Character Of Soil Phosphorus Loss From Sloping Cropland In The Hilly Area Of The Central Sichuan Basin During The Corn Growing Season

Soil and water loss of sloping cropland in the hilly area of the central sichuan basin is the most serious soil erosion areas in sichuan province.Due to the prominent contradiction between human and land, that increase a large number of scattered farmland every year. In addition, the unreasonable tillage practice. That not only leads to serious soil erosion and land productivity decline, but also a large number of P loss accelerated eutrophication process. So, this study about the simulated rainfall experiments and runoff plot experiment were employed to investigate characteristics of surface erosion, subsurface runoff and phosphorus loss among different tillage practices(flat planting, longitudinal ridge and cross ridge)and different slops(10°、15°、20°) during the corn maturity on scattered sloping cropland in the hilly area of the central sichuan. It aimed to clear purple soil erosion and dynamic characteristics of phosphorus loss. That reveal the relationship between the growth of com plants and soil loss of phosphorus removal, to lay the foundation for improve the agricultural non-point source pollutant migration mechanism theory and predictive model construction, and serve the sustainable agricultural development of hilly area of the central Sichuan basin and the three gorges reservoir area ecological environment construction. Main research results are as follows:(1) The continuation of runoff with time undulate or zigzag increasing trend generally under the three tillage practices during the corn growth.Runoff and sediment loads were the most serious under the longitudinal ridge, Runoff loss of up to156.84L·m-2,sediment loss of up to719.569g·m-2. Cross ridge effect was best in terms of sediment erosion control, but it’s subsurface runoff was larger。(2) The dynamic change trend of total phosphorus and dissolved total phosphorus were consistent under every tillage practice, phosphorus loss of longitudinal ridge was most serious.The dissolved total phosphorus loss of flat planting was68%of total phosphorus. Longitudinal ridge accounts for72%, and cross ridge accounts for73%.Particulate phosphorus loss is relatively few. Higher proportion of dissolved total phosphorus by subsurface runoff, all were around82%. Tillage practice impact on the concentration of phosphorus in runoff is small, and phosphorus loss mainly depends on changes of runoff. Although, the total of subsurface runoff were less compare with surface runoff, but phosphorus content very high(3) The dynamic change of sediment available phosphorus loss and erosion of law sediment dynamics were similar. Sediment available phosphorus loss for the total order: longitudinal ridge> flat planting> cross ridge. Sediment available phosphorus loss of longitudinal ridge were about1.4-2.2times higher than flat planting,2-3.2times higher than cross ridge. Significant difference of total loss was found in every tillage practice at the early stage of the cron growth, no significant difference at later growth stage.(4) The time producing runoff earlier, the greater the runoff with the increase of slope. The time producing runoff were earliest in seedling stage and tasseling stage time producing runoff at the latest. Runoff was the largest on20°slope, that were about1.4-2times higher than10°slope, and1.3-1.6times higher than15°slope. Sediment yield were about14.3-19.7times higher than10°slope, and3.8-6times higher than15°slope.(5) Available phosphorus loss were increased with the rainfall duration increased on the every slopes, and available phosphorus loss amount were increased with the increase of slope. That was the largest on20°slope, scope of the available phosphorus loss was12.87-35.49mg·m-2, that were about6.2-12.7times higher than10°slope, and3.1-3.7times higher than15°slope.So, AP loss of sediment affected by sediment erosion and corn plant growth.(6) Total phosphorus loss in surface runoff increased with the slope increase, but total phosphorus loss in subsurface runoff was the opposite.The dissolved total phosphorus was the major form of phosphorus loss in runoff. The dissolved total phosphorus in surface runoff ratio increased with the increase of the slope, and all higher than65%; The proportion of dissolved total phosphorus loss accounts in subsurface was higher,10°slope range as follows:64%-97%,15°lope range as follows:66%-93%,20°slope range as follows:57%-96%.