Study On Water Yield Effect Of Summer Soybean Winter Rape And Simulation Of Irrigation Schedule Model In Guanzhong Area

Water is an important element affecting crop growth and development.However,the precipitation in Guanzhong area is uneven and there are generally unreasonable irrigation methods,resulting in low efficiency of water resources utilization.Therefore,adopting reasonable irrigation system can improve crop yield and realize efficient utilization of water resources.Taking summer soybean and winter rape as the research object,this study was carried out by different water treatments combined with crop model simulation.Using the field test data,aiming at the parameter correction and verification of aquacrop model,evaluate the adaptability of the model to simulate the dynamic changes of growth and development and yield of summer soybean and winter rape,analyze and evaluate the simulation results of the model under different water treatment conditions,and provide a theoretical reference for its production and planting in Guanzhong area;Based on the calibrated aquacrop model,the precipitation in the growth period of summer soybean and winter rape for 59 years from 1961 to 2019 was divided into different typical precipitation year types by using the drought index,and three year types of wet year,normal year and dry year were obtained.The effects of different irrigation quotas on irrigation yield in different growth periods under different year types were discussed,The irrigation system and management measures for maintaining high yield and ecological benefits in summer soybean winter rape farmland ecosystem in Guanzhong Plain were discussed.The main research results are as follows:（1）The effects of different water treatments and environmental factors on crop growth process and yield composition were revealed.Based on the field data,the effects of different irrigation amount and irrigation period on the growth and development,leaf area index LAI,aboveground biomass,yield and evapotranspiration of summer soybean winter rape were systematically studied.In the early stage of summer soybean,with the increase of irrigation,the growth of leaf area index is not significant.The water shortage in the key growth period will affect the formation of biomass in the later stage,and the amount of biomass is positively correlated with the yield.There are great differences in meteorological factors such as precipitation,air temperature and relative humidity in crop growth season under different precipitation year types,resulting in fluctuations in crop yield,irrigation water and water use efficiency of precipitation.Crop water consumption has a positive correlation with temperature,a negative correlation with relative humidity and precipitation,a very significant negative correlation with daily average temperature and a very significant positive correlation with relative humidity.（2）To evaluate the applicability of aquacrop model to the simulation of summer soybean winter rape in Guanzhong area.Based on the experimental data,the aquacrop model was calibrated and verified,and its ability to explain and simulate the dynamic changes of summer soybean winter rape growth and development,canopy coverage,soil water content,aboveground biomass accumulation,yield and water use efficiency under different water conditions were comprehensively evaluated.Aquacrop model can better simulate the dynamic changes of summer soybean winter rape growth and development,canopy coverage,soil water content,aboveground biomass accumulation,yield and water use efficiency.The standard root mean square error nrmse of canopy coverage is in the range of 4.4-17.4%;The standard root mean square error of soil water content nrmse is between 3.19-14.6%;The standard root mean square error nrmse of aboveground biomass is between 4.6-19.3%;The standard root mean square error nrmse of yield is between 1.57-4.8%.The model can better simulate the growth and development of summer soybean winter rape and the dynamic change of soil water content.（3）The most suitable irrigation schedule under different precipitation years in Guanzhong area was obtained.The aquacrop model was used to simulate the different irrigation amount and irrigation time of summer soybean Winter Rape under different precipitation years.In order to achieve the maximum water use efficiency and maximum yield,the optimal irrigation system in Guanzhong area under different precipitation years was selected.The pod setting stage of summer soybean is the key stage of its yield formation.In wet years,a higher yield of 2780kg·hm^-2can be obtained without irrigation,and the water use efficiency can reach 0.76kg·m^-3.Irrigation is selected in this period in normal water years and dry years.The irrigation quota is 45 mm and 70 mm respectively,and the yields are 2699 kg·hm^-2and 2486kg·hm^-2respectively,and the water use efficiency is 0.7 kg·m^-3and 0.82 kg·m^-3respectively.The sprouting period of winter rape is the key period of yield formation.Irrigation in this period can significantly increase yield and have large water use efficiency,which can achieve the goal of water saving and high yield.Without irrigation in wet years,a higher yield of 4511 kg·hm^-2can be obtained,and the water use efficiency can reach 0.79 kg·m^-3.Irrigation is selected in the sprouting period in normal water years and dry years,and the irrigation quota is 45 mm and 70 mm respectively,The yields were 5059 kg·hm^-2and 5037kg·hm^-2respectively,and the water use efficiency was 0.74 kg·m^-3and 0.7 kg·m^-3respectively.This study can provide information support for the field management of summer soybean and winter rape in Guanzhong area,and can better realize the effect of efficient utilization and high yield of water resources.It should be noted that the parameter calibration in this study is mainly adjusted manually,which may lead to deviation in the accuracy of the model.In the future research,the optimization algorithm will be applied in the parameter adjustment process,which can improve the efficiency of model parameter adjustment and the accuracy of the model.In addition,this study only uses aquacrop model to study a test area in Guanzhong area,and the verification and application under the test environmental conditions.In the future,it is necessary to carry out a large number of studies in the test areas with different soil characteristics in different areas of Guanzhong,collect a large number of field test data,establish the database of aquacrop model,and optimize the irrigation system in different areas of Guanzhong.