Use of residual leaf area index and light interception as criteria for spring-grazing management of a ryegrass-dominant pasture

Abstract

Detailed measurements of herbage accumulation were made on a ‘Grasslands Nui’ perennial ryegrass (Lolium perenne)-dominant, ‘Grasslands Huia’ white clover (Trifolium repens) pasture under 4 late spring grazing intensities, based on residual leaf area index (LAI), and 2 grazing frequencies based on light interception. Lax grazing during late spring (residual LAI 0.9–3.0) resulted in rank stalky herbage, whereas hard grazing (residual LAI 0.1–0.9) resulted in more leafy herbage and higher ryegrass tiller density. For the 46 weeks of the experiment, 16.5 and 14.61 DM/ha accumulated with hard and lax spring grazing respectively. During autumn, delaying grazing until 2 weeks after 95% light interception markedly increased green herbage accumulation compared with grazing at 95% light interception, without significantly reducing ryegrass tiller density or white clover content. It is concluded that in spring, in contrast to other seasons, management of ryegrass-dominant pasture to control reproductive development is a considerably more important criterion than management to control leaf area and light interception. Control of reproductive development can be achieved by close grazing, topping, and closing paddocks for conservation, and will provide pasture which is leafy and digestible in summer.

Keywords:

• Grazing management
• leaf area index
• light interception
• Lolium perenne L.
• ‘Grasslands Nui’ perennial ryegrass
• reproductive development