Spatial Characteristics Of Soil Nutrients And Farmland Productivity Of Cultivated Land In Shaanxi Province

In this study, the cultivated land in Shaanxi Province was taken as the research object, based on survey and quality evaluation of cultivated land fertility project in Shaanxi Province. The number of effective samples of organic matter(OM)、total nitrogen(TN)、available phosphorus(AP)and available potassium(AK)obtained in this study is 109344、54507、108882、109833 respectively. Through traditional statistical analysis and geostatistical analyst, combined with GIS technology, study the spatial variability and spatial distribution of soil nutrients of cultivated land in Shaanxi Province. Establishing reasonable farmland evaluation system, evaluate the quality of cultivated land by using AHP and fuzzy comprehensive evaluation method, then grade of obtained results. The research results are useful for macrocontrol on the provincial scale and decision support management for farmland management, providing basis for scientific management of farmland the structural adjustment of agricultural supply side, and laying the foundation for the realization of agricultural modernization.The main results of this study are as follows:(1) At the present stage, the average content of organic matter,total nitrogen,available phosphorus and available potassium in cultivated land of Shaanxi Province is 14.44g/kg, 0.90 g/kg, 17.45 mg/kg, 146.27mg/kg respectively. Soil nutrients content in cultivated land of Shaanxi Province overall is in the middle level. Comparing soil nutrients in different administrative division, the contents of organic matter, total nitrogen present as follows: Southern Shaanxi > Guanzhong Area >Northern Shaanxi; the content of available phosphorus in different administrative division shows that: Guanzhong Area > Southern Shaanxi >Northern Shaanxi; available potassium in different administrative division presents that: Guanzhong Area > Northern Shaanxi >Southern Shaanxi.(2) The nugget coefficient of four types soil nutrients in Shaanxi province and different administrative division are all between 0.25 and 0.75, and the spatial correlation of each index is in the medium level. The most noteworthy is that the spatial correlation of soil total nitrogen is higher than others. In addition, the fractal dimension of each index is between 1.87 and 1.95. It shows that the spatial heterogeneity of soil total nitrogen is the weakest compared with others. According to the value of Moran’s I, the characteristic of spatial aggregation is obvious. Based on the above three methods, the results showed that the characteristic of spatial aggregation is obvious, the space structural of total nitrogen is better than others, and, available phosphorus and available potassium have weaker spatial correlation compared with other two the nutrients.(3) Spatial distribution characteristics of soil nutrients showed as follows: organic matter, total nitrogen and available phosphorus have the similar spatial distribution characteristics. It showed that the three nutrients’ content reduced from south to north: Southern Shaanxi > Guanzhong Area >Northern Shaanxi. For soil available potassium, soil available potassium has higher level content. And the content of available potassium in cultivated land of Guanzhong Area is higher than the other two regions.(4) Based on the research of soil nutrient spatial characteristics, combined with the actual situation of Shaanxi Province, the evaluation system of cultivated land in Shaanxi Province was established, and the quality of provincial land was evaluated by using AHP and fuzzy comprehensive evaluation method. The comprehensive index of soil fertility(IFI) of Shaanxi Province is between 0.38 and 0.92. The score showed that Southern Shaanxi > Guanzhong Area >Northern Shaanxi. The evaluation result was divided into ten levels according to IFI. High-quality cultivated land is mainly located in Ankang, Hanzhoung, Weinan, Baoji, Xianyang and Xi’an; Medium-quality cultivated land mainly distributed in Yanan, Baoji and Xianyang; Inferior-quality cultivated land is mainly distributed in Yulin city and Yanan city.