Salt (NaCl) application as a tool to reduce the annual grass weed, ripgut brome, in New Zealand South Island hill/high country pastures

Abstract

Ripgut brome (Bromus diandrus) is an annual grass weed that is prevalent on high country properties in the South Island of New Zealand. Its seeds contaminate wool and carcasses. The effect of a single application of salt (50 kg ha−1), in autumn or spring, was tested as a tool to reduce ripgut brome at four sites in high country properties in the South Island. Salt application increased sodium levels in the soil and ripgut brome plant tissue and attracted grazing livestock. In response to salt application, there was a reduction in ripgut brome fecundity across all sites, and a reduction in height and an increase in bare ground at some sites. Spring application was more effective than autumn application in reducing ripgut brome. Salt application is a useful tool to increase grazing intensity and reduce ripgut brome, although a higher application rate with repeat applications within and between years may be required for longer-term control.