Soil Phosphorus Release to the Water Bodies in the Upland Fields of Yellow Soil Areas and Impacting Factor

Soil phosphorus release to the water bodies in the upland fields of yellow soil areas and impacting factor was studied in Guizhou province. The results showed that the content of dissolved active P of surface runoff from various upland fields of yellow-soil were significantly different, which the concentrations of dissolved active P of runoff correlated with the contents of available-P, amorphous oxides of A1, and organic matter in the soils. The amount of soil phosphorus release to the water bodies affected by the level of applying P fertilizer and the process of corn growth, which with fertilizing from 150 to 900 kg P205 ha^-1 in the soil with high P level, the average contents of dissolved active P in the permeability-water of the soil increased from 0.020 mg L^-1 to 0.137 mg L^-1. The amount of soil phosphorus release to the water bodies also affected by environmental factor, which the amount of soil phosphorus release significantly increased under the conditions that temperature is 30℃-35℃, water/soil ratios is 15：1-25：1, submergence-time by water is 12-18 h and pH value of acid rains is 3.82-3.73.

Effects of land use change on hydrological cycle from forest to upland field in a catchment,Japan

Understanding the effects of land use change on the hydrological cycle is very important for development of sustainable water resource in an upland field catchment.In this study,soil and hydrological properties in an upland field catchment,which was reclaimed partially from a forest catchment,were compared with another forest catchment.The soil properties of surface and subsurface layers were investigated in the two catchments.The soil was compacted and waterholding capacity of soil in the upland field catchment became smaller after the reclamation from forest to upland field,which decreased infiltration rate and water storage in the soil layers.We found that peak discharge and direct runoff in the upland field catchment increased compared with the forest catchment.Annual evapotranspiration from the upland field catchment tended to be lower due to the change in vegetation type and soil properties.Furthermore,a semi-distributed hydrological model was applied in the upland field catchment to understand the integrated effects of reclamation on the hydrological cycle.The model parameters,which were determined using a nonlinear optimization technique—the Shuffled Complex Evolution method(SCE),were compared between the two catchments.The Nash and Sutcliffe coefficient was used to evaluate the model performance.The simulated results indicated that evapotranspiration was decreased and change in discharge was more obvious in the surface layer.We considered that declined infiltration and water storage and increased peak discharge and direct runoff have a negative impact on water resources in the upland field catchment.This study will provide information for forest managers in planning and making decisions for land and water resource management.