A municipal scale eco-balance analysis of carbon and nitrogen cycle in Japanese agriculture

摘要

Nitrogen (N) and carbon (C) flow concerning Japanese agriculture were quantified at a municipal scale in Japan for the year 2005 to analyse the influence of different N flows on the environment. Based on activity data from statistics and inventory data from literature, the farmland soil surface nitrogen balance (FSSNB), global warming potential (GWP) and the amount of agricultural production were calculated for each municipality. The average FSSNB of municipalities ranged from -40-10,210 kg N/ha/yr with a weighted mean of 166 kg N/ha/yr. The carbon input to Japanese farmland soil ranged from 0-39.4 Mg C/ha/yr, with a weighted mean of 1.22 Mg C/ha/yr for whole Japan. Livestock production was found to have high influence on the C and N flows. The agricultural production as well as GWP of municipalities showed a positive correlation to FSSNB. Thus, reduction of FSSNB can also reduce GWP, however, the agricultural productivity will also decrease under the present practices. An re-allocation of manure is required to reduce the N load from extremely high regions, but also changes in agricultural production structure that integrate livestock and arable farms are required to manage the N flow related to Japanese agriculture in a more sustainable way.