Characteristics Of Carbon Loss In Slope Farmland In Purple Soil With Contour Ridges During Maize Growth Stages

The soil erosion of sloping farmland in the purple soil area is serious,which not only makes the soil layer thinner,but also causes the potential nutrient loss,which seriously affects the sustainable utilization of soil and the sustainable development of regional agriculture.Therefore,this paper takes the purple soil sloping field in hilly area of central Sichuan as the research object,and adopts the method of combining the field simulated rainfall and the micro plot experiment,the dynamic characteristics of runoff and runoff DOC mass concentration and the erosion of sediment variation characteristics of total organic carbon,dissolved organic carbon and particulate organic carbon in Sloping Farmland under different rainfall intensity,slope and erosion stage were systematically discussed.To clarify the impact of runoff mode on DOC migration flux,clarify the main way of DOC migration,in order to provide scientific basis for prediction and effective prevention and control of soil and water resources and loss of organic carbon in sloping fields.Main research results are as follows:?1?Rainfall duration for the sureface runoff and sediment yield was obviously of rainfall intensity,slope,erosion stage in the growth period of maize,all of which showed an increasing trend with the extension of rainfall duration;The effect of rainfall redistribution on the surface runoff and sediment yield was obvious,the expression is that the tasseling stage is the smallest and the seedling stage is the largest;The time of production is different in interflow,the lag of varying degrees to the generation of surface runoff,interflow was not positively correlated with rainfall intensity and slope,but with the increase of erosion degree,interflow also increases.?2?The dissolved organic carbon in surface soil increased with rainfall duration as the soil infiltrated,it moved to the deep layer,the DOC mass concentration of surface runoff decreased gradually with the prolongation of rainfall duration,and the higher the rainfall intensity and slope,the higher the initial value of DOC mass concentration of the rainfall intensity,slope and erosion stages during the growth period of maize;because of the deep migration of DOC in the surface soil,the mass concentration of DOC in interflow increased first,with the increase of infiltration water,the dilution effect increased,and its mass concentration decreased;the DOC concentration of surface runoff and interflow,which is the largest in the seedling stage and the least in the tasseling stage.In different rainfall intensity,slope and erosion stage,the migration flux of DOC in interflow is higher than that of surface runoff DOC migration flux,and the minimum value is 1.18 times the migration of surface runoff,the maximum is 2.04 times,and the interflow is the main way of runoff DOC migration,which can not be ignored.The migration flux of DOC in surface runoff increased with the increase of rainfall intensity,slope and erosion degree,and the effect of rainfall intensity on DOC migration flux was the largest in 1.5mm2min^-1 rainfall intensity;The migration flux decreased with the increase of slope,and the migration flux increased with the increase of the erosion degree.?3?The content of organic carbon gradually decreased with the extension of rainfall duration,and the accumulation of organic carbon in sediment was obvious,and the concentration ratio was in 1.01-3.05,in different rainfall intensity,slope and erosion stage during the growth period of maize;With the increase of slope,rainfall intensity and erosion degree,the content of organic carbon gradually decreased,and the enrichment ratio decreased,and the effect of maize growth period on the content of organic carbon was not consistent.?4?The mass fraction of sediment particles increased with the increase of rainfall intensity,slope and erosion degree during the growing period of maize,and the content of organic carbon in sediment particles was determined by the mass fraction of sediment particles and the content of organic carbon in sediment particulate matter,so the variation of the amount of organic carbon content of sediment particles in the rainfall intensity,slope and erosion stage is slightly different.Particulate organic carbon content increases with rainfall intensity,the influence of the slope is more complicated,sheet erosion is the largest and the rill erosion stage is the smallest in different stages of erosion;the relatively low organic carbon content of sediment particles,the maximum is only 2.82 g2kg^-1.?5?Due to the relative concentration of natural rainfall and the longer time scale,the content of soluble organic carbon in sediment showed a trend of decreasing gradually with the development of the growth period of maize in different rainfall intensity,slope,erosion stage,the change range of sediment soluble organic carbon content was 0.51-4.38 g2kg^-1,and the proportion of soil organic carbon pool was smaller,but the adsorption of DOC on soil minerals is the main process of immobilization of organic carbon in deep soil.The content of soluble organic carbon in sediment decreased with the increase of slope and erosion degree,while the influence of rainfall intensity on the sediment was the largest under the rainfall intensity of 1.5mm2min^-1.In a word,the loss of organic carbon in runoff and eroded sediment is greatly influenced by rainfall intensity,slope and erosion stage.The loss of organic carbon increases with the increase of rainfall intensity,slope and erosion degree,and the influence of different growth stages on it is obvious,the smaller the plant canopy,the loss of organic carbon.The extent of soil organic carbon loss can be reduced by reducing rainfall intensity,slowing down slope,controlling erosion degree and increasing vegetation coverage.