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Irrigation Scheduling: How Much Water and When

Irrigation · July 2025 · 5 min read

Efficient irrigation scheduling ensures crops receive the right amount of water at the right growth stage without wasting resources. Using evapotranspiration data and soil moisture monitoring, you can optimize water use and protect yields during critical reproductive periods.

Crop Water Use by Stage

Corn water demand peaks at 0.30–0.35 inches per day during tasseling and silking, while soybeans peak at 0.25–0.30 inches during pod fill. Early vegetative stages require much less water, making it important to match irrigation to actual crop demand rather than applying a fixed schedule. Soil moisture sensors at multiple depths help verify whether irrigation is reaching the active root zone.

The Checkbook Method

The checkbook method tracks soil moisture like a bank account — rainfall and irrigation are deposits, and daily crop ET is a withdrawal. Start with a full soil profile, subtract daily ET from local weather station data, and add precipitation. When the balance drops to about 50% of available water-holding capacity, it is time to irrigate.

Deficit Irrigation

Deficit irrigation intentionally applies less water than full ET replacement during less sensitive growth stages to conserve water for critical periods. Corn tolerates moderate stress during vegetative growth but not during pollination. Soybeans are most sensitive during pod fill, so prioritize full irrigation from R3 through R6 if water is limited.

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