Ecological assessment of grass associations in the Balkan Mountains conditions

ABSTRACT Creation of plant associations with maximum stability of yields in the regional ecological conditions for which they have been designed is key in modern agriculture. The present study aimed to investigate the impact of the environment on productivity and stability of six grass associations (red fescue, pure stand; red fescue and birdsfoot trefoil; red fescue, tall fescue and birdsfoot trefoil; red fescue and Kentucky bluegrass; red fescue, Kentucky bluegrass and alfalfa; red fescue, Kentucky bluegrass and birdsfoot trefoil) in four locations (mountain slope with eastern, western, northern and south-eastern facing direction). Methods of dispersion, regression and nonparametric analysis were used to evaluate the stability of the mixtures. According to the productivity during the 13-year study period and the calculated stability parameters, the triple mixture of red fescue, Kentucky bluegrass and alfalfa was the highest yielding mixture, but this mixture also manifested itself as unstable. The lower yielding mixed sward of red fescue and Kentucky bluegrass and the pure stand of red fescue were also distinguished by low adaptive ability. In the conditions of the Middle Balkan Mountains, the mixture of red fescue, tall fescue and birdsfoot trefoil was characterised to have the most favourable combination of productivity and ecological stability, and was considered suitable for growing in a wide range of environmental conditions. As a whole, the swards on the mountain slopes with eastern and south-eastern exposure were more productive but had low stability compared to those grown on western and northern exposure.