Research On Water Supply And Demand And Irrigation Schedule Optimization Of Corn In Heilongjiang Province Based On AquaCrop Mode

In the context of climate change,regional crop water supply and requirements,yield,amd agricultural irrigation are affected by temperature,radiation,and precipitation.Under the general trend of increasingly severe water shortage,the relationship between crop water requirement（ET_c）,irrigation water requirement（I_r）,yield and water use efficiency（WUE）under climate change is beneficial to improve the agricultural application of irrigation,and formulating a reasonable irrigation schedule could provide a basis for the rational distribution of irrigation water resources in the actual area.Based on the daily meteorological data of 26 meteorological stations in Heilongjiang Province from 1960 to2020,this study uses the calibrated and verified Aqua Crop model to simulate the maize growth periods,and elucidates the changes in water supply and requirement,yield and WUE during the maize growth periods under climate change.The spatial and temporal distribution characteristics were explored to explore the relationship between ET_c,yield,I_r and WUE during the maize growth periods,to clarify the irrigation schedule of different hydrological years under the rainfed and irrigation scenarios of Heilongjiang Province,to formulate irrigation strategies for different hydrological years,and to optimize the irrigation schedule.The results of the study are as follows:（1）The annual average minimum temperature（min T）,maximum temperature（max T）,radiation,reference crop evapotranspiration（ET₀）,precipitation,ET_c,Ir,and WUE during the maize growing periods were 13.15℃,24.9℃,19.73MJ/m²,565.15mm,433.92mm,444.81mm,188.95mm,11.423 ton/ha and 2.6 kg·m^-3.In terms of spatial distribution,min T and max T show a decreasing trend from south to north,with the highest temperature in the southwest region;radiation showing a decreasing trend from west to east;precipitation showing a trend of increasing first and then decreasing from west to east;ET₀,ET_c,I_r,and yield showing a trend of decreasing first from west to east and then increasing;WUE showing a trend of increasing first and then decreasing and then increasing from west to east。（2）The min T,max T,ET_c,I_r,yield and WUE increased by 0.042°C,0.156°C,2.98mm,1.4 mm,0.35 mm and 0.063kg·m^-3 per decade,respectively,during the maize growth periods,radiation and ET₀ decreased by 0.006MJ·m^-2 and 1.35 mm per decade.The ET_c in the western part of the study area was high but showed a decreasing trend.Except for the central part,the precipitation showed an increasing trend,and the yield and water use efficiency showed an increasing trend.The drought in the western region showed a trend of easing.（3）In extremely dry years,dry years,normal years,and wet years,maize ET_c and ET_a decreased first and then increased from the west to the east during the four types of hydrological years.I_r exhibited a decreasing trend from the west to the east.Compared with the irrigation scenario,the rainfed scenario’s average yield only decreased by 2.18,0.55,0.03,and 0.05 ton/ha,while the WUE increased by 0.32,0.4,0.33,and 0.21 kg·m^-3in the extremely dry years,dry years,normal years,and wet years,respectively.The results indicated that in the normal and wet years,the WUE was high in the central regions,and irrigation did not significantly increase yield;further,we determined that irrigation should not be considered in these two hydrological years in Heilongjiang Province.In the extremely dry and dry years,irrigation was necessary because it increased the yield,even though the WUE decreased.This study provides a theoretical basis for studying the regional irrigation schedule in Heilongjiang Province.