Effects Of Main Control Cultivation Factors On The Formation Of Yield Gap And Nitrogen Use Efficiency Gap In Wheat After Rice Stubble

In this study,by collecting the data of 21 years（1998-2018）literature on the main cultivation measures（sowing date,density and nitrogen fertilizer）,compared with the optimum sowing date,the conventional sowing density of 220-240×104/hm2,and the conventional nitrogen fertilizer application of 225-240 kg/hm2,the change range of yield and yield components was quantitatively analyzed;And through two years in Suining,Xuzhou,wheat after rice stubble sowing time（suitable sowing and late sowing 20 days）,density（D180,D240,D300）and nitrogen application（N225,N270,N315）experiments.The effects of sowing date,density and nitrogen fertilizer application on wheat yield,canopy structure,dry matter accumulation and nitrogen fertilizer absorption and utilization were studied.And the main controlling cultivation factors and the mechanism of the difference between wheat yield and efficiency in wheat after rice stubble were analyzed.The main results are as follows:1.Effects of main cultivation measures on Yield and yield components of Winter Wheat.Comprehensive analysis of the effects of main cultivation measures（sowing date,nitrogen fertilizer and density）on the yield of winter wheat showed that the sowing time of winter wheat had the most significant effect on the yield.Early sowing and late sowing significantly reduced the yield of winter wheat,the average yield decreased by 12.54%,the number of spike decreased by 6.19%,the kernel per spike decreased by 3.69%,and the minimum reduction of 1000-kernel weight was 1.19%,the sowing date mainly changed the spike per unit area and the kernel per spike,and then affected the yield.Compared with the conventional nitrogen fertilizer application rate of 225-240kg/m2,the yield,spike,kernel per spike and 1000-kernel weight decreased with excessive application of nitrogen fertilizer,but not significantly.Although reducing nitrogen increased the 1000-kernel weight,it decreased the spike and kernel per spike,which led to the decrease of yield.Compared with the conventional sowing density of 220-240 × 104/hm2,the density of winter wheat was reduced by more than 45 × 104/hm2.Although the kernel per spike and the weight of 1000-kernel were significantly increased,the decrease of the spike was greatly affected,which led to the decrease of the yield.The average decrease of the yield was 9.05%.With Excessive increase of sowing density,the spike per unit area increased,but the number of the kernel per spike and the 1000-kernel weight decreased significantly,and the change of yield was small.2.Effects of main cultivation measures on canopy structure of Winter Wheat.Experimental study on sowing date,nitrogen fertilizer and density in 2017-2019.In this experiment,wheat after rice stubble was sowed for 21 days late,the number of tillers decreased by 15.54%at jointing stage,which resulted in the decrease of the number of wheat population.The leaf area index and canopy light interception rate of late sowing wheat in rice stubble at flowering stage decreased significantly,which reduced the photosynthetic rate and respiratory rate of wheat population,and then led to the decrease of yield.the leaf area index,photo synthetic interception rate,photosynthetic rate and respiratory rate of population increased significantly by increasing nitrogen fertilizer application and sowing density of wheat after rice stubble,compared with the conventional sowing density of 240 × 104/hm2,the density increased When 60 × 104/hm2 was added,the photosynthetic rate and respiration rate of the population increased by 3.39%and 8.90%,and the yield increased by 2.64%;compared with the conventional application of 225-240kg/hm2,the photosynthetic rate and respiration rate of the population increased by 11.68%and 22.47%,and the yield increased by 8.04%.Therefore,the proper increase of sowing density and nitrogen fertilizer is beneficial to promote the photosynthetic production capacity at the flowering stage of wheat,and then improve the yield of wheat.3.Effects of main cultivation measures on dry matter accumulation and nitrogen absorption and utilization of Winter Wheat.Different cultivation measures had significant effects on the dry matter and nitrogen accumulation in different growth stages of wheat after rice stubble.The late sowing of wheat after rice for 21 days reduced the dry matter and nitrogen accumulation from sowing to jointing by 23.13%and 20.58%compared with the optimum sowing.Late sowing reduced dry matter and nitrogen transport of vegetative organs before anthesis by 24.00%and 6.02%,respectively.In addition,late sowing reduced the accumulation of matter and nitrogen after anthesis,agronomic efficiency and nitrogen absorption efficiency of nitrogen fertilizer,and then reduced the yield of late sowing wheat after rice stubble;increased nitrogen fertilizer and sowing density significantly increased the accumulation of dry matter and nitrogen in each growth period,dry matter and nitrogen transport in vegetative organs before anthesis,matter and nitrogen accumulation after anthesis,and then increased the yield of wheat after rice stubble.In addition,increasing the application density reduces the agronomic efficiency of nitrogen fertilizer and improves the nitrogen utilization rate;increasing the application of nitrogen fertilizer reduces the agronomic efficiency and nitrogen utilization rate of nitrogen fertilizer.In conclusion,the effect of sowing time on winter wheat yield is the most significant,followed by nitrogen and density.The main reason for the decrease of wheat yield in rice stubble was the decrease of population quality,the decrease of photosynthetic capacity,the accumulation and transportation of dry matter and nitrogen,the agronomic efficiency of nitrogen fertilizer and the efficiency of nitrogen fertilizer absorption and utilization.Therefore,it is an important technical way to improve the yield by adjusting the sowing date,increasing the sowing density and nitrogen application,and coordinating the yield components.