The experiment was conducted to evaluating the effects of fertilizer and harvesting age on agronomic performance, chemical composition and economic feasibility of Desho (Pennisetum Pedicellatum) grass under irrigation, in Ethiopia. A factorial arrangement with four fertilizer types (control, urea, compost and urea + compost), and three harvesting ages (90, 120 and 150) with three replications were used. Data on morphological characteristics of the grass were recorded. Based on the data collected, harvesting age was significantly affected the agronomic parameters of the grass. Plant height (PH), number of tillers per plant (NTPP), number of leaves per plant (NLPP), number of leaves per tiller (NLPT), dry matter yield (DMY), leaf length (LL) and leaf area (LA) were increased with increasing harvesting age, while leaf to stem ratio (LSR) showed a decreasing trend. NDF, ADF and ADL content were also increased with increasing age, while ash declined with age. Fertilizer was also significantly affected the agronomic parameter of Desho grass. A mixture of 50 kg urea (U)/ha and 6,000 kg compost/ha was provided the highest NTPP, NLPP, NLPT, and DMY, while NF (control) was the lowest in all parameters. Highest NDF, ADF, ADL and ash content were recorded at the control group. In general, using a mixture of 50 kg urea (U)/ha and 6,000 kg compost/ha fertilizer is the most important for long-term Desho grass production which provides a high benefitcost ratio. Further research is needed in different organic and inorganic fertilizer combinations.