A field experiment was conducted to investigate the effects of six fertilization treatments

no fertilization (CK)

conventional fertilization (CF)

90% of CF (90%CF)

80% of CF (80%CF)

fertilization with slow release complex fertilizer (CRF)

and organic-inorganic fertilization (MF)

on runoff and leaching losses of nitrogen in paddy field. Major results were as follows: Application of fertilizers sharply increased the concentrations of total nitrogen (TN) and ammonium nitrogen (NH4+-N) in surface water. The concentrations reached peak values in 2 days and then rapidly decreased and stabilized at below 15% of the peak values in 7 days after fertilization. It was the critical period to control runoff losses of nitrogenin one week after fertilization. Reducing fertilization could significantly reduce the concentration of nitrogen in surface and leaching water. Except for CK

the amount and rate of TN losses from different treatments through runoff were 8.81～15.78 kg/hm2 and 2.58%～4.96% of applied N

respectively. The losses of runoff TN from 90%CF

80%CF

CRF

and MF were 22.05%

34.16%

44.17% and 33.52% lower than that from CF. Similarly

the amount and rate of TN losses from different treatments through leaching were 18.86～40.39 kg/hm2 and 3.55%～11.77% of applied N

respectively. The TN losses from 90%CF

80%CF

CRF

and MF were 24.57%

26.52%

53.29%

and 26.97% lower than that from CF. Reducing 20% of fertilizer N not only could reduce the runoff and leaching losses of TN

but also could ensure rice yield and improve utilization of nitrogen.