The first study was carried out to determine the effects of application of varied levels of fertilizer (NPK 15-15-15) and harvest time on yield and chemical composition of Panicum maximum cv. Mombasa in Shika, Northern Guinea Savannah of Nigeria.The experiment was laid out in 4x3 factorial arrangements in Randomised Complete Block Design (RCBD) with 3 replicates (Blocks). The 2 factors were fertilizer levels (0, 200, 300 and 400 Kg/ha NPK 15-15-15) and harvest time (8, 10, and 12 weeks after planting, WAP). The fresh and dry matter yields of Panicum maximum cv. Mombasa were influenced positively with increasing levels of fertilizer and harvest time. Total dry matter increased significantly (P<0.05) from 2.30 tonnes/ha in the control to 4.20 tonnes/ha in 400kg fertilizer applied treatment and total fresh weight also increased significantly (P<0.05) with age, from 8.6 tonnes/ha at 8th week to 21.00 tonnes/ha at week 12 after planting. Results from the study revealed that Crude protein content of the forage increased significantly (P<0.05) from 7.83% in the control (0kg/ha NPK) to 11.66% in treatment with 400kg/ha NPK. Crude fibre decreased from36.94% in the controlto33.96% in treatment with 400kg/ha NPK. CP of Panicum maximum cv. Mombasa declined with maturity (from 10.29%at 8to 9.24% at 12 weeks after planting). CF and Ash's percentages increased (P<0.05) with age. DM, OM, CP and NFE of the forage were highest in week 8 after planting and declined thereafter. ADF values indicated a decrease as NDF values showed an increase as fertilizer levels were increased. NDF and lignin content of the forage increased with age. P (from 1.46 g/kg at in the control to 1.75 g/kg in treatment with 300kg/ha NPK) and K (from 4.73 g/kg at in the control to 8.42 g/kg in treatment with 300kg/ha NPK) content of the forage was affected positively whereas Ca and Na did not change significantly (P>0.05) with fertilization. It can be concluded that the application of NPK (15-15-15) at the rate of 400kg/ha improved the nutritive value and yield of Panicum maximum cv. Mombasa. Panicum maximum cv. Mombasa was at its best nutritive value at 8th week after planting but yielded more dry matter at 12th week after planting. Thus, farmers are encouraged to apply NPK (15-15-15) at 400kg/ha and harvest Panicum maximum cv. Mombasa at 10th week for better forage in terms of nutritive value and yield. The second experiment was conducted to investigate the effects of Concentrate inclusion levels on nutrients digestibility and Nitrogen balance in Red Sokoto bucks fed Panicum maximum cv. Mombasa based diets. The Concentrate inclusion levels were 15, 30, 45 and 60 % (Treatments 1, 2, 3 and 4, respectively). Twelve (12) Red Sokoto bucks were randomly assigned to the four treatments in a Completely Randomised Design (CRD).Dry matter digestibility was significantly (P<0.05) higher in bucks fed diet containing 60% Concentrate (75.21%) compared to the other three Treatments. Bucks fed diet containing 60% Concentrate had the highest (P<0.05) Organic matter digestibility (75.32%) compared to the other Treatments. Nitrogen free extract and Neutral detergent fibre digestibility followed a similar pattern of change as in Organic matter. Bucks fed Treatments with 45 and 60% Concentrate inclusion showed significantly (P<0.05) higher ether extract digestibility compared to those fed 15 and 30 %. Crude fibre digestibility was significantly (P<0.05) higher in bucks fed diet containing 30% Concentrate (84.59). Treatments 3 and 4 were similar, whereas Treatment 1 recorded the lowest (68.74%) crude fibre digestibility. Crude protein digestibility increased with increasing Concentrate levels. Highest (P<0.05)CP digestibility values were observed in bucks fed diet containing 60% Concentrate (81.77%) while bucks fed diet containing 15% Concentrate recorded the least values. Acid detergent fibre digestibility followed a trend similar to that of crude protein. Nitrogen intake increased significantly (P<0.05) with an increase in Concentrate levels. Bucks fed diet containing 60% Concentrate (8.36g/day) were significantly higher (P<0.05) in Nitrogen intake. Faecal nitrogen loss decreased significantly (P<0.05) as Concentrate inclusion levels increased (from 1.52 g/day in treatment with 60% Concentrate to 2.32 g/dayin treatment with 150%), while Urine nitrogen loss followed a trend opposite to that of faecal nitrogen loss. The highest (P<0.05) Total Nitrogen excreted was observed in treatment 3 (3.00g/day). Nitrogen retained was similar in bucks fed diet containing 30 and 60% Concentrate but was significantly higher (P<0.05) in bucks fed diet containing 15 and 45% Concentrate. Nitrogen absorbed as a percentage of intake and Nitrogen retained as a percentage of intake followed the same pattern. Bucks fed diet with 60% Concentrate inclusion were significantly higher (P<0.05) while bucks fed diet containing 15 and 45% Concentrate were lower in these parameters. In conclusion, the inclusion of Concentrate in Panicummaximum cv. Mombasa based diet increased the diet's intake, digestibility and Nitrogen retention in Red Sokoto bucks. It is therefore recommended that farmers could incorporate 60% Concentrate in a Panicummaximum cv. Mombasa based diet for improved digestibility and nitrogen retention in Red Sokoto bucks.