根际沉积碳与秸秆碳共存下作物与微生物氮素竞争机制及其调控

Plant-microbial competition for nitrogen in rhizosphere in rhizosphere under straw returning regime: mechanisms and manipulation

根际沉积碳与秸秆碳输入是植物-土壤-微生物交互作用的纽带,对土壤微生物群落结构和功能具有巨大的影响。然而,这些碳的输入会使氮素发生强烈的生物固持作用,造成土壤微生物与植物之间的氮素竞争。这不仅会对作物生长产生负面影响,而且会改变土壤有机碳氮的稳定性。国内、外前期的研究工作虽对秸秆还田后土壤有机质的周转情况有一定认知,但受传统研究方法局限,并未全面阐述植物源有机碳在作物与微生物氮素竞争以及在土壤微生物群落结构与功能演替过程中的驱动作用。在当前我国大力推荐秸秆全量还田的大背景下,理解全量秸秆还田下作物与微生物氮素竞争机制及其调控途径对建立合理的秸秆还田管理措施、改善土壤有机质稳定性并提高氮素利用率具有重大意义。本文综述了秸秆还田下作物与微生物间的氮素竞争规律,以及根际沉积碳与秸秆碳共存下根际激发效应的发生机制及其生态重要性,同时介绍了根际沉积碳与秸秆碳共存下植物和微生物间氮素竞争的关键微生物菌群研究的主流观点和方法,并提出根际沉积碳与秸秆碳共存下作物与微生物氮素竞争机制及其调控途径,以期为提升作物对氮素的吸收以及土壤中氮素的利用效率,减少传统化学肥料的施用,增加土壤有机质的稳定性提供理论基础。

Rhizodeposit-and straw-carbon(C)inputs steer the plant-soil-microbes interactions and have great impacts on microbial community structure and function.However,these C inputs will cause a strong microbial processed nitrogen(N)immobilization and subsequently enhance N competition between crops and microbes.This can potentially have a negative effect on crop growth and alter the stability of soil organic C(SOC).Although previous studies have largely explored the SOC turnover under straw returning,it is still unable to illuminate the role of plant-derived organic C in the process of the plant-microbe N competition and in the structural and functional successions of soil microbial community.As straw returning is vigorously promoted in China recently,it is crucial to understand the mechanism and regulation measures regarding plant-microbe N competition for a superior straw returning management,and subsequently to improve the stability of SOC and the use efficiency of soil N.This paper reviewed the rule of plant-microbe competion for N under straw-return regime,and the possible mechanism of rhizospheric priming effect under the coexistence of straw-and rhizodeposit-C,and its ecological importance.Meanwhile,we introduced the mainstream viewpoints and methods for identifying the involved microbial species in the process of N competition between crops and microbes under the coexistence of rhizodeposit-and straw-C,and provide a potential manipulation way for improving the plant N uptake and soil N use efficiency and increasing organic matter stability with lower chemical fertilizer input.