Spatial and Temporal Variations of Barley Yield under Deficit Irrigation Management (Case study: Kermanshah province, Mahidasht region)

Crop response to deficit irrigation and its effects on crop yield are of the important factors for determining the optimum level of deficit irrigation. Crop growth simulation models such as WOFOST are tools which can be used for studying the impacts of deficit irrigation on crop yield. The combination of crop growth simulation models and geographic information system (GIS) provides a platform for researchers to analyze the impacts of spatial and temporal variations of effective biophysical factors on crop growth. Crop growth monitoring system (CGMS) which is developed to forecast crop yield, simultaneously applies point-based crop growth simulation model of WOFOST in the various units of a region and the results of CGMS can be presented in GIS. In this study, available facilities of CGMS have been used in order to study temporal and spatial variations of crop yield under deficit irrigation management in Mahidasht, Kermanshah. The study area was divided to 440 homogenous units in terms of bio-physical and socio-economic conditions. Then growth of winter barley was simulated under four patterns irrigation management (full irrigation and 20, 40 and 60% deficit irrigations) using previously calibrated crop file in the region and daily weather data (1992 – 2008) of the existing meteorological stations of the area and the neighboring regions. Results indicated that the crop yield (Biological and grain) in the middle of the plain was higher than that  in the  surrounding area. Moreover, results showed that percentage of grain yield reduction was more severe than biological crop yield reduction in the deficit irrigation. The percentage of crop yield reduction  varied over the various units in the study area. In addition, results showed a significant difference (α=1%) between crop yields in  different years.