Development Characteristics And Quantitative Evaluation Of Different Parent Material Of Soils In Humid Climatic Region Of Central Subtropical

To explore the morphology, physical and chemical properties and mineralogical characteristics and establish the degree of soil development evaluation system, we chose Le’an county which belongs to hilly region of central Jiangxi Province as the sampling area and modern analytical techniques were used to study four different soil parent material standard soil samples: granite, quartzite, red sandstone and argillaceous rocks. The results showed that:(1) The characteristics of morphology of soil developmentFrom the point view of RR to analysis soil development degree, the interaction of parent material and elevation have significant impact on soil development. Interaction factors of granite parent material with the second altitude gradient and granite parent material and with third elevation gradient have significant differences between other factors. The order of RR index at the same altitude gradient is: Q>AR>RS>G. The grading of the degree of soil structure development of the four kinds of parent materials have significant differences, argillaceous rocks parent material is level 4, and the degree of development is relatively deep.(2) The characteristics of physical and chemical properties of soil developmentThe results of physical and chemical properties of different parent materials and levels showed that, the soil bulk density distributed in 1.00-1.50 g/cm3 of different soil parent material. By the mechanical composition, the most concentrated distribution were granite parent material, mostly as sand clay loam, the other three parent material were relatively increased span, argillaceous rocks were most heavy clay. From the silt and clay radio by mechanical composition, the parent materials have significant impact on the silt and clay radio, there were significant difference between granite and quartzite, red sandstone, the silt and clay radio of quartzite and red sandstone were obvious less than that of granite and argillaceous rocks, meaning quartzite and red sandstone developed deeper. The soil of central Jiangxi Province were typical acid soils, the soil pH developed by quartzite and red sandstone were less than that of granite and argillaceous rocks. The freeness of Fe in different soil parent material was significant different, the development degree of granite was weak from the point view of freeness of Fe. The interaction of quartzite with the altitudinal gradient of 200-400 m was significant different with other factors, under this condition, the soil can produce the maximum adsorption and cation exchange, reaching a well development degree.(3) The characteristics of mineralogy of soil developmentThe results of XRD diffraction peaks of different samples showed that, the mainly composed clay minerals of four kinds of soil parent material were kaolinite, water mica, 1.4nm mineral and montmorillonite. The composition and content of each parent material at different levels were different. The composed clay minerals of granite parent material were kaolinite, water mica, 1.4nm mineral and montmorillonite, the relative content of kaolinite was the most reaching 90%, the highest value ofkaolinite and illite radioG-3-2 that reflect the degree of soil development was 341.71. The composed clay minerals of quartzite parent material were kaolinite, water mica, 1.4nm mineral and montmorillonite, the relative content of kaolinite decreased compared to granite, and the highest value ofkaolinite and illite radio decreased to 199.74, meaning the degree of development slightly weakened compared with granite. Significant difference of clay minerals in the soil compared with other parent materials on the red sandstone parent material was that the content of montmorillonite was relatively high, the value ofkaolinite and illite radioshowed a further decrease, meaning a weaker of the development degree. The relative content of kaolinite of argillaceous rock parent material was the largest among the four parent materials, the highest content reached 95.1%, the value ofkaolinite and illite radio was obvious up to 1069.53, meaning the deepest development degree, at the meantime, the impact of topography need to be considered to the degree of development of small shallow.(4) The establish of the degree of soil development evaluation systemBased on the results above, there was a correlation between the index of degree development with soil property, where a highly significant correlation between the freeness of Fe and clay content, a significant correlation between reddening rate index and sticky powder ratio, sticky powder ratio and total as well as freeness of Fe, freeness of Fe and pH. The mainly index factor of clustering were the content of sand, silt, clay and free Fe. From the results of clustering, the same parent material soil in was not necessarily classified as a class, at the same time, different levels of same profile may also be divided in different categories. A comprehensive evaluation of the degree of development by quantify the degree of soil development, the highest score was up to 0.937 of AR-1-3 with argillaceous rocks parent material, and a higher development degree of the profile of the top five were all argillaceous rock development soil samples. A comprehensive of morphological, physical-chemical properties and mineralogical characteristics, the highest development degree was argillite parent material soil.