The rapid method for predicting crop growth rate in sorghum was derived based on the evaluation of 3 cultivars, namely Bravo L (late maturing), and Bravo E, and NK 2505 (early maturing), in 3 planting dates (30 April; 14 and 28 May, 1990’ in Research Station, College of Agriculture, Isfahan University of Technology. According to the results obtained, variation in grain yield and crop growth rate were at the same direction, and cultivars with a higher crop growth rate at 50% flowering stage had higher yields. The highest dry matter for the cultivars in all the planting dates was accumulated after 1500 growing degree days. Therefore, according to the high correlation coefficient between the average actual crop growth rates and the highest values of dry matter accumulation, the following equation was revealed to be the best predictor for crop growth rate in sorghum.
Average crop growth rate= -2.28+ o.0093 (Dry matter accumulation after 1500 growing degree days).
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