Assessment of Soil Fertility Using Fuzzy Membership Functions and AHP in Paddy Fields (Case Study: Research Fields Goldasht, Amol)

Considering the effective role of soil fertility in advanced agriculture, preparing soil fertility map for better planning and achievement of specific management on based soil spatial variability seems necessary. The purpose of this study was to prepare a soil fertility map for rice, based on the effective parameters on soil fertility including organic carbon, total nitrogen, available phosphorus and potassium, clay and cation exchange capacity by integrated AHP with two types of Kandel and S-shaped fuzzy membership functions. For this purpose, soil samples were collected in 50 observation points and their physical and chemical properties were measured. Interpolation of these points for the studied parameters was done by kriging method. Then the fuzzy map of each parameter was prepared by defining the S-shaped and Kandel membership functions and weighted using AHP method. Finally, by integrating them in GIS environment, soil fertility map was prepared for rice. Fertility maps obtained from S-shaped and Kandel membership functions showed that 95.73% and 53.68% of the studied area have high and very high fertility, respectively. Comparison of fertility maps through re-sampling points to control the accuracy of the maps showed that the fertility map resulting from S-shaped fuzzy membership function (64%) is more efficient and realistic than Kandel membership function (40%). Therefore, the integration of AHP with the S-shaped fuzzy membership function can quantify and classify the soil fertility of the studied area and be useful for managing fertilizer use and monitoring soil nutrition changes.