title: Nitrogen loss through lateral seepage in near-trench paddy fields.
abstract: A near-trench paddy field experiment with five urea application rates (0-360 kg N ha(-1) in 90-kg increments) was conducted on a paddy soil in the Taihu Lake Region of China to elucidate N losses through lateral seepage during three rice (Oryza sativa L.) growing seasons. The total N (Nt), NH4(+) -N, and NO3(-) -N concentrations in the lateral seepage water increased with increasing N rates. The seasonal Nt fluxes by lateral seepage varied from 6.8 to 25.6 kg N ha(-1) for urea application rates of 90 to 360 kg N ha(-1). Lateral seepage accounted for 4.7 to 6.6% of the Nt applied, implying that lateral seepage was an important pathway of N loss from near-trench paddy fields. The cumulative N loss via lateral seepage was significantly related to N fertilization rate (P = 0.05). Floodwater level was also identified as a main factor affecting N losses via lateral seepage from paddy fields, as indicated by a positive linear relationship (R2 = 0.43) between floodwater level and daily lateral flow during the flooded period (P = 0.05). Under the conditions of these experiments, a shallow floodwater depth of 50 mm, urea application rates of 90 kg N ha(-1) or less, and no rainfall within 1 wk after N application reduced N losses by lateral seepage from paddy fields.
authors.affiliation: Dep. of Environmental Engineering, College of Natural Resources and Environmental Science, Zhejiang Univ., Hangzhou, China. liang410@zju.edu.cn
authors.forename: Xin-Qiang
authors.initials: XQ
authors.lastname: Liang
authors.forename: Hua
authors.initials: H
authors.lastname: Li
authors.forename: Ying-Xu
authors.initials: YX
authors.lastname: Chen
authors.forename: Miao-Miao
authors.initials: MM
authors.lastname: He
authors.forename: Guang-Ming
authors.initials: GM
authors.lastname: Tian
authors.forename: Zhi-Jian
authors.initials: ZJ
authors.lastname: Zhang
mesh_terms: D000383:Agriculture / Q000379:methods; D002681:China; D004784:Environmental Monitoring; D005308:Fertilizers; D009566:Nitrates / Q000032:analysis; D009584:Nitrogen / Q000032:analysis*; D012275:Oryza; D000644:Quaternary Ammonium Compounds / Q000032:analysis*; D011891:Rain; D014508:Urea; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D005308:Fertilizers; D009566:Nitrates; D000644:Quaternary Ammonium Compounds; D014874:Water Pollutants, Chemical; D014508:Urea; D009584:Nitrogen