不同类型土壤中微生物驱动水稻根际氮素转化的差异及其对氮素吸收利用的影响

To solve the problem of low nitrogen use efficiency and serious non-point source pollution in rice production in our country, we would carry out the following researches: ① Three representative soil types would be selected to study their effect on rhizosphere effect，nitrogen transformation and related soil microbes in rice root rhizosphere soils at the main growth stages of rice. This would reveal the changing pattern of rice rhizosphere in key growth stages and its effect on microbes-driven rhizosphere nitrogen transformation in different soil types. ② The effects of soil types on nitrogen uptake and utilization of rice under different nitrogen levels would be studied to reveal the effects of soil types on nitrogen uptake efficiency of rice plants, and to propose the main points of nitrogen management techniques to gain efficient nitrogen utilization in rhizosphere of different soil types. In conclusion, in this study, rice root rhizosphere would be taken as the perspective, rhizosphere microbial community would be taken as a point of entry, to systematically reveal the impact of the changes of soil rhizosphere effect on rhizosphere nitrogen transformation process, and to identified the variance of rice nitrogen utilization under different soil types and its relationship between rhizosphere nitrogen transformation process. The study could provide a theoretical basis for nitrogen management techniques aiming at efficiently utilizing rhizosphere nitrogen in different soil types.

为解决我国水稻生产中氮肥利用率低，农业面源污染严重，急需科学“减肥”的实际问题，开展以下针对性研究：①选用3种有代表性的土壤类型，研究其在水稻主要生育期对根际效应及根际土壤氮素转化过程的影响，对水稻根际氮素转化过程的影响、对相关功能微生物的影响。揭示不同土壤类型中，水稻根际效应在关键生育期的变化规律及其对水稻根际微生物驱动氮素转化过程的影响。②研究土壤类型对不同氮肥水平下水稻氮素的吸收利用的影响机理，揭示土壤类型对水稻氮吸收效率的影响，提出针对不同土壤类型中根际氮素高效利用的氮肥管理技术要点。综上，本研究以土壤和根系的互作界面—根际为视角，以驱动水稻根际氮素转化过程的根际微生物群落为切入点，系统揭示土壤类型引起的水稻根际效应变化对根际氮素转化过程的作用，找出水稻氮素吸收利用在不同土壤类型下的差异及其与根际氮转化的关系，为提出针对不同土壤类型中根际氮素高效利用机理的氮肥管理技术提供理论依据。

不同质地土壤类型中，水稻根际效应在关键生育期的变化规律和对水稻根际氮素转化过程的影响不尽相同。在不同生育期，水稻根际效应都会显著增强土壤的硝化过程，提高土壤硝态氮含量。根系分泌物的pH值变化虽然不大，但是分泌的有机酸含量在不同处理中差异较大。从微生物分子生态学角度研究土壤可知，施肥和根际效应都会显著影响土壤微生物种群beta多样性，水稻的根际效应显著提高了土壤微生物的种群间多样性和微生物OTU数量。水稻根际土壤中的优势种群主要有gamma变形菌、acidimicrobiia，delta变形菌等。在不同土壤类型下，水稻的氮素吸收利用对不同氮肥处理有差异化地响应。HN和LNM处理在壤土和粘土中最有利于水稻地上部氮素积累，而在砂壤土中，以SBF处理最佳。而不同土壤类型中，LNM最适宜水稻根系氮素积累。不同土壤类型中，LNM处理都可以得到最佳的产量，而砂壤土中，SBF处理也可以得到与LNM一样高的产量水平。综合以上研究结果，我们提出了针对不同土壤类型中根际氮素高效利用的氮肥管理技术。壤土和粘土非常适合采用减氮配施有机肥的方式进行水稻氮肥管理，砂壤土中，一次性基施缓控释肥也同样可以达到最佳的产量。