In recent years, a number of alternative sources of organic matter have been discovered, such as producís made of waste materials and recycled into composts or as meal of meat and bone. Meat and bone meal, a by-product of the meat industry, is rich in N and P and hence it can be a viable alternative to mineral fertilizers. This study determined the direct effect of different doses of meat and bone meal (MBM) used as fertilizer on the content of mineral N in soil. The effect of MBM fertilizer applied at rates of 1.0, 1.5, 2.0, and 2.5 t ha-1 was compared with no fertilization. The experiment was conducted in the years 2007-2009 at the research station in Balcyny, Poland. MBM was applied every year for 3 yr, with the following crop sequence: 2007 winter wheat (T. aestivum), 2008 winter rape (Brassica rapa L. subsp. oleífera (DC.) Metzg.), and 2009 spring wheat. Determination of mineral N (NO3--N and NH4+-N) were taken from the 0-30 cm layer, each year, during the full plant vegetation. The study found that changes in the mineral N content in soil depended on the dose of MBM and the crop species in a sequence. Each 0.5 t of MBM above 1.0 t ha-1 increased the mineral N content by an average of 4 mg. MBM applied every year at 2.0 and 2.5 t ha-1 produced a 2.33- and 2.56-fold increase in the mineral N content compared to unfertilized soil. The rate of release of NO3--N was found to be the highest at those sites in all the years of study, while that of NH4+-N was highest during the first 2 yr of study. The levels of NO3--N lay within the range of very low fertility. A strong correlation was found between NO3--N and NH4+-N content in soil and the N content in winter and spring wheat (Triticum aestivum L.) grain and in winter rapeseed (Brassica rapa L. subsp. oleífera (DC.) Metzg.) The NO3--N and NH4+-N compounds released from MBM were a good source of N for the plants.