减施化肥对水稻土壤氮循环微生物的活性与多样性的影响

In order to protect the desired agricultural productivity and sustainability, application of green manure is the most practical option in rice production systems. It has been demonstrated that green manure plays an important role in improving rice yield when decreasing the application rates of fertilizer. Most research focused on the ratio of green manure to fertilizer and the effects of different green manure/fertilizer ratios on the rice yield, the nutrient of paddy soil, physico-chemical properties of paddy soil and the numbers of culturable microbes in the soil. However, the effects of fertilizer reduction when applied with green manure on nitrogen-fixing bacteria, ammonia oxidizers and denitrifiers in paddy soil are still unknown. This project will focus on the effects of fertilizer reduction on nitrogen-cycle related functional microbes in a paddy field based on a 5-year Monitoring Experiment Station in Minhou County, Fujian Province. Rice will be applied with the same rate of green manure (Chinese milk vetch, MV) in our project. Six treatments will be setup as 100% chemical fertilizer (CF), MV+100% CF, MV+80% CF, MV+60% CF, MV+40% CF, MV, and no CF and MV as controls. To look into the effects of fertilizer reduction on quantity and diversity of functional communities in paddy soil, culture-independent methods based on the analysis of nifH, amoA and nirK genes will be used in this study. The results of this project will be helpful to understand the function of nitrogen-cycle related functional microbes in the process of replacement of fertilizer by MV.

在翻压绿肥的情况下适当减少化肥用量，既可保持水稻产量又可保持土壤的可持续利用。目前研究多集中在绿肥和化肥的配施比例的探讨以及不同配施比例对水稻产量、稻田养分、土壤理化性质以及可培养微生物数量的影响，而关于翻压绿肥后减施化肥用量对氮素功能菌的影响的研究尚属空白。本课题拟以福建省闽侯县5年定位试验站稻-紫云英轮作系统为材料，设置对照（不施紫云英和化肥）、单施100%化肥、紫云英+100%化肥、紫云英+80%化肥、紫云英+60%化肥、紫云英+40%化肥以及单施紫云英共7个处理，采用基于nifH、amoA以及nirK基因为基础的分子生态学方法，深入研究紫云英轮作下化肥减量对水稻土壤氮素功能菌的数量、群落结构和组成、固氮酶、硝化和反硝化作用活性的影响以及氮素功能菌与土壤特性、固氮酶活性、硝化和反硝化作用及农艺性状之间的相关性。研究结果可为合理配施绿肥、减施化肥的水稻可持续发展的施肥模式提供理论依据。

本项目以紫云英配施减量化肥的水稻土壤为研究对象，研究了翻压绿肥配施减量化肥（对照CK、单施化肥NPK、紫云英配施80%化肥MF80、紫云英配施60%化肥MF60以及紫云英配施40%化肥MF40）对土壤功能菌（固氮菌、氨氧化菌和反硝化菌）的影响。结果表明，紫云英可以替代40%的化肥仍可维持水稻产量不减产，即MF60是较适宜的施肥模式。紫云英配施减量化肥有利于提升分蘖期土壤肥力和固氮菌的数量，紫云英的施用和化肥用量都是影响土壤固氮菌群落结构的重要因素。同时紫云英配施减量化肥有助于收获期土壤肥力和氨氧化潜势的提升；翻压紫云英处理增加了土壤氨氧化细菌丰度而降低了氨氧化古菌丰度；相较于化肥，紫云英对氨氧化细菌的群落结构影响较大，氨氧化细菌相较于氨氧化古菌在氨氧化过程中起重要作用。与单施化肥相比，紫云英配施减量化肥降低了nirK和nirS型反硝化菌丰度；翻压紫云英显著影响了nirK型反硝化菌群落结构，而对nirS型无显著影响；反硝化作用活性与nirK型反硝化菌丰度呈显著正相关。该项目研究结果可为合理配施绿肥、减施化肥的水稻可持续发展的施肥模式提供理论依据。