麦稻茬口期内施氮对土壤养分及微生物碳源利用的影响

Effects of Nitrogen Application on Soil Nutrients and Microbial Carbon Source Utilization during Wheat-rice Stubble Period

为解决麦秆还田后土壤微生物与苗期水稻争氮的生产问题,采用模拟土柱试验,通过设置四种处理(无麦秆无氮肥(CK)、麦秆还田+无氮肥(CM)、麦秆还田+尿素(SN)、麦秆还田+沼液(SZ)),分析了在麦秆还田后1 d和21 d的土壤有效养分和微生物碳源利用能力的变化。结果显示,CM处理的有效氮含量较CK处理下降20.58%,表明麦秆还田后无氮肥施入造成土壤有效氮含量下降;麦秆还田显著增加了土壤速效钾(AK)和有效磷(AP)的含量,其中,SZ处理的AK和AP含量增幅最大,分别达22.07%和23.20%。所有麦秆还田处理的AWCD值和Shannon指数均高于CK,麦秆还田整体提高了土壤微生物碳源代谢活性和功能多样性。相较于CM,添氮处理更有利于微生物群落分布均匀性。主成分分析和相关性分析表明土壤中的磷钾养分会促进微生物对碳水化合物和聚合物的利用和转化,而SN处理的微生物活性和代谢功能在21 d时可能受到抑制。综上,麦稻茬口期麦秆还田添加沼液更有利于改善后茬水稻苗期营养供应和土壤生态水平。

In order to solve the problem of nitrogen(N)competition between soil microbes and rice seedlings after wheat straw returning,soil columns were constructed to analyze the changes of soil available nutrients and microbial carbon source utilization capacity at 1 and 21 days after straw returning.Four treatments were set as follows:no wheat straw returning+no N addition(CK),wheat straw returning+no N addition(CM),wheat straw returning+urea addition(SN),wheat straw returning+biogas slurry addition(SZ).The results showed that CM treatment decreased available N content by 20.58%compared with CK treatment,indicating that wheat straw returning without N fertilizer addition led to reduction in soil available N.Available potassium(AK)and available phosphorus(AP)were significantly increased by all treatments with wheat straw returning,among which the extent of increase was highest in SZ treatment with AK and AP being increased by 22.07%and 23.20%,respectively.Compared with CK,higher AWCD value and Shannon index were observed in all treatments with straw returning,indicating that straw returning improved microbial carbon source metabolic activity and functional diversity.Compared with CM,N addition benefited the evenness of microbial community.Results from principal component analysis and correlation analysis indicated that soil P and K could promote microbial utilization and transformation of carbohydrates and polymers,while the microbial activity and metabolic function of SN treatment may be inhibited at 21 days after straw returning.In conclusion,wheat straw returning with biogas slurry addition in wheat-rice stubble stage may contribute to better nutrient supply and soil ecological level during the later rice seedling stage.