Methods to Determine the Timing of Maize Irrigation When Irrigation Amount is Restricted

Abstract

【Objective】 To reverse the continued decline of dwindling water resources in northern China, most regions have proposed to restrict groundwater extraction for irrigation. Optimizing irrigation timing and making most of natural precipitation and irrigation water is essential to minimizing crop yield loss due to the reduced irrigation amount. The purpose of this paper is to study the optimization of timing of maize irrigation. 【Method】 Models relating maize yield and water usage were established based on crop growth model and soil water-heat coupling model. The model parameters were determined based on data measured from 2017—2020 from a maize field at Wenyuhe Experiment Station in Shanxi province. Meteorological data measured from 1957—2018 at the station was used in the frequency analysis for determining the irrigation amount by dividing the frequency from 5% to 95%. We optimized the timing of the irrigation assuming that the irrigation amount varied from 45 to 105 mm, and the times of irrigation varied from 1 to 5. The K-M model was used to determine the relationship between cumulative evapotranspiration and cumulative precipitation between two adjacent irrigations. Using the meteorological data measured from 2009 to 2018, the model was applied to optimize the irrigation timing, from which we compared the yield-increasing benefits obtained from the K-M method, the dynamic irrigation water limit method, and the empirical irrigation method. 【Result】 The correlation coefficient between the cumulative evapotranspiration and the cumulative effective precipitation under different irrigation amount was greater than 0.92. With the increase in irrigation amount, the parameter M in the K-M method, which characterizes the irrigation amount, increased. 【Conclusion】 Evaluation of the three methods for determining the optimal irrigation timing based on yield, benefit and water use efficiency showed that, compared with the empirical irrigation method, the K-M method was the best, followed by the dynamic irrigation water limit method.

Keywords

• crop growth model
• low limit of irrigation
• evapotranspiration method
• irrigation time
• limited irrigation