Crop and livestock production for dual-purpose winter canola (Brassica napus) in the high-rainfall zone of south-eastern Australia

Abstract

Dual-purpose use of canola (Brassica napus) for forage in winter before seed production is a practice recently developed in southern Australia. The feasibility for dual-purpose spring canola (B. napus annua) in the medium-rainfall zone (450–650mm) has been demonstrated commercially, with significant adoption. Testing of later-maturing, dual-purpose winter canola (B. napus biennis) in long-season, high-rainfall areas (>650mm) has been restricted to mechanical defoliation or crash grazing. We conducted a series of six field experiments to evaluate the crop and livestock productivity of dual-purpose winter canola, involving a variety of stocking rates, grazing regimens and different cultivars at Canberra, ACT, and Young, NSW, in south-eastern Australia in 2007 and 2008. European winter canola cultivars sown between 21 March and 21 April provided 800–1100 dry sheep equivalent (DSE) grazing days/ha in Canberra and 1550–2600 DSE grazing days/ha in Young with little impact on subsequent yield (range 2.6–5.8t/ha), provided the sheep were removed from crops prior to bud elongation. Grazing occurred between 18 June and 1 September in Canberra and between 16 June and 14 August in Young and generally had no effect on harvest index or oil content. High stocking rates for short duration (126DSE/ha for 7 days) reduced sheep live-weight gains and meat production by ∼50% (110g/day; 92kg/ha) compared with stocking rates of low (22DSE/ha for 47 days) or moderate (43DSE/ha for 22 days) stocking rates (mean 220g/day; 182kg/ha) despite similar overall grazing pressure (882–1034 DSE grazing days/ha). The flexibility in sowing date and grazing times afforded by the vernalisation characteristics of winter canola make it an ideal, flexible option in high-rainfall mixed-farming systems. Winter canola could complement or even replace the traditional later-sown spring cultivars (for dual-purpose and/or grain-only production) in areas with high rainfall (>650mm) where early sowing opportunities (March) and cooler spring temperatures can maximise yield. Our results demonstrate significant potential for high livestock production and high grain and oil yield from dual-purpose winter canola in high-rainfall environments.