风沙半干旱区玉米/花生间作缓解花生氮阻遏的微生物生态学机制

Maize-peanut intercropping can alleviate the Nmin inhibitory effect of peanut, and the underlying mechanism has been widely studied, which mainly focused on the nitrogen (N) forms and root exudates in soil. Given that there are close relationships between soil microorganism and soil N form, plant root and root exudate, soil microorganism might have direct and/or indirect influences on the N fixation of legumes. Lots of researchers suggested that maize-peanut intercropping can deeply impact soil microbial community structure, however, how does maize-peanut intercropping alleviate the Nmin inhibitory effect by regulating of soil microbial community structure has been rarely studied. Depend on the National Agricultural Experimental Station for Agricultural Environment, Fuxin, this project plans to exam the effects of maize-peanut intercropping combined with N fertilization on the soil microbial community structure and their function; demonstrate the relationship between soil microbiota and function genes participate in N cycling and soil N forms; combined with soil environmental factors, try to explore the effect of core microorganisms and their functions on N fixation ability of peanut and the driving factors. With the above research, it is expected to reveal the underlying mechanism of alleviation of Nmin inhibitory effect by maize-peanut intercropping from the aspect of microbial ecology, and also provide new theoretical basis on the promotion of N use efficiency by maize-peanut intercropping.

玉米和花生间作能够缓解花生氮阻遏效应，关于其机理已经有很多研究，但主要集中在土壤氮素形态和根系分泌物方面。由于土壤微生物与土壤氮素形态、作物根系及其分泌物之间具有很密切的关系，因此土壤微生物可直接或间接对豆科作物的固氮能力产生影响。虽然很多研究表明间作可改变土壤微生物群落结构，但目前对玉米花生间作减缓氮阻遏效应的微生物生态学机理尚缺乏系统研究。本项目依托国家农业环境阜新观测试验站的玉米花生间作长期定位微区试验，研究玉米花生间作复合氮肥梯度对土壤微生物群落结构及其功能的影响；明确间作下土壤微生物群落结构和氮素循环关键功能基因与土壤氮素形态之间的关系；结合土壤理化指标的变化，探讨核心微生物物种及其功能对花生根瘤固氮能力的影响及其驱动因子，以期从土壤微生物生态学角度揭示玉米花生间作缓解花生氮阻遏效应的潜在机理，为风沙半干旱区玉米花生间作缓解花生氮阻遏效应，进而提高氮肥利用率提供科学支撑。

玉米和花生间作能够缓解花生氮阻遏效应。本项目依托国家农业环境阜新观测试验站的玉米花生间作长期定位微区试验，系统研究了玉米和花生间作对花生结瘤特性、氮循环功能基因丰度、氮储量、作物氮素吸收利用特征及产量的影响。主要结果如下：（1）氮肥对花生存在“氮阻遏”效应，而间作提高了花生根瘤数和根瘤鲜重，但间作在减缓“氮阻遏”效应方面存在负作用，且随着施氮量增加该负作用增强。(2)在氮素吸收利用方面，间作优势明显（氮吸收当量比NER>1），其中玉米氮素吸收能力为主要贡献者（NERm为0.73—0.93）；随施氮量增加间作优势减弱，且主要体现在玉米的氮素吸收能力降低。（3）土壤中AOA amoA基因丰度高于AOB amoA基因的丰度。AOB amoA的丰度与硝化潜势（NP）无显著相关性，而AOA amoA的丰度与NP呈显著负相关。随机森林分析表明，AOB/AOA，特别是关键物种AOB/AOA是重要的预测的NP的变量。关键物种AOB/AOA与土壤C/N呈负相关。间作提高了花生和玉米土壤中关键物种AOB/AOA和土壤C/N的差异。关键物种AOA和AOB的氮循环基因和碳水化合物酶相关基因富集分析进一步支持了施氮和间作通过调控铵盐浓度和土壤C/N来调控土壤AOB/AOA，进而调节土壤硝化潜势的观点。（4）间作使nifH基因丰度平均提高26.5%。SEM分析表明间作系统内生物固氮而非矿质氮肥提高了花生土壤N素积累，其中花生根瘤鲜重（NFW）和nifH丰度可解释土壤46%的全氮（STN）变异。NFW和nifH对STN有正向影响（P < 0.05）。NFW（系数0.507）和nifH丰度（系数0.511）对STN变异的贡献几乎相同。NFW仅受施氮量的调节，nifH丰度主要受种植模式的影响。（5）项目获得辽宁省农业科学院科技创新一等奖1项，在国内外期刊发表论文2篇。