نوع مقاله : مقاله کامل علمی پژوهشی
نویسندگان
1 دانشجوی سابق کارشناسی ارشد گروه علوم خاک/دانشگاه ولی‌عصر (عج) رفسنجان
2 عضو هیأت علمی
3 دانش‌آموخته‌ی دکترای علوم خاک/ دانشگاه شهرکرد
4 عضو هیأت علمی گروه علوم خاک/ دانشگاه ولی عصر (عج) رفسنجان
چکیده
کلیدواژه‌ها
عنوان مقاله [English]
نویسنده [English]
Background and objectives: Land suitability evaluation as part of a sustainable agricultural system, leads land utilization to a direction, which can preserve land quality in a desirable level while ensuring the highest income. In the traditional studies of land suitability evaluation, the land units fit between two classes can only view one of the primary classes are defined for land suitability. Therefore, the method is not able to show the continuous reality of land and soil spatial variability. The development of modern methods (such as fuzzy logic) has solved this problem to a great extent. Therefore, the main objective of this research was to determine the optimum depth of soil for quantitative land suitability evaluation for wheat production using the fuzzy sets theory and comparison of two different fuzzification methods of land suitability classes in the Shahediyeh region, Yazd.
Materials and methods: After crop harvesting and taking soil samples from three depths of 0 to 30, 30 to 60 and 60 to 100 cm in 90 observation points, and from genetic horizons of representative pedon, which excavated in the region, the parameters needed for land suitability evaluation of wheat were measured. Then, land suitability classes were calculated using the square root method and were compared in three depths from 0 to 30, 0 to 60 and 0 to 100 cm. Fuzzy calculations used for this study were conducted in two different ways. In the first method, fuzzification of land index calculated for wheat was conducted as trapezoidal fuzzy intervals. In the second method, firstly the variables used to calculate the land suitability classes for wheat, including climatic parameters, and soil and topographic characteristics, were defined as fuzzy numbers, and then the land index was calculated as a triangular fuzzy number. To obtain the numerical values of the result of applied fuzzy method (defuzzification process), the centroid method was used. Finally, to show the different land suitability classes, the resulting numbers were converted to degrees of fuzzy membership. To compare the results of two fuzzy methods used for different depths, the similarity index that presented by Sarma, was used.
Results: The compatibility percentage between the results of representative pedon and observation points was remarkable (more than 60 %) only for 0 to 100 cm depth. In addition, the highest compatibility percentage of land suitability class was related to comparison of 0 to 60 and 0 to 100 cm depths in each of the two fuzzy methods. This fact shows that 0 to 60 cm depth could be a relevant alternative for the optimal depth to evaluate land suitability for wheat in the Shahediyeh region. The results also showed that there was no difference between two fuzzy methods for all land suitability classes and at all the studied depths.
Conclusion: Overall, considering the depth of 0 to 30 and/or 0 to 60 cm in the traditional studies of land suitability evaluation for wheat is not sufficient compatible with the results of representative pedon. Therefore, if the study is not intended to offer detailed information on the type of limitations for civil actions, use of the results of representative pedon to a depth of 100 cm based on the traditional method is sufficient and it does not need to fuzzy calculations.
کلیدواژه‌ها [English]
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