Land Suitability Evaluation for Dryland Wheat Production in Fars Province based on Climatic and Physiographic Factors and Integrated TOPSIS-AHP Model in GIS Environment

In recent decades, one of the most important challenges to the safe cultivation of dryland cereal grains in Iran has been the lack of information on the suitable lands with a great potential to grow such crops. Considering the strategic importance of wheat, identification of suitable lands and areas for planting this crop based on environmental data assessment can result in the sustainable production of wheat in different regions (Farajzadeh, 2002).
Nowadays, the capabilities and potentials offered by the Geographic Information System (GIS) to analyze the temporal and spatial features of land data are widely acknowledged. Using GIS to generate a land suitability map for a particular crop can illustrate the suitability of the distribution model for that crop in each map unit for the land units in the area. Geographic information system and remote sensing can be used separately in this type of study. However, using them simultaneously can significantly increase the efficiency of the study (Sarmadian et al., 2003). The investigation of climatic parameters in relation to the needs of each crop allows for an accurate assessment of the agricultural condition of the area under study. Moreover, it can aid in the identification of the most sustainable areas and the most suitable agricultural crops based on the atmospheric and physiographic parameters. In this study, attempts were made to identify and introduce the most suitable areas for dryland wheat production in Fars province using GIS software and its analysis output as well as the TOPSIS-AHP model.
In this study, first, the ecological requirements of dryland wheat were determined based on the available resources. Then, given the ecological needs of dryland wheat, all the necessary meteorological data was collected from the stations. Meteorological layers including the average temperature and the annual, autumn and spring precipitation interpolated by Inverse Distance Weighted (IDW) method – due to less error and more precision – in Arc GIS 10.3 environment in raster format with a pixel size of 30 meters. For the spatial analysis and preparation of the maps of slope layer, slope direction and elevation, the DEM of the region was executed, using Arc GIS software. The hierarchical analysis process (AHP) was used for weighting the criteria. Ultimately, the multi-criteria evaluation method of TOPSIS was used for the final analysis and modeling.
The results of the analysis of AHP questionnaires showed that among the factors influencing dryland wheat cultivation in Fars province, the annual precipitation rate and the average annual temperature with a weight of 0.325 and 0.212, respectively, were the most important factors, and the physiographic factors such as slope, with the weighing value of 0.30, are of the least importance for the experienced experts of agriculture in Fars province. This is in line with the results of Bhagat et al., 2009 who found that precipitation and temperature were, respectively important climatic elements in identifying suitable land areas for dryland farming. Then, the desirability rate of the agricultural areas of Fars province for wheat cultivation was determined based on the TOPSIS model. In this map, the surface of province was categorized into five groups in terms of the potential for dryland wheat cultivation, and the first group, which includes 13.63 percent of the total area of the province, was classified as a very good area for dryland wheat cultivation, which mostly consisted of the west and northwest regions of Fars province. The results obtained by the final map of the suitable areas for dryland wheat cultivation indicate that the western and northwest areas of the province are suitable for plant growth in every respect. Therefore, recognizing the suitability of these areas and prioritizing them for dryland grain cultivation, which is reliant on atmospheric precipitation, is of paramount importance. On the other hand, approximately 28 percent of the area of the province was found to be weak and very weak for growing dryland wheat, which includes the north-east and east regions, among them, Abadeh, Khorrambid, Bavanat, Neyriz, and some parts of Eghlid and Larestan, are the regions where it is virtually impossible to find a land area that is suitable and economically feasible for the dryland cultivation of wheat.