Producers can increase net returns in dual-purpose crops by up to $500 a hectare and achieve other benefits including weed control through careful grazing management.
While producers must obviously weigh up the economics of using dual-purpose crops for their forage or grain value, trial work funded by the Grains Research and Development Corporation (GRDC) and undertaken by CSIRO Agriculture has identified ways of optimising grain yield and grazing potential.
CSIRO Agriculture research scientist Dr Susie Sprague presented the key findings of extensive trials conducted in southern NSW at Greenethorpe at a GRDC Update last year.
The trials used a range of grazing and defoliation intensities and lock-up times to explore their impact on yield recovery in wheat and canola crops with different maturities.
Dr Sprague said the trials demonstrated that optimum economic outcomes can involve later, moderate grazing periods outside traditional “safe” windows with careful management to avoid damage to developing reproductive structures.
Dr Sprague said early sowing with a suitable maturity type for the sowing date maximises forage and grain potential.
“The timing of lock-up and residual biomass influence grain yield recovery in wheat and canola,” Dr Sprague said.
Dr Sprague said trial results suggest leaving more than 1.5 tonnes per hectare of residual biomass in spring canola and more than 2.5 to 3 tonnes per hectare of residual biomass for winter canola at stem elongation for 2.5 to 3.5t/ha grain yield.
The results also suggest leaving more than 0.5t/ha residual biomass at stem elongation - growth stage 30 (GS30) - for wheat for 4 to 5t/ha grain yield.
“If producers are grazing beyond stem elongation, they should manage stock to protect developing reproductive structures and leave more residual biomass to avoid a yield penalty,” Dr Sprague said.
Dr Sprague said the period of grazing can increase net crop returns by up to $500/ha - for example, 2000 sheep grazing days at 25c/day - and have a range of systems benefits including weed management, reduced crop height and reduced grazing pressure on pastures.
“Grazing mostly has little impact on yield, but yield increases or decreases can occur,” Dr Sprague said.
“Yield increases occur under seasonal conditions where smaller crop canopies conserve soil water and fill grain more in dry seasons.
“Yield losses, compared to ungrazed crops, occur in crops grazed after the ‘safe’ stem elongation period – GS30 in cereals or stem elongation in canola - but can also occur when crops are grazed heavily in the ‘safe’ period.
“This can occur if flowering is delayed, but also if the residual biomass at lock-up does not allow the crop to recover a critical biomass at flowering to reach a target yield potential.
“Grain yield potential in both wheat and canola is set around the time of flowering and hence biomass levels at this stage set the upper yield that is possible.
“Actual yield levels depend on seasonal conditions after lock-up, but if a target yield is nominated, grazing can be managed so residual biomass is sufficient for the crop to attain the critical flowering biomass to achieve that target yield.
“Such an approach also allows crops to be grazed during a ‘sensitive’ stage after reproductive stem elongation.
“During this period crops can be grazed without yield penalty, as long as reproductive structures are not removed and residual biomass is sufficient to reach critical flowering biomass to achieve target yield.”
Dr Susie Sprague, CSIRO Agriculture research scientist
(02) 6246 5387; 0466 643 227
Ellen McNamara, Cox Inall Communications
0429 897 129