The effects of amount of fertilizer on the tillering, development of the inflorescence, heading and seed yield in Green panic (Panicum maximumJacq. var. trichoglume) and Kazungula setaria (Setaria anceps Stapf cv. Kazungula) were examined. Fertilizer levels were 6 kg/a (control: abbreviated to C) and 12kg/a (high fertilizer treatment: abbreviated to HF) of a compound fertilizer (N-P_2O_5-K_2O=13-13-13%). 1 ) In Green panic, although the emergence rate of tillers reduced from nine leaf stage to eleven leaf stage of the main stem, after that until expanding stage of flag leaf of the main stem it increased in HF, but not in C. While in Kazungula setaria, the number and the emergence pattern of tillers were not different between C and HF. 2 ) In Green panic, the inflorescence development was faster in HF than in C. Therefore, in HF the heading started early and the number of heads increased. The maximum rate of heading was observed at ten days after the heading began in HF while at thirteen days in C. In Kazungula setaria, the development of inflorescence was not different between HF and C. Therefore, no large differences were observed in the time of heading, the number of heads and the time of the maximum heading rate. 3 ) In Green panic, the mean head length tended to be larger in HF. Also, the number of primary branches and seed weight per head increased in HF as well as the mean head length. Therefore, in HF the seed weight per plant increased about 30%. In Kazungula setaria, the mean head length, number of primary branches per head, seed weight per head and plant were not different between C and HF. These results show that the seed yield of Green panic was remarkably affected by high fertilizer treatment, but that of Kazungula setaria was not affected.