Impact of Fertilizing with Organic Composted Mixture onthe Qualityof Natural Grass Stands in the Semi-mountain Regions of Bulgaria

The impact of a composted mixture of Pteridium aquilinum L. with cattle manure on the composition and quality of natural grass stand, transitional type Chrysopogon gryllus- Agrostis capillaris in the conditions of the Central Balkan Mountain in Bulgaria was observed. Surface treatment with the composted mixture increased the share of useful legumes and grass fodder species. The percentage share of the components in the grass mass increased by 24.15 and 9.00%, respectively. Graphical regression models were developed to predict the amount of calcium, nitrogen, phosphorus and cellulose through the percentage of legumes and grasses in the treated grass stands, which in practice is significantly more economical and fast. Grass stands fertilized with 2000 kg/da composted mixture (with the highest share of legumes) had the highest content of crude protein (with 29.9%), crude fat (with 44.0%) and minerals (with 10.6%). The highest in vitro digestibility of the dry matter was observed in the variants treated with 1000 kg/da and 3000 kg/da composted mixture, where the excess in the values of the indicator was from 4.0 to 4.7% compared to the control. A high positive correlation was found between the indicators of dry matter yield with the content of crude protein (r = 0.84), minerals (r = 0.82), calcium (r = 0.96), phosphorus (r = 0.95), nitrogen (r = 0.84) and cellulose (r = 0.93) in the dry matter of the treated grass stands.