Integrating dual-purpose wheat and canola into high-rainfall livestock systems in south-eastern Australia. 2. Pasture and livestock production

Abstract

In south-eastern Australia, low winter temperatures often reduce pasture growth and thus winter herbage supply relative to livestock requirements. Grazing of vegetative grain crops in winter is one strategy that might overcome this feed gap. In a study with young sheep over two seasons near Canberra, ACT, we compared pasture-only grazing with three separate crop–livestock systems in which the sheep grazed long-season wheat, winter canola or a combination of these, for intervals over the period May–August. We measured forage biomass, sheep grazing days (SGD) and liveweight accumulated per ha. Crop-grazing treatments resulted in much more winter forage for grazing sheep (t DM ha–1): in 2010, one crop 2.5–3.0, two crops 3.5 v. pasture only 1; in 2011, one crop 2, two crops 3 v. pasture only 1.4. In the first season, grazing one crop resulted in ~2000 extra SGD ha–1 and the accumulation of more liveweight per ha than in the pasture-only treatment; grazing of two crops resulted in >3500 extra SGD ha–1. Equivalent values in the second, drier season were: one crop, ~1000 extra SGD ha–1; two crops, 2600 extra SGD ha–1. Spelling of pastures during crop grazing led to extra pasture growth, such that in each of the two seasons, 40% of the total benefit in extra SGD per ha came from the extra pasture. The results indicate that, like grazed wheat, grazed canola can provide valuable winter forage, especially when used together with wheat. The data also provide the first quantification of the effect of crop grazing on pasture spelling and subsequent pasture supply, and suggest value in the incorporation of grazing wheat and canola into grazing systems in the high-rainfall zone.