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