Determining Economical Irrigation Depths in a Sandy Field Using a Combination of Weather Forecast and Numerical Simulation

Abstract

Advancement of modern technologies has given numerical simulations a crucial role to effectively manage irrigation. A new numerical scheme to determine irrigation depths was incorporated into WASH 2D, which is a numerical simulation model of crop response to irrigation. Based on two predicted points of cumulative transpiration—water price and quantitative weather forecast—the scheme can optimize an irrigation depth in which net income is maximized. A field experiment was carried out at the Arid Land Research Center, Tottori, Japan, in 2019, to evaluate the effectiveness of the scheme on net income and crop production compared to a tensiometer-based automated irrigation system. Sweetcorn (Zea mays L., Amaenbou 86) was grown in three water balance lysimeters per each treatment, filled with sandy soil. The scheme could achieve a 4% higher net income, due to a 7% increase in green fodder yield, and an 11% reduction in irrigation amount, compared with the automated irrigation method. These results indicate that the numerical scheme, in combination with quantitative weather forecasts, can be a useful tool to determine irrigation depths, maximize net incomes which are farmers’ targets, and avoid large investments that are required for the automated irrigation system.