Green manures refer to soil fertility building crops, which may be broadly defined as crops grown for the benefit of the soil.They have been use in traditional agriculture for thousands of years but today's they are still limited utilized by farmers.A  Lysimeters experiment was conducted at Sakha Agricultural Research Station,Egypt to assess the effect of green manures, and phosphorus fertilizer on some soil properties, phosphors use efficiency and yields of barley (in winter season 2016/2017) following by maize (in summer 2017). The experiment was arranged in split plot design with three replicates. The main plots were devoted to green manures: control (without green manure), as Lentil plants (Lens culinaris Medikus) and as Rocket plants (Eruca sativa L.); the sub plots were arranged in four rates of mineral phosphorus fertilizers: control: (without addition),7.5, 11.25 and 15.5 kg P₂O₅ fed^-1.The obtained results illustrated that using green manures i.e., lentil and rocket before planting barley significantly improved soil properties; increased the availability of the nutrients (NPK), and total porosity. Interaction between green manure as a rocket with mineral P-fertilizer rate at 15.5 kg P₂O₅ fed^-1 attained the highest values of biological yield, harvest index, grain weight, and nutrients-uptake of NPK of barley and maize. The use of rocket as green manures with mineral phosphorus fertilizer at a rate of 11.25 kg P₂O₅ fed^-1(75% of RD)maximized barley and maize yields and phosphorus use efficiency.So,the study concluded the importance of using green manures to improve soil fertility and properties and mineral phosphorus fertilizer use efficiency.