Soil Fertility Characteristics And Comprehensive Evaluation In Qinling-bashan Mointainous Area

A total of3047sampling points were collected from the area of1347km2in HanyinCounty,Shaanxi Province employing GPS devices. After processing the specific value usingthreshold method,2420effective sampling points were kept. According to interrelatedprinciples, TN, SOM, AN, AP, AK and pH value were chosen to determinate. The softwareSPSS19was used to get the basic data of soil nutrients from the lab processing. In order toreveal spatial distribution characteristics of soil nutrients, ArcGIS spatial analysis module wasemployed to generate kriging interpolation map. Attribute recognition model based on entropyweight and AHP was used to evaluate the soil fertility in Hanyin County. In addition, as forthe area of farmland, this paper intended to research in quantitative methods of farmlandproductivity. In terms of the field investigation, field sampling and chemical analysis, theautomatic and quantitative evaluation procedure were realized by adopting the modified GreyRelation Model which was improved by utilizing analytics hierarchy process and fuzzy math.Results show as follows:(1) The contents and spatial distribution of soil nutrients were different in Hanyin County:the content of AN was high, belonging to the fist level under the classification standard of soilnutrients in Shaanxi Province, and the content of TN, SOM, AK belonging to the third level,and the AP belonging to the fourth level. The average pH value was6.454, which presentedsoil sub-acidity. The variation of standard deviation was AN>AK>AP>SOM>pH>TN. Thevariability coefficient of soil nutrients was ranged from0.098to0.826, and pH's C.V. was thelowest variability (0.098); the other soil nutrients' C.V. fluctuated between0.1and1,moderate variability, and their variation degree was AP>AN>AK>SOM>pH.(2) The results revealed a general trend that the high soil fertility was in northern andsoutheastern areas and low fertility was in the middle and southwestern areas. In general, theoverall level of soil fertility in typical area was higher. The trend had great relevance of SOM.The area of soil which comprehensive value of soil fertility over3.75was172.53km2,12.59%for its total；the value between3.55to3.75contained643.53km2,46.97%for its total;furthermore, under3.55there were553.89km2,40.43%for its total.(3) The grey correlation degree about farmland productivity in the study area wasbetween0.52and0.92. The farmland productivity could be classified into5grades. Grade1 area accounted for7.32%, grade2for15.41%, grade3for21.61%, grade4for32.47%andgrade5for32.47%of the total area, respectively. The results also indicated that the farmlandproductivity in the area was inferior to the mid-level grades. Meanwhile, the farmlandproductivity levels and the landforms had closely correlation.