For the first time in the conditions of the Uzbekistan area photosynthetic activity and yield of green biomass of a Columbus grass (Sorghum almum Parodi) are studied. Rates of formation of leaves, a sheet index, pure photosynthetic efficiencyand yield of green mass during all vegetative period of plants are defined. It is noticed that in flowering of plants the size of a sheet index reaches the greatest size and the maximum of net productivity of photosynthesis is revealed. The effect of different quantity of mineral fertilizers on Columbus grass photosynthetic activity and its yield of green biomass had been analyzed.