Nitrogen stock and farmer behaviour under rice policy change in Japan.

Mitigating the environmental impact of nitrogen (N) derived from agricultural production is a significant issue in our progression towards a sustainable society. This study aims to estimate the N stock (i.e., as the accumulation of N input into farmland that is neither taken up by the crops nor discharged into the environment, but rather remains in the soil) related to rice production in Japan and to identify the relationship between the economic behaviour of rice farmers and N stock. The results indicate a persistent reduction in N stock since the early 1990s, caused mainly by the change in N input by a change in government policy away from production subsidies to more extensive use of market mechanisms. It seems clear that production subsidy policies provide little incentive for farmers to reduce their N input; however, even if the introduction of market mechanisms, farmers may not properly evaluate the contribution of N stock to agricultural production. Consequently, it may be difficult to achieve the optimal level of N stock from an environmental impact perspective. To achieve the optimal N stock, the relationship between farmer behaviour and N stock needs to be better understood.