Abstract
A study was conducted to determine the influence of N fertilizer on productivity and protein content of Brachiaria mutica (Forsk.) Stapf, Cynodon dactylon (L.) Pers., and Setaria splendida in Uganda. Total dry matter (DM) yields during four growing seasons ranged from 12.5 t/ha (Brachiaria without N) to 45.7 t/ha (Cynodon with N at 1792 kg/ha per year). Significant differences were found in DM yields among the different N levels within each species. Brachiaria and Cynodon exhibited strong responses to N up to 448 kg/ha per year with a slight additional response up to 896 kg/ha per year. Setaria responded only slightly to the N treatments. The greatest return in terms of DM yield of the grasses occurred at the lower N increments.
The N enhanced the mean crude protein (CP) percentage and total CP yield of the grasses. The mean CP content increased with increasing increments of N from 7.4 to 14.5 percent. The mean CP percentages of the grasses at the highest N level were almost double that of the controls. The CP percentages continued to increase with increasing increments of N beyond levels that gave maximum DM yields. The greatest efficiency of protein production occurred at a somewhat higher N level than the optimum for DM.
