Dual purpose canola: recent results from southern NSW

Canola crops were grazed during vegetative growth in three trials conducted in Wagga Wagga NSW in 2007. All experiments included various grazing periods and were combined with either 1) a range of cultivars, 2) sowing rate and row spacing, or 3) intensity of grazing. Due to seasonal conditions yields were low in all trials (maximum 1 t/ha) with grazing significantly reducing yields. Grazing for 18 days at 23 DSE (dry sheep equivalents) reduced biomass of Hyola 75 from 1793 kg/ha pre-grazing to 731 kg/ha post-grazing. This treatment yielded 69% of the ungrazed control despite dry conditions and flowering 11 days later than the control. Grazing intensity determined the magnitude of the delay in flowering. Heavy grazing (leaves and main stem) delayed flowering by 10-14 days while light grazing (removal of leaf only) delayed flowering by only 4 days. This delay was not due to delaying floral initiation, as this has already occurred by the 4th leaf stage (pre-grazing). Canola will recover from heavy grazing as it is able to re-shoot from axillary buds, however, development will be significantly delayed. Choice of cultivar and sowing rate strongly influenced early biomass available for grazing. The hybrid cultivar (Hyola 75) produced much greater biomass than conventional and triazine tolerant (TT) cultivars. Increased sowing rate also led to higher early biomass production.