Effects Of Green Manure Rape Returning Stages And Nitrogen Fertilization On Maize Development And Nitrogen Utilization

In order to explore the suitable return stages of green manure rape and the effects of nitrogen fertilization on maize yield and nitrogen utilization with green manure rape returning The experiment was conducted in a split-plot design,The main plots were the stages of green manure rape returning,including:initial flowering stage（G1）,full-bloom stage（G2）,pod development and maturation stage（G3）and the control of winter fallow field（G0）,The subplots were for five nitrogen levels during maize cultivation including:0 kg·hm^-2（N0）,135kg·hm^-2（N135）,270 kg·hm^-2（N270）,405 kg·hm^-2（N405）,540 kg·hm^-2（N540）,and 540kg·hm^-2（N540）;The nylon net bags with green manure rape were buried to study the decomposition and nutrient release characters of rape at different growth stages.The conclusions are as follow:The decomposition and nutrient releasing characters of rape at different stages were fast at first and then slowed down.At stages of initial flowering and full-bloom,the regulations were almost the same,of which the cumulative release percent of nitrogen and phosphorus were both more than 80%,the cumulative release percent of carbon and potassium were more than 87%and 90%,respectively.In 2019 and 2020,the phosphorus release percent at pod development and maturation stage were only 71.65%and 65.43%,for the nitrogen and carbon,the data were 68.04%and 51.90%,and 77.16%and 57.64%,respectively.The release percent of potassium were relatively higher by more than 84%.Compared with the control of winter fallow field,rape returning at stages of initial flowering and full-bloom improved the ear traits of corn,increased the dry matter and nitrogen accumulation of corn at corn-silk and maturation stages,and improved the dry matter and nitrogen transport capacity of the vegetative organs as well,by promoting the photosynthate transportation and distribution to the grain.Among the treatments,the rape returning with applying N270 at full-bloom stage gained the highest yield.The numbers of grains in row and per ear,and yield increased by 7.43%,11.05%,and 13.94%,respectively;Compared with the control of winter fallow field,the dry matter and nitrogen accumulation at corn-silk and maturation stages increased by 18.39%and 10.86%,24.70%and 10.05%,the amount of dry matter and nitrogen transportation increased by 149.05%and 42.04%,respectively;while with rape returning at pod development and maturation stage,the average dry matter accumulation amount at corn-silk and maturation stages decreased by 7.26%and5.96%,nitrogen accumulation decreased by 7.95%and 9.50%,the transportation efficiency of vegetative organs to the grain also significantly reduced,with dry matter and nitrogen transportation decreased by 4.68%and 4.81%,respectively.Compared with the control of winter fallow field,rape returning at initial flowering,full-bloom,and pod development and maturation stages under nitrogen application,the soil organic matter content increased by 8.25%,11.14%,and 3.02%,the total nitrogen content increased by 2.74%,4.08%,1.60%,and the content of alkali-hydrolyzable nitrogen increased by 7.79%,12.77%,4.12%,respectively.Among them,rape returning at full-bloom stage combined with N270 nitrogen remarkably enhanced the content of soil organic matter,total nitrogen,and alkali-hydrolyzable nitrogen.