Effects Of Exogenous Organic Acids On Phosphorus Forms And Availability In Coal Mine Reclamation Soil

Phosphorus is one of the essential nutrients for plant growth and development and plays a vital role in the soil ecosystem.However,the low content of available phosphorus in coal mine reclaimed soil restricts the reconstruction and restoration of the mining area ecosystem,and the natural low molecular weight organic acids secreted by plants can activate phosphorus in soil.Therefore,in order to systematically elaborate the effects of exogenous organic acids on the forms and availability of phosphorus in coal mine reclaimed soil,this paper takes the soil of coal gangue filling reclamation area in the Huainan mining area as the research object.The content of nine low molecular weight organic acids in different depths of soil in the reclamation area was determined by high-performance liquid chromatography.The distribution characteristics of low molecular weight organic acids in reclaimed soil and their coupling relationship with soil nutrient factors were studied.At the same time,by analyzing the adsorption characteristics of three dominant low molecular weight organic acids selected from reclaimed soil,the best adsorption conditions were found.On this basis,the soil of the phosphorus application group,phosphorus application plus organic acid group,and control group was cultured under the best adsorption conditions,and the changes of soil available phosphorus and various forms of inorganic phosphorus before and after culture were measured and analyzed,so as to explore the activation effect of organic acid on phosphorus availability in coal gangue reclaimed soil.Through experiments,the main conclusions of the study are as follows:（1）Compared with the farmland soil,the organic acid composition of the soil in the coal gangue reclamation area is more,but the organic acid content is relatively low.The composition and content of low molecular weight organic acids in the soil of different sampling points in the reclamation area were affected by the dominant plant species in the area,and oxalic acid was the main soil organic acid.Secondly,the accumulation of organic acids in the soil will affect the available phosphorus content and p H value in the soil.（2）The results of single factor experiment showed that the adsorption capacity of three organic acids in reclaimed soil increased with the increase of the initial concentration of organic acids increased first,and then decreased with the decrease of soil particle size,and the increase in temperature was beneficial to the adsorption of organic acids.The results of the orthogonal experiment showed that the order of influence of various factors on the adsorption capacity of tartaric acid in reclaimed soil was as follows:organic acid concentration,soil particle size,and environmental temperature.The order of influence of various factors on the adsorption capacity of oxalic acid and malonic acid was as follows:organic acid concentration,environmental temperature,and soil particle size.The organic acid concentration had the most significant effect on the adsorption capacity of the three organic acids.The optimum adsorption conditions for tartaric acid in reclaimed soil were as follows:tartaric acid concentration 15mmol/L,soil particle size 1mm～0.25mm,and ambient temperature35°C.The optimum adsorption conditions for oxalic acid in reclaimed soil were an oxalic acid concentration of 15mmol/L,a soil particle size of 1mm～0.25mm,and an ambient temperature of 40°C.The optimum adsorption conditions for malonic acid in reclaimed soil were a malonic acid concentration of 15mmol/L,a soil particle size of0.25mm～0.15mm,and an ambient temperature of 35°C.（3）The content of available phosphorus in reclaimed soil is low,and the inorganic phosphorus components mainly exist in the form of phosphate(O-P,Ca₁₀-P,etc.)with low availability,accounting for 72.52%of the total inorganic phosphorus,and the content of inorganic phosphorus components with high availability is less.The addition of exogenous phosphorus fertilizer can significantly increase the content of available phosphorus and inorganic phosphorus in reclaimed soil.Compared with the phosphorus application group,the addition of tartaric acid,oxalic acid,and malonic acid in reclaimed soil can reduce the content of Ca₈-P and Fe-P in soil inorganic phosphorus components to varying degrees,and increase the content of Ca₂-P.Correlation analysis showed that soil-available phosphorus was significantly positively correlated with different forms of inorganic phosphorus(except Ca₁₀-P),and the correlation coefficient of Ca₂-P was the largest,with a correlation coefficient of 0.998.The increment of available phosphorus was significantly positively correlated with Ca₂-P activation,and the correlation coefficient was 0.825.At the same time,the results of path analysis showed that Ca₂-P contributed the most to the formation of available phosphorus.Therefore,the activation of Ca₂-P can promote the formation of available phosphorus.The above results indicate that organic acids have an activation effect on phosphorus in reclaimed soil and can promote the release of phosphorus in reclaimed soil.The order of this promotion effect is malonic acid>oxalic acid>tartaric acid.Figure[23]Table[22]Reference[132]...