title: Nitrogen removal function of recycling irrigation system.
abstract: The purpose of this study was to clarify the nitrogen (N) purification capacity of a paddy field in a recycling irrigation system. Irrigation water was sampled at 12-h intervals during the irrigation period from April to September 2003. In addition, ponded water in a paddy field was collected at three points (inlet, centre and outlet). Total amounts of N were 30.7 kg ha(-1) in inflow and 27.8 kg ha(-1) in outflow. Thus, the net outflow load was -2.9 kg ha(-1). The N removal rate constant when N removal is expressed as a 1st-order kinetic was 0.017-0.024 m d(-1). This value is close to values of wetlands and paddy fields in the literature. We found a good correlation between recycling ratio and N removal effect. These results indicate that the recycling irrigation system accumulates N in the irrigation/drainage system, and thus the paddy field does a good job of water purification by removing N.
authors.affiliation: National Institute for Rural Engineering, 2-1-6, Kan'nondai, Tsukuba city, Ibaraki 305-8609, Japan. thitomi@nkk.affrc.go.jp
authors.forename: T
authors.initials: T
authors.lastname: Hitomi
authors.forename: I
authors.initials: I
authors.lastname: Yoshinaga
authors.forename: Y W
authors.initials: YW
authors.lastname: Feng
authors.forename: E
authors.initials: E
authors.lastname: Shiratani
mesh_terms: D000383:Agriculture / Q000379:methods; D003247:Conservation of Natural Resources; D017753:Ecosystem; D007564:Japan; D009584:Nitrogen / Q000032:analysis*; D010758:Phosphorus / Q000032:analysis; D007507:Therapeutic Irrigation; D014872:Water Movements; D014874:Water Pollutants, Chemical; D014876:Water Pollution; D018508:Water Purification; D014881:Water Supply
chemical_list: D014874:Water Pollutants, Chemical; D010758:Phosphorus; D009584:Nitrogen