O11-02 : Nitrous oxide (N2O) emissions from agricultural soils have been mitigated after inoculating N2O-reducing denitrifiers to granular organic fertilizer

Shen Weishou¹,Gao Nan¹,Camargo Estefania²,Shiratori Yutaka³,Wei Wei¹,Kakuta Hiroko¹,Nishizawa Tomoyasu⁴,Isobe Kazuo¹,Otsuka Shigeto¹,Senoo Keishi¹
1Grad. Sch. Agri. Life Sci., Univ. of Tokyo, 2Federal Univ. of Rio Grande do Sul, 3Niigata Agri. Research Instit., Ibaraki Univ. College of Agri.
Soils are main source of N₂O emissions due to nitrogen (N) fertilizer use. The aim of this study is to develop a novel N₂O mitigation method through inoculation of N₂O-reducing denitrifiers into granular organic fertilizer. Totally 41 N₂O-reducing denitrifier strains, previously isolated from various rice paddy soils, were evaluated after inoculation into the granular organic fertilizer in soil microcosms. Attempts have been made to improve N₂O reduction of the candidate strains, including addition of CuSO₄ into culture media, starvation of inoculant cells, and use of 2 mm-sieved soil and fertilizer. The results show that N₂O reduction has been enhanced for specific genera of candidate strains in culture conditions after addition of Cu. Tens of strains are more effective to reduce N₂O at 2 mm-sieved soil or fertilizer than at 4 mm-sieved soil or non-sieved fertilizer, in particular at N₂O emission peak in soil microcosms. However, starvation of the inoculant cells has contrasting effect on N₂O mitigation. Finally, ten effective strains have been selected for field plots in Tokyo and Niigata. The N₂O fluxes in the field plots are being measured after application of the inoculated granular organic fertilizer now. Our preliminary results suggest that N₂O emissions have been mitigated after inoculation of Herbaspirillum spp. into the granular organic fertilizer.

keywords:Denitrification,global change,greenhouse gas,microbiological technology,organic fertilizer