عنوان مقاله [English]
Determination of land suitability for specific productivity is considered as one of the land management tools that makes land use sustainable along with planning to increase production. Agro-ecological zoning refers to the recognition of a set of conditions that allows the economic planting of each crop with regard to the weather conditions of desired region. Alfalfa, as one of the most important forage plants with high quality forage, soil nitrogen fixation and soil erosion reduction, can play an important role in crop rotation. In Iran, alfalfa annual species have been distributed mainly to the northwest, west and south. Considering the good adaptation of alfalfa species to climatic and topographic conditions in western Iran, recognition of appropriate areas to cultivation of this product can lead to soil fertilization, rangeland rearing and forage production. Therefore, this research was carried out with the aim of identifying suitable areas for cultivating this plant based on climatic factors (rainfall, mean temperature of growth period, minimum temperature and maximum temperature) and topographic factors (elevation, slope and aspect) using Dynamic Analysis Hierarchical Process (AHP).
Material and methods
At first step, the response of the annual alfalfa to the climatic factors (rainfall, mean temperature of growth period, minimum temperature and maximum temperature) and topographic factors (elevation, slope and aspect) was determined and evaluated based on available resources. Then, the raster layers of the each mentioned factors were classified for Kermanshah province located in the west of Iran. To determine the importance of each of factors as criteria, scientific resources and the opinion of the experts were used as input in the AHP. In this regard, the weight of each layer was determined and accordingly, the integration of the layers was performed in the Geographic Information System (GIS). Finally, the final layers of the arable and pasture lands of Kermanshah province were classified into three highly suitable, semi- suitable and non- suitable zones.
Results and discussion
The results of AHP showed that the important of climatic factors (weighs= 0.833) were more than topographic factors (weighs= 0.167) on the growth of annual alfalfa. Among the climatic factors, the highest importance was observed for rainfall, the mean temperature of plant growth period, maximum and minimum temperatures, respectively. Among the topographic variables, aspect, slope and elevation had vital importance, respectively. The results also showed that the suitable arable and pasture lands for growing alfalfa were 4570 and 6898 km2 , respectively, equivalent to 19 and 28 percent of the total land area of the province. In fact, considering the area of arable and pasture lands of Kermanshah province (9105 and 11849 km2 , respectively), the areas susceptible to growing annual alfalfa were 50% of the total agricultural land and 59% of the total rangeland lands of the province. These areas include parts of the northeast, center and parts of the west of the province in the agricultural land and the eastern, northeastern, parts of the center, west and northwest in the rangeland area. The rainfall of about 500-450 mm, the proper temperature and slope are characteristics of this area, which makes these areas suitable in terms of suitable ecological conditions for alfalfa cultivation. The most suitable agricultural lands within the province belong to the Songhor, Kermanshah, Islamabad and Javanrood, respectively, and the largest area of susceptible rangeland belongs to the Songhor, Kermanshah, Salas Babajani and Islamabad, respectively.
In general, the results indicate that annual alfalfa is suitable for cultivation in more than half of the arable and pasture lands. This results show the high potential of Kermanshah province for the cultivation of the crop as a suitable plant in crop rotational as well as rangeland regeneration. The use of this information could allow the selection of areas susceptible to annual alfalfa cultivation to improve crop and pastures management.