Simulation Study On The Impact Of Climate Changeon Double-Cropping Rice Yield In Nanchang Region

Climate change and the development of science and technology are the main factors affecting contemporary agricultural production.In recent years,due to the increase of CO₂concentration,the global climate is experiencing significant changes characterized by warming,and the frequency of extreme climate disasters is increasing,which has a lot of impact on agricultural production.Jiangxi Province is the main province for rice planting in China.Double-cropping rice accounts for the largest proportion of rice planting in the country.Double-cropping rice planting in Nanchang is the most widely used.The model is used to simulate the changes in double-cropping rice production in Nanchang under future climate conditions,and put forward adaptive response strategies.It is of great significance for the production of double-cropping rice in Nanchang to cope with the impact of future climate change.Based on the two-year experiment and observation data of double-cropping rice in Zhongshang village,Changdong Town,Nanchang County from 2018 to 2020 and meteorological data in the study area,Ceres-rice double cropping rice production model was established,and the model was simulated and verified.The future climate scenarios under the emission concentration path of rcp4.5 and rcp8.5 were selected as the research object,and the climate change in Nanchang region in the next 50 years（2021-2070）was analyzed Based on the analysis and correction of scale data,the validated Ceres-rice model was used to simulate the changes of phenological period and yield of double cropping rice in Nanchang in the future.On this basis,the possible coping strategies of climate adaptability in the future were analyzed and put forward by changing the model factors affecting the yield of double cropping rice.The main research results are as follows.（1）The verified double cropping rice model has achieved good results in simulating phenological period and yield of early and late rice in Nanchang area.After the simulation and verification,the standard root mean square error（nrmse）of simulation results was11.67%（the effect was good）in the validation of late rice flowering stage,and the nrmse values of other phenological stages and yield simulation and validation were less than 10%（the effect was very good）,and the model could be well applied to simulate the double cropping rice production in Nanchang area.（2）Under the emission concentration path of RCP4.5 and RCP8.5,the future climate change in Nanchang is as follows:compared with the base year（1961-2019）,the annual average precipitation shows an increasing trend,and its value will be higher than the average value of the base year after 2036;the daily maximum temperature and daily minimum temperature show an increasing trend;the annual precipitation,daily maximum temperature and daily minimum temperature under the high emission scenario（RCP8.5）are greater than the medium low temperature In the emission（RCP4.5）scenario,the solar radiation showed an increasing trend,but the solar radiation value in the high emission scenario（rcp8.5）was lower than the average value in the reference year（1961-2019）.（3）Under the emission concentration path of RCP4.5 and RCP8.5,the future yield of early rice and late rice in Nanchang is lower than that in the experimental year,and the yield reduction of early rice is more obvious.In the rcp4.5 scenario,the yield of early rice and late rice increased with time,but in 2070,the yield of early rice and late rice still decreased by 24.25%and 24.47%respectively compared with the base year;in the rcp8.5scenario,the early rice yield showed a decreasing trend with time,and the late rice yield was increasing,and the early rice and late rice yield in 2070 were still reduced by 38.43%and 31.26%respectively compared with the base year.In rcp4.5 scenario,the yield of early rice and late rice was higher than that of rcp8.5 in the same period,and the number of days required for flowering and whole growth period was slightly greater than that in rcp8.5scenario.The extension of growth period may lead to the increase of yield.（4）Discovered in the research on the adaptive strategy of double-cropping rice production to cope with the impact of climate change,it is concluded that the adjustment of nitrogen application ratio（topdressing nitrogen）has a positive and positive impact on early rice yield.Under RCP 4.5 scenario,the best treatment is 2035(the yield of early rice increased by 14.56%and 8.06%respectively under the two nitrogen application modes,and the optimal yield of early rice under RCP8.5 scenario is 19.82%（2035s）compared with that before adjustment 52%（2070s）.The effect of adjusting nitrogen application rate on late rice was only positive under RCP4.5 scenario,and the best yield increase was 3.45%（2070）compared with the base year,but had no significant effect on the yield of late rice under RCP8.5.With the adjustment of nitrogen application rate,the phenological period in RCP4.5 situation was prolonged with time,and in RCP8.5 situation,the phenological period showed a trend of shortening with time.The results showed that the best nitrogen application rate was 5:3:2,which was compared with the experimental results of nitrogen application（6:3:1）,which may be due to the change of climate scenarios which changed the response of rice yield to the optimal nitrogen application rate.Reasonable change of sowing date can improve the final yield of rice to a certain extent.From 2021 to 2035,the best yield of double cropping rice can be obtained if the sowing date of early rice and late rice are advanced by about 15 days and 10 days respectively;from 2035 to 2050,the total yield of double cropping rice will be higher if the sowing date of early rice and late rice are advanced about 10 days;during 2050-2070,the total yield of double cropping rice may be the best if the sowing date is delayed by 10-15days.Therefore,the early rice planting strategy can be used as a reasonable way to reduce rice yield in the future.The results showed that,in order to reduce the negative impact of climate change on the yeild of double cropping rice in Nanchang area in the future climate situation,reasonable nitrogen application methods and changing the sowing date of double cropping rice can be used as adaptive coping strategies for future double cropping rice production,and the specific effects need to be further verified in practice.