The Development Of Soil Surface Crust And The Relationship Between Soil Crust Development And Rainfall Splash Erosion

Through rainfall simulating under laboratory, and making slice of sampling, the project researched in the soil crust development, and studied the dynamic rule of erosion factors which were raining and soil erosion factors during soil crust development. In the same time, the research was to find the critical condition of all factors in the process of soil crusting, and to filter the critical factor that could affect soil surface crust. The aim of this research was to confirm the rule of soil crusting and the factors affecting the process of soil crusting, and to analyze the relationship between the development of soil crust and rainfall splash erosion, furthermore to study the effect of soil crust on the process of erosion. We hope to provide scientific bases for soil erosion.Knowledge and conclusions educed from the study are following:Firstly, primary difference between depositional crust and structural crust has been described. During rainfall processing, soil surface would become granulated, and there would be a layer of soil crust, which was dominated by depositional crust. And there were two kinds of granulated layer, which were a layer covered with stones and a layer covered with aggregates. Whereas, soil crust dominated by structural crust was developed through raindrop striking and soil grain renewably arrangement.Secondly, essential law of soil crust formation was obtained: When coarse sand exceeded 50%, soil crust dominated by depositional crust would be formed. When soil clay exceeded 30% and soil aggregated degree was less than 140%, soil surface tended to form soil crust dominated by structural crust. And soil crust dominated by depositional crust would be developed, if soil aggregated degree exceeded 140%, furthermore soil clay and silt content was great.Thirdly, the difference of soil surface crust was obtained under different terrain. The results showed that, soil structure would be changed and the stabilization of soil aggergates would be changed under different land use, so therewould be difference of soil surface crust development.Fourthly, the effect of PAM that reduced soil crust formation has been taken. The research showed that PAM could improve soil structure, and greatly increase the stabilization of soil aggregates, so soil crust development would be decreased.Fifthly, soil grain that controls rainfall splash erosion was obtained, the influence of soil clay was very great during initial stages of rainfall. With rainfall going on, soil coarse sand and fine sand would control the splash erosion. But when soil crust was completed, soil clay again waould become the primary factor.Sixly, soil structural factors that influence raindrop splash greatly have been taken. The results showed that the influence of soil infiltration coefficient was very great, when rainfall time was 5 minute. With continuing of rainfall, the influence of soil-aggregated degree was very great.Seventhly, mutual effect between soil crust and raindrop splash was studied, the result showed that splash erosion rate was greatly increased, once soil surface crust was formed.Eighthly, the effect of PAMon rainfall splash erosion has been taken. Because of the aggergation of PAM, the stabilization of aggregates was greatly increased, and the rate ofrainfall splash erosion was small.But with rainfall going on, the rate of splash erosionwould be greatly increased.