The aim of the study was to evaluate the effect of diversified nitrogen fertilization doses and application of various doses of herbicide Starane 250 EC on the total protein efficiency and carbohydrate:protein ratio of meadow sward. Two-factor field experiment was established on permanent meadow in the spring of 2007 in Żelków near Siedlce in a randomized subblock design in three repetitions. First experimental factor was diversified nitrogen fertilization in the amounts of: A1 0 kg N ha^-1, A2 90 kg N ha^-1, A3 180 kg N ha^-1, and A4 270 kg N ha^-1. The second experimental factor was herbicide Starane 250 EC applied at the doses of: B1 control group, B2 half a dose (150 g basic active substance ha^-1), B3 one dose (300 g basic active substance ha^-1), and B4 1.5 dose (450 g basic active substance ha^-1), according to the recommended instruction, namely 1.2 dm³ ha^-1. Plot size was 9 m². In every growth season, three cuts were harvested. In the study, total protein content (%) and soluble sugar content (%) in the meadow sward were determined. The obtained results were evaluated statistically with the analysis of variance for two-factor experiments. Mean differentiation was verified with the Tukey's test at the significance level of P ≤ 0.05. Significant effect of subsequent nitrogen fertilization doses on the protein efficiency of the meadow sward was demonstrated. With the increase in the nitrogen dose, the carbohydrate:protein ratio decreased and reached minimal, border nutritional values with the highest fertilization level. Diversified herbicide Starane 250 EC doses did not cause significant differences in protein efficiency or in the carbohydrate:protein ratio.

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