Evaluation of soil fertility map for bean cultivation in Eghlid Plain by using Hybrid Fuzzy-AHP and GIS techniques

The increase in the performance of cultivated plants is under the influence of various features including the soil properties. The nutrient elements of the soil are among the important soil features. The soil fertility should be studied to determine the proper level of fertilizer application. The improper use of chemical fertilizers with no attention to soil fertility not only does not increase the quality and quantity of the products but also imposes extra costs while unbalancing the level of nutritional elements of the soil and causing environmental problems. In this regard, the determination of soil fertility and providing a soil fertility map sounds necessary. In this study, the soil fertility of Shadkam plain in Eghlid county of Fars province was determined to prepare the soil fertility map for the cultivation of bean. The soil fertility map was obtained by a fuzzy system using a hierarchical analysis in a GIS environment. To this end, soil sampling was conducted from 210 locations and the input data including organic matter, potassium, phosphorous, iron, manganese, zinc, and copper concentrations were measured.  The interpolation of each soil element was achieved by the inverse distance weight (IDW) model in the GIS environment. Then, a membership function was prepared for each factor to obtain the fuzzy map considering their corresponding critical values. Finally, each layer was allocated with weight using the analytic hierarchy process. Based on the relative weight of each criterion, the highest relative weight (0.354)  was obtained for organic carbon while iron showed the lowest (0.031)  relative weight. The results also indicated that 0.3, 80.3, and 19.4% of the studied region can be categorized as very poor, poor, and moderate groups in terms of fertility for bean cultivation, respectively.