The effect of different winter and early spring removal treatments on Themeda triandra in the tall grassveld of Natal.

Abstract

Themeda triandra dominated tall grassveld was mown to different heights, mown and trampled with sheep or burned, from mid-April through to mid-November, and the effect of treatments on the parent tiller, the subsequent production of lateral tillers and plant vigour monitored during the post-treatment period. Regrowth of parent tillers was appreciable only where clipping was lenient (to 10 cm). Burning destroyed all parent tillers. Lateral tillers developed poorly on all plots mown in early and mid-winter and on those burned in late winter and early spring. Lateral tillers yielded best all over treatment times when cutting was intense (to 5 cm). Herbage yields from lateral growth were higher when treatments were applied in April and August, than when applied in June or October. Regrowth vigour, measured in December and January was greater the more lenient the treatment, and was poor when defoliation was delayed to October. Even in control plots, flowering of T. triandra occurred in only 52% of the parent tiller population. The apices of the non-flowering tillers were damaged by a wasp, Oscinella truncata, whose effect increased in severity as defoliation intensity increased.

Keywords: burning; clipping; cutting; defoliation; herbage; herbage yield; lateral tillers; natal; oscinella truncata; plant vigour; regrowth; south africa; tall grassveld; themeda triandra; tillers; ukulinga research station; yield