The effect of manipulated plant species diversity of semi-natural permanent grassland on forage production and quality.

So far, most experiments investigating environmental as well as agricultural benefits of plant diversity in grassland have dealt with sown grassland, whereas permanent grassland has been poorly examined. In the Grassland Management Project (GRASSMAN) in the Solling Uplands (Germany), the biodiversity of permanent grassland has been manipulated by herbicides to obtain either pure grass swards or swards with relatively high amounts of forbs and legumes, on top of untreated control swards. These swards were subjected to different management intensities, regulated by both the cutting regime and the nutrient supply. The aim of this study was to compare the forage quality in terms of crude protein and fibre content as well as the yield of the different swards. Furthermore, the role of species richness as well as that of functional biodiversity, that is to say the distribution of the functional groups, for yield formation was examined. Neither the species composition of the sward nor its functional diversity influenced the yield in this experiment. The swards rich in legumes and forbs tended to have a better quality than the control and grass-rich swards.