Yanko KOZHOUHAROV, Vladimir LINGORSKI
Abstract. The purpose of this study was to establish the changes in productivity and chemical composition of forage biomass in decades of vegetation period of a natural meadow Agrostis capillaris-Festuca fallax type in the Rhodope Mountains (Smolyan region, Southern Bulgaria). The productive potential of the grass stand was dependent on age of the grasses and the level of mineral fertilization. The greatest yields were obtained after fertilization – 3.92 t.ha-1 (N160P80) and 3.68 t.ha-1 (N80P80). Most crude protein (320-325 g.kg-1 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. With the same period, the crude fat content decreased significantly but this reduction was greater in unfertilized control. Nitrogen-free extract substances content increased with the age of grasses and decreased with increasing of mineral fertilization levels. This chemical indicator varied from 350 g.kg-1 dry matter after N160P80-fertilization to 370 g.kg-1 in control. The advance of vegetation had a negative effect on the crude ash content as at the end of vegetation period it decreased almost 3 times. The crude ash values varied in small limits – from 81 g.kg-1 dry matter (N160P80) to 90 g.kg-1 (in unfertilized control). 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.
Key words: natural meadow, forage biomass, decade accumulation, indicators, the Rhodope Mountains (Southern Bulgaria).