title: Scenario analysis for reduction of effluent load from an agricultural area by recycling the run-off water.
abstract: We reviewed rates of nitrogen (N) removal in paddy fields and wetlands. Then we developed a numerical model to simulate N flow in an agricultural paddy field area and analyzed scenarios for recycling the agricultural run-off, including field drainage, from an agricultural area with an irrigation/drainage system. In it, we considered N removal in paddy fields, a regulating reservoir, and canals. The review showed that the rate constant for N removal in paddy fields and wetlands was 0.025 m/d under natural conditions and 0.01 m/d under dark conditions. The scenario analysis of recycling paddy field run-off within the model area indicated that a large amount of the effluent load occurred during the transplanting period and that recycling could reduce the effluent N load. The effluent N load would be equal to the inflowing N load at a 48% recycling rate. In this scenario, paddy fields accounted for most of the reduction in the effluent N load, and the mean removal rates per unit area of paddy field and regulating reservoir were 53.6 g ha(-1)d(-1) and 222.6 g ha(-1)d(-1) , respectively.
authors.affiliation: National Institute for Rural Engineering, Tsukuba Science City 305-8609, Japan.
authors.forename: E
authors.initials: E
authors.lastname: Shiratani
authors.forename: I
authors.initials: I
authors.lastname: Yoshinaga
authors.forename: Y
authors.initials: Y
authors.lastname: Feng
authors.forename: H
authors.initials: H
authors.lastname: Hasebe
mesh_terms: D000383:Agriculture; D003247:Conservation of Natural Resources; D017753:Ecosystem; D009584:Nitrogen / Q000302:isolation & purification*; D012275:Oryza; D014872:Water Movements; D014876:Water Pollution / Q000517:prevention & control*; D018508:Water Purification / Q000379:methods*
chemical_list: D009584:Nitrogen