The objective of this study was to determine the effect of long term organic fertilization supplemented by mineral fertilizers on the grassland productivity. A ten-year-long experiment was conducted in mountainous conditions, in the south of Poland. Six treatments were evaluated: unfertilized control (UC), mineral P and K fertilization (PK), mineral P, K and N fertilization (NPK), sheep manure fertilizations (SM10 and SM15) and sheep manure supplemented with mineral P and K (SM10PK). The botanical composition, dry matter of the yield and the content of total nitrogen, phosphorus and potassium were determined every year. During the ten years of the experiment, changes in the botanical composition were observed. Fertilization, both mineral and organic one, resulted in the increasing grass participation at a reduced percentage of forbs up to 18% on average for all treatments. Some new grass species, Holcus mollis, Trisetum flavescens, Dactylis glomerata and Phleum pratense, appeared after ten years of fertilization. The PK and SM10 treatments were characterized by an increased percentage of legumes. The highest herbage production was noticed at the NPK fertilization (4.55 t DM ha-1). Fertilization significantly influenced the N content in plant biomass, with the highest N concentration effected by the PK treatment. Plants with manure fertilization, SM10, SM15 and SM10PK were characterized by similar N concentrations. The mineral fertilization NPK and control UC resulted in lower N uptake. It can be concluded that the highest potential of biomass production was achieved by sheep manure fertilization at the dose of 10 t ha-1 supplemented with mineral P and K fertilization (SM10PK).

22.1.2017