Soil Crust Development Of Four Typical Soils And Its Regional Differences In China

Soil crust is a thin ,compactive soil layer which is being formed under the raindrop impact, aggregate cracking and soil grain rearrangement, and its formation is a common phenomena occurring in arid, semiarid and sub-humid climate areas. There are so many types of soils in our nation, and these physical, chemical properties are different, then the developments of soil crust are different too. Four typical soils in our country(loess soil, purple soil, red soil, black soil) are studied in this paper. By comparing the differences among soil crust development of each soil, the author finds the main reason of the differences, and the regional differences of the four typical soil regions in China. Main conclusion as follows:Under the simulated rainfall condition, times needed for the soil crust development of each four soils are 30min,40min,50min,80min respectively, and it's called soil crust ability in this study.The main reason of the different soil crust development of four soils are fended by analyzing the aggregate size distribution differences of each soil and the three indicators which can explain the aggregate stability. the more the soil organic matter content is, the more macroaggregate has in the soil, this can explain that the soil organic matter content decide the differences of aggregate size distribution, and then decide the soil crust ability; the soil which has more water-stable aggregate and the less PAD is less crustable, so both the soil organic matter content and the clay content are the main factor influencing the soil crustability of different soils in this study.Four typical soil regions are studied in this paper : l)in the loess plateau region, it's special climate and the rainfall always occurred in June, July each year makes the very low content of soil organic matter; as the loess soil are formed by wind ,it's clay content is also lower then the other soils, so soil crust developed very easily in this region.2)in the purple soil region, because the Sub-tropical monsoon climate is warm and humid, the soil organic matter content are normally low in this region; purple soil is a kind of Litho logical soil, and this makes that it has very low clay content, so it also has high probability in the purple soil region.3)in the red soil region, it's climate property of high temperature and Humidity makes the intensive weathering ,so the soil organic matter content is low .although it has the high clay content, soil crust developed easily in this region.4) in the black soil region, it's low temperature cause the very high organic matter content; black soil has high clay content, so soil crust developed very difficult in this region.