Field experiments were carried out over 2002-2004 at the Experiment Station of the University of Technology and Agriculture at Mochełek, in the vicinity of Bydgoszcz, on a very good rye complex soil. High biomass yields were recorded for all the nonpapilionaceous plants researched, grown in stubble intercrop. Upon no nitrogen fertilization, sunflower showed to be most productive. The treatments which involved a high nitrogen dose (90 kg·ha^-1) oil radish yielded significantly higher that phacelia. The plant produced also significantly more post-harvest residue mass than sunflower and phacelia, and also used nitrogen applied prior-to-sowing most considerably. An increase in the dose from 0 to 90 kg of nitrogen resulted in an increase in its accumulation in the plant biomass by 74.4 kg (82.7% of the nitrogen applied), as compared with the non-fertilized treatments. Sunflower used only 49.0 kg (54.4%), while phacelia – 48.2 kg (53.6%). The nitrogen fertilization applied in the experiments significantly increased the overground plant biomass yield of the crops researched. The greatest reaction to N fertilization was demonstrated by oil radish. The dry matter yield of this plant increased by 26.5% due to the application of 45 kg·ha^-1, as compared with the yield collected from unfertilized objects. Increasing the nitrogen dose from 45 to 90 kg·ha^-1 resulted in an 18.4% increase in the dry matter yield of radish. The effectiveness of nitrogen fertilization of sunflower was definitely lower and was, respectively, 14.6 and 7.0%. There was observed a relatively low infection with fungal pathogens in sunflower and phacelia, much higher in radish. A significant effect of the fertilization dose on the health status of the plant roots was found. Sunflower roots were most healthy when 45 kg·ha^-1 was applied, and the most heavily infected when treated with 90 kg N·ha^-1. Radish fertilization with nitrogen, irrespective of the dose, increased the root infection with fungi. There was found no clear effect of the nitrogen fertilization dose on the health status of phacelia roots. The pathogenic fungi isolated from infected roots of plants grown as intercrops were dominated by Alternaria alternata, as well as Fusarium spp., especially F. solani, F. avenaceum and F. culmorum.