Challenges of reducing excess nitrogen in Japanese agroecosystems

Fertilizer N use in Japan has decreased by about 30% from 1960 to 2000, while keeping a little increase in cereal yields. This has resulted in a significant increase in apparent nitrogen use efficiency, in particular for rice. On the other hand, national N Icad on the environment associated with the production and consumption of domestic and imported agricultural products has almost tripled during this period, mainly due to the dramatic increase of imports of food and feedstuffs. The environmental problems, including water and air pollution, caused by the excessive loads of N are serious public concerns and there is an urgent need to minimize N losses from agricultural production. In order to meet the necessity for reducing the environmental impacts by excess N, political and technological measures have been taken at regional and country levels. In recent years, the Japanese government has embarked on a series of policies to encourage transition to an environmentally conscious agriculture. Promoting proper material circulation with reducing fertilizer impact and utilizing biomass and livestock wastes is emphasized in these policies. The effectiveness of environmental assessment and planning for reducing regional and national N Icad has been discussed. Implementation of environmentally friendly technologies and management, both conventional and innovational, have been developed and adopted in Japanese agriculture. The effectiveness of conventional technologies in reducing environmental reactive N has been re-evaluated. Innovative technologies, such as use of controlled availability fertilizers and livestock wastes compost pellets, are being investigated and extended.A comprehensive approach that applies political and technological measures with closer cooperation is necessary to control reactive N in the environment.

作 者： Kazuyuki YAGI Katsuyuki MINAMI   作者單位： Kazuyuki YAGI(National Institute for Agro-Environmental Sciences (NIAES), Tsukuba 305-8604, Japan)

Katsuyuki MINAMI(Kitasato University, Sagamihara 228-8555, Japan) 

刊 名： 中國科學C輯（英文版）  SCI 英文刊名： SCIENCE IN CHINA SERIES C (LIFE SCIENCES)  年，卷(期)： 2005 48(z2)  分類號： P5  關鍵詞： nitrogen use efficiency   nitrogen load   environmental impacts   nitrogen fertilizer   Japan  

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