秸秆条带还田影响东北春玉米农田氮素转化和利用的机制研究

The amount of straw production from spring maize cultivation is so enormous that straw returning (SR) to soil is widely performing for the green development of agriculture in northeastern China. Also, it is significant for improving the soil quality and easing the negative ecological effects from straw burning. The “N competition” is occurred by using full-thickness SR approach, while the strip SR might be promising to crack the above issue. Therefore, to give an insight to answer this practical question, the effects of various SR modes on the transformation and utilization of nitrogen is worth to evaluate, as well as their mechanism. A field including plot and micro-plot experiments will be conducted in this proposal to examine the difference between full-thickness SR and strip SR with four treatments as follow: full-thickness SR with plow tillage (PTS), strip SR with plow tillage (PSS), full-thickness SR with rotary tillage (RTS), strip SR with rotary tillage (RSS). 15N isotope tracer and Monolith 3D sampling methods will be used for determining N transformation and localization in plant-soil system, the real time qPCR and Illumina MiSeq high-throughput sequencing technology would be induced to detect the abundance of functional genes (nirK, nirS, nosZ and amoA ) and microbe structure related to N cycling in soil. Thus, we could evaluate the effects of different SR modes on N dynamic in soil from the view of N transformation and utility and microbe molecular knowledge. We believe the theory of N cycling in soil under SR will be improved our results, the practical SR approach could be supported by deeper theory from this research as well.

东北春玉米产区秸秆产量巨大，秸秆还田作为农业绿色发展的重要措施，在改善农田土壤质量及生态问题中发挥重要作用。传统秸秆全层还田存在秸秆腐解与作物生长“争氮”问题，秸秆条带还田为解决上述问题提供了可能。因此，为给生产实践问题提出理论依据，秸秆还田方式对农田土壤氮素转化及利用的影响及其机制亟待系统深入研究。本申请项目将以玉米翻耕/旋耕耕作方式下的秸秆全层还田/条带还田为研究对象，利用15N同位素示踪技术及Monilith 3D空间取样法研究不同秸秆还田方式对农田土壤氮素转化及利用特征影响，使用荧光定量PCR和高通量测序技术分析土壤氮循环密切相关微生物的nirK、nirS、nosZ基因和amoA基因丰度和群落结构组成，从土壤氮素利用和分子生态学角度阐明秸秆还田方式对农田氮素动态变化的作用机制。研究结果将有利于完善秸秆还田条件下农田土壤氮素循环的相关理论，为秸秆还田农艺措施提供理论依据和技术指导。

东北春玉米产区秸秆产量巨大，秸秆还田作为绿色农业发展的重要措施。本项目围绕秸秆还田方式对土壤氮素转化及利用的影响及机制开展了研究。以秸秆带状还田（RSS，旋耕条带还田；PSS，翻耕条带还田）和传统全层还田处理（RTS，旋耕全带还田；PTS，翻耕全层还田）为研究对象，利用15N同位素示踪、Monilith 3D空间取样法、荧光定量PCR和Illumina MiSeq高通量测序技术分析研究农田土壤氮素动态及相关微生物的特征与规律。结果表明：.RSS和PSS较RTS和PTS处理平均提升9.5%玉米地上部氮素吸收量，PTS和PSS处理有较高的土壤矿质氮储量。0-30 cm土壤剖面，PSS处理有更高水平NH4+-N水平分布，RTS和PTS处理在0-30 cm RSS和PSS处理在30-60 cm土壤剖面分别有较高水平NO3--N分布。RSS和PSS处理提升了10.5%土壤硝化潜势和22.4%净氮矿化速率，说明上述方式在生育后期可改善农田土壤矿质氮转化能力。在拔节期，RSS和PSS处理0-60 cm土层15N同位素分布比例高于RTS和PTS处理（78%，80% vs 72%，73%），而其他组分比例较低。说明拔节期前RTS和PTS处理损失了更高比例的肥料源氮素，成熟期表现一致，使得土壤中残留15N同位素比例，而RSS和PSS处理在籽粒和茎秆部分15N同位素比例更高。.与RTS和PTS处理相比，RSS和PSS处理提高了2.7-3.6倍amoA-AOB基因拷贝数，1.2-3.1倍amoA-AOB和反硝化细菌nirK、nirS、nosZ的Chao1指数，1.8-2.1倍amoA- AOB香农指数。RSS和PSS处理增加了Mesorhizobium属相对丰度占比，但Burkholderia、Bacteria_unidentified和Azoarcus属反硝化细菌相对丰度具有较低占比。多元置换方差分析表明，秸秆还田对微生物群落结构和土壤理化性质解释程度分别达60.3%、60.6%，耕作因素为5.5%、13.7%，未能解释部分为29.6%、22.4%。相关分析表明，SOC、TN、NO3--N和>0.25 mm粒径团聚体水平对其氨氧化和反硝化过程微生物群落多样性具有显著的影响。.项目研究结果及结论将有利于完善秸秆还田条件下农田土壤氮素循环的相关理论，为秸秆还田农艺措施提供理论依据和技术指导。