Optimal Sowing Date Of Winter Wheat In Jiangsu Province Under Climate Change

In view of the short duration,limited spatio-temporal conditions,and no consideration of climate change and other problems in previous studies,this study aimed to stabilize and increase winter wheat yield in Jiangsu Province,took optimization of winter wheat sowing date as the main means,and took Meta-analysis and DSSAT model simulation as the main research methods.We selected different winter wheat varieties("Yangmai 16" and"Yangmai 23"),different meteorological stations(Ganyu,Gaoyou,Nanjing and Kunshan)and meteorological data of different periods(1980-2018 and 2031-2060)to systematically study the suitable sowing dates of winter wheat in Jiangsu Province,in order to provide reference for guiding local farmers to rationally use sowing dates to deal with climate change.It provides a theoretical basis for further improving the productivity of winter wheat.The main conclusions are as follows:(1)The results of Meta-analysis showed that the sowing date of winter wheat in Jiangsu Province showed a general trend of delay with the change of time in recent 20 years.Taking October 19 as the normal sowing date,the winter wheat sowing 13-17 days later in Jiangsu Province had a significant increase in yield.Appropriate late sowing can stabilize the winter wheat yield in Jiangsu Province by affecting the spike number of winter wheat.As the years went on,the effect of late sowing on yield reduction appeared earlier and earlier,and(weak)spring winter wheat had better adaptability to sowing date.(2)In the verification of DSSAT model,the model can well represent the crop parameters of "Yangmai 16" and "Yangmai 23".From 1980 to 2018(historical stage),the effective accumulated temperature during the whole growth period of winter wheat showed an extremely significant increasing trend(P<0.01).From 2031 to 2060(the future RCPs scenario),the effective accumulated temperature during the growth period showed a significant or extremely significant increasing trend,and the performance of RCP8.5 scenario effective accumulated temperature>RCP4.5 scenario effective accumulated temperature.In the historical stage and future RCPs scenario,the diurnal sequence of anthesis and maturity all showed a decreasing trend with the increase of years.Compared with the base year,the day sequence of anthesis and maturity in different sowing dates was also advanced,and with the postponing of the year,the number of days advanced was more and more,and the number of days advanced in different RCPs scenarios was RCP8.5>RCP4.5.(3)In the historical stage,the yield of "Yangmai 16" and "Yangmai 23" showed a decreasing trend with the postponing of sowing date,and the suitable sowing date was October 15.In future RCPs scenario,the suitable sowing date was delayed compared with the historical stage:Under the RCP4.5 scenario,the suitable sowing date of "Yangmai 16"fluctuated significantly in different regions,while the suitable sowing date of "Yangmai 23"was approximately October 15.Under the scenario of RCP8.5,the suitable sowing date of"Yangmai 16" was mostly November 5,and the suitable sowing date of "Yangmai 23" was October 15 to November 5.With the postponing of the year,the yield of "Yangmai 16" and"Yangmai 23" in Jiangsu Province was shown as historical stage>RCP4.5 scenario>RCP8.5 scenario.Regional analysis showed that the potential winter wheat yield in Jiangsu Province was decreasing from south to north(Kunshan>Nanjing>Gaoyou>Ganyu).