Abstract
Recently, nitrate-nitrogen (NO3-N) pollution in groundwater was identified as a serious problem in Gunma prefecture. The rate of satisfying the environmental quality standard(EQS) for NO3-N concentration in Gunma prefecture was lowest in Japan from 2000 to 2004. However, a significant decrease in NO3-N concentration was observed in 2005. Therefore, the factors contributing to the decrease were statistically examined. The results suggest that the area of dry field, livestock head count, and agricultural population significantly contributed to the decrease in NO3-N concentration. The enforcement of the Law on Promoting Proper Management and Use of Livestock Excreta might reduce NO3-N discharge into groundwater.
