The studies were carried out in 1990–2001 in central Poland on a natural moderately wet meadow site. The objects were two meadow mixtures: early and mid-early. The aim of the study was to evaluate the changes of botanical composition of these mixtures in yields during
12-year utilisation. The annual yields of mixtures were rather similar but differed significantly in the years of utilisation. It was affected by meteorological conditions. It was found that changes in botanical composition of mixtures were noticeable since the first year of utilisation. It was determined first of all by competition between components of mixtures and the weather conditions. The most persistant and agressive components of early and mid-early mixtures were Arrhenatherun elatius especially cv. Skrzeszowicki, Festuca arundinacea cv. Brudzynska and Rahela, Dactylis glomerata cv. Brudzynska. Poa pratensis cv. Skrzeszowicka and Festuca rubra cv. Nakielska were persistant but less competitive components. Cultivars of Lolium perenne and Festuca prate nsis remained in the sward only for two or three years.