Effects of clipping frequency on tiller development of crested wheatgrass and hybrid bromegrass at vegetative and reproductive stages

Abstract

Information on the tiller development of hybrid bromegrass (Bromus inermis × Bromus riparius) is limited. The objective of this study was to evaluate the effect of clipping frequency at the vegetative and reproductive stages on the tiller development and concentrations of sugars of c.v ‘AC Knowles’ hybrid bromegrass compared with c.v ‘Kirk’ crested wheatgrass (Agropyron cristatum L.). This experiment was conducted in a greenhouse using the tillers of the vernalized plants dug from the field. The experimental design was a randomized complete block design (RCBD). Grasses were clipped once or four times at either vegetative or reproductive stage. Regardless of the growth stage, four clippings reduced the tiller number of hybrid bromegrass by 25.9% compared with the undefoliated control, while single clipping had no impact. The four clippings had no impact on the tiller number of crested wheatgrass, while single clipping increased its tiller number on average by 50.4% at both growth stages. Crested wheatgrass produced 16.6% more tillers than hybrid bromegrass under the single clipping. The two grass species had a similar number of axillary buds under different clipping treatments. The axillary bud size of crested wheatgrass was larger than hybrid bromegrass. All axillary buds were viable under the two clipping treatments for both grasses. Four clippings significantly decreased the stem base glucose concentration of the two grasses and the root sucrose concentration of crested wheatgrass. Hybrid bromegrass was less tolerant to frequent clippings than crested wheatgrass. Therefore, intensive grazing of hybrid bromegrass pasture may result in a thin stand.