title: Nutrient balance in a paddy field with a recycling irrigation system.
abstract: We studied nutrient balance in a paddy field that had a recycling irrigation system and evaluated the effect of the irrigation system on nutrient balance during the irrigation period, from April to August 2002. Chemical fertilizer was the main input of phosphorus; the soil absorbed about 56% of it. The amount of nitrogen supplied by the irrigation system was higher than in a representative paddy field, and the amount of nitrogen fertilizer used was decreased because the irrigation water was partly reused. About 20% of applied nitrogen was lost by denitrification. The net outflows of phosphorus and nitrogen were -0.37 and -3.98 kg ha(-1), respectively. These results indicate that our study paddy field performed well in removing phosphorus and nitrogen compounds from runoff water. A recycling irrigation system can be considered an effective way of reducing the amounts of water and fertilizer used and reducing the outflow nutrients.
authors.affiliation: Japan Soc. for the Promotion of Science, 6 Ichibancho, Chiyoda-ku, Tokyo, 102-8471, Japan.
authors.forename: Y W
authors.initials: YW
authors.lastname: Feng
authors.forename: I
authors.initials: I
authors.lastname: Yoshinaga
authors.forename: E
authors.initials: E
authors.lastname: Shiratani
authors.forename: T
authors.initials: T
authors.lastname: Hitomi
authors.forename: H
authors.initials: H
authors.lastname: Hasebe
mesh_terms: D003247:Conservation of Natural Resources; D005308:Fertilizers; D007564:Japan; D009584:Nitrogen / Q000032:analysis*; D012275:Oryza / Q000378:metabolism; D010758:Phosphorus / Q000032:analysis*; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014881:Water Supply
chemical_list: D005308:Fertilizers; D014874:Water Pollutants, Chemical; D010758:Phosphorus; D009584:Nitrogen