Response Of Dryland Crop Yield To Climate Change And Difference In Water Use Efficiency Under Different Fertilization And Cropping Systems

Global climate change is significantly impacting grain yield,and the focus of current agricultural sustainable development is to decrease the negative impacts of climate change to maintain high grain yield.However,the adaptability of crop yields to climate change under different field management measures is unclear.In addition,water is an important factor restricting agricultural production in arid and semi-arid areas.Disclosing the impact of different field management measures on farmland water balance elements and water use efficiency is of great significance for improving agricultural water use efficiency and developing a high-yield and high-efficiency agricultural production system.Objectives of this study were to investigate the responses of crop yields to climate change,water balance components,and water use efficiency of winter wheat and spring maize under different fertilizations(no fertilization,chemical fertilization,manure fertilization,and chemical and manure fertilization)and different cropping systems(continuous winter wheat cropping,continuous spring maize cropping and wheat-wheat-maize rotation)based on a 35-year in situ experiment of the southern Loess Plateau.The long-term trends and inter-annual fluctuations of different climate variables during 1985-2020 were analyzed,and the responses of crop yields to long-term and inter-annual climate changes under different fertilizations and different cropping systems were discussed.The Hydras-1D model was used to simulate the dynamic changes of water balance components in winter wheat and spring maize fields under different fertilizations and different cropping systems over a period of 35 years,and their differences in water use efficiency were analyzed.The following conclusions were drawn:(1)From 1985 to 2020,the average of temperature,maximum temperature,minimum temperature,and sunshine hours in the study area showed a significant upward trend.The average annual precipitation was 584.7 mm with an insignificant upward trend and large inter-annual fluctuations.During the growth period of winter wheat,the average of maximum temperature,minimum temperature,and sunshine hours had a significant upward trend,while the average relative humidity had a significant downward trend.The fluctuation range of precipitation during the growth period and growth year were 171.7～373.8 mm and318.4～890.5 mm,respectively,but their long-term upward trends were not significant.The average of maximum temperature,minimum temperature,and sunshine hours during the growth period of spring maize had a significant upward trend,while the average relative humidity,precipitation during the growth period,and precipitation during the growth year had no significant trend.The fluctuation range of precipitation during the growth period and the growth year were 225.2～629.6 mm and 359.5～820.8 mm,respectively.(2)Fertilization treatments increased yield and yield variability.The impact of interannual climate variations on yield increased with the level of fertilization,while increased fertilization decreased the sensitivity of yield to climate trend changes.In this study,NPM had the most significant increase in yield,with the largest annual fluctuation,but was least affected by long-term climate trends.(3)The average normalized yield index of wheat-wheat-maize rotation in the study area was 6.5% and 18.3% lower than that of continuous winter wheat cropping and continuous spring maize cropping,respectively.The yield of continuous spring maize cropping was less affected by inter-annual climate fluctuations and long-term climate trends.Compared to continuous winter wheat cropping,wheat-wheat-maize rotation reduced the impacts of inter-annual climate fluctuations and long-term climate trends on yield.(4)The optimized Hydrus-1D model had high reliability in simulating the hydrological changes in the study fields.Fertilization significantly increased crop transpiration and reduced drainage in the 3 m soil profile.The differences in crop growing seasons and uneven precipitation lead to the differences in water balance components under continuous cropping systems,but the rotation system balanced this difference.Fertilization significantly improved water use efficiency.The rotation system in this study had lower water use efficiency due to lower yields.