Agroecological Zoning of Wheat in the Borujen Watershed: Rianfed and Irrigated Wheat Cropping System Evaluation

Agroecological zoning is multidisciplinary model that could be applied to create spatial database, due to evaluation and agricultural land use planning. This study was performed in order to evaluate the wheat cropping system with agroecological zoning methodology in the Borujen watershed. Therefore the long term daily climatic database was made from 18 synoptic and climatic stations that covered whole of study area. Potential evapotranspiration was calculated using ET Calculator software base on Penman-Montith method. The WOFOST model showed acceptable performance during validation for predicting yield and development stages of wheat cultivars under potential and water limited conditions. Wheat yield production was simulated for all stations, and then the outputs of model were interred to ArcGIS software setting. The output data of model was interpolated using Spline function for yield estimation overall study area. Results showed, mean potential yield of wheat was varied 6.2 to 6.9 t ha-1 overall study area, so that the central and northern east basins are more suitability for yield production in potential mod. Mean water limited yield of wheat was varied 2.4 to 3.7 t ha-1 overall study area, so that the eastern south basins (Imam Qeis basin) are more suitable for wheat in rainfed or water limited conditions.The results of yield gap analysis in different wheat cropping systems performed on four different agro-ecological zones, include of Zone1: yield gaps = 4.2-6.2 Mg/ha, Zone 2: yield gaps = 3-3.6 Mg/ha, Zone 3: yield gaps < 2.4 Mg/ha, and Zone 4 is unsuitable area. Analysis of water balance pattern in the study area showed that, the main factors that affected on yield gap are rainfall distribution and low temperature during moisture growing period. This study demonstrates that WOFOST model has the good capability for wheat yield simulation in potential and water limited conditions and can be used as suitable approach to analyze the cropping systems at regional scales.