Six commercial varieties of sorghum (Sorghum

vulgare) and one of millet (Pennisetum americanum), as well

as six millet lines from The International Crop Research

Institute for the Semiarid Tropics (ICRISAT), Hyderabad,

India, were evaluatedTo identify materials of sorghum and

millet suitable for forage production during the springsummer

period, and to determine the determinants of crop

yield,. Crop Growth Rates (CGR), Relative Growth Rates

(RGR) and Net Assimilation Rates (NAR) were estimated.

Total Dry Matter (TDM) was positively and highly correlated

to CGR in both harvests, but TDM was not significantly

correlated with RGR or NAR during the first harvest. The

only significant correlation during the second harvest was

between TDM and NAR (-0.730). CGR in the second harvest

was highly correlated (r = 0.932) to Leaf Area Index (LAI)

during this harvest, but not during the first one. The largest

correlation observed for CGR during this harvest was with

crop height at first harvest (r = 0.763). For both harvests LAI

and Specific Leaf Area correlated directly with TDM in a

highly significant manner, while Leaf Weight Ratio

correlated inversely TDM. It was concluded that CGR was

the main determinant of dry forage yield.