf adaptations (waxy coating, sunken stomata).