Estimate your crop's water need, irrigation requirement and watering schedule using your crop, soil, area, weather and irrigation method.
Estimate your crop's water need, irrigation requirement and watering schedule.
Water requirements change with weather, soil, crop growth and rainfall. Use the result as a planning guide and check the soil and crop regularly.
This tool will help you understand:
Crop water requirement is the amount of water a crop needs to grow properly and produce a good harvest. This depends on the crop type, growth stage, weather conditions, soil type, and many other factors. Different crops need different amounts of water, and the same crop needs different amounts at different growth stages.
Irrigation water requirement is the additional water that must be supplied through irrigation after rainfall has been considered. Not all rain that falls becomes available to the crop — some runs off, evaporates, or drains below the root zone. Irrigation fills the gap between what the crop needs and what rainfall provides.
Different crops have different water needs because of their growth patterns, leaf area, root depth, and how they use water. Vegetables like tomatoes and lettuce generally need more frequent irrigation than crops like maize or wheat. Understanding your specific crop's water needs helps you irrigate more effectively.
Hot, dry, and windy conditions increase water loss from crops and soil. On hot days, crops lose more water through transpiration. When it's cloudy or humid, water loss is lower. This is why irrigation needs change from day to day and season to season — you cannot use the same irrigation schedule all year round.
Crops do not use the same amount of water throughout their life. Seedlings need gentle, frequent watering. During rapid vegetative growth, water demand increases. Flowering and fruit development are often the most water-sensitive stages. As crops mature, water needs often decrease. Matching irrigation to growth stage improves efficiency and crop quality.
Sandy soils drain quickly and hold less water, so they often need more frequent, smaller irrigation applications. Clay soils hold more water but absorb it slowly and can become waterlogged. Loam soils balance water storage and drainage. Understanding your soil type helps you choose the right irrigation frequency and amount.
Rainfall can supply some or all of your crop's water needs, reducing or eliminating the need for irrigation. However, not all rainfall is effective — some runs off, evaporates, or drains below the root zone. After rain, always check soil moisture before irrigating again to avoid over-irrigation.
ETo (reference evapotranspiration) is a measure of how strongly the weather can remove water from a well-watered reference surface. It depends on temperature, humidity, wind, and sunshine. ETo helps us estimate how much water your crop might lose to the atmosphere under current weather conditions.
Kc (crop coefficient) adjusts the weather-based water demand to your specific crop and its growth stage. Different crops have different Kc values, and the same crop has different Kc values at different growth stages. The relationship is: Crop water need = ETo × Kc.
Crop water use is estimated using the relationship ETc = ETo × Kc, where ETc is crop evapotranspiration, ETo is reference evapotranspiration from weather, and Kc is the crop coefficient for your crop and growth stage. This is the standard FAO methodology used worldwide.
Irrigation requirement is approximately crop water demand minus effective rainfall. You then divide by irrigation system efficiency to get the gross amount that must be delivered. Not all water applied reaches the crop — some is lost during conveyance and application.
Irrigation efficiency is the percentage of water that actually reaches the crop root zone. If your system is 70% efficient, you need to apply about 143 litres for every 100 litres the crop needs. Improving efficiency can significantly reduce water waste and pumping costs.
Water needs vary greatly by crop, location, season, and growth stage. As a reference, 1 mm of water over 1 hectare equals 10,000 litres. A vegetable crop might need 5-8 mm per day during peak demand (50,000-80,000 litres per hectare), while a drought-tolerant crop might need 3-5 mm per day (30,000-50,000 litres per hectare).
Pump runtime = required water volume ÷ actual pump flow rate. If you need 30,000 litres and your pump delivers 5,000 litres per hour, you need approximately 6 hours of pumping. Always measure your actual pump flow rate — rated flow may differ from actual performance.
The best way is to check soil moisture around the root zone. Simple methods include feeling the soil, observing plant stress, or using a soil moisture meter. Irrigate when the soil has dried to the point where the crop may begin experiencing stress, but before permanent damage occurs.
Check soil moisture before irrigating. Don't irrigate immediately after rain. Use appropriate irrigation amounts for your soil type. Monitor for runoff or waterlogging. Remember that more water is not always better — over-irrigation can waste water, increase costs, leach nutrients, and harm crop roots.
Monitor soil moisture regularly. Irrigate before the crop shows severe stress. Consider your crop's critical growth stages. Plan for peak water demand periods. Have a backup water source if possible. During hot, dry periods, you may need to irrigate more frequently.
Repair leaks and broken emitters. Improve irrigation scheduling based on actual crop need and weather. Use appropriate irrigation methods for your crop and soil. Mulch where agronomically suitable to reduce soil evaporation. Control weeds that compete for water. Maintain proper system pressure and uniformity.
Calculate energy or fuel cost based on pump power and operating hours. Add water purchase costs if applicable. Include maintenance and equipment costs. Compare irrigation cost to expected production benefit to ensure irrigation is economically worthwhile for your situation.
When water is limited, prioritize critical growth stages. Consider reducing irrigated area rather than under-irrigating the entire field. Choose crops with lower water requirements where suitable. Improve irrigation efficiency. Use water harvesting where appropriate. Plan for expected water shortages rather than reacting when they occur.