Determination of the yield response factor for field crop deficit irrigation

Abstract

The irrigation network of Taleghan Dam Reservoir was used to determine yield response factor for 
maize (Zea mays), winter wheat (Triticum aestivum), and barley (Hodeum vulgare) in the Qazvin Plain of 
Iran. Dependent variable actual crop yield and independent variables including climate data were 
obtained from Qazvin Plain Irrigation Company. Data were gathered from five fields in Qazvin province 
between 2002 to 2009. Potential evapotranspiration was calculated by the Penman-Monteith method. 
Actual evapotranspiration (ETa) was measured based on the irrigation requirement at the fields. Yield 
response factor (Ky) was obtained for four crop stages including vegetative, flowering, grain filling, and 
ripening, and calculated for the total growing period. The Ky values for maze, winter wheat and barley in 
different stages of their growth periods including vegetative, flowering, grain filling, ripening and total 
growing period were equal to (0.48, 1.45, 0.55, 0.29 and 1.55), (0.60, 0.68, 0.87, 0.69 and 1.20) and (0.50, 
0.82, 0.75, 0.57 and 1.10), respectively. The bias error less than 15% between averages of estimated and 
observed yields verified the results. These results were compared with Ky obtained by FAO and other 
studies separately. There is a satisfactory correlation between Ky calculated using this research and 
other studies.