Calculate daily and seasonal crop water needs based on crop type, growth stage, area, and evapotranspiration (ET).
Calculate daily and seasonal crop water needs based on crop type, growth stage, area, and evapotranspiration (ET). Get instant, accurate results for your farm.
Crop water requirement (ETc) = Reference ET (ETo) × Crop Coefficient (Kc) × Stage Factor. This is the amount of water lost through transpiration and evaporation that must be replaced by irrigation or rainfall.
A: Use a local weather station, agricultural extension service, or online tools like FAO CLIMWAT or CIMIS (California). Many weather apps now provide daily ETo. If unavailable, estimate from pan evaporation (ETo ≈ 0.7 × pan evaporation).
A: ETo (reference evapotranspiration) is the water use of a standardized reference crop (short grass) under optimal conditions. ETc (crop evapotranspiration) is the actual water use of your specific crop, calculated as ETo × Kc (crop coefficient). ETc is what you need for irrigation scheduling.
A: Subtract effective rainfall from ETc to get net irrigation need. Effective rainfall is typically 70-80% of measured rainfall (some runs off, some evaporates). If rainfall exceeds ETc, skip irrigation and let soil moisture recharge. Use a rain gauge to track actual rainfall.