| In this thesis,the cultivated land in Qinba mountain area of Shaanxi province was taken as the research object,and based on the project of cultivated land quality evaluation in Shaanxi province,the nutrient data of 1343 soil sampling sites were detected by scientific and reasonable methods,the spatial characteristics of soil nutrients and the quality of cultivated land in Qinba mountain area of Shaanxi province were analyzed and studied by using geostatistical methods,in order to provide scientific reference value for the overall arrangement and rational fertilization of cultivated land in Qinba mountain area,it provides scientific basis for the management of cultivated land and the supply-side reform of agriculture,and guides scientific farming.The results of this study are as follows:(1)Comparison of soil nutrient interpolation models in the study area.By comparing standard prediction error,root-mean-square error,average standard error,root-mean-square error and average error,the optimal variance function model of soil nutrients in cultivated land includes exponential function and Gauss function.The optimal semi-variance function model of organic matter,pH and available phosphorus is exponential function,the optimal semi-variance function for total nitrogen and available potassium is Gauss’ s function.(2)The general characteristics of soil nutrient content of cultivated land in the study area.After a logarithmic transformation,the available phosphorus content of soil basically conforms to the normal distribution,and the original data of the remaining nutrient content conforms to the normal distribution.In terms of quantity,the soil nutrients of cultivated land show great similarity and consistency with the soil nutrients of sampling sites,and in terms of space,the soil nutrients have different distribution characteristics in all directions of the study area.The quantitative characteristics of soil nutrient content of cultivated land in the study area.The content of soil organic matter was high,the range was 11.30 g/kg-34.15 g/kg,the average value was 20.77 g/kg,the content of total nitrogen was very high,the range was 0.71g/kg-2.18 g/kg,the average value was 1.33 g/kg;The content of soil available potassium was lower,the range of variation was 58 mg/kg-257.72 mg/kg,the average value was 120.78 mg/kg,the content of soil pH was lower,the range of variation was5.27-8.30,the average value was 6.86.The soil nutrient content was in the middle level in general,and the soil as a whole was slightly acidic.(3)The spatial characteristics of soil nutrient content in the study area.The correlation between organic matter and total nitrogen was 0.856,and the correlation between pH and available phosphorus was-0.08.The Global Moran’ I index of soil available phosphorus was the largest,and the Global Moran’ I Index of soil organic matter was the smallest.(4)Soil nutrient content of cultivated land was analyzed by topographic factors.Soil nutrients of cultivated land show different characteristics in different topsoil texture,soil type,slope,altitude and geomorphology,and the spatial variability coefficient of soil nutrients is quite different under different factors.(5)The results of cultivated land quality evaluation in the study area.The quality grade of cultivated land is divided into ten grades.The area of the fifth grade is the most,accounting for 19.73%.The area of the eighth grade is the least,accounting for2.99%.The average quality grade of cultivated land in Qinba mountain area of Shaanxi province is 4.82,which is higher than that of the whole province(5.71)and lower than that of the whole country(4.76).In view of different quality grades of cultivated land in Qinba mountain area,this study put forward different measures to protect cultivated land and improve it,in order to provide theoretical guidance for improving the quality of cultivated land. |
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