Determination of Irrigation Depths Using a Process Model and Quantitative Weather Forecast.

A method of determination of irrigation depth using a process model of crop response to irrigation and weather forecast was presented. To optimize each irrigation depth, a concept of virtual income, which is proportional to an increment in transpiration amount during an irrigation interval, was introduced. A numerical model, WASH_2D, that simulates water, solute, and heat transport and crop response in two dimension was used to determine irrigation depth for corn grown in sandy field with drip irrigation system in Japan. Results indicated that predicted water content agreed well with observation and net income was slightly higher than treatment irrigated by an automatic irrigation system. These results revealed that proposed strategy can at least alter automatic irrigation systems and save costs for equipments such as soil moisture probes, dataloggers and solenoid valves.