Distribution and Seasonal Variation of Nitrate Nitrogen Concentration in Water Environment around Nishikibaru Plateau, Aya Town, Miyazaki

Abstract

  Organic farming attracts attention as an environment-friendly agriculture. In organic farming, livestock manure compost and organic fertilizers are applied without chemical fertilizers or pesticides. However, these organic fertilizers are decomposed into nitrate ions in the soil, and most of the portion which is not absorbed by the crops is leached underground. Nitrate nitrogen is a causative agent of eutrophication in the water environment, and there is a risk of methemoglobinemia for infants to drink water. In this study, environmental water samples were collected once every two weeks for a total of 10 locations around Nishikibaru plateau, in Aya town, Miyazaki, where organic farming is flourishing and measured those nitrate nitrogen concentrations. As the result, the concentration was stable in only one of the 10 locations, especially at a concentration exceeding 10 mg/L from around April. However, it is considered adequate to be careful about drinking spring water in the water environment around the Nishikibasu plateau in Aya Town at present.