Simulating The Influences And Countermeasures Of Climate Change On The Maize Production With The APSIM-Maize Model

Climate is an important input factor for crop growth and yield formation.To ensure future food security under global climate change,it is of great significance to evaluate the impacts of climate change on agricultural production and explore the optimal combination of various agronomic countermeasures.In this study,the Guanzhong Plain in Shaanxi Province was chosen as an target region to explore the influences of climate change on maize production in China.Firstly,the APSIM-Maize model was parameterized and validated based on the experimental data of summer maize（variety“Zhengdan958”）for 2009-2012 in Yangling and those of spring maize（variety“Xianyu335”）for 2017-2018 in Changwu of Shaanxi Province.Then,based on historical climate data for 1971-2010 in two locations,a total of 36 global climate models（GCMs）and NWAI-WG Statistical downscaling method were utilized to project future climate change for 2031-2060（2050s）and 2071-2100（2090s）under two emission scenarios of the Representative Concentration Pathway of RCP4.5 and RCP8.5.Finally,combined with projected climate data,the validated APSIM-Maize model was used to simulate the maize development and yield formation under potential and rainfed conditions with 20 different combinations of sowing dates and planting densities.We explored the major climatic impact factors on maize growth in this region and quantified maize potential productivity.We also evaluated the impacts of future climate change on maize potential productivity and the effectiveness of interactions of sowing dates and planting densities to cope with the negative impacts of climate change in the Guangzhong Plain,.Some main results and conclusionts have been obtained as follows.（1）In model calibration and validation,the determination coefficient（R²）were 0.95,0.90and 0.76 between simulated and observed values of anthesis,maturity and grain yield;the root mean squared error（RMSE）were 2 and 5 days for anthesis and maturity dates;and the normalized root mean squared error（NRMSE）was 12%for grain yield.The results indicated that the APSIM-Maize model had great adaptability in modeling the maize growth and yield formation in the Guanzhong Plain of China.（2）Based on historical climate for 1971-2010 under the normal sowing dates and planting densities,simulated average potential and rainfed yields for summer maize were 8756 and4236 kg ha^-1,and 13138 and 6163 kg ha^-1 for spring maize.There could be a 52%and 53%of yield increase through full irrigation,respectively.Precipitation was the major climatic impact factor on maize growth in this region.Proper delaying sowing date with increasing planting density could effectively increase maize potential productivity and water use efficiency in this region.The potential and rainfed yields for summer maize could be improved by 20.0%and24.2%;and could be improved by 21.7%and 22.8%for spring maize.The potential and rainfed water use efficiency for summer maize could be improved by 22.7%and 20.8%;and could improved by 14.4%and 20.0%for spring maize.（3）In the future climate scenarios,the average temperature,solar radiation and precipitation in the maize growth period could be increased.Climate change would shorten maize growing season,increase evapotranspiration,and decrease potential productivity.Temperature rise is the major climatic impact factor.The potential and rainfed yields would decrease by 14.5-37.1%and 23.9-51.2%for summer maize;and would decrease by 14.1-36.7%and 20.1-47.0%for spring maize.The potential and rainfed water use efficiency would decrease by 19.7-44.2%and 24.0-50.8%for summer maize and would decrease by 24.6-51.2%and 22.5-45.2%for spring maize.（4）Later sowing with a higher planting density could effectively mitigate the negative effects of climate change on maize growth.When 1-2 weeks delayed with increasing density to 8-10 plants m^-2,the loss of potential and rainfed yield on account of climate change could be reduced by 7.8-13.1%and 1.1-5.6%for summer maize,and by 12.4-24.0%and 3.1-17.0%for spring maize,respectively.The water use efficiency would also increase obviously,especially under full irrigation scenario.It would increase 10.2-18.1%for summer maize,and22.7-35.9%for spring maize.However,the asynchronous change of potential and rainfed yield under the optimal combinations of sowing dates and planting densities would result in an increased yield gap under most scenarios because of influence of drought stress.It was concluded that future climate change could reduce the maize potential productivity in the Guanzhong Plain of northwest China.Optimization of sowing dates and planting densities could be effective countermeasures to alleviate the negative impacts.However,water stress would remain as a serious issue that restricts local maize yield improvement.Therefore,incorporating heat or drought tolerant cultivars,proper irrigation,water retention strategies（e.g.plastic film mulching）with other agronomic measures might help to more effectively alleviate the negative impacts of future climate change on local maize production in the future.