The use of different N sources for the treatment of permanent grassland and effect on forage quality

During an experiment conducted in Serbia, near the city of Šabac over two growing seasons (2012/13 and 2013/14), the yield and quality of grassland treated with an organo-mineral fertilizer (farmyard manure 30 t ha-1 +10 wt.% zeolite) was monitored and compared to fertilization with pure manure (30 t ha-1), spring nitrogen application (50 kg/ha N), treatment with pure zeolite, and treatment without the addition of fertilizers. All fertilizers were spread in the autumn of 2012. Nitrogen was exceptionally applied in the spring of 2013 and 2014. Dry matter (DM) yield and forage quality were evaluated during the growing season, in two forage harvests. In addition to yields, the chemical composition of the biomass, concentrations of total protein fractions and in vitro DM digestibility were examined in detail. The biomass yields of both cuts in the first season were considerably higher after the application of manure with zeolite, pure manure and mineral nitrogen, compared to the control and zeolite. No significant differences among the treatments were noted with regard to the chemical composition of the biomass, or the effect of the type of fertilization on DM digestibility of the biomass from the natural grassland. The application of the organo-mineral fertilizer considerably reduced the share of NPN in total protein, compared to pure manure