Wheat varieties that compete well against weeds could help farmers by allowing wheat yields to remain high in spite of weed pressure.
This may also aid in controlling weed growth following harvest.
Competitive wheat varieties may be especially important for organic farmers who generally face higher weed populations in their fields.
So how do we increase the competitive ability of spring wheat? Are there management practices that can be used? Can we identify traits that make wheat more competitive?
Heather Mason is a graduate student at the University of Alberta looking to answer some of these questions. She is working on a project to determine the competitive ability of spring wheat varieties grown in conventional and organic management systems.
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Her trials were conducted at the Edmonton Research Station and at New Norway, Alta., in collaboration with Steven Snider of Little Red Hen Mills organic farm.
Farmers and researchers alike haveobserved that taller plants can be betterat reducing weed populations and withstanding weed pressure.
As well, plants that produce many tillers are thought to be more competitive and management practices such as changing planting date, row spacing and seeding rate may be used to overcome weed pressure.
Mason chose nine spring wheat varieties that differ in height and tillering capacity and tested these varieties to determine if such theories hold true for spring wheat grown under conventional and organic management systems.
The experiment was conducted at two organic sites and one conventional site over two years.
Wheat varieties were seeded at single and double seeding rates. The single rate was 75 pounds per acre.
To guarantee substantial competition for the wheat, half of the plots were cross-seeded with tame oats and the other half were not.
Natural weed populations were allowed to flourish at the organic sites while the conventionally managed site was sprayed for broadleaf weeds as they occurred.
Results from 2003 are available and Mason is still working on data from 2004. Preliminary results show that the overall yield of plots grown under conventional management was 27 percent higher than the yield of organically managed plots. Competition from tame oats reduced wheat yields regardless of management system.
Doubling the seeding rate of spring wheat resulted in overall higher yields and reduced biomass in the tame oats.
At the organic sites, the reduction of tame oat biomass as a result of doubling the seeding rate was more pronounced than at the conventional site.
If the 2004 results are similar, increased seeding rates could be a valuable tool for organic wheat producers to suppress weed populations.
In terms of plant height and tillering capacity, no real trends were observed that would indicate these traits give spring wheat a competitive advantage over weeds.
Some of the wheat varieties performed better under organic than conventional management and vice versa.
For example, the early maturing variety Park, released in 1969, performed better as weed pressure increased. The newly released semi-dwarf variety CDC Go, with its large leaf area and unique plant structure, yielded well under all management systems.
If outcomes like this are observed again in the 2004 data, it may indicate that some varieties are better suited to organic production.
This might pave the way for breeding wheat varieties specifically for organic production.
The Organic Connections conference in Saskatoon on Nov. 14-16 will include further information on this project and on the organic wheat program at University of Alberta.
This column was written with the help of Heather Mason, a MSc student at the University of Alberta under the supervision of Dean Spaner. She can be reached at hmason@ualberta.ca
Frick is the Prairie co-ordinator for the Organic Agriculture Centre of Canada located at the University of Saskatchewan. Frick can be reached at 306-966-4975, at brenda.frick@usask.ca, or www.organicagcentre.ca.The opinions expressed in this column are not necessarily those of The Western Producer.
