Researches on the Evaluation of the Farmland Productivity at County Level Based on GIS

With the development of the project of Formula Fertilization by Soil Testing in China, in order to investigate the soil condition, fertility level, nutrients status, soil degeneration status and the farmland integrated productivity of China, the government decided to start up the project of the evaluation of the farmland productivity with the field investigation data and the analysis assay data, which were obtained in the project of Formula Fertilization by Soil Testing. Based on the spatial analysis function of the geographic information system (GIS), such as overlay analysis and spatial interpolation, using soil image, present land use map and administrative map of the project area, this research decided evaluation unit and connected the field investigation data and the analysis assay data. Considering the actual conditions of the project area, the experts selected sixteen affected factors from four aspects as land management, land growing situation, profile situation and soil nutrient content, and the evaluation system of farmland fertility was built up. Aimed at the affected factors, it adopts the Delphi method to identify the membership function of several affected factors and introduces analytical hierarchy process (AHP) to calculate the weight of evaluating factors. On the basis of these data, this research used the additive model to calculate the Integrated Fertility Index (IFI) and also analyses its space distribution. Because the results are in line with the local situation of the city, this result can be applied to agricultural production.