Spatial Variation Of Soil Nutrients And Its Influential Factors In Huangshan City

As a very complicated natural complex,soil is the most important component of the terrestrial ecosystems on the Earth and an important resource on which the human life depends on.Soil nutrients are a key factor affecting the productivity and health of soil.Therefore,the research on the spatial heterogeneity of soil nutrients will reveal their spatial distribution and variation,and the influences of natural and human factors on their spatial heterogeneity.Moreover,it will provide a scientific basis for the improvement of soil quality and nutrient use efficiency and for the implementation of the precision agriculture development based on regionalized management.This research was conducted to investigate the variations in the contents and abundance of six nutrients(including organic matter,available phosphorus,rapidly available potassium,available iron,available copper,and available zinc)in the soil in Huangshan City,Anhui Province,during the period from the second national soil survey to the farmland soil fertility evaluation.The theories and methods of traditional statistics and geostatistics were employed,with the help of mathematical statistical software and spatial analysis software.The best semivariogram models for the six nutrients were constructed.The spatial distribution patterns of the six nutrients and the influential factors were analyzed systematically,with an emphasis on the effects of soil types,the texture of topsoil,topographic factors,and land use on the spatial heterogeneity of these nutrients.The research results are as follows:1.In accordance with the national classification of soil nutrient content,the soil in the study area contained abundant available iron and available copper,whose contents were classified as Class I;the contents of organic matter,available phosphorus,and available zinc were classified as Class II;the content of rapidly available potassium was medium to low,thus classified as Class IV.Compared to the results of the second national soil survey,the available phosphorus content rose 24.83%,the largest increase among the nutrients,while the available zinc content showed the largest decline of 21.18%.The content of rapidly available potassium was up 6.03%,the smallest variation among the six nutrients.According to the variation coefficients,the variations in the contents of organic matter,rapidly available potassium,available iron,available copper,and available zinc were moderate,while the variation in the available phosphorus content was large.2.The contents of the six soil nutrients all showed semivariance and their spatial heterogeneity can be well fitted by an exponential model.The natural or structural factors,such as the soil types,texture of topsoil,and topographic conditions,were the major factors that influenced the spatial heterogeneity of organic matter,available phosphorus and rapidly available potassium.The spatial heterogeneity of available iron,available copper,and available zinc were affected by both structural and human factors,such as the land use types,planting system,fertilization mode,etc.3.The spatial distribution patterns of soil nutrients in Huangshan varied significantly.Due to the human factors,the distribution patterns of trace elements in soil were more complex and less regular than those of organic matter,available phosphorus,and rapidly available potassium.It was found that the soil in Qimen County and Xiuning County had relatively high nutrient contents,while the soil nutrient contents in the eastern region of She County were generally low.So the soil management should be enhanced in order to increase the overall soil fertility of the study area.4.The contents of the six nutrients also varied significantly between types of soil in Huangshan City,mainly due to the different types of parent materials.The contents of organic matter and rapidly available potassium tended to increase as the soil particle size decreased from sandy soil to clay soil.The trace elements were more abundant in clay and loamy soils than in sandy soil.And the soil texture had little influence on the content of available phosphorus.5.The slope of land was strongly and positively correlated with the contents of organic matter,rapidly available potassium,and available phosphorus,while it was strongly and negatively correlated with the available iron content.Elevation showed a significant negative correlation with the organic matter content and a strong positive correlation with the contents of available phosphorus,rapidly available potassium,available iron,and available copper.Moreover,different fertilization modes,or different types of land use,also caused great variations in the contents of trace elements in soil.