Grasslands with legumes, as the basic source of nitrogen, should play an essential part in organic agriculture systems. The proportion of grasslands of the total area of all types of organic croplands in Poland in 2002 highlights its importance (>45% of the total 41 thousand ha) (Zastawny et al., 2003). Grasslands are the obvious basis of organic livestock production. They provide cheap but valuable roughage that can serve as the only forage for ruminants in the summer period. They also allow access to range and natural grazing behaviour for stock, as an essential element of organic agriculture (Jankowska-Huflejt et al., 2004). The condition of grasslands and the quality of produced forages have a major influence on animal health, their condition, welfare and the quality of animal products. Conversely, the management on grasslands is stimulated by livestock production.