Vertical Migration Characteristics of PAM and Its Effect on Soil Micro-aggregates in Red Soil of Tea Garden After PAM Application

Polyacrylamide(PAM),as a new type of soil and water conservation measures,plays an important role in soil and water loss control,but the study about the soil suitability of PAM in the tea garden is not so much,and the study about the environmental behavior of PAM in tea garden soil is even less.Therefore,test areas with different concentrations of PAM were set in the red soil tea garden of southern China in order to analyze the vertical migration characteristics of PAM and its influences on soil micro-aggregates and soil particles in the tea garden.The PAM application rates were designed to have 6concentrations(0g/m2,1.5g/m2,3g/m2,4.5g/m2,6g/m2,and 7.5g/m2),and soil samples were collected in May,July and October so as to analyze the vertical distribution as well as the impact of PAM on soil micro-aggregate composition and stability under the condition of different concentrations of PAM.The results showed that,under different concentrations of PAM,the residues of PAM gradually reduced after sampling for 3times.Soil micro-aggregates and the advantage size fraction of soil particles under different concentrations of PAM had no significant difference with those in control treatment during 0—20cm soil layer.Samples at 3different periods showed that,under different concentrations of PAM,the larger the soil micro-aggregates and soil particles were,the more quickly the different treatment of PAM affected the content of their particles,and vice versa.Under the PAM measures,the degree of aggregation in soil micro-aggregates had a slight increase,while the dispersion coefficient had a slight decrease when compared with those in control treatment.