Soil microbial community and self-sustaining nitrogen supply in unfertilized paddy soil

Research Project

Project/Area Number	16K12644
Research Category	Grant-in-Aid for Challenging Exploratory Research
Allocation Type	Multi-year Fund
Research Field	Design and evaluation of sustainable and environmental conscious system
Research Institution	Hirosaki University
Principal Investigator	SUGIYAMA Shuichi 弘前大学, 農学生命科学部, 教授 (00154500)
Project Period (FY)	2016-04-01 – 2018-03-31
Project Status	Completed (Fiscal Year 2017)
Budget Amount *help	¥3,640,000 (Direct Cost: ¥2,800,000、Indirect Cost: ¥840,000) Fiscal Year 2017: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000) Fiscal Year 2016: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
Keywords	水田 / 窒素固定 / 土壌 / 細菌群集 / 窒素 / 窒素固定遺伝子 / 水田土壌 / 無施肥 / 水稲栽培 / メタン抑制 / 地球温暖化 / 持続的農業 / 窒素循環 / 無肥料 / 微生物
Outline of Final Research Achievements	High-yield paddies exist even without fertilizer application for a long period of time in Japan. In this study community structure of nitrogen fixing bacteria and capacity of nitrogen supply of soil were compared between four paddies. The soils were incubated under flood condition for eight weeks and capacity of nitrogen supply of the soils and abundance changes in nitrogen fixing bacteria were examined. Results : (1) The amounts of increased inorganic nitrogen during the incubation corresponded with the yield level of unfertilized paddies.(2)The clear differentiation of nitrogen fixing bacterial communities were found between the four paddies. (3) Most bacteria that increased their abundance during the incubation belonged to methane oxidizing bacteria. This result suggests that the bacteria responsible for nitrogen fixation in paddy soil utilize methane oxidation as its energy source and thus contribute to reduction of methane emission from paddies.