Abstract: Losses of soil phosphorus from pear orchards and vegetable gardens different in fertilization and field management in Dongtan of Chongming were monitored to study loads,pathways and temporal distribution of the losses from the rain-fed croplands and their affecting factors,and effects of fertilization and field management on the loss.It was found that the amount of phosphorus lost with runoff water,leaching water or sediment exceeded the critical concentration of waterbody eutrophication;Soil phosphorus loss occurred mainly with runoff sediment,which contributed 70.7%-82.2% to the total phosphorus loss.Phosphorus loss took place mainly in June,August and October,and the phosphorus loss in these three months accounted for 71.6%-73.0% of the total phosphorus loss in a year.Correlation analysis of affecting factors shows that the soil phosphorus loss from rain-fed croplands was highly related to precipitation,rainfall erosivity,runoff,phosphorus concentration in runoff,etc..Compared with the conventional fertilization and field managements,the practices of maintaining coverage of vegetation,using mulch films and running accurate drip irrigation could effectively decrease the yield of runoff and sediments and the phosphorus concentrations therein and hence the total soil phosphorus loss.In the pear orchard and vegetable field studied,the total phosphorus loss load decreased by as much as 20.6% and 12.6%,respectively.

Key words: Dongtan of Chongming, phosphorus loss, affecting factor, non-point source pollution, eutrophication prevention