The characteristics of nitrogen and phosphorus loss from rice field by natural rainfall runoff were studied in Shuangqiao Farm of Jiaxing city

located at the Yangtz river delta region. The experiment was conducted using the fifteen plots method with an irrigation water-supported system. From results

we could get these information as follows: firstly

the highest total nitrogen (TN) concentration was 22.15 mg/L

and 4.84 mg/L for total phosphorus (TP) which exceeded more than the criterion for TN and TP regulated by our national government. Secondly

dissolved nitrogen was the predominant losing nitrogen form in runoff

of which nitrate nitrogen had about a percentage of 40~80

and 3.4~27 percent only for ammonium nitrogen

however

there was 76~79 percent of particular phosphorus moving in runoff. Thirdly

the discharge of nitrogen and phosphorus with runoff losing from rice field was 0.23~0.80 kg/hm~2 and 0.07~0.15 kg/hm~2 respectively

which both was less than one percent of the nitrogen fertilizer input. Finally

it was found that rainfall and fertilizer were two main factors influencing nitrogen and phosphorus loss in runoff

and there was a significant relativity among rainfall

fertilizer input and nitrogen and phosphorus loss load.