Research On Soil Phosphorus Adsorption In The Chai River Basin And Its Riparian Area Of Dianchi Lake

The adsorption/desorption characteristic of phosphorus is an important effect on its validity and leaching process of migration in the soil. We analysis the adsorption/desorption characteristic of phosphorus in soil profile which from six different zones of the Chaihe drainage area at south of the Dianchi lake’ catchment. Combine with the soil column leaching experiments, we aim to illuminate the phosphorus leaching process of the P-riched farmland at south of the Dian Lake, and provide some data for the prevention of the agricultural non-point source pollution. The result below:1.From the upstream area of Chaihe to Dianchi lake’ catchment, soil texture has become gradually from silty clay to clay loamy and then to clay, but soil texture was the same in buffer zone and farmland of Dianchi lake’s riparian. The content of total phosphorus (3.32g/kg)and total nitrogen (1.16g/kg) of Chaihe upper section area was significantly higher than that content of total phosphorus (1.29g/kg) and total nitrogen content (0.22g/kg) of Dianchi lake’catchment, but there was no significant difference in the content of Olsen-P in these areas. The content of organic carbon in Dianchi lake’ catchment (21.84g/kg) was significantly higher than the farmland (8.07g/kg) in upstream area of Chaihe; at the same time, the content of organic carbon in buffe of Dianchi lake’s catchment (31.22g/kg) was significantly higher than the content of soil organic carbon in farmland of Dianchi lake’s catchment (12.47g/kg), phosphorus content was significantly lower than Lake District farmland, but the content of total phosphorus and total nitrogen content was no significant difference between buffer and farmland.2.The soil phosphorus adsorption equilibrium constant (K), the maximum adsorption capacity (Qmax) and buffer capacity (MBC) were significantly different in the areas that we studied, the K range of0.03-0.23L/mg, Qmax range of322-500mg/kg, MBC range of1.14-108.70mg/kg. The soil phosphorus adsorption equilibrium constant K (0.07L/mg), the maximum adsorption capacity Qmax (400.81mg/kg) and buffer capacity MBC (30.14mg/kg) of upper section area in farmland of Chaihe were significantly less than the K (0.14L/mg), Qmax (439.40mg/kg) and MBC (63.40mg/kg) of Dianchi lake’s catchment, and K (0.10L/mg), MBC (46.94mg/kg) of farmland in Dianchi lake’s catchment was significantly less than K (0.18L/mg), MBC (79.88mg/kg) in buffer of Dianchi lake’s catchment. This indicated that the phosphate adsorption capacity and buffer capacity of the soil in Dianchi lake’s catchment than upper farmland on the segment in Chaihe, while the phosphate adsorption with soil capacity and buffer capacity in buffer were also significantly higher than the farmland in Dianchi lake’s catchment. But soil phosphorus saturation DPS (10.35%) of upper section in Chaihe was significantly higher than Dianchi lake’s catchment (8.64%),also the saturation DPS of buffer (5.94%) was significantly smaller than farmland(11.34%) in Dianchi lake’s catchment. This indicated that soil phosphorus leaching potential in upstream area of Chaihe was higher than the soil in Dianchi lake’s catchment, while the leaching potential of buffer was less than the farmland in Dianchi lake’s catchment. The soil phosphorus adsorption equilibrium constant K, the maximum adsorption capacity Qmax and buffer capacity MBC decreased significantly with increasing depth of soil, that indicated the soil phosphorus adsorption capacity and buffering capacity of deep soil higher than that of topsoil; however the DPS is significantly reduced with increasing soil depth, indicated the potential for leaching was decreased with increasing soil depth.3.From the upstream area of Chaihe to Dianchi lake’ catchment, the desorption rate (DR) of soil was gradually decreased.The desorption rate DR (5.10%) of farmland in the upper section of Chaihe basin was significantly higher than desorption rate of the section of Dianchi lake’catchment (4.78%). Soil phosphorus desorption rate DR of farmland (4.9%)in Dianchi lake’ catchment was significantly greater than the buffer (4.7%),indicated that the phosphate adsorption in soil of upstream area of Chaihe was weaker than Dianchi lake’catchment, and the phosphorus that adsorpted in soil was easily desorpted, while adsorption capacity in soil of farmland in Dianchi lake’ catchment was weaker than the buffer. With the increasing of soil depth, phosphorus desorption rate is significantly lower, that indicated the ability of phosphorus adsorption in deep soil was stronger than the surface soil.4. No matter the level of soil bulk density and pore size, the content of phosphorus leaching in the soil of0-40cm was significantly higher than that in the soil of40-100cm. In the same level of soil, regardless of the level of soil bulk density, that the filtrate phosphorus of30-60um aperture was significantly higher than the soil of>60um aperture; under the conditions of the same level soil and the same pore size, that the content of phosphorus leaching in soil of bulk density (1.25g/cm3) was significantly higher than the soil of bulk density (1.45g/cm3). The content of phosphorus in the filtrate were associated with the content of Olsen-P, they showed a significantly positive correlation.