The Effects Of The Soil Modifiers On The Bioavailabilitv Of Phosphorus And The Physical Properties In Acid Soils

The acidic soil in South China has the characteristics of strong leaching,high weathering and so on which makes the soil structure itself very fragile and unstable.In addition,the strong cultivation intensity in this area leads to the formation of red soil with strong viscosity,large acidity and poor physical structure,and the potential productivity of soil is not normal.In this study,the typical red soil and paddy soil in the south of China were selected as the research objects,the biological availability of phosphorus and physical structure characteristics were studied,and a variety of common soil improvers were used which aimed to study the comprehensive effect of these modifiers on acid soil improvement.The main conclusions obtained are as follows:1.Biochar,fly ash and lime which are added to soil can increase the pH value of the soil.In the improved soils,the effect of biochar on improving the DGT-P and effective phosphorus content of the soil is the best(pH = 8.5),while the addition of the three modifiers can effectively increase the phosphorus content of 0.01 M KCI.What is more,the addition of the modifier can increase the bioavailability of soil phosphorus by increasing the adsorption rate and desorption rate of soil solids and reducing the reaction time of phosphorus release from soil to pore water.The results of inorganic phosphorus analysis showed that the addition of modifier could increase the content of Al-P and Ca-P in soil.The content of Fe-P was reduced.The addition of modifier changed the affinity of Fe to phosphorus adsorption,which was helpful to improve the bioavailability of fixed phosphorus and the increase of dissolved phosphorus in soil.The main reason of the increase of the dissolved phosphorus is the addition of modifier changed the pH value of soil and the direct diffusion of phosphorus in the modifier.2.Three kinds of modifiers can increase the soil liquid limit,reduce the soil plastic limit,increase the water content range of the soil.At the same time,with the addition of the modifier,the average weight diameter(MWD)and the geometric mean diameter(GMD)of the soil are obviously increased(p<0.05).The modifier can improve the soil's retention ability.The modifier can also reduce the soil cohesion,improve the soil viscosity effectively,improve the soil structure,and reduce the root growth of the plant and the resistance of cultivation.3.When different biochars were added to the soils,the pH value of two kinds of soils was increased,among which,the increase of DLB was the most.In the improved soils,the biochars could increase the total phosphorus and the available phosphorus content of the soils.But only rice straw biochar(RSB)could significantly increase the content of total phosphorus(P<0.05)in the improved soil,indicating that biochars could increase the availability of phosphorus in the soil,but the increased phosphorus content depends on the type of biomass.Ultisols and Alfisol under the effect of RSB(2%w/w)could change the phosphorus adsorption of soil and adding 46.23%39.18%respectively.The change of phosphorus adsorption of soil with biochar affinity,is helpful to improve the bioavailability of fixed phosphorus.Increase of dissolved phosphorus in soil,is mainly due to the biochar changed the soil pH value,and the direct diffusion of phosphorus in biochar.