O11-01 : Nitrous oxide (N2O) reducing denitrifiers inoculated to soil have mitigated N2O emission and promoted red clover growth

Gao Nan¹,Shen Weishou¹,Kakuta Hiroko¹,Nishizawa Tomoyasu²,Nagamine Tadashi³,Takaya Noriko³,Isobe Kazuo¹,Otsuka Shigeto¹,Senoo Keishi¹
1Grad. Sch. Agri. Life Sci., Univ. of Tokyo, 2Ibaraki Univ. College of Agri., 3ROM Co., Ltd
In Japan, soils are main source of N₂O emissions, and contribute 25% of the total anthropogenic N₂O sources, mainly due to nitrogen (N) fertilizer use. Moreover, the excessive use of chemical fertilizers in agriculture has various adverse effects on soil quality, soil ecological services, and thus crop productivity. Therefore, development of environmentally-friendly bio-fertilizers has been attempted worldwide. The aim of this study is to achieve effective strains for development of the bio-fertilizers. Seven N₂O-reducing denitrifier strains (Azospirillum sp. and Herbaspirillum sp.), previously isolated from rice paddy soils, were inoculated into soil after application of chemical fertilizer in greenhouse. The red clover (Trifolium pretense L.) germination rate was significantly higher after inoculation of the N₂O-reducing denitrifier strains. The fresh weight, seedling height and leaf area were greater in soils inoculated with the N₂O-reducing denitrifier strains than non-inoculated soils. Moreover, the N₂O emission was mitigated after inoculation of the N₂O-reducing denitrifier strains in comparison with non-inoculated treatments. In conclusion, the N₂O-reducing denitrifiers could promote red clover germination rate and growth, and mitigate N₂O emission from soils as well. It will be practical to develop the bio-fertilizer by using these N₂O-reducing denitrifiers.

keywords:Bio-fertilizer,denitrification,greenhouse gas,plant growth promotion rhizobacteria,soil fertility