The aim of the study to evaluate selected methods of permanent grassland renovation under different soil-climatic conditions in north-eastern Poland. Studies are carried out in three farms: in Dymnik (Rychliki commune, Warmińsko-Mazurskie Province), in Kąty Milewskie (Jasionówka commune, Podlaskie Province) and in Kodeń (Kodeń commune, Lubelskie Province) specialized in beef cattle breeding with bulk fodder from permanent grasslands. Renovation of permanent grasslands was performed in spring 2012. Depending on sward degradation, the method of undersowing or complete cultivation was applied by sowing mixtures of grasses and legumes with the consideration of soil-water conditions and the way of sward utilization. Botanical composition of sward and yielding are determined. Total protein and soluble carbohydrate content are determined using NIRFlex N-500 apparatus with ready calibrations of the INGOT® firm. Results of study presented in the paper come from the years 2012 and 2013. The enrichment of species composition resulted in significant increase of biomass and of the yield of total protein and soluble carbohydrates. Utility value of the sward was also improved. Due to direct undersowing with a slot seeder, the yield of total protein from permanent grasslands increased by 300 kg ha-1 on average (by 250 kg ha-1 on pastures and by 400 kg ha-1 on meadows) and the yield of soluble carbohydrates increased by 150 kg ha-1 (by 100 and 200 kg ha-1 on pastures and meadows, respectively).