Abstract
In this study, the growth periods of summer maize were divided into seedling, booting and flowering-grain stage. Based on the simulation results of AquaCrop model, the drought loss sensitivity of summer maize in different growth periods was analyzed. The sensitivity curves fitting using the soil moisture content of the effective root zone and the fixed soil layer both indicated that the booting stage was the most sensitive to water stress, which was the critical period for irrigation, followed by the seedling stage. Compared with the curve parameters fitted by the soil water content of the effective root zone, the maximum Biomass Loss Rate fitted by the fixed soil layer water content was higher and the Drought Hazard Index corresponding to the disaster-causing point and the turning point in the seedling stage moved backward. Accordingly, the best irrigation opportunity may be missed and resulting in a large reduction in production if an irrigation scheme is formulated at the seedling stage based on the sensitivity curve of summer maize fitted by the water content of a fixed soil layer. This study also adapted the Jensen model to calculate the normalized moisture sensitivity coefficient and studied the response of final crop yield to water deficit in different growth periods. The results showed that the normalized moisture sensitivity coefficients at the seedling stage, booting stage, and flowering-grain stage were 0.251, 0.524, and 0.224, respectively, which verified the rationality and feasibility of using the cumulative loss of biomass to measure the final yield loss.
Highlights
In recent years, drought has become one of the most serious natural disasters in the world as the global warming continues to intensify
The product of water production efficiency and cumulative crop transpiration is used as biomass (Eq 2), and the final yield is the multiply of biomass and harvest index (Eq 3). 2.The traditional leaf area index describing the crop growth and development process is replaced by canopy cover, and the crop senescence process is described by canopy growth coefficient and canopy decay coefficient, which quantifies the crop growth and senescence process and greatly improves the simulation accuracy of the model (Steduto et al 2009; Raes et al 2009; Hsiao et al.2009)
Where n is the number of days summer corn is exposed to water stress in a certain growth period; minCWDj and maxCWDj represent the minimum and maximum value of accumulated crop water deficit in this growth period in all simulated years respectively; θj represents the soil water content on the jth day of the growth stage under the rain-fed condition simulated by the AquaCrop model; θWP is the water content at the wilting point, and θF is 70% of the field capacity
Summary
Drought has become one of the most serious natural disasters in the world as the global warming continues to intensify. Drought disaster sensitivity is a study on the loss rate of aboveground biomass under various drought intensities at different growth stages from a dynamic perspective, which is of great significance to accurately identify the critical water sensitive periods of summer maize growth and formulate accurate irrigation schemes. It is because of its dynamic nature that the expression form of applying it to the improvement of agricultural drought index is complex, which is not conducive to popularization and application. In this study, according to the crop evapotranspiration and final yield of summer maize under sufficient moisture and rainfed conditions simulated by AquaCrop crop model in Shijin Irrigation District from 1951 to 2016, the Jensen model was used to calculate the crop moisture sensitivity coefficient to verify the rationality and feasibility of selecting biomass accumulation as a measure in the study of drought sensitivity, and lay the foundation for the improvement of subsequent agricultural drought indicators
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