A RECENT study into biomass production has produced positive results for graingrowers who are concerned about low biomass at the end of winter.
Field trials at Farrell Flat and Waite Campus showed researcher Alec McCallum that biomass accumulation might not be as big of a problem as farmers first thought.
"Having reduced biomass at the end of winter does not mean it will remain that way at the end of the season," he said.
The trials showed that increasing plant density can improve winter biomass accumulation and that barley was the most tolerant to cold and produced the most biomass.
Mr McCallum worked in collaboration with University of Adelaide researchers and SARDI and a few important points were discovered.
"Low temperatures limit wheat biomass and slow development in winter, while extended growing period from low temperatures creates a higher maximum biomass that occurs later in the season," he said.
"Low temperatures in spring and summer are favourable to total biomass."
Most importantly, Mr McCallum said the amount of biomass present at the end of winter did not impact on final biomass.
The objective of the trial was evaluate using agronomy for improved cereal biomass accumulation in suboptimal temperatures.
Farrell Flat's average winter temperature was 2.8 degrees Celsius to 14 degrees C, while Waite's was 8-15.8 degrees C.
"There is a high frost risk and a lot of growers are choosing to sow late to avoid that frost," Mr McCallum said.
"This means crops are establishing in low air and soil temperatures in late May and June, resulting in low biomass over winter and impacting grain and hay yield late on."
Mr McCallum's theory is that winter biomass can be increased by canopy cover and light interception. Both sites were sown a few days a part in late May and early June.
Four crops were sown - Scepter wheat, Compass barley, Mulgara oats and Bevy rye.
Two plant densities were sown - one at 150 plants a square metre and 300sqm. Three row spacings were also sown - narrow at 15 centimetres, wide 30cm, broadcast 0cm. "This was to get a variety of canopy covers," Mr McCallum said.
"The colder climate at Farrell Flat is actually producing more biomass per degree day and zadoc growth stage.
"Increasing plant density also increases biomass over winter."
INCREASED plant density increased biomass across winter in a field trial undertaken by University of Adelaide researcher Alec McCallum.
In two sites at Farrell Flat and the Waite Campus, a difference in biomass per growth stage was recorded.
Mr McCallum said Farrell Flat plants grew slower, but had gained more biomass per growth stage.
"Slower development is extending the growing season but allowing more time to produce more biomass in each growing stage," he said.
Mr McCallum said by doubling plant density, early on in the season, biomass had doubled.
"By the end of winter, there was about a 15 per cent increase in biomass at Waite and 24pc at Farrell Flat," he said.
But by the end of the season, Mr McCallum said there was no difference in high or low plant densities.
"Increasing plant density won't have a big impact on grain yield, but if you are grazing crops, early on there is a benefit," he said.
In hay yields at Farrell Flat, row spacing and crop type had a significant effect.
"Wide row spacing had the lowest biomass, whereas narrow and broadcast had the highest," Mr McCallum said.
"It showed that denser plants and intercepting more light was having an increase in biomass."
Different crop types, rye and wheat, had the lowest biomass, but barley had the highest. A cool spring that slowed plant development actually resulted in more biomass at harvest.
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