集団茶園系のノンポイントソースによる硝酸負荷の実態　－静岡県牧之原台地における事例－

抄録

The authors measured the nitrate concentration of river water from a catchment basin of the collective tea fields in the Makinohara plateau in Shizuoka prefecture, from June 2002 to May 2003. About 1,000 kg · ha^-1 · y^-1 of nitrogen fertilizer has been used in the tea fields for about 30 years. The annual average NO₃-N concentration and pH were 24.4 mg · l^-1 and 4.9, respectively. NO₃-N concentration decreased as a result of a comparatively small amount of precipitation, and repeated. The total annual nitrogen outtlow from the tea fields was 428 kg · ha^-1 · y^-1. The ratio of nitrogen load to the amount of applied nitrogen fertilizer was 79.2 %. NO₃-N load was affected by discharge from the tea fields.