Nitrogen loss characteristics via runoff in typical rice planting areain Northeast China under different planting managements

A field experiment was carried out during 2011 rice growing season to investigate the effect of fertilizer management on reducing nitrogen loss via surface runoff in a typical rice system in Northeast China. The field experiment in Panjin City included five treatments: control (CK), traditional management (TR), rice-crab symbiotic management (CR), organic rice management (OR), and reducing fertilizer management (RR). The amount of nitrogen loss was determined from collected surface runoff (using collection tank) for nitrate nitrogen, ammonium nitrogen and total nitrogen contents under each treatment. The results showed that the amount of ammonium nitrogen loss was significantly higher than that of nitrate nitrogen in paddy fields. The amount of ammonium nitrogen loss under TR was not significantly different from that under CR. Compared with TR, however, the amount of ammonium nitrogen loss under RR and OR dropped by 26% and 73%, respectively. Compared with ammonium nitrogen lost by drainage under TR treatment, that under CR, RR or OR treatments dropped by 23%, 34% or 67%, respectively. With respect to total N content, no significant change was noted between TR (5.89 kg?hm²) and CR (6.15 kg?hm²). Also compared with the amount of total nitrogen loss under TR, that under CR (4.76 kg?hm²) dropped by 19%. OR had the least total N content (1.93 kg?hm²) among the treatments, significantly lower (67%) than that of TR.