عنوان مقاله [English]
Introduction planning is essential for increasing production per unit area of strategic agricultural products. In this regard, land suitability evaluation is one of the most important key steps. While the FAO framework for land suitability evaluation is the most commonly used method, to overcome problems related to vagueness in definition and other uncertainties, methods such as Micro LEIS system models can be useful. Terraza, Cervatana and Almagra are the models of Micro LEIS package that are used to evaluate land suitability for agricultural activity. Considering the limitations in water resources required to produce this strategic product, the present research focuses on evaluation of Khodaafarin region lands suitability by Micro LEIS models for this utilization type.
Materials and Methods This research was carried out in an area of about 16555 ha in Khodaafarin, an important region in agricultural production, located in East Azerbaijan province, northwest of Iran. The major geological formation is composed of Quaternary sediments with sandstone. According to climatic data from Khomarlo synoptic weather forecasting data station, the average annual precipitation and temperature of the region are 281 mm and 14.7 °C, respectively, and the soil moisture and temperature regimes are Aridic border to Xeric and Thermic. The study area was divided to 11 land units by geopedology method. In each land unit, a soil profile was dug, described and sampled for physico-chemical analysis. After preparing soil samples in the laboratory, soil physico-chemical routine analyses, which are important in soil classification and evaluation, were completed by standard methods, and then studied soils were classified by the 12th edition of soil taxonomy. To conduct land suitability investigations, three models of Micro LEIS package including Terraza (to determine bioclimatic deficiency), Cervatana (to determine land capability) and Almagra (to determine the suitability evaluation of the studied area) were used. Finally, according to adopted models, land capability and suitability class and sub-class were determined in actual and potential condition for sugar beet, and their maps were prepared by Arc Map 10.2.
Results and Discussion According to the results obtained from description of soil profiles and physical and chemical analyses, soils can be classified as a different family of Aridisols and Entisols on the basis of USDA soil taxonomy system. Based on the Terraza model, bioclimatic deficiency class for the studied utilization type is C3 (h2-f3) or h2 moisture deficit and f3 frost risk classes, whose combination leads to C3 final class. This class revealed that during the growth period, 2-5 months annually the temperature goes under biological zero and production would decrease by 20 to 40%. Therefore, it is recommended to have safe irrigation and frost risk management. The results of Cervatana model indicated that for slope, climate, erosion and soil limitations with various degrees, 77.01% of the study area was placed in S2 land capability class. Also, 18.16% and 4.83% were classified as S3 and N1 classes, respectively. Among the above-mentioned factors, soil depth limitation was identified as the most restrictive and climate as the mildest one all over the study area. According to S2 class suggested by the Almagra model, 82.98% of the study area is acceptable for this utilization type. Suitability class for 7.62% of the study area is S3, which would increase the costs. Also, 9.4% of the study area is never suitable for sugar beet due to intensive limitation of soil useful depth and texture, which leads to S5 class. The nature of the limiting factors in land units suggests that they might be resolved. Based on this fact, in 19.64% of study area suitability class can shift to the upper one due to land improvement, while in 22.99% of the study area it is impossible for such a shift. In other parts, although some of the limitations can be solved, land suitability class remains stable and only their sub-class changes.
Conclusion Considering land evaluation and the nature and professional use of Micro LEIS system models, Terrraza, Cervatana and Almagra models should be used hierarchically. Hierarchical use of models can help reduce costs because it is designed as a multiple-stage approach of land evaluation that assesses various biophysical properties of lands step by step. Accommodation of the values related to the studied land properties within the specified range presented in the models indicates that these models are calibrated for evaluating this utilization type in north-west of Iran. Therefore, traditional evaluation systems can be replaced by Micro LEIS system. According to the obtained actual and potential suitability class for sugar beet, it seems that it is a reasonable utilization type in the study area. Land improvement does not have a significant effect on the rise of land suitability class and profitability; nevertheless, it is recommended to have pilot land improvement programs to find factors which might have been ignored and might bring about further limitations.