In grape production, cover crops play a key role in soil protection and nutrient cycling. Thus, since grapevine requirements for P are low, adequate management of cover crops may provide sufficient P for growth. This paper evaluates the effect of black oats, as a cover plant, on the P solubilization in rock phosphate and its availability to the vine cultivated in succession. To test this hypothesis, we evaluated the plants growth parameters and P uptake in grapevines grown in succession to black oats in pots in a greenhouse experiment. The results showed that the soil sterilization decreased P availability to black oats, but not to grapevine. The soil fertilization with rock phosphate increased the P accumulation in oat and grapevine plants, although no further effect was observed from the use the cover crop. The plant height and dry mass contents were higher for grapevine in soils fertilized with rock phosphate and covered with black oats.