Changes of botanical composition of grass stands under different types of management

A field trial with Bromus catharticus Vahl. cv. Tacit, Arrhenatherum elatius (L.) P. Beauv. ex J.S. et K.B. Pres1 cv. Median, Festuca pratensis Huds. ev. Otava and Dactylis aschersoniana Graebn. cv. Tosca sown in rows 125 mm, was established in the year 1996 in Prague (chernozern, altitude 281 m a.s.l., average precipitation 472 mm per year, average year temperature 9.3degreesC). The stands were cut one or three times per year. The mass was removed or once or twice mulched. The share of the botanical species (by weight method), number of present species and agrobotanical groups (grasses, legumes, other dicotyledonous) coverage were measured from the third to the sixth year of vegetation. The results were evaluated by the analysis of variance (Tukey alpha = 0.05) and by time series analysis (forecasting) by the Statgraphics Plus programme, version 4.0. The species number increased rapidly with the three times cut variant during the four years, from 4 to 25 species, under the other management it was in average from 7 to 14 species, in the sixth year. The highest share of the sown species with the lowest reduction during the years was at Arrhenatherum elatius (41-72% in the sixth year). Bromus catharticus was extinct in the fifth year. The species chosen had a higher importance for conserving of the original botanical composition than the way of harvest. There was the significantly lower ground cover with the variant one cut per year (oil average less than 70%). Mulch covered 15-64% of the surface in dependence on the dry mass yield and mulching frequency. The plants coverage was highest on the two or three times harvested variants (75-80%D).