The aim of the field experiment carried out in 2007-2009 was to evaluate the yielding of pasture mixtures cultivated in organic farming. The study was conducted at the Institute of Soil Science and Plant Cultivation - Agricultural Experimental Station Grabow (Mazowia province). In the scheme of the experiment, the first factor was a dose of natural fertilization and the second factor was a percentage of legume seeds. Three doses of organic fertilization were applied as: 5, 10 and 15 t manure per 1 ha. The percentage of legumes seeds (white clover, red clover, bastard clover) in mixture was: 20, 35, 50%, the rest: Italian ryegrass, perennial ryegrass (2n), perennial ryegrass (4n), meadow bluegrass, red fescue, meadow fescue, cocksfoot, timothy. Mixtures were utilized in two ways of utilization: mown-grazed and grazed-mown system. The study showed that the highest total dry matter yields gave mixtures with 20% percentage of legume seeds in sowing, but significant differences were observed in the second year of utilization, in total yields. Differentiated organic fertilization had significant influence on dry matter yields. Increased dose of organic fertilization caused an increase of mixture yield. The combination, where legumes were sown in 20% and dose of organic fertilization was 15 t.ha -1 gave the highest dry matter yield. Differentiation of total protein yield between tested mixtures depended on organic fertilization dose. In mown-grazed utilization system, the highest total protein yields was obtained in mixtures fertilized with the dose of 15 t.ha -1 and in grazedmown utilization system - with the dose of 10 and 15 t.ha -1.
