This study was conducted at the Agricultural Research and Experiments Farm , Faculty of Agriculture, Benha University during two seasons (2018/2019 & 2019/2020).This is to investigate the effect of combined fertilization rates  which were (low, medium and high)  yield and chemical content of some summer and winter forage crops. The experimental designed was conducted to evaluate the yield and chemical content of [some summer forage grasses guar (Cyamopsis tetragonolobe), cowpea ( Vigna sinensis ), pearl millet (Pennisetum typhoides) and summer sudan grass (Sorghum bicolor) and winter forage grasses berseem (Trifolium alexandrinum) and barley (Hordeum vulgare)], under three complete combined rates fertilizer of high (90:60:30 kg NPK/fed.), medium (60:40:20 kg NPK/fed.) and low (30:20:10 kg NPK/fed.), in addition to the control (without fertilization). Their interactions and its effect on  yield and their chemical content, where the split plot design was used once , where the forage grasses were placed in the main plots, while the combined fertilization rates were placed in the sub-main plots, where three cuts were taken during the two study seasons. The results showed:A clear superiority of the treatment with a high rate of the combined fertilizer (90:60:30 kg NPK/fed.) for all summer and winter forage grasses in the characteristics of the contents of fresh and dry forage yield (ton/fed) during each of the two growing seasons with slight differences. The increase which was significant with successive leguminous forage grasses after forage grasses compared to cultivation of forage grasses after leguminous forage crops with the use of a high rate of complete fertilizer of (N:P:K), the results also showed the superiority of the same treatment in the parameters of the chemical content of the forage (the percentage of protein and carbohydrate content). The results concluded that it was recommended to plant leguminous forage crops after grasses forage crops with the use of a high complete fertilizer rate (90:60:30 kg NPK/fed) in order to obtain the highest productivity and chemical content of forage grasses and maximize their utilization as animal feed to reduce the forage gap.