Influence Of Biochar On P Sorption,Desorption And Its Transformation In Soil

Phosphorus is one of microelements which is necessary for plant growth.When P fertilizer is applied into the soil,it was easy to turn into insoluble phosphorus and fixed by soil particles.Thusutilization of phosphate fertilizer in this season is only 10%-25%.Meanwhile P is the main element of the eutrophication.Appliocaiton of excessive P not only causes a waste of resources,but also has potential risk for environmental.Biocar has been widely used as a soil amendent which has high surface area and high P content.At present,most studies have shown that biochar can increase the content of available P in soil.However,there is still few research on the effects of biochar on the transformation of soil phosphorus under conditions of with or without exogenous fertilizer.Nither effects of biochar on soil phosphorus adsorption and desorption is not clear.The project aimed to evaluate the effects of biochar on soil phosphor.Frist,by means of isothermal adsorption experiment,the effects of biochar on soil phosphorus adsorption was studied.Then,the effects of biochar on the transformation of soil P and exogenous P were evaluated byincubation experiment(with and without phosphate fertilizer)to know The majors results and conclusions are as follows:(1)The adsorption experiment showed that the addition of 0.5% and 1% biochar could promote the P adsorption for all concentration.But when the proportion of biochar addition was 3% and 6%,the biochar inhibited the phosphorus adsorption when the equilibrium concentration under the 100 mg/L,and promoted the phosphorus adsorption when the equilibrium concentration exceed the 100 mg/L.Desorption test results showed that the soil phosphorus desorption in the 0.5% biochar testament was relatively high.Therefore,biochar could promote the phosphorus adsorption on the calcareous soil.But should pay attention to the proportion of the biochar,a right amount of biochar could not only reduce the leaching loss of phosphorus,but also desorb the absorption for plants to use.(2)The results of culture experiment(without Phosphate fertilizer)showed that the biochar could significantly increase the content of Olsen-P in soil,and the contents of Olsen-P in soil increased with the increase of biochar usage.Hedley-P results showed that the contents of different phosphorus species of treatments with biochar were higher than control,and they were increased with the increase of biochar dosage;The contents of NaHCO3-Po,NaOH-Po and HCl-Po were increased with the increase of induction time,both the increment and range of treatments with biochar were higher than control,and they were increased with the increase of biochar dosage.Which indicated that biochar promoted the transformation of soil phosphorus from inorganic to organic.(3)The results of culture experiment(with Phosphate fertilizer)showed that the biochar reduced the availability of the Phosphate fertilizer in the soil.Hedley-P results showed that the contents of H2O-P of treatments with biochar were lower than that of the control,but the contents of other phosphorus species were higher than that of the control;the contents of H2O-P,HCl-Pi and HCl-Po were decreased with the increase of induction time,while the contents of NaHCO3-Pi,Na HCO3-Po,NaOH-Pi and NaOH-Po were increased with the increase of induction time.And the increase range of NaHCO3-Po and NaOH-Pi of the treatments with biochar were higher than that of the control.Through the transformation of Phosphate fertilizer,We could find that the biochar promoted the outer Phosphate fertilizer translate to NaHCO3-Pi,NaHCO3-Po,NaOH-Pi and NaOH-Po.