Characteristics Of Phosphorus Transformation And Microbial Response In Abandoned Red Soil Paddy Fields

Paddy field abandonment is a common phenomenon in south China.Paddy field abandonment has significantly changed soil environment and greatly affected soil nutrient conversion and microbial activities In the case of paddy fields under cultivation,fixed phosphorus fertilizer is applied to the soil every year,but phosphorus is easily fixed by the soil,and the utilization rate of fertilization in the season is only about 10～25%.Paddy fields after abandonment,phosphate fertilizer input to stop,although can be plant in the soil microorganisms using less phosphorus,but continued community succession in paddy fields so as to explore the changes of paddy soil phosphorus library after abandonment characteristics,this article on abandonment long-term trial red paddy（started in 1991）,and illustrates three different fertilization research background（CK,NK and NPK）changes of soil total and available P,and changes and trends of different active P components in red paddy fields of southern China after 8 years of abandoned tillage.Changes of soil aggregate composition,phosphorus content and phosphorus storage in aggregates;The main research results obtained in this paper are as follows:（1）Soil TP and Olsen-P content in NPK treatment was significantly higher than that in the other two treatments before and after paddy field abandonment.Abandonment reduced soil TP and Olsen-P content,and soil with high P（NPK treatment）was more sensitive to abandonment and decreased by a larger amount.（2）The results of Hedley-P grading showed that the content of P in soil before and after paddy field abandonment was Residual-P>Na OH-P_o>Na OH-P_i>Sonic-P_i>Na HCO₃-P_o>HCl-P>Sonic-P_o>Na HCO₃-P_i>Resin-P;The content of P component in NPK soil was significantly higher than CK and NK,and there was no significant difference between NK treatment and CK treatment.The decrease of inorganic P component was larger than that of organic P component after tillage.（3）From the activity of P component,residue-P was the most stable P,and the content of P was basically unchanged after tillage,while labile P（resin-P+Na HCO3-P_i+Na HCO₃-P_O）,the moderately labile P（Na OH-P_i+Na OH-P_o+Sonic-P_i+Sonic-P_o）and the low labile P（HCl-P）showed a decreasing trend.the moderately labile P contributed the most to the decrease,followed by labile P.（4）Before and after paddy field abandonment,the proportion of aggregates with different particle sizes in the three treatments was basically the same,and the proportion of aggregates with large particle sizes in 2000-250μm was the highest.After abandonment,the composition of soil aggregates in NK treatment had little change,while in NPK treatment,he proportion of>2000μm particle size agglomerates increased significantly.（5）Phosphorus content of soil aggregates was evenly distributed in all soil aggregates with different particle sizes.Abandonment had no effect on phosphorus content of soil aggregates treated by CK and NK,while phosphorus content of soil aggregates with different particle sizes decreased significantly in NPK treatment after abandonment.（6）The soil with the largest p storage was 2000-250μm aggregate.After paddy field abandoned,the phosphorus storage of NK treatment did not change,but significantly reduced the phosphorus storage of 2000-250μm and<53μm aggregates in NPK treatment.（7）The abundance of 16S r RNA gene in bacteria was significantly negatively affected by tillage abandonment,but the abundance of ITS r RNA gene in fungi was not affected.（8）Compared with bacterial community,the difference of fungal community between different fertilization treatments was greater before and after tillage.（9）In CK treatment and NK treatments,the effect of abandoned tillage on fungal community was greater,and the change degree of NPK treatment was consistent with CK treatment and NK treatment.The bacterial community was affected by the phosphorus content of soil itself,and the difference was that abandoned tillage had a greater effect on the bacterial community treated by NPK than CK and NK.The change of soil bacterial community was more significant than that of soil fungal community in NPK treatment.