The aim of the study was to determine, with a spring rape yield test, the potential manurial value of plant residues of legume-grass mixtures. The forecrop (in the years 1998–2002) was an experiment with four legume-grass mixtures. The spring rape cv. “Mazowiecki” was sown in spring 2003. The experiment was performed on gray-brown podsolic soil of quality class IIIb. All cultivation and agricultural practices were carried out in accordance with the relevant recommendations and directions. Rape was harvested for green forage. The yield of spring rape grown after legume-grass mixtures and the effects of their mineral fertilization were studied. Soil abundance in nutrients was determined after five years of sward application and spring rape growth. Changes in the concentrations of organic substance and nitrogen in the soil observed after legumegrass mixture harvest had no significant influence on spring rape yield. The after-effects of nitrogen fertilization were significantly negative. Depending on the forecrop and fertilization level, rape dry matter yield varied from 5.17 to 7.81 t per ha. The highest increase in mass was recorded on the plot where spring rape was grown after mixtures of Lotus corniculatus with Dactylis glo merata, and Trifolium repens with Lolium perenne.