Soil Taxonomy And Soil Fertility Evaluation Of Three Major Tobacco-Planting Areas In Shaanxi

In this research, three typical soil profiles, which sampled from three different locations of tobacco-planting areas in Shaanxi including LuoNan, LongXian, XunYang, were studied by field investigation, indoor physical and chemical analysis and mathematical statistics. Based on the different physical and chemical properties of the three soil profiles, soil genesis, diagnostic horizons and diagnostic surface horizons were determined and identified there taxonomic classification. With the Fuzzy comprehensive evaluation method, topsoil fertility from these three tobacco-planting areas was evaluated and classified by a fertility hierarchy system. In brief, this research intends to provide theoretical support for future management and production practices in the Shaanxi tobacco-planting areas. The results show that:(1)The soil texture of three major tobacco-planting areas in Shaanxi has shown that: the soil bulk density of LuoNan and XunYang tobacco-planting areas, which located in Southern Shaanxi hilly areas, is vary from 1.56 to 1.71 and 1.54 to 1.70 respectively, and the content of different soil particle size is clay > silt> sand. The B horizon of XunYang profile identified an appearance of clay accumulation with high soil viscosity. The soil bulk density of LongXian tobacco-planting areas, which located in Weibei terrace plain area, is ranged from 1.49 to 1.53 in all horizons, and the content of different soil particle size is sand> silt> clay with the loamy clay texture. These three plots are highly clay content, and the porosity of these three plots are less than 50%, the soil compactness is kind of hard. With the chemical composition analysis, we can find the content of SiO₂, Al₂O₃ and Fe₂O₃ is relatively stable and SiO₂> Al₂O₃> Fe₂O₃. In LuoNan and XunYang tobacco-planting area, the sum of SiO₂, Al₂O₃ and Fe₂O₃ is greater than 85% of the total content of soil mineral. In LongXian tobacco-planting area, the sum of SiO₂, Al₂O₃ and Fe₂O₃ is greater than 75% of the total content of soil mineral.(2)In the categorization, the three soil profile categorized into 2 orders, 2 groups and 3 subgroups, the taxonomic classification of LuoNan tobacco-planting area which located in southern Shaanxi hilly area is typic ferri-udic argosols. The taxonomic classification of XunYang tobacco-planting area which located in southern Shaanxi hilly area is typic hapli-udic argosols. The taxonomic classification of LongXian tobacco-planting area which located in Weibei terrace plain area is typic calci-ustic argosols. (3)In the lower categorization, based on the differentiation of the soil particle of control horizon and soil temperature conditions, three different soil families were classified. The soil family of LuoNan tobacco-planting area is viscous ferri-udic argosols, the soil family of LongXian tobacco-planting area is viscous calci-ustic argosols, the soil family of XunYang tobacco-planting area is loamy hapli-udic argosols.(4)With the application of Fuzzy comprehensive evaluation method, soil fertility was evaluated. These three tobacco-planting areas categorized into 2 different level of soil fertility. The integrated fertility index of The LuoNan, LongXian, XunYang tobacco-planting area are 0.9252, 0.8314 and 0.8210 respectively. According to the former research on soil fertility classification in Shaanxi province, in which the level of soil fertility in Shaanxi province was categorized into 8 levels, the soil fertility in LuoNan, LongXian, and XunYang tobacco-planting area was classified into level 1, the most fertile soil. To be concluded that, the soil in this three tobacco-planting areas are high fertility with high production potential, and are suitable for the growth of tobacco.