Irrigation and Its Management
Definition of Irrigation
- Irrigation is the art and science of supplying water to the land or soil in controlled amounts for the purpose of crop growth and production.
- It supplements rainfall and ensures water availability in the root zone during the crop growth period.
FAO Definition: “Irrigation is the artificial application of water to soil for the purpose of supplying moisture essential for plant growth.”
Objectives of Irrigation
- To ensure adequate moisture for crops.
- To make up deficiency of rainfall.
- To supply water during critical growth stages.
- To improve crop yields and cropping intensity.
- To leach salts and maintain soil productivity.
- To facilitate intercultural operations (land preparation, fertilizer use).
Management of Irrigation Water
Meaning; Management of irrigation water = judicious, timely, and efficient application of water to crops, aiming at higher production per unit of water with minimum losses.
Principles of Irrigation Water Management
- Right time of irrigation → scheduling.
- Right amount of water → depth of irrigation.
- Right method of application → surface, sprinkler, drip, etc.
- Right quality of water → avoid salinity/alkalinity hazards.
Criteria for Irrigation Scheduling
- Soil-based criteria: Field capacity, permanent wilting point, available water holding capacity. Irrigation when 50% available water is depleted.
- Crop-based criteria: Critical crop growth stages (e.g., crown root initiation in wheat, tasseling–silking in maize, flowering in pulses). Visual plant indicators (leaf rolling, color, angle).
- Climatic criteria: IW/CPE ratio method (Irrigation water depth : cumulative pan evaporation). Evapotranspiration (ET) models.
- Physiological criteria: Canopy temperature, stomatal resistance.
Improved Water Management Practices
- Laser land leveling → uniform water distribution, saves 20–30% water.
- Alternate Wetting and Drying (AWD) in rice.
- Deficit irrigation → applying less water than full requirement to save resources.
- Rainwater harvesting & recycling → on-farm ponds, percolation tanks.
- Conjunctive use → use of surface + groundwater.
- Mulching → reduces evaporation losses.
- Fertigation through drip → saves water + nutrients.
Quality of Irrigation Water
- EC (Electrical Conductivity): Salinity hazard.
- SAR (Sodium Adsorption Ratio): Sodicity hazard.
- RSC (Residual Sodium Carbonate): Alkalinity hazard.
- Safe limits must be checked before irrigation to avoid soil degradation.
Water Use Efficiency (WUE)
- Definition: Ratio of crop yield to the amount of water used (kg/ha-mm).
- Ways to improve WUE:
- Proper irrigation scheduling.
- Improved methods (drip, sprinkler).
- Short-duration, drought-resistant varieties.
- Crop diversification (low water requiring crops).
- Integrated nutrient + water management.
🇮🇳 Indian Concerns in Irrigation Water Management
Water Resources in India
- Total annual water availability: ~4000 billion m³.
- Utilizable water resources: 1122 billion m³ (690 surface + 432 groundwater).
- Agriculture consumes ~80–85% of total water resources.
Irrigated Area in India
- Net sown area: ~140 Mha.
- Net irrigated area: ~70 Mha (~50%).
- Major sources: Groundwater (64%) > Canals (23%) > Tanks (2%) > Others (11%).
- India has the largest irrigated area in the world.
Irrigation Efficiency
- Surface irrigation: 30–40%.
- Canals: 35–40%.
- Groundwater irrigation: 65–70%.
- Drip irrigation: 90–95%.
- Sprinkler irrigation: 70–80%.
- In India, average irrigation efficiency is low (~38%), leading to wastage.
Problems/Concerns in India
- Over-exploitation of groundwater; In states like Punjab, Haryana, UP, Gujarat.
- Waterlogging and salinity; Canal command areas (Punjab, Haryana, parts of Rajasthan). Over-irrigation causes secondary salinization.
- Low adoption of micro-irrigation; Drip + sprinkler adoption only ~20% of potential area.
Important Data for Exams
- India accounts for ~17% of world population but only 4% of world water resources.
- Irrigation potential created: ~113 Mha.
- Critical need: Increase water productivity (kg/m³), not just land productivity.
- Micro-irrigation can save 30–50% water and increase yield by 20–40%.
