New lines put weeds in shade

New WA trial results have increased knowledge - about competitive wheat lines - which could give growers the option of keeping weedy paddocks in crop.

Field trials at Eradu and Wongan Hills were held in 2010 and 2011 by the Department of Agriculture and Food (DAFWA) as part of Grains Research and Development Corporation (GRDC)-funded integrated weed research.

As well as providing new information about the competitive wheat lines - highly vigorous lines intended to be provided to Australian wheat breeders for inclusion in germplasm development - the trials have highlighted marked differences between existing commercial varieties in their ability to suppress weeds.

The competitive wheat lines have been developed by CSIRO Plant Industry's Greg Rebetzke and tested by Gurjeet Gill, of the University of Adelaide, under a GRDC-funded project.

DAFWA researcher Peter Newman, who led the WA field trials, said the lines could produce up to double the biomass of commonly grown varieties by the early tillering stage, effectively shading out weeds. Increased root growth also enabled the wheat to out-compete weeds for water and nutrients.

"In weedy situations, competitive wheat lines also yield more, so there is the double advantage of greater yields and fewer weed seeds," Mr Newman said.

The WA field trials compared three of the competitive wheat lines with commonly grown varieties Mace, Magenta, Bonnie Rock and Wyalkatchem, as well as Baudin barley.

At Eradu, which contained 80 ryegrass plants per square metre and was weedier than the Wongan Hills site, trials were seeded into yellow, sandy soils.

"At the end of the year, plots seeded to one of the competitive lines, as well as plots seeded to Magenta and Baudin, contained the lowest number of annual ryegrass tillers at 180 tillers per square metre," Mr Newman said.

"In comparison, the plot seeded to Wyalkatchem contained the highest number of tillers at 520 per square metre, and three times as many weed seeds.

"The competitive wheat line which best suppressed weeds also yielded well - 2.76 tonnes per hectare, compared with 2.86t/ha for the highest yielding commercial variety Magenta, 2.67t/ha for Mace, and 2.65t/ha for Bonnie Rock.

"Baudin barley yielded 4.17t/ha in the Eradu trial - 146 per cent of Magenta's yields."

Mr Newman said that although the best performing competitive wheat line did not reduce weed seeds more than Magenta in 2011, it was important to remember that lines with even greater competitiveness were in the genetics pipeline.

As well, another competitive wheat line which had performed well in 2010 had been significantly affected by leaf disease in the 2011 trials, so its weed suppressing ability and yields could not be properly assessed.

Mr Newman said the 2010 trials revealed that the competitive lines yielded almost as well as the commercial lines during very dry conditions, and despite their big canopies did not fall over during the dry finish to the season.