چكيده لاتين :
Introduction
Land use suitability is the ability of a given type of land to support a defined use. The suitable areas for agricultural use are determined by evaluating the environmental components and understanding of local biophysical restraints. The topographic characteristics, climatic conditions and the soil quality of an area are the most important determinant parameters of land suitability evaluation (Almashkreki et al., 2011). Bhagat et al. (2009) analyzed land suitability for cereal production in Himachal Pradesh (India). In this study different parameters including climatic variables (precipitation and temperature), topographic (elevation), soil type and land cover/land use have been used in order to evaluate land suitability for cereals food-grain crops. The possibility of further expansion of cultivation area under each cereal crop was also determined. Golestan province is one of the most important region for crop production in Iran. In this study, geographical information system (GIS) and multi-criteria evaluation (MCE) were applied to evaluate the feasibility of agricultural lands in Aq-Qalla township for annual alfalfa (Medicago scutellata L. Mill.) cultivation.
Materials and methods
This research was conducted in northern part of Iran, Aq-Qalla township in Golestan province. The climate of this region is under the influence of Alborz Mountains, Caspian Sea, the southern wildernesses of Turkmenistan and forests. The suitability of current agricultural lands in Aq-Qalla township for annual alfalfa cultivation, were evaluated by matching the environmental requirements of crop and the land characteristics. For this purpose, required data and information of the study area were collected during 2013, and thematic maps were provided. Climatic data were collected from 43 weather stations located in Golestan province. The digital elevation model (DEM) dataset with a 40×40 m resolution and township boundary of the study area were obtained from Natural Resources Organization of Golestan province. The soil nutrient data were collected from 300 sampling sites distributed in Aq-Qala township, including EC, pH, Texture, N, P, K, Ca, Fe, Zn and Organic matter. Kriging and IDW methods were applied for interpolation of environmental variables. The digital environmental layers overlaid and integrated in GIS in respect to Analytical Hierarchy Process (AHP) weights. The weight of factors for feasibility were obtained from local experts, through a pairwise comparison of statistical analysis in Expert Choice software (ver. 2000). Zoning of lands carried out in four classes including: highly suitable (S1), suitable (S2), semi-suitable (S3) and non-suitable (NS). This system was based on matching between land qualities/characteristics and crop requirements. Highly suitable, suitable and semi-suitable lands were expected to have a crop yield of 80-100%, 60-80% and 40-60% of the yield under optimal conditions with practicable and economic inputs, respectively. Non-suitable lands were assumed to have severe limitations which could rarely or never be overcome by economic use of inputs or management practices (Ghaffari et al., 2000).
Results and discussion
Results of AHP questionnaires analysis showed that among the factors affecting land suitability, climate (0.559) and topography (0.113) criteria had the highest and least weight, respectively. In this AHP model inconsistency ratio is about 0.002. This indicates that the comparisons of criteria were perfectly consistent, and the relative weights were suitable for use in the land suitability analysis in Aq-Qala. The results showed that 23.1% and 47.2% of these areas were high suitable and suitable for alfalfa cropping, respectively. These zones had enough precipitation, suitable topography and high fertility. The semi-suitable and non- suitable regions (about 30% of area) were located in the northwest, east and south of Aq-Qalla township. In these zones, the environmental requirements of annual alfalfa were not fitted to ecological variables of agricultural land. The results showed that the topography and climatic characteristics (temperature and precipitation) of this region were suitable for annual alfalfa growth.
Conclusion
In this study, the limiting factors were: high EC (about 30 dS.m-1), deficiency of organic matter, K and Ca. Therefore, analyzing the soil quality is essential for understanding the environmental degradation processes in the region. Proper land management practices, leaching, drainage, land preparation, crop rotation, specific irrigation methods and using resistant crop are helpful methods to increase crop yield in this area.
Keywords: AHP, Geographical Information System, Kriging, Land suitability
References
Al-Mashreki, M.H., Akhir, J.B.M., Rahim, S.A., Desa, K.M., Lihan, T., and Haider, A.R. 2011. Land suitability evaluation for sorghum crop in the Ibb governorate, Republic of Yemen, using remote sensing and GIS techniques. Australian Journal of Basic and Applied Sciences 5: 359-368.
Bhagat, R.M., Singh, S., Sood, C., Rana, R.S., Kalia, V., Pradash, S., Immerzeel, W., and Shrestha, B. 2009. Land suitability analysis for cereal production in Himachal Pradash (India) using Geographical Information System. Journal of Indian Society Remote Sensing 37: 233-240.
