Irrigation opens feed window for dual-purpose crops

Mackillop Farm Management Group project officer Felicity Turner says the GRDC-funded trial at Bool Lagoon, under pivot irrigation, had its challenges, with the lowest rainfall on record in 2014 and some treatments being abandoned in 2016, due to prolonged waterlogging.

But the recently released results have helped farmers come up with a “good agronomy package.”

It confirms the need to not graze canola too early but also maintain enough residual biomass through winter, particularly when grazing canola, to ensure there is no grain yield penalty.

The trial tested CSIRO’s recommendations to wait until the six to eight leaf stage to graze canola and lock it up before bud elongation.

The importance of leaving three tonnes a hectare of dry matter for winter types and 1.5t/ha for spring types of biomass was also observed.

The results showed lightly grazed canola crops tended to yield more than heavy grazing – at 2.95t/ha compared with 2.41t/ha – but the early June-sown Hyola 575CL only yielded 1.17t/ha as it was not able to recover.

“It shows you can go too far and need to leave enough growth, particularly in the winter canolas,” she said.

Both spring and winter wheats need more than half a tonne of residual left after winter grazing.

Wheat crops should not be grazed until plants are fully anchored and stock should be removed before wheat paddocks reach growth stage 30.

Mrs Turner said the most significant differences in yield in the trials were varietal, with later maturity, winter season varieties being able to fully utilise the longer growing season created through irrigation.

They are capable of out-yielding the spring varieties when sown at the correct time.

In 2015, Manning wheat yielded an average of 7.9t/ha with no yield penalty for grazing, while Trojan averaged 6.8t/ha ungrazed or 4.1t/ha grazed.

In the canola, the winter types (Hyola 970CL and Hyola 971CL) outyielded the spring type varieties in both 2014 and 2015, and also produced the greatest amount of biomass when grazed.

Mrs Turner said the selection of weed-free paddocks was also important.

The need for pest management was higher in the early-sown crops. Early sowing also increased the disease pressure, but grazing did help open up the canopy.

“We have found the same as in other trials – there is no yield benefit from sowing wheat too early, aside from the grazing value,” she said.

BOOL Lagoon trial site host Bruce McLean says the potential for grazing early-sown irrigated crops is massive, but requires careful planning.

“It was great to see the opportunities around grazing canola and wheat crops established with irrigation and then taking them through to grain, but there are certainly a few problems to contend with around snails and slugs,” he said.

“More nutrition is needed as the crop is in the ground for a lot longer and if you take nitrogen out of the crop in grazing you need to put it back.”

Four sowing dates were evaluated each year from late summer to the beginning of winter.

The trial was managed by the NSW DPI through the Mackillop Farm Management Group, with SARDI providing technical support and site management.