The loss of soil phosphorus has become an important threat to the eutrophication of surface water. Red soil is widely distributed in China

and its distribution area is large. The study on phosphorus accumulation and loss in red soil can provide scientific basis for controlling agricultural non-point source pollution and preventing regional surface water pollution. In this study

5 common land use patterns including pasture

leisure land

dry land corn

vegetable land

and greenhouse were selected

and using artificial rainfall simulation method

the forms of phosphorus accumulation

the characteristics of phosphorus transfer with surface runoff and the environmental threshold under different land use types in red soil region were studied. The result showed that: (1) Soil Olsen-P contents of red soils ranged from 6.81 to 178.17 mg/kg

CaCl2-P contents ranged from 0.29 to 8.26 mg/kg

and NaOH contents ranged from 30.34 to 369.81 mg/kg

P accumulated in red soil among the different land use patterns; (2) The PSI ranged from 31.95 to 47.05 in red soil under different land use patterns

and the mean values were as follows: Grassland > Corn field > Vegetable field > Leisure area > Greenhouse; (3) The concentration of TP in surface runoff of red soil was 0.245~2.073 mg/L

TDP was 0.023~0.308 mg/L

and PP was 0.223~1.826 mg/L under different land use patterns. The average concentrations and losses of TP and PP in surface runoff of different rainfall events were consistent with the Olsen-P content in the soil surface layer

the average concentrations and losses of TDP in the order of greenhouse > Vegetable field > Corn field > Grassland > Leisure area and Greenhouse > Vegetable field > Grassland > Leisure area > Corn field

respectively. PP was the dominant form of TP in runoff under different land use patterns

which account for 82.46%~90.15% of TP; (4) There was a very significant positive correlation between soil Olsen-P and NaOH-P and CaCl2-P. As the content of Olsen-P increased

the NaOH-P and CaCl2-P increased

and there was an obvious "Change-point"

36.17 mg/kg was determined as the red soil phosphorus environmental threshold. It was also pointed out that there was a significant positive correlation between the runoff TP concentration or loss and soil NaOH-P content.