Effects Of Biochar On Phosphorus Adsorption And Wheat Growth

In this paper, rice straw was first used as the main subject, three kinds of rice straw biochar under different pyrolysis temperature were produced. The effects of these three kinds of rice straw biochar on soil phosphorus adsorption under different application dosage were studied. Secondly, this paper investigated the effect of different sources of biochar which include rice straw, wheat straw, com straw and peanut shell on soil phosphorus adsorption and soil properties as well as the growth of wheat by pot experiment. The results are as follows:(1) The pyrolysis temperatures could affect the basic physical and chemical properties of rice straw biochar.The application of rice straw biochar could decrease soil phosphorus adsorption,while the adsorption capacity increased with an increasing pyrolysis temperature.Both Langmuir and Freundlich equation can be used to describe the adsorption thermodynamics process of phosphorus on straw biochar and the saturated adsorption capacity decreased as the application dosage increased.The pesuo-first and pesuo-second order model kinetics equation could both describe the adsorption kinetics of phosphorus on straw biochar.(2) The thermal and kinetics studies found that the application of four different biochar pyrolyzed under 600 ℃ at a dosage of 4 % had negative effects on soil phosphorus adsorption and followed an order of maize> rice straw> peanut shell>wheat straw. The thermodynamics experiment shows that the equilibrium adsorption could be best described by Langumiur model indicating that the adsorption process was a single layer chemical adsorption. Both pesuo-first order model and pesuo-second order modelfitted the kinetics data well, which indicates that the two kinetic models can describe the adsorption kinetics of phosphorus on soil surface after application of biochar.(3) Finally,results of soil incubation experiment showed that the application of four kinds of biochar could promote the growth of wheat by increasing the concentration of soil ammonium nitrogen, organic matter, available phosphorus and other nutrients and improving soil fertility.After the employment of wheat straw,com stalks, rice straw, peanut shell biochar,phosphorus content in wheat stem was improved by 51.19 %～10.42 % while the content of phosphorus in the leaves increased by 39.54～106.23 %. Compared with the control,the soil ammonium content increased by 29.09 %～14.87 %, contents of organic matter reached 104.51%～106.52%, the available phosphorus improved by 73.78%～50.31%;the employment of wheat straw biochar improved the net photosynthetic rate of wheat straw by 22.80 %.These were due to the fact that the employment of biochar increase soil fertility as well as the basic properties of biochar.In this paper,a series of factors including pyrolysis temperature,biomass sources,application dosage were investigated through soil incubation and pot incubation experiments to study the effects of biochar on the transformation of soil phosphorus. The results found that biochar can be used not only as an exogenous additive into the soil to increase the available phosphorus in soil, but also be as a promoter for improving the effectiveness of exogenous phosphorus in acidic soils.