From prickly acacia to pasture – key lessons from a mechanical control field study

Abstract

As a result of years of community, industry and government research and innovation, a range of herbicide and mechanical options are available for the control of prickly acacia (Vachellia nilotica). However, in recent years, mechanical control options have become less favoured due partly to the perceived risks of mass prickly acacia germination and the high follow-up control requirements. A field study, conducted during 2015 – 2017 at a property near Richmond in north-west Queensland, examined pasture and seedling responses to mechanical control (dozer pushing) of mature prickly acacia. Results were compared with adjacent untreated (control) sites. Prickly acacia seedling counts were initially higher in pushed areas but due partly to ensuing low rainfall, no new saplings have established at either site during the study. Average pasture cover increased from 1.4% to 30% and 3.2% to 53.4% at the untreated and dozer pushed treatment sites respectively. In this case, the landholder gained prickly acacia foliage fodder and improved pasture cover in the following years with negligible follow-up control.
The study demonstrates the benefits of mechanical control of prickly acacia if undertaken in the right circumstances.