抄録
Public interests on introducing sustainable agriculture have recently been increasing especially in Shiga prefecture, Japan, where the green payments program for certified eco-farmer started in 2004. It is essential to introduce a comparable method so that we can evaluate an environmental improvement brought by the alternative practices. In this study, we compare the environmental impact induced by conventional and by sustainable rice paddy field cultivation that reduces the use of fertilizer and water consumption. The inventory analysis is applied throughout the cultivation process and the fertilizer production process for nitrogen, phosphorus, energy consumption, carbon dioxide, methane and nitrous oxide. Furthermore, we specified those substances in eutrophication of water system impact, global warming impact and energy consumption indices. By each of specified indices, environmental impacts of both agricultures are evaluated quantitatively. As a result, it is clarified that large part of energy consumption in rice paddy field cultivation results from agrochemical and fertilizer production process, therefore, the reduction of agrochemical and fertilizer application is effective to decrease energy consumption. In addition, the reduction rates of energy consumption, eutrophication potential and global warming potential are estimated quantitatively. This result clearly shows that introduction of water conservation method can mitigate not only eutrophication potential of water system but also global warming potential and energy consumption.
