稻草还田对水稻土固氮基因(nifH)组成结构和多样性的影响

以中国科学院桃源农业生态试验站长期定位施肥试验为平台,选取稻草还田(C)、氮磷钾(NPK)、氮磷钾加稻草还田(NPK+C)和不施肥对照(CK)4个处理,在晚稻的分蘖期、孕穗期和成熟期分别采集土样,利用实时定量PCR(Q-PCR)和末端限制性片段多态性(T-RFLP)等分子生物学方法研究长期稻草还田对水稻土含nifH基因固氮微生物群落丰度、组成和多样性的影响.结果表明：与对照相比,稻草还田和单施化肥处理均显著增加nifH基因的丰度(分蘖期除外),NPK+C处理中含nifH基因的微生物数量最高;nifH基因组成也受到长期施肥的影响,其中CK处理nifH基因组成与各施肥处理明显不同,C与NPK处理间nifH基因组成存在一定差异,而NPK与NPK+C处理间无显著差异.长期施肥不会引起含nifH基因微生物群落多样性的显著改变.可见,稻草还田不仅引起nifH基因群落的组成发生变化,而且导致其数量显著增加,因而可增加土壤的固氮能力.

Effects of rice straw returning on the community structure and diversity of nitrogen-fixing gene (nifH) in paddy soil.

Taking a long-term fertilization experiment in Taoyuan Agro-ecosystem Research Station under Chinese Academy of Sciences as the platform, and selecting four treatments (no fertilization, CK; rice straw returning, C; nitrogen, phosphorus and potassium fertilization, NPK; and NPK+C) as the objects, soil samples were collected at the tillering, booting and maturing stages of rice, and the abundance, composition and diversity of nifH containing bacterial community were measured by real time quantitative PCR and terminal restriction fragment length polymorphism (T-RFLP), aimed to understand the effects of rice straw returning on the nifH containing bacterial community in paddy soil.  Compared with CK, treatments NPK+C and NPK increased the abundance of nifH containing microorganisms significantly (except at tillering stage), and NPK+C had the highest abundance of nifH containing microorganisms. Under the effects of long term fertilization, the composition of nifH gene community in CK differed obviously from that in the other three treatments. The nifH composition had definite difference between C and NPK, but less difference between NPK and NPK+C. Long term fertilization did not induce significant changes in nifH diversity. Therefore, long term rice straw returning not only induced the changes of nifH gene community composition, but also resulted in a significant increase in the abundance of nifH containing community, and hence, the increase of soil nitrogen fixing capacity.