Can We Increase The Competitive Ability Of Spring Wheat?

By Brenda Frick, Ph.D., P.Ag., and Heather Mason, M.Sc. candidate

Wheat varieties that are competitive 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 varieties may be especially important for organic farmers who generally face higher weed populations in their fields; however, conventional farmers may also benefit from wheat varieties competitive against weeds.

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 currently working on a project to determine the competitive ability of spring wheat varieties grown in both conventional and organic management systems.

Farmers and researchers alike have observed that taller plants can be better at reducing weed populations and withstanding weed pressure. As well, plants that produce many tillers are thought to be able to better resist competition from weeds. In addition, management practices such as changing planting date, row spacing and seeding rate may be used to overcome weed pressure.

Heather 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 both conventional and organic management systems in north central Alberta. The experiment was conducted at two organic and one conventional site over a 2-year period.

Wheat varieties were seeded at single (75 lbs/acre) and double seeding rates. To guarantee substantial competition for the wheat, half of the plots were cross-seeded with tame oats; 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.

Currently, the 2003 results are available and Heather is still working on data from the 2004 growing season. Preliminary results from this experiment show that the overall yield of plots grown under conventional management was 27% 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 the biomass of 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, it may be that increased seeding rates could be a valuable tool for organic wheat producers to suppress weed populations in the field.

In terms of plant height and tillering capacity, no real trends were observed that would indicate that these traits generally help in giving 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 may then pave the way for breeding wheat varieties specifically for organic production.

Heather Mason is a M.Sc. student at the University of Alberta under the supervision of Dr. Dean Spaner. Her trials were conducted at the Edmonton Research Station in Edmonton, AB and at New Norway, AB in collaboration with Steven Snider of Little Red Hen Mills organic farm. Heather can be reached at hmason@ualberta.ca

Brenda Frick, Ph.D., P.Ag., is the Prairie Coordinator for the Organic Agriculture Centre of Canada at the College of Agriculture, University of Saskatchewan. She welcomes your comments at 306-966-4975 or via email at brenda.frick@usask.ca .

This article first appeared in The Western Producer, and is published here on the OACC website with permission.