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.
Enter reference evapotranspiration (ETo) in mm/day (from local weather station), crop coefficient (Kc) for your crop, growth stage multiplier, field area in hectares, and irrigation efficiency. Click calculate to see crop evapotranspiration (ETc), daily water requirement in cubic meters, and seasonal water estimate.
The crop water requirement calculator estimates daily and seasonal water needs for your crops based on reference evapotranspiration (ETo), crop coefficient (Kc), growth stage, and field area. This helps you plan irrigation schedules, size irrigation systems, and manage water resources efficiently.
A: Kc is a factor that adjusts reference evapotranspiration (ETo, measured from grass) to a specific crop. Kc varies by growth stage: initial stage 0.3-0.5, development 0.7-0.9, mid-season 1.0-1.2 (peak water use), late season 0.6-0.9. Examples: corn Kc mid = 1.2, wheat Kc mid = 1.15, tomato Kc mid = 1.05, cotton Kc mid = 1.15.
A: ETo (reference evapotranspiration) is available from: local agricultural weather stations, national meteorological services, FAO CLIMWAT database, or online tools (like the FAO Penman-Monteith calculator). ETo is typically measured in mm/day and varies by location, season, and weather. Typical values: temperate summer 3-5 mm/day, hot arid 6-10 mm/day, tropical 4-6 mm/day.
A: 1 mm of water over 1 hectare = 10 cubic meters (because 1 ha = 10,000 m², 1 mm = 0.001 m, 10,000 × 0.001 = 10 m³). So if ETc is 5 mm/day and your field is 2 ha, daily water need = 5 × 10 × 2 = 100 m³/day. Divide by irrigation efficiency (e.g., 0.85 for drip) to get actual water to apply: 100 ÷ 0.85 = 118 m³/day.