Improvement And Application Of AquaCrop Model Based On The Compensation Effect Under Plastic Mulching

In recent years,climate change has a profound impact on agricultural production activities in Northwest China,especially in the arid and semi-arid areas of Northwest China,crop production is more sensitive to climate change.However,in the context of climate change,it is not clear whether mulching can lead to excessive consumption of soil water,whether it can still maintain stable yield and increase yield in different rainfall years,and mitigate the impact of climate change.Crop model is widely used in the prediction of the impact of climate change on crop yield and the assessment of its long-term effect.It is a powerful tool to solve the above problems.In this study,mulching experiments were carried out in Yangling of Shaanxi Province for many years.The applicability of Aqua Crop model in Guanzhong area of Shaanxi Province was verified through the actual observation of soil moisture,temperature,crop growth and yield in winter wheat summer maize rotation system.Firstly,the compensation coefficient of film mulching accumulated temperature is calculated by observing the growth period of crops,and the compensation effect of film mulching temperature is coupled with the Aqua Crop model to verify the simulation effect.Secondly,the compensation coefficient of film mulching accumulated temperature is recalculated by the method of logistic equation fitting.Based on the new compensation coefficient,the compensation effect of film mulching accumulated temperature is coupled and verified with Aqua Crop model.This paper focuses on solving the problem that the parameters of crops treated by mulching and not mulching are inconsistent in the process of simulating crop development by Aqua Crop model.Thirdly,using the improved Aqua Crop model to simulate and study the effects of the growth,yield and water use of the mulched winter wheat summer maize rotation system in different rainfall years under the condition of climate change.The main conclusions are as follows:（1）The Aqua Crop model has a good simulation accuracy in the growth and yield formation process of mulching winter wheat summer maize rotation system in Guanzhong area.Therefore,the Aqua Crop model can be used to predict and evaluate the productivity of mulch.However,the Aqua Crop model ignores the compensation effect of film mulching,which makes it unable to simulate the effect of film mulching on the growth and development of crops such as the process of ground temperature change.（2）Based on the original quantitative method to calculate the accumulated temperature compensation coefficient,both winter wheat and summer maize from sowing to seedling stage is greater than that from seedling to overwintering（tasseling）,which indicates that the effect of mulching on the early stage of temperature increase is better.Coupling the compensation effect of film mulching with Aqua Crop model,the simulation of each index of the model is closer to the measured value,which the crop parameters consistent with CK.（3）Using logistic equation to simulate plant height and biomass of winter wheat and summer maize,the law of plant height and biomass changing with accumulated temperature is basically the same.The simulation is based on the Aqua Crop model improved by the quantitative method of logistic equation.The root mean square error（RMSE）between simulated and measured canopy coverage values ranged from 1.6%to 7.6%,the RMSE of biomass values ranged from 0.607 to 1.995 t hm^-2,and the RMSE of soil water storage values ranged from 14.7 to 28.4 mm.The simulation effect is better than that of the model with film covered module and the improved Aqua Crop model based on the original quantitative method.（4）Since the 1960s,the annual average temperature in Guanzhong area（Wugong,Baoji and Xi’an area）has been increasing and the rainfall has been decreasing.Due to the temperature rise,the growth period of wheat and maize was shortened.especially since1980s,the growth period of Wheat in Wugong,Baoji and Xi’an was significantly reduced,with a reduction of 4.45,6.18 d decade^-1and 9.56 d decade^-1;the maize decreased by 2.76,4.82 d decade^-1and 5.94 d decade^-1.（5）The mulching had higher yield than control,and its coefficient of variation was small under different precipitation year types.Also,the mulching can still obtain the grain yield,and it can promote yield compared with the control under drought climate.Additionally,the mulching can effectively reduce the evaporation of soil surface layer during maize seedling stage,conserving more rainfall in soil,which is needed for maize growth in later stage.Although mulching increased soil water consumption,it effectively improved water use efficiency of maize by conserving soil water and stabilizing crop yield.The summer maize mulching in Guanzhong can adapt to climate change effectively and deal with drought climate to a certain extent,it has a good effect of increasing production and stabilizing production.