Impact of fertilizing on biodiversity in pasture ecosystems

Biodiversity in grazing systems determines production efficiency, system stability and resilience, and nutrient retention. In this relation during the period 2016-2018, a scientific research experiment was conducted on a natural grass stand of the Nardus stricta L. type at an altitude of 1400 m in the area of Chuchul (Bulgaria) of the following rates of fertilization: 1. Untreated (Control); 2. Annual fertilizing with N60P60; 3. First-year fertilizing with N60, and second and third with P60; 4. First-year fertilizing with P60, and second and third with N60; 5. First and second year fertilizing with N60, and third with P60; 6. First and second year fertilizing with P60, and third with N60; 7. First year fertilizing with N60, second year with P60, third year with N60; 8. First-year fertilizing with P60, second year with N60, third year with P60. The aim of the article is to analyze the impact of fertilizing with mineral fertilizers on the biodiversity of a pasture ecosystem and to propose an appropriate way of fertilizing to improve the species diversity of useful components in the grass stand. Biodiversity was determined by the indicator botanical composition of the grass stand, and the species diversity of the components in the grass stand by botanical groups was observed under eight variants of variable mineral fertilizing. It was found that the fertilization increased share of perennial grasses and motley grasses. The species Nardus stricta L., defining the type of pasture, was replaced from the more useful types of grasses, such as: Nardus stricta L., Agrostis capillaris L., Phleum alpinum L., Festuca ovina L., Festuca rubra L., Agrostis alba L., Chrysopogon gryllus L., Dactylis glomerata L., Lolium multiflorum L. The fertilizing effect is most significant in the third year, when both the representatives of grasses and legumes were significantly increased.