Research In Soil Water During Development Of S1 Paleosol In Guanzhong Plain

The complete loess-paleosol sequence in the Loess Plateau records abundant information about the global and regional environmental changes since the Quaternary. It provides a comprehensive basis for us to study the paleoclimate. The Guanzhong Plain in the south of the Loess Plateau is an important agricultural production base in China. The precipitation is less, but more developed agriculture, which is related to the soil water properties formed by the loess strata under special environment.The physical and chemical properties of soils developed in different soil environments,which directly affects the soil water characteristics. We choosed the paleosol of S₁ which developed in the last interglacial paleosol during the late Pleistocene in the southern margin of the Chinese Loess Plateau, being located in the Caijiapo section in Baoji area and Yangling area as all object of study. Based on the bulk density,total porosity,soil water-stable aggregates, particle size, organic matter , CaCO₃, Saturated hydraulic conductivity ,Water characteristic curve measurement,the characteristic of water percolation and retention in different soil layers were identified.We discussed the relationship between the climatic cycle and the soil-forming process with the characteristic of soil water in the last interglacial paleosol during the late Pleistocene , Revealing the characteristics of soil water and its vertical migration in Guanzhong Plain,and provided a theoretical reference for the soil environment and soil water environment of the Loess Plateau. Obtained the following main conclusions:?1? The bulk density increased gradually with the depth of the soil , and appeard a larger value in the S₁S₁?S₁S₂?S₁S3?0-35cm, 75-125cm,175-235cm?,respectively; The total porosity decreased with the increase of soil depth, and appeard a larger value in the S₁L1? S₁L2?35-75cm? 125-175cm?,respectively. Bulk density and total porosity presented a "three peaks and two valleys" trend.?2? The particle size of the silt content was the highest, followed by sand and clay. The soil can be classified as silty clay loam. <0.002 mm particles curve changed significantly,presented a "three peaks and two valleys" trend, could better reflect the changes in the summer monsoon; The content of water-stable aggregates is high, about 79.87%,Which indicated that the soil structure was good and experienced a certain degree of soil development in warm and humid climatic conditions; The content of organic matter fluctuated with the increase of depth,and has a strong positive correlation with the soil clay content,appeard a larger value in the S₁S₁?S₁S₂?S₁S3?0-35cm, 75-125cm,175-235cm?,respectively. It presented a "three peaks and two valleys" trend.?3? CaCO₃ content were the highest in the top, gradually reduced to the lower part,remaining the same after reaching a certain depth, and the content were about 1% of the lower part. The content of CaCO₃ in the middle and lower part were close to zero,Indicating that the leaching of S₁ development is strong, almost all of the carbonate with the soil water leaching, migrating out of the S₁.?4? Water conductivity characteristics of S₁: The soil saturated hydraulic conductivity fluctuated with the increase of the soil depth, and the whole was slightly reduced. and appeard a larger value in the S₁L1?S₁L2?35-75cm?125-175cm?,respectively; appeard a smaller value in the SiS₁?S₁S₂?S₁S3?0-35cm, 75-125cm,175-235cm?,in contrast.It formed soil water-bearing layers and water-resistant layers.?5? Water retention characteristics of S₁: The measured values of water characteristic curve could be fitted well with the VG model, as a reference for the conversion of soil water suction and water content. The soil water content decreased significantly with the increase of suction in the low suction range, but changed gently in the high suction range.Saturated water content and field capacity showed fluctuations with the increase in depth,reflected that the soil water characteristics had strong spatial variability. Soil available watercontent appeard a larger value in the S₁S₁?S₁S₂?S₁S3?0-35cm, 75-125cm, 175-235cm?,respectively, showing that the soil had good water retention capacity. Soil bulk density, structure, texture, organic matter content, and other factors in different climate environment and soil-forming process are all have impact on the characteristic of soil water.we researched soil water from physicochemical characteristics and intensity of pedogenesis, explored the infiltration and retention capacity of loess strata, discussed on soil water-bearing layers and water-resistant layers, which is not only important in science and reality to reveal the enriching rules of loess groundwater, but also has practical significance to soil reservoir construction and agricultural development.