CHANGES IN THE SOIL NITROGEN CONTENT CAUSED BY DIRECT AND RESIDUAL EFFECT OF MEAT AND BONE MEAL

Animal meat and bone meals need to be used for crop production since they have been eliminated from feeds in animal nutrition following the breakout of BSE (Bovine Spongiform Encephalopathy) in cattle. The Decision of the Council of the European Union of 4 December 2000 prohibited adding processed animal protein to feeds for cattle, pigs and poultry. In Poland, this ban was imposed by the decision of the government of 1 November 2003. Meat and bone meals can be an alternative source of nutrients to mineral nitrogen and phosphorus fertilizers because they are rich in these two elements; in addition, they contain calcium, micronutrients and organic substance. The objective of this study has been to evaluate the direct and residual effects of meat and bone meal (MBM) applied in different doses on the content of total nitrogen and its mineral forms in soil, which can indicate a potential threat of environmental contamination and demonstdose the uptake of nitrogen by plants. In 2006-2010, field tests were carried out at the Experimental Station in Baldy, owned by the University of Warmia and Mazury in Olsztyn. The field trials were set up on typical brown soil. The first order experimental factor was the MBM dose (1.0, 1.5, 2.0 and 2.5 t ha(-1) year(-1) and 2.0, 3.0, 4.0 and 5.0 t ha(-1) every two years); the second order factor was the year of the experiment (4 years). The four-year experiment shows that changes in the soil content of mineral nitrogen forms depended on the dose of MBM, species of crops and weather conditions. Meat and bone meal introduced to soil in large doses, irrespective of the frequency of application, caused a significant increase in the soil's richness in total and mineral nitrogen against the mineral fertilization. The content of N-NO3- in soil increased significantly due to the residual effect of large doses of MBM (4.0 and 5.0 t ha(-1)) and the annual application of 2.5 t MBM ha(-1). All the determined concentrations of N-NO3- in soil were within the range of very low levels. The lowest content of Nmte. was detected in soil after winter wheat in the third year of the investigations, which was characterized by an uneven distribution of precipitations, and the amount of N-NO3- was the lowest in the first year, after winter triticale. The crops took up more nitrogen from soil enriched with MBM (except for the smallest dose) than from fields given mineral fertilization.