Abstract: In order to clarity effects of different nitrogen application levels on soybean yield and soil microflora after replanting in winter wheat. In this work, we set four nitrogen treatments of 0 kg·hm^-2(N₀)、225 kg·hm^-2(N₁)、375 kg·hm^-2(N₂)、525 kg·hm^-2(N₃) in wheat season set during 2017-2018. Additionally, we introduced dilution plate method and MPV dilution method so as to study the effects of different nitrogen application rates of summer-sowing soybean yield and soil microflora in winter wheat. The results demonstrated that nitrogen application in wheat season had significant effect on soybean yield and soil microflora. From the results, we can deduce that the summer-sowing soybean yield, the number of soil bacteria, fungus, actinomycetes, ammonia bacteria and aerobic azotobacter have also increased at first and then decreased as nitrogen application rate in winter wheat enhanced. The suitable nitrogen application rates of N1 and N2 in wheat season can promote the growth and reproduction of soil microbial population, which can also optimize the flora structure and improve the yield of soybean. The excessive nitrogen application (N3) could stimulate nitrification and increase the number of denitrifying bacteria and reduce the soybean yield, accelerate nitrogen loss in soil and thereby reduce nitrogen use efficiency. Taking fully the amount of nitrogen applied in winter wheat season is 225~375 kg hm^-2 into consideration, the highest yield of summer-sowing soybeans reached an average of 2 988.93 kg·hm^-2. Comparing with the CK two-year soybean production, the average yield increased by 24.05%. It is beneficial to improve the microbial flora of the soybean soil and regulate the soil ecological environment which also provide a theoretical basis for the rational application of nitrogen in the post-annual soybean.

Key words: nitrogen application level, summer-sowing soybean, post-effects, soil microflora, yield

摘要： 为揭示冬小麦不同施氮水平对复播大豆土壤微生物区系的后效影响,于2017-2018年在小麦季设置0、225、375和525 kg·hm^-2 4个施氮处理,分别记作CK、N₁、N₂和N₃,采用稀释平板法和MPV稀释法研究冬小麦不同施氮量对复播大豆土壤微生物区系的影响。结果表明,麦季施氮量对复播大豆土壤微生物区系具有显著的后效作用。随着麦季施氮量的增加,复播大豆产量、土壤细菌、真菌、放线菌、氨化细菌及好气性自生固氮菌数量呈先上升后下降的趋势,硝化细菌和反硝化细菌数量呈不断上升的趋势;其中,麦季适宜的施氮量(N₁、N₂)更能促进土壤微生物总数的生长繁殖,优化菌群结构,提高后茬大豆产量;而过量施氮(N₃)刺激硝化、反硝化细菌数量的增加,降低大豆产量,加速土壤中氮素损失,降低氮肥利用率。综合考虑冬小麦季施氮量为375 kg·hm^-2时,复播大豆产量达到最高,平均为2 988.93 kg·hm^-2, 两年大豆平均增产23.59%,并有利于改良后茬大豆土壤微生物区系,调节土壤生态环境。本研究结果为周年轮作模式下后茬大豆合理施氮提供了理论依据。

关键词: 施氮水平, 复播大豆, 后效作用, 土壤微生物区系, 产量