Nitrogen pushes HRZ barley to 10-tonne yields
GroundCover™ Issue: 110 | Author: Catherine Norwood
Barley nitrogen trials in Tasmanian have produced a yield difference of more than 45 per cent between the worst and best-performing plots, with the highest-yielding crop producing more than 10 tonnes per hectare. The results (Table 1) also indicate that growers can push yields and still remain within malting protein limits.
However, the premium for malt barley has fallen in recent years, and disappeared completely in the past year, putting malt barley on even terms with feed barley, so that even if protein levels are too high, advisers suggest pushing yields could be the bigger profit driver.
Southern Farming Systems Tasmanian trial manager David Kohler says the aim of the GRDC-sponsored trial was to demonstrate the potential for increased yields, rather than malt barley quality.
“In Tasmania, barley has been almost entirely grown with malting quality in mind, even though only half the barley grown ends up being sold for malting. Growers tend to be overly cautious when growing malt barley.
“There are some deeply ingrained beliefs about the total amount and timing of nitrogen fertiliser required to maintain grain within the nine to 12 per cent protein limits that breweries require. This trial challenges that thinking,” he says. “It offered the opportunity to push the limits of barley and should make growers more confident to target higher yields in future seasons.”
Mr Kohler says the Tasmanian malt barley market is relatively static, at around 15,000t a year, while the feed market, estimated at 85,000t a year, is growing. “By concentrating on higher yields, rather than protein content for malting, growers could potentially increase their overall income, and from the results of this trial may well push malt barley yields to more than 9t/ha.”
The trial was irrigated and used the malt varieties Gairdner, Westminster and Henley, although only Gairdner and Westminster are accepted by the major Tasmanian brewers. Oxford, also included in the trial, is a new high-yielding feed variety.
The trial was planted at Cressy, in northern Tasmania, on 24 May 2013, and harvested on 16 January 2014. Three different seeding rates were used for each variety targeting 180, 250 and 320 plants per square metre. Diammonium phosphate (DAP) was applied at the rate of 120 kilograms/ha, along with nitrogen applied at three different rates – 70kg/ha (targeting grain yields of 5t/ha), 260kg/ha (targeting grain yields of 7.5t/ha) and 400kg/ha (grain yields of 10t/ha).
The best-performing crop was Oxford, which yielded 10.29t/ha, in response to the mid-range nitrogen application and a seeding rate targeting 250 plants/m2. Westminster showed the greatest response to nitrogen and seeding rates, with yields increasing from 7.07t/ha to 9.05t/ha. “Overall, grain yield was higher for the mid and high-nitrogen treatments, and protein was highly responsive to nitrogen treatments,” Mr Kohler says.
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GRDC Project Code SFS00025