When South Australian grain grower Bruce McLean and his agronomist James Heffernan heard researchers were setting new yield benchmarks for wheat in Tasmania, they wanted to see the results for themselves.

“When we heard what FAR Australia’s Nick Poole was doing in Tassie, we jumped on a plane to see what was going on,” Bruce says.

“With Tasmanian wheat crops yielding up to 17 tonnes a hectare (in trial plots), we wanted to see if we could achieve that on the mainland.”

A small group of local growers and agronomists encouraged and supported Nick to set up a trial at Millicent, which later became the GRDC Hyper Yielding Crops (HYC) SA site.

To date, the highest plot yield achieved at Millicent was 12.7t/ha in 2021. But for many growers in SA’s south-east, having local trials has been a focal point for learning about what it takes to grow high-yielding crops.

Alongside the Millicent GRDC HYC trials and field days is GRDC’s HYC awards program. This agronomic benchmarking program offers growers the chance to enter one paddock of wheat and barley to compare their paddock and management with growers locally and nationally.

Yearly differences

Although 2022 lacked the sunshine required to boost grain yields as high as 2021 levels, Bruce was stunned to find there was still enough to allow his Anapurna wheat to achieve its estimated yield potential.

Using crop models, which include rainfall, temperature and solar radiation data, researchers estimated that Bruce’s Anapurna wheat had the potential to produce 9.3t/ha of grain. However, when the paddock was harvested on 18 February 2023, weighbridge tickets showed it actually yielded 9.6t/ha.

The effort was enough to earn Bruce the 2022 GRDC HYC award for growing the ‘Highest wheat yield as a percentage of yield potential’. These awards recognise the participants who achieved the yield closest to their theoretical potential yield.

Bruce puts the results down to implementing the key messages of the GRDC HYC initiative:

• growing a variety suited to local conditions that has the potential to produce a high-yielding crop;
• sowing at a time to ensure crops reach flowering at the ‘optimum’ time to minimise the risk of frost, heat and moisture stress;
• supplying sufficient nitrogen by growing pulses or legumes and strategically applying fertiliser; and
• protecting the crop from disease.

“We’ve seen massive production increases by adopting better varieties and agronomic practices,” Bruce says.

Nutrition and waterlogging

According to Bruce, one of the shifts that has helped improve grain yields is delayed nitrogen application.

“In the past, early nitrogen applications created a big canopy, which would create more disease pressure, lodging and extra tillers with smaller heads, which wouldn’t fill with grain.

“We’re now applying more nitrogen than we had previously, but our grain protein content being about 11.2 per cent suggests we aren’t over-applying it.”

Bruce delayed urea application for his award-winning crop until 20 September, when 200 kilograms/ha was applied. On 7 October, a further 100kg/ha of urea was applied. The total nitrogen applied was 147kg/ha.

Through a previous GRDC investment, working with Agriculture Victoria researchers Malcolm McCaskill and Penny Riffkin, Bruce learned the optimum phosphorus level for his cropping paddocks was between 50 and 60 milligrams per kilogram.

“When the price of phosphorus fertilisers dropped, we applied capital dressings to build levels and have maintained them in the optimal range ever since,” he says.

The superior tolerance to waterlogging is a feature of the red wheat feed varieties that has been a big advantage for growers in SA’s south-east.

“The wet winter months cause the water table to come up from underneath, so soils are at capacity, which always makes waterlogging our biggest challenge,” he says. “We don’t have enough soil depth to install raised beds.”

While Bruce has sown Anapurna again this year, he is also trying some RGT Cesario. Trials at the Millicent HYC site have shown a slight yield advantage over Anapurna.

Fungicide is always applied proactively. In 2022, he applied fungicide at growth stages 32, 39 and 65.

Agronomy benchmarking

Participating in the GRDC HYC awards gives growers a report that allows them to compare their paddocks and management with others.

Bruce’s herbicide spend per hectare was in the lowest 25 per cent of 2022 award paddocks in SA, with a total spend of less than $98/ha.

One reason for this was his purchase of an Integrated Harrington Seed Destructor (iHSD) in 2016. He originally bought the hydraulic version but now operates a vertical version on a Claas 770 harvester. His other harvester does not have a weed seed destruction mill.

“We need to be using every tool available to drive down the weed population,” he says. “Annual ryegrass is a major issue in the high-rainfall environment.”

Bruce says he likes to have the option to bypass the iHSD if crop moisture is too high and there is a deadline to finish the job.

“Even though we are 100km from the coast, we experience the cold and moist conditions that blow inland from early evening, which limits the hours we can harvest in a day,” he says.

“We grow Persian clover for seed production, and the vine can be quite green in those cool conditions, so the mills might be turned off. But 90 per cent of the time, we are leaving everything hooked up and working.”

When he has run his harvesters side by side, Bruce says he has seen far fewer weeds germinate in the sections where the harvester with the mills was used.

“Also, the new vertical design with the direct drive has improved the longevity of the mills. We find the mills are now lasting a couple of seasons.”

Since buying the iHSD, he has seen significant benefits: “The mills are certainly helping to lower our weed seedbank.”

Weeds strategy

Bruce says having the mechanical option for destroying weed seeds at harvest is part of an integrated package that includes double knocks, double breaks, robust herbicide mixes, crop competition and cutting hay or silage.

He cites growing a Persian clover seed crop as another useful tactic to drive down the annual ryegrass seedbank. This involves making silage or taking out grass weeds early and allowing the clover to outcompete grass regrowth.

Another change Bruce has made is using a Reefinator to rip through a layer of shallow limestone in the topsoil to increase the size of the bucket of nutrients and moisture. He has seen a 70 per cent increase in root mass since using the machine to ameliorate the soil.

“We’ve seen up to 1.5t/ha grain yield increase where we did a trial in a paddock a couple of years ago,” he says. “It’s really brought the bottom 30 per cent of the country up to another level.”

In thinking back over the past five years, Bruce says GRDC’s HYC initiative has made the biggest difference to crop yields. He also cites GRDC’s investment in the iHSD as worthwhile.

“I have also found going to GRDC workshops on grain storage useful, as about 40 per cent of our grain is supplied to dairy farmers through the year,” he says.

Bruce is inspired by chasing higher grain yields and producing the highest returns for the inputs applied.

“If you told me 10 years ago we would have been growing up to 10t/ha of wheat, I probably would have laughed at you,” he says.

“It’s been great to have the awards over a number of years to build up a picture across different seasons and to have (FAR Australia project officer) Jen Lillecrapp take all the measurements for the awards.

“We’d love to see the work that Nick Poole and his team have been doing to access and screen new varieties, assess nitrogen inputs and compare fungicide strategies continue. It’s been valuable research that has been delivering results for growers."

More information: Bruce McLean, bwmclean@bigpond.com