The aim of this study was to determine the content of elements N, P, K, Ca, and Mg in the dry mass of perennial fodder legumes, mowed in the optimal growth phase. The experiment with perennial legumes of alfalfa (Medicago sativa), red clover (Trifolium pretense) and bird's-foot trefoil (Lotus corniculatus L.) was set up as a random block system in four replicates on valley-brown soil and was conducted for two years. The green mass of perennial legumes in the first and second mowing was harvested at the end of budding/ beginning of flowering phase. In the third and fourth regrowth, mowing of the biomass was done after 5 weeks. Immediately after each mowing, representative sample of green biomass was taken from each replicate of each legume tested. The content of nitrogen, phosphorus, potassium, calcium, and magnesium in the dry plant material was determined. The content of nitrogen and potassium in the fodder of alfalfa and red clover was higher in the first year of the study, which was not the case for bird's-foot trefoil. The dry matter of alfalfa on average had the highest content of nitrogen (39.8 g kg-1 DM) and calcium (19.6 g kg-1 DM), bird's-foot trefoil of phosphorus (10.6 g kg-1 DM) and potassium (26.1 g kg-1 DM), and red clover of magnesium (3.7 g kg-1 DM). In the dry mass of bird's-foot trefoil the average content of nitrogen was 39.0 g kg-1 DM, phosphorus 10.6 g kg-1 DM, potassium 26.1 g kg-1 DM, calcium 15.7 g kg-1 DM, and magnesium 3.5 g kg-1 DM.
Key words: nitrogen, macroelements, alfalfa, red clover, bird's-foot trefoil
Željko Lakić PI Agricultural Institute of Republic of Srpska, Banja Luka, Bosnia and Herzegovina Mirjana Žabić University of Banja Luka, Faculty of Agriculture, Republic of Srpska/Bosnia and Herzegovina Tihomir Predić PI Agricultural Institute of Republic of Srpska, Banja Luka, Bosnia and Herzegovina