Sadao Eguchi1,2, Nanae Hirano1, Shin-Ichiro Mishima1, Kazunori Minamikawa1
1 Institute for Agro-Environmental Sciences NARO (NIAES), Kannondai 3-1-3, Tsukuba, Ibaraki 305-8604, Japan
2 E-mail sadao@affrc.go.jp
Abstract
Indirect nitrous oxide (N2O) emission from Japanese agricultural soils is accounted as comparable to direct N2O emission derived from inorganic or organic nitrogen (N) fertilizers in Japan. This paper tries to evaluate the mitigation potential of indirect N2O emission by reducing N leaching and runoff in different land uses at different prefectures in Japan. We used the national scale agricultural activity data of different prefectures from 1985 to 2005 and the N leaching and runoff monitoring data in Japan published after 1980. The N leaching and runoff values in vegetable and tea fields under various improved agricultural practices such as organic fertilizer application, slow release fertilizer application with reduced N application rate, cover cropping for green manure, etc., showed about 25% to 30% lower values from those under conventional practices, suggesting that such improved practices are similarly effective to mitigate indirect N2O emission from agricultural fields.