Elevation of suitable areas for wheat cultivation in Bagheh plain of Shush city using multi-criteria decision making method

Ecological agricultural zoning is a tool for proper assessment of land resources, better planning and management of cultivation in order to achieve sustainable agriculture.  Due to the importance of Khuzestan province in the country's agriculture and the strategic nature of wheat production, in this study, the zoning of wheat production potential in the DashtBagheh region of Khuzestan was done. Modern GIS technology is widely used in such studies to prepare land suitability. Separated agro-climatic zones can provide the ground for optimizing and expanding the growth of agricultural products (Balgaku, 2016). Cultivation of land can be attributed to the potential of the region in terms of food distribution and the availability of climatic factors. In a study using GIS and RS, Beijing region of China was divided into four regions in terms of winter wheat cultivation based on the weight of variables: appropriate, relatively appropriate, inappropriate and very appropriate (Wang et al., 2011).In another study evaluating arable lands such as wheat, barley and sunflower in Spain, environmental factors, topography and soil including altitude, slope, soil texture, temperature, rainfall, day length and the impact of each on this The plants were studied and then combined with the above data by weighing each layer in the GIS environment and finally mapped the susceptible areas (Khan et al., 2010). Due to the importance of the subject, the aim of this study is to use fuzzy methods and multi-criteria decision models (Analytic Hierarchy Process (AHP)) in order to identify suitable areas for wheat cultivation in Bagheh plain of Shousha city in Khuzestan province. It is worth mentioning that in this study, the most important parameters affecting wheat cultivation before entering the model were selected using statistical methods, which distinguishes it from previous studies.

Climatic characteristics included average, minimum and maximum temperatures as well as annual rainfall. Also, environmental factors including topographic characteristics (slope) and soil characteristics (chemical and physical) were considered. Soil characteristics were determined from the data of 96 soil profiles obtained from semi-detailed studies in the region. Zoning of different soil characteristics and climatic variables was done the inverse distance weighting (IDW) method.  Then, using membership functions, a fuzzy map of each of the effective parameters in determining the areas prone to wheat cultivation was prepared.  Then, using the Analytic Hierarchy Process (AHP) model, the weight of each layer was determined and finally, in the GIS environment, a land suitability map was prepared for wheat cultivation. In this study, linear membership functions have been used. This function has four parameters that determine the shape of the function. Trapezoidal, triangular, S-shaped or L-shaped membership functions can be defined by selecting appropriate values for different states (Carter and Grime, 1994). Weighing to the layers was done to prepare the final map of land suitability. The weight parameter is an important parameter for relating the factors used in land suitability. Because each of the characteristics has a different effect on wheat cultivation, weighting was done using AHP method.the AHP is a method that makes it easy to weigh parameters. AHP relies On a pairwise comparison of each of the parameters. Each of the factors is in the range of 1 to 9 according to the importance of determining the suitable areas for wheat cultivation, according to Table 2.

To prepare an interpolation map for each input data was used IDW method. The accuracy of the IDW method in mapping each of the variables showed that the climatic parameters have higher accuracy than the soil variables. Based on the evaluation statistics, the highest and lowest accuracy in climatic variables were obtained for the mean temperature (R2 = 0.99) and maximum temperature (R2 = 0.96), respectively.  However, the highest interpolation accuracy in the studied soil properties was related to the percentage of exchangeable sodium (R2 = 0.81) and the lowest accuracy was observed in the interpolation and zoning of soil clay.  The results of the AHP method showed that the greatest importance in preparing the land suitability map is related to rainfall with the highest weight and the least importance is related to the slope with the lowest weight. The results showed that the western part of the study area is suitable for wheat cultivation based on soil, climate and topographic characteristics of the area.  It occupies about 46% of the total area of the study area (4220 hectares) and parts of the south and north of the study area have the most unsuitable conditions for wheat cultivation.

In this study, suitable areas for wheat cultivation were studied using the fuzzy AHP method in the GIS environment. For this purpose, the zoning map of each parameter was first determined using the IDW model method. Then, using membership functions, a fuzzy map of each of the effective parameters in determining the areas prone to wheat cultivation was prepared. Then, using the AHP model, the weight of each layer was determined and finally, in the GIS environment, a land suitability map was prepared for wheat cultivation. According to the results, it is clear that this method has high accuracy in determining areas prone to wheat cultivation.