Herbage mass thresholds rather than plant phenology are a more useful cue for grazing management decisions in the mid-north region of South Australia
Lewis P. Kahn A C , Judi M. Earl A and Millie Nicholls BA Agricultural Information and Monitoring Services, 625 Cluny Road, Armidale, NSW 2350, Australia.
B Mid-North Grasslands Working Group, PO Box 12, Brinkworth, SA 5464, Australia.
C Corresponding author. Email: lewis@aimsag.com.au
The Rangeland Journal 32(4) 379-388 https://doi.org/10.1071/RJ10003
Submitted: 28 January 2010 Accepted: 28 July 2010 Published: 26 November 2010
Abstract
Research was conducted in the mid-north of South Australia over the period 2000–05 to evaluate the effects of different grazing management cues on composition and production of a grassland. The management cues were based on calendar, plant phenology or herbage mass thresholds using grazing exclusion as a control. There were five grazing treatments: (i) regional practice (RP), where sheep grazed continuously for the period April–December; (ii) autumn rest, where sheep grazing was restricted to June–December; (iii) spring rest, where sheep grazing was restricted to April–August; (iv) high density and short duration (HDSD), where herbage mass thresholds determined when grazing occurred and for what duration; and (v) nil (NIL) grazing by domestic herbivores. Mean annual estimates of herbage mass were highest for NIL and HDSD and inclusion of the estimate of herbage consumption by sheep resulted in greatest primary plant production in HDSD. The contribution of perennial grasses to herbage mass declined with RP and seasonal grazing treatments. Frequency of perennial grasses was unaffected by grazing treatment but the number of perennial grass plants increased over time in RP and seasonal treatments. HDSD allowed maintenance of basal cover whereas bare ground increased with RP and seasonal treatments. Litter accumulated in NIL but this was associated with a decline in perennial basal cover. Seasonal grazing treatments did not provide an advantage over RP and there appeared to be no benefit from including phenology in management decisions. In contrast, HDSD resulted in a stable and productive grassland ecosystem, with stocking rate estimated at 78% greater than other treatments. These features offer a desirable mix for future industry adoption in the mid-north of South Australia.
Additional keywords: grazing exclusion, management cues, perennial grasses, seasonal grazing, short duration and high intensity grazing.
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