Effect Of Biochars On Phosphorus Leaching And Its Action Mechanism In Black Soil

The aim of this paper is to explore the effect of biochar on the phosphorus leaching of black soil,then to provide reference and basis for regulating non-point source pollution by using biochar.The biochars were prepared by simulating leaching experiments with indoor soil column under different addition ratios?0,0.6%,1.2%,3.6%,6%?.The biochars were prepared by using corn straw,rice husk and pine.The content of total phosphorus and various phosphorus in leaching solutions,the volume of leaching solution and the cumulative leaching volume were studied in the leaching soil column.The effects of adsorption-desorption phosphorus from biochars and the mixtures of biochar and clay mineral were revealed,and the characteristics of biochars were revealed.The results showed that the effect of pine biochar on the leaching volume was better.The accumulated leaching volume was negatively correlated with the amount of biochar,and the cumulative leaching volume of 6% was significantly lower than that of other treatments.In terms of species,the accumulated leaching loss of phosphorus on pine biochar was the least.In terms of the addition ratio,the cumulative leaching loss of phosphorus on the corn stover and pine biochars was significantly less than that of other treatments when the ratio was 1.2%;When the ratio of adding rice biochar was 3.6%,the accumulated leaching loss of phosphorus was less.The effect of biochar on the vertical migration of phosphorus was as follows: pine biochar> corn straw biochar> rice husk biochar treatment;1.2%> 0.6%> 3.6%> 6% treatment.The selection of suitable species and the addition of biochar can effectively reduce the vertical migration and leaching loss of phosphorus in the soil.With the addition rate of biochars increase in the black soil,the amount of phosphorus adsorption decrease after the first increase;when the biochar application rates was 1.2%,the phosphorus adsorption capacity was maximum.Different biochars adsorption phosphorus capacity in black soil as follows: pine biochar>corn stalk biochar>husk biochar.The black soil mixed with pine biochar phosphorus adsorption capacity was the largest,the value was 0.697 mg·g^-1.Phosphorus adsorption and desorption volume increased with concentration of phosphorus solution increasing,but the rate of increasing was gradually smaller.Phosphorus adsorption curve was consistented better with Langmuir isotherm equation.Under different biochars additions,the adsorption capacity of phosphorus in biochars-clay mineral complex increases with the increase of phosphorus concentration in the solution.The Langmuir equation can better describe the different biochars species and the addition of the ratio of the mixture of clay mineral to the phosphorus adsorption process.Biochars-clay mineral complex showed slightly stronger adsorption compared with single clay mineral.For the clay mineral species,the biochar-montmorillonite complex has the highest adsorption capacity to phosphorus,and the desorption capacity is the weakest.Secondly,it is biochar-vermiculite complex;The adsorption of biochar-illite complex was the weakest.For the types of biochar,the adsorption capacity of the the pine wood biochar-clay mineral complex is higher than that of the corn straw biochar-clay mineral complex and the rice husk biochar-clay mineral complex.And the desorption capacity is just the opposite of the adsorption capacity.For the addition ratio of biochars,the adsorption capacity of the biochar-clay mineral complex is the highest when the three biochar addition ratios are 1.2%.