Are there benefits of pasture species diversity in hill country?

Abstract

We conducted an experiment at two hill country sites in the North Island to determine whether more diverse pasture swards were beneficial in terms of pasture herbage yield and resistance to weed invasion. In this study diversity was characterised by variation in the number (between 0 and 8) of functional groupings of pasture plant species. Seed mixtures were oversown into sprayed resident pastures in low and high fertility paddocks and steep and easy slopes within those paddocks. We measured pasture yield in terms of net herbage accumulation in spring and autumn of 1999-2000 and the botanical composition of the harvested material, identifying unsown species in the plots. The dominant influences on pasture yield were site, fertility and slope, rather than species diversity. The presence of particular functional groups was also weakly associated with differences in pasture yield. Increasing the number of functional groups sown had a negative effect on the invasion of unsown species, and their contribution to yield, and this may be the main benefit of pasture diversity. Keywords: functional groups, hill country, pasture yield, species diversity, weed invasion