Effect of the herbicides Stratos Ultra (1000 and 2000 ml/ha) and Pulsar 40 (1000 and 1200 ml/ha) on the degree of weed infestation and productivity of birds foot trefoil was studied in the experimental field of the IMSA-Troyan during the 2010-2012 period on light grey pseudopodzolic soil. It was found that the herbicide Pulsar 40 applied at the dose of 1200 ml/ha, had high selectivity and was suitable for foliar treatment at the 2-4 leaf stage of birds foot trefoil, its herbicidal efficacy reaching 65, 76 and 98% during the years. The herbicide Stratos Ultra applied at the two doses of 1000 and 2000 ml/ha, was more unstable with regard to the dry mass yield. The produced yields of dry mass varied within a greater range depending on the degree of weed infestation, shown herbicidal effect and meteorological conditions. The yield was influenced to a greater extent by the herbicide type and to a smaller one by the dose of its application.

Abstract. Under the agro ecological conditions of Troyan varieties Bright, Georgia 1, Nueltin, Witt, Pardee, Roseau, Steadfast, Trevig of birds foot trefoil were examined on following indices: dry mass yield, plant height, and morphological composition of sward. The introduced varieties Nueltin (9.0 t/ha -1 ), Pardee (18.2 t/ha -1 ), Roseau (12.8 t/ha -1 ) had the highest dry mass yield in the first, second and third years of the test period. The highest stem per plant was the second year and varieties Bright (47.9 cm) and Nueltin (47.6 cm) were the highest. The highest average leafiness have varieties in the first year of the test period, when it reached 51.2%. The stems prevalent in grass composition in the second year, and generative organs were low during the three years of study. These average results for the period indicate that varieties Witt and Georgia 1 could be success fully cultivated in the agro ecological conditions of Troyan.

Abstract. During the period 2010-2012, two experiments were carried out in unused natural meadows and pastures at altitude of 1100 m and 1530 m, with sample plot size of 10 m². Five agro technical measures were studied in the following variants: In natural meadows: 1. without application of measures (control); 2. cleaning of plots from trees, shrubs and stones, cutting and harvesting; 3. cleaning of plots from trees, shrubs and stones, nitrogen-phosphorus fertilization with 80 kg N ha ) and phosphorus (90 kg P 2 O 5 ha -1 ) fertilization and respectively with organic-mineral fertilization-manure 7 t ha -1 , 60 kg N ha -1 and 70 kg P 2 O 5 ha -1 contributed to the increase of the grass stands productivity of unused natural meadows in the highest degree. Average for the period of investigation, more green and dry mass were obtained, exceeding the control with 69.9 and 120.5% and with 54.0 and 74.0%, richer in the crude protein, the crude fat and the calcium. Grazing of the old grass cover of unused natural pastures combined with application of mineral fertilizers 75 kg N ha , 60 kg P 2 O 5 ha -1 led to an acceleration of growth and development of the grass plants and increase the productivity of grass stands. The resulting green mass (12.2-13.2 t ha -1 ) was higher than the control and with higher nutritive value. The applied measures contributed to increase the share of grasses in the grass stand. The fertilization with organic and mineral fertilizers contributed to increase the content of crude protein in the forage and decrease the crude fibre.