农田黑土旱田改稻田土壤氮素转化与关键微生物特性研究

The drive of structural adjustment and economic benefits of agricultural products, the area of rice has reached 5.3 million hectares in Heilongjiang province. Make paddy soil nutrients and microorganisms easily affected when a large area of upland had been changed to paddy. In order to protect mollisoil resources in our country, it is necessary to explore the characteristic of this change on nitrogen transformation and key microorganism in mollisoil after upland had been changed to paddy. In this project, we use the mollisoil after which land use had been changed as the research object, using q-PCR, MiSeq high-throughput sequencing and microarray technology, and the combination of conventional physicochemical method, focusing on (1): Responses of nitrogen transformations and key microorganism (ammonia oxidizing bacteria, ammonia oxidizing Achaea and denitrifying bacteria) to land use change from upland to paddy field in mollisoil farmland, and main controlling factors; (2) investigating the effect of change from upland to paddy on key functional genes abundance and related microbial communities in the process of soil nitrogen transformation; (3) analyzing of microbial groups in the soil from the aspect of microbial functional gene diversity. Clarify dominant microbial flora which involved in soil nitrogen nutrient cycling in the cropping system and bacterial community difference. The project output will help people more comprehensive understanding of drought change paddy soil nitrogen cycling and microbial control mechanism, the change trend of drought to paddy soil fertility, and provide theoretical support for the conservation and utilization of soil resources.

农产品的结构性调整和经济效益驱动，黑龙江省水稻面积达到5300万亩，大面积旱田改种为稻田，易使土壤养分及微生物受到影响。为保护我国黑土资源，有必要从氮素转化及关键土壤微生物方面探究黑土旱田改稻田后的变化特征，本项目利用黑土旱田改稻田后的系列耕层土壤为研究对象，拟采用q-PCR、MiSeq测序和微生物基因芯片微阵列技术，结合黑土的理化性质，重点研究：（1）农田黑土氮素转化及相关土壤微生物（氨氧化细菌、古菌和反硝化细菌等）对旱田改稻田的响应规律及主控因素；（2）探讨旱田改稻田对农田黑土氮转化过程中关键功能基因丰度以及相关微生物群落变化的影响；（3）从微生物功能基因多样性层面分析土壤功能微生物类群，阐明旱田改稻田后参与氮素循环并占主导地位的微生物菌群差异。项目产出成果有助于人们更全面地理解旱田改稻田的土壤氮素循环及微生物调控机制，旱田改稻田土壤肥力的变化趋势，为保护和利用黑土资源提供理论支撑。

东北黑土在我国粮食生产上占有重要位置，是我国重点保护的土壤生态资源。本项目以东北黑土为研究对象，研究了旱田及旱田改种稻田（改种1~10年、10~20年、20~30年和大于30年）土壤的理化性质、土壤酶活性、微生物数量、几种氮循环相关功能基因及微生物群落结构的变化，研究结果表明：（1）旱改稻后显著提高了土壤pH、水分和铵态氮含量；但降低了土壤有机碳和硝态氮含量；（2）旱改稻后土壤脲酶活性显著降低，但对蛋白酶和硝酸还原酶活性影响不大；（3）旱改稻降低了土壤中的硝化细菌数量，提高了耕层土壤亚硝化细菌的数量，并提高了15~30 cm耕层土壤的反硝化细菌的数量；（4）旱改稻后，nifH基因丰度显著增加；AOA和AOB基因丰度出现大幅度的下降，说明旱改稻后土壤固氮作用增强，硝化作用显著降低；参与反硝化作用nirS、 narG和nosZ基因丰度均出现了增加趋势，且随着改种年限的延长有所上升；（5）旱改稻后nifH固氮微生物多样性指数增加，并随着改种年限的增加呈下降趋势；AOA和 AOB氨氧化微生物多样性指数受土地利用方式的影响不同，旱改稻后AOA多样性指数增加，改种20-30年达到最大值；旱改稻对AOB无影响；norB反硝化菌多样性指数变化与AOA相似，旱改稻20-30年时达到最大值；nosZ多样性指数各处理间无差异，但旱改稻降低了丰富度指数；（6）土壤含水率、pH、有机质含量对土壤nifH、AOA、AOB、norB和nosZ群落结构组成均影响显著；除此以外，全氮对土壤AOA 和nosZ群落结构的组成影响显著；土壤norB群落结构的组成还受到全氮和硝态氮含量影响；(7) 旱改稻改变了土壤团聚体微生物群落结构。研究结果初步表明东北黑土区旱改稻后土壤理化性质发生明显改变，微生物群落结构变化较大。旱改稻后土壤硝化作用减弱，反硝化作用显著加强，且随着改种年限的增加有增强趋势。该成果有助于人们更全面地理解旱改水的土壤氮素循环及微生物调控机制，为保护和维持黑土持续生产力提供科学依据。