Effect of selective defoliation on species in mixed swards

Sown pastures of Paspalum dilatatum (and other species) in Natal are subject to degradation by Eragrostis plana (mshiki) invasion. The ratio between these two grasses, growing together in small plots, was governed primarily by the relative heights, and secondarily by the relative frequencies, of defoliation. The Paspalum held its own only when it was cut neither shorter nor more frequently than the mshiki. Additional nitrogen supplied to a nitrogen-rich soil was beneficial almost entirely to the mshiki. Less frequent defoliation of the sward as a whole was harmful to the Paspalum. A treatment simulating mid-summer closure of a pasture, for silage purposes, benefited whichever grass was being suppressed. It is concluded that regular mowing of pastures after every grazing, and light, frequent grazing offers the best promise of mshiki control.Keywords: defoliations|swards|grasses|pastures|KwaZulu Natal Province|degradations|invasions|defoliation frequencies|defoliation heights|nitrogen|grazing|treatments|mowing|controls|invasive species|tuftines