CHANGES IN ENERGY AND PROTEIN VALUE OF THE FORAGE BIOMASS IN DECADES ON A NATURAL MEADOW IN THE RHODOPE MOUNTAINS (SOUTHERN BULGARIA) AND POSSIBILITIES OF THEIR PREDICTION

The purpose of this study was to establish the changes in energy and protein value of the forage biomass in decades of vegetation of a natural meadow Agrostis capillaris-Festuca fallax type in the Rhodope Mountains (Smolyan region, Southern Bulgaria). Most crude protein content (320-325 g.kg-1 a dry matter) contained the forage at the beginning of grass vegetation, while in the same period the crude fiber were at least. It was observed an opposite dependence with advance of vegetation. The greatest values of the crude protein yields were reported between 71st–92nd day (from 91.9 to 97.0 t.ha-1) after N80P80- and between 71st–102nd day (from 105.9 to 110.5 t.ha-1) after N160P80-fertilization. Most feed units per 1 ha were obtained after fertilization with N160P80 - 2509.4 FU and with N80P80 - 2225.5 FU. The energy nutritiousness of the grass forage (irrespective of fertilization levels) increased the values of IE, FU, MFU and GFU during in decades of the active vegetation. For all of the aforesaid indicators that process continued until 71st day after the beginning of vegetation and the lowest values had of a 184th day (in the end of vegetation). The established equations for predicting of energy and protein value of the forage biomass in decades have a high statistical reliability.