Use of glyphosate to prevent development of reproductive tillers and extend vegetative growth of bent grass (Agrostis castellana)

Abstract

The effect of glyphosate on seedhead development of bent grass (Agrostis castellana) was evaluated in an experiment at 2 sites in south-western Victoria.Application of glyphosate at 0.1350.225 kg a.i./ha on 7 November and 7 December 1993 prevented the formation of seedheads and stimulated the plant into renewed vegetative growth in response to following summer rain. The treatment with 0.135 kg a.i./ha of glyphosate, applied on 7 November, increased digestible dry matter of the regrowth by 20% and protein content by 70% compared with the unsprayed control which was dominated by seedheads. These results reflect the amount of new growth in treated plots and thus should not be confused with either the 'spraytopping' technique which aims to sterilise seeds after seedhead emergence or 'hay freezing' which and aims to preserve the feed value of existing vegetation by 'chemically curing' standing hay. We conclude that application of glyphosate at 0.135 kg a.i./ha in early November has the potential to reduce the dominance of bent grass, creating an opportunity for follow up fertiliser and management techniques to maintain productive pastures.