Temperature is an important weather parameter affecting the growth and development of the crop. The growing degree days (GDD) indicate the thermal index required for the onset of phenophases in crop. A two-year (2008-09 and 2009-10) field experiment was conducted at the B.C.K.V Instructional Farm to investigate the effect of GDD on leaf growth rate (LGR), crop growth rate (CGR) and leaf area indices (LAI) of wheat and mustard grown under sole (T 1 and T 2) and intercrop situations, [2 wheat:6 mustard (T 3), 4 wheat:4 mustard (T 4) and 6 wheat:2 mustard (T 5)]. The experiment was laid out in a RBD design with 6 replications having a plot size of 50 m 2. The experimental soil has pH of 6.92, organic carbon 0.63%, total N 0.06%, available P 2O 5 18.47 kg/ha and available K 2O 127.22 kg/ha. The experimental site is under tropical humid climate. From the results, leaf growth rate, crop growth rate and leaf area index were found to be polynomial function of GDD. The results also suggested that the effect of GDD on different growth indices of wheat and mustard were strongly expressed in 4 wheat:4 mustard row ratios which might be adopted in the Gangetic Plains of New Alluvial zone of West Bengal.
