| Soil nutrients are a reflection of soil properties and nature,and are the basis for the evaluation of cultivated land fertility.It is of great significance to study the characteristics of soil nutrient changes in cultivated land in this region for the sustainable use of cultivated land.This study uses the agricultural area of Fukang City as the research area,soil nutrient survey data based on three periods(1982,2010,2018),Using the methods of traditional statistics,geostatistics,and geological information atlas,the spatial characteristics,grade changes and influencing factors of soil organic matter,alkaline nitrogen,available phosphorus,and available potassium in the study area were analyzed.Analytic hierarchy process and comprehensive index method were used to complete the evaluation of cultivated land fertility in Fukang City.The main results are as follows:(1)After nearly 40 years of change judging from the average value of soil nutrient content in the plow layer,the content of available phosphorus and available potassium showed an upward trend in general,and the overall trend of organic matter content decreased first and then increased,and the alkaline nitrogen increased first and then decreased,All nutrients showed moderate variation.In addition to the lower alkaline hydrolysis nitrogen content,the rest are at intermediate or upper levels.(2)Spatial autocorrelation of soil nutrients was tested by a semi-variance function and Morans’ I autocorrelation index.The main fitting models of the semivariance function are the exponential model and the spherical model,The four types of nutrient nugget coefficients are all between 25%～75%,showing a moderate spatial correlation.The Z value of soil nutrients in each period was greater than 1.96,and the nutrients had a spatial correlation globally.The Morans’ I indices are all greater than 0,and the spatial correlation is positive.(3)The spatial distribution of soil nutrients in different periods is very different.The area of change of organic matter and alkali-hydrolyzed nitrogen in the past 40 years is mainly concentrated in the central plain area,and the change in the north and south is small;the change of available phosphorus in the early stage is mainly the change in the north and south,and the overall change in the later stage;the available potassium did not change much in each period.The changes in soil nutrient levels in the past 40 years are as follows:organic matter and alkaline-hydrolyzed nitrogen are mainly repetitive changes,available phosphorus is mainly continuous change,and the types of available potassium are not much different.(4)Different influencing factors have different correlations with nutrients.Analysis of terrain and socio-economic factors found that each nutrient was significantly negatively correlated with altitude,and available phosphorus and available potassium were significantly negatively correlated with slope.Except for quick-acting potassium,the other nutrients were significantly negatively related to regional GDP,organic matter was significantly negatively related to the area of cultivated land,the per capita net income of farmers had no significant effect on available phosphorus,and the other negatively correlated.(5)The total area of cultivated land in this study was 55253.24 hm2.Among them,the area of Grade Ⅳ land is the largest,accounting for 47.00%of the total area.Grade Ⅰ land accounts for 9.29%of the total area,the second-level land accounts for 7.76%,the third-level land accounts for 26.79%,and the fifth-level land accounts for 9.16%.The primary land is mainly distributed in the central plain area.The soil types are mainly fluvo-aquic and irrigated desert soil,and the secondary land and primary land are staggered.The tertiary land is mainly distributed in the central plain and near the Gobi area.The soil type is mainly gray desert soil,fluvo-aquic soil,meadow soil.The soil type is mainly gray desert soil. |
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