SOIL fertility was and still one of the most important factors controlling the productivity of crops. A field experiment was conducted at Sakha Agricultural Research Station, Egypt to assess the effect of green manure, bio-N fertilizer and mineral nitrogen fertilizer on some soil properties, mineral nitrogen fertilizer efficiency (i.e., N-use efficiency) and yield of onion (in winter season 2015/2016) following by maize (in summer 2016). Treatments included bio-N-fertilizers, mineral nitrogen fertilizer and green manure. The results showed that using all green manures (i.e., Egyptian clover and fenugreek) before planting onion significantly developed soil properties; increased availability of the studied nutrients and total porosity. Inoculations with bio-fertilizer maximize these effects on soil properties and yield of onion and maize. Interaction between fenugreek with bio-fertilizer and mineral N-fertilizer at 120 kg fed-1 attained the highest values of total onion yield, averages of bulb weight, diameter, dry matter content and nutrients-uptake of NPK in the first season after green manure application. After cultivation of maize, the highest values of grain and dry stalks yields, 100-grain weight and NPK-uptake were obtained with the interaction of Egyptian clover with bio-fertilizer and N-fertilizer at 90 kg fed-1. The use of Egyptian clover as green manure with bio-fertilizer increased N-use efficiency for onion at 60 kg N fed-1 and for maize grain yield was at 120 kg N fed-1. So, the study concluded importance of using green manures to improve soil properties and use efficiency of mineral nitrogen fertilizer.