Characteristics of N, P and COD Loads in a Catchment Composed of Paddy Fields, Forage Fields, Tea Fields and Landfill in a Hilly and Mountainous Area of Japan

Abstract

We examined the influences of agricultural land uses on water qualities and chemical loads of some drainage canals and a river in a catchment in Kagawa Prefecture, Shikoku, Japan. The results were as follows ; (1) The types of land use affect chemical loads and water qualities in different ways. (2) Nitrogen highly affects the river water in an area, including tea fields and landfill. (3) Forage fields are mainly responsible for soluble phosphorus and organic substance (estimated from COD) loads. (4) Wastewater drained from the landfill contained a high amount of NH_4-N, which affected nitrogen loads more than the amount of NO_3-N drained from the tea fields.