Impact of mineral fertilization on the botanical composition and productivity of a degraded mesophytic meadow in the region of the Central Balkan Mountain.

In the period 2016-2019, at the Research Institute of Mountain Stockbreeding and Agriculture, Troyan (Bulgaria), a field experiment was conducted to establish the impact of annual mineral fertilization on the bioproductive indicators of a degraded grassland with a predominant participation of grasses in mountain conditions. The data analysis shows a significant excess in dry mass yield in the variants with annual application of the combination N12P12 (4.03 t/ha) followed by the annual application of combined fertilization by N8P8 (3.41 t/ha). The values of the indicator exceeded the control by 156.77% and 124.71% (P < 0.001), respectively. The grasslands with combined application of N10P10 (3.34 t/ha) and with alternative alternation of nitrogen and phosphorus (N7/I P7/II P7/III/N7/IV - 3.31 t/ha) had a slight difference in the values of the studied trait, but with high provability compared to the control 120.10% and 118.47%, respectively (P < 0.001). The lowest productivity (2.91 t/ha) (but with a proven excess compared to the control) were the treated grasslands from the second alternative variant (P6/I N6/II P6/III/N6/IV). The excess over the control was 92.06% (P < 0.001). The applied fertilization rates contributed to the desired changes in the individual groups and species of the botanical composition of the degraded grassland. The dominant legume species were: Trifolium hybridum L., Vicia sativa L., Lotus corniculatus L. and Medicago lupulina L., and of grasses - Festuca arundinaceae Scherb., Festuca rubra L. and Agrostis capillaris L. The highest share of motley grasses were registered in the grasslands treated annually with N8P8 (by 39.3% compared to the control) and the lowest in the grasslands treated annually with N12P12 (by 18.4% compared to the control). [ABSTRACT FROM AUTHOR]