Effect Of Long-term Fertilization On Soil Clay Mineral Composition And Its Evolution Characteristics

Clay mineral is an important component of the soil, the type and quantity influence soil properties. Over a long period of time, soil parent material of primary aluminum silicate minerals desalination base gradually while form secondary clay minerals, the weathering process is affected by climate, environmental conditions and other factors; High strength human disturbance such as cultivation and fertilization could change the physical, chemical and biological characteristics of soil, which affects soil fertility and mineral weathering. Weathering and transformation of soil clay minerals under long-term fertilization, The evolution characteristics was different from that in natural environment. In this study, Jilin Black soil, Ansai loessial soil and Qiyang Red soil were selected for the research, with different fertilization treatments (CK, NPK or NK, OM, NPK+OM) and natural soil (orchard, shrub or fallow). Hydrothermal conditions and clay mineral composition in the three regional are significant difference, is benefit to the comparative study of soil clay minerals differences in the natural environment and the long-term fertilization treatments under the influence factors of the formation, transformation characteristics. The purpose of this research is to analyze differences in clay mineral composition between natural environment and fertilization by using X-ray diffration, X-ray fluorescence spectrometry, selective solvent, combined with the soil physico-chemical properties and nutrient content, soil clay mineral weathering intensity and evolution process. Discuss the clay mineral weathering intensity and different evolutionary process under different fertilization. The main results were as follows:1) The Black soil, Loessal soil and Red soil under different climate environment have different nutrient content, significantly different in the different treatment (between different fertilizer treatments and natural soil). Organic matter, total nitrogen content is Black soil> Red soil> Loessal soil; different fertilizer treatments NPK+OM or OM, nutrient content of soil increased significantly, CK significantly reduced; orchards, abandoned/shrubs, CK present gradually reduce trend. Long-term fertilization of chemical fertilizer which reduces the pH of Black soil, Red soil; the content of cation exchange capacity is Black soil> Loessal soil> Red soil. 2) Clay mineral types of Black soil, Loessial soil and Red soil are different. Clay minerals of Black soil are illite, vermiculite, mixed-layer minerals of illite and smectite and kaolinite; Loessial soil minerals are illite, chlorite, kaolinite and montmorillonite, Red soil minerals are illite, kaolinite, vermiculite (+HIM) and hydroxy interlayered vermiculite. illite and vermiculite are significant negative correlation of Black soil and Loessial soil; Black soil illite is positively associated with the exchangeable K+. in loessial soil, chlorite and organic matter, exchangeable Mg+show significant positive.3) Types of clay mineral composition of different treatments soil is similar, but the content is different. CK, NPK of Black soil have a increased content of illite, and decreased content of montmorillonite, mainly because of illite weathering release more potassium for crop use, form vermiculite and montmorillonite; NPK+OM contain rich N, P, K nutrient elements to promote transformation of illite to vermiculite. Human disturbance (cultivation, fertilization) have small impact on the composition and content of clay mineral of Loessial soil in different treatments. Fallow field of Red soil show an increase in illite, a decrease in kaolinite, artificial cultivation fertilization promoted the transformation of clay mineral weathering.4) The structure of the clay mineral evolution occurred during soil mineral weathering: transformation from trioctahedral to dioctahedral minerals has taken place. The value of Sa, Saf in soil clay show Black soil> Loessal soil> Red soil, Red soil weathering strongly and has rich allitization, mineral weathering transformation is more obvious. From north to south with the change of climate by continental monsoon, warm temperate semi-humid semi-arid, humid subtropical monsoon, climate warming, precipitation increased, promotes the weathering of minerals, so the dioctahedral minerals increase.5) Different types of soil iron, aluminum oxide content is obvious difference, the content of free iron/Fed and the value of Fed/Fet show Red soil> Loessal soil> Black soil, while the value of Feo/Fed show Black soil> Loessal soil> Red soil. The content of amorphous iron present a significant difference between different soil types, In Red soil and Loessal soil, amorphous iron and organic matter content was significantly positively related. Cultivation promotes release of free iron from the mineral weathering process, and application of organic manure hinder iron oxide aging, amorphous iron content increasing.