Agro-ecological zoning of the Qazvin area for wheat (Triticum aestivum L.) using RS and GIS

In many parts of the world, there is not enough precise information about suitable land for cultivation. On the other hand, variability of weather, soil and topography result in different agro-ecological conditions which may be suitable or unsuitable for some crops (Ghaffari et al., 2012). Land evaluation is one of the applied methods to achieve sustainable agriculture.Agro-ecological zoning is one of the land evaluating method that can be used to find better lands and improve the planning and management of land resources. This research was performed to perform agro-ecological zoning across Qazvin for cultivation of wheat. Providing a comprehensive database of land resources properties for planning and organizing of optimal land use, land suitability evaluation in each of the Agro-ecological zones was aimed as well by using parametric method (square root), calculation of wheat potential yield and land production potential in each of the agro-ecological zones. Finally in order to extract the zoning maps of each soil profile a database in the GIS environment was created. Study area: The present study was conducted across Qazvin which is located in 36° 00' 27" and 36° 11' 6" N latitude and between 50° 16' 58" and 50° 20' 16" E longitude. The study area is 16618 hectares. Isohyet map: In order to prepare the Isohyet map, since there was a few number of meteorological stations in the study area isohyet map was supplied by the Directorate General of Qazvin weather. IDW was used as interpolation. To obtain isothermal map, the regression equation was used between annual mean temperature and height temperature.. Length of growth period map: To obtain length of growth period map, the, potential evapotranspiration during growth period was calculated by Cropwat software across for selected weather stations (Nirugah, Bagh Kousar, Qazvin and Boyin Zahra). After Growth period maps were obtained based on stations, isothermal and isohyet lines. The soil map: For soil mapping, aerial images 1/40000 area and the IRS images as auxiliary data were used in field studies. Morphological properties of 61 soil samples were measured. then soil families were determined and finally the soil map was prepared. Land use map: Landsat 7 ETM+ and IRS satellite images in 2011 were used to prepare a land use map. Agro-ecological zoning map: Agro-ecological zoning map of the study area was obtained by combination of agro-climatic data (Isohyet map, Isothermal map, Length of growing period map), agro-edephic zoning (Soil Map, Slope Map, Land use map) and using the Union function in GIS environment. Land suitability evaluation: In order to evaluate the Land suitability in Agro-ecological zoning, conformity of the land characteristics in each defined zone with wheat growing requirements was done and the final class of land was measured. Potential yield: To estimate the Potential yield in the region, FAO model (Sys et al., 1991), was used. After overlapping desired maps in the GIS, the study area was defined and separated into 43 Agro-ecological zones. Land suitability evaluation Based on square root method, 34.14%, 43.16%, 14.94%, 4.03% and 3.72% of land were located in the classes including highly suitable land (S1), moderately suitable (S2), marginally suitable (S3), unsuitable (N) and unstudied (NS), respectively. Potential yield of wheat was obtained 6666 kg.ha-1 by using the FAO method. The main aim of this study was agro-ecological zoning of Qazvin for agricultural planning. By overlay agroclimatic and agro-edaphic zoning maps, 43 agro-ecological maps were obtained. Land suitability and potential land production evaluation were performed in each zone for wheat based on parametric method (square root). The results showed that climatic properties did not create significant limitations for wheat cultivation. Limitations related to soil properties results showed that the central part of the study area was the most suitable zone. In addition, soil depth and gravel percentage in the northern part beside salinity, alkalinity, lack of organic material and gypsum are the major limiting factors in the southern part of the area. Our results indicated that agro-ecological zoning is an essential tool for agricultural planning. In this approach, key and important components, as a similar set, characterized potential agricultural capacity and its limitations for decision makers and planners.