Weed Control for Seed Growers in Direct Seeding Systems

Neil Harker

Agriculture and Agri-Food Canada

Lacombe Research Centre

Lacombe, AB

Can I Be a Seed Grower and Direct Seed?

What is Different?

• More volunteers - primary challenge
• Dependence on glyphosate burn-off treatment
• • all volunteers will not emerge before burn-off
• Some HT Canola volunteers may escape burn-off treatment
• • keep good field records
  • tank-mix glyphosate with a phenoxy
• No pre-harvest glyphosate on seed crops

What Can be Done?

• Volunteers
• • replant same variety year after year
  • • the current variety registration system is not helping
    • 30-40 new varieties with few important differences
    • frustration of guessing which variety will be popular
    • spend some time changing the system so that only significant improvements Þ new varieties
  • avoid semi-dwarfs (tend to have higher dormancy)
  • extend rotations (ß volunteers and diseases)
  • make arrangements to exchange land with neighbours (broken hay land - grow Foundation)
  • fall harrowing immediately after harvest
  • • also good for straw and chaff management
    • but watch for dandelions and winter annuals

Pre-harvest Glyphosate Acres Treated - W. Canada

What Can be Done?

• Pre-harvest glyphosate in non-seed years
• • need to get it into the system for perennial weeds
• Agronomic Management of Weeds
• • use silage, forages and winter crops if possible, i.e., diversify the rotation to keep weeds off balance
  • chaff collection (Martin Entz - U of Man.)
  • Weed Management Research at Lacombe
  • • plant competitive varieties (avoid semi-dwarfs)*
    • increase crop seeding rate*
    • reduce weeds with early-cut barley silage*

Barley Variety Effects on Wild Oat

Wild Oat Biomass - 1997

Barley Yields - 1997

Optimal Cropping Systems - Effects on Weeds

• Objective:
• • Combine several agronomic factors at optimal levels as the first level of management against weeds - herbicides are 2° consideration
• Materials and Methods
• • Barley/Pea Rotation
  • Early & normal seeding dates
  • 1 and 1.5X seeding rates
  • Fall- versus Spring-banded fertilizer
  • 0 and 1/2 herbicide rates (change to 1/3 and 2/3)

Seeding Rate and Herbicide Rate
Cleavers dry wt. - Barley

Seeding Rate and Herbicide Rate
Barley Yield

Barley Silaging Effects on Wild Oat Populations

• Objective:
• • Assess wild oat populations after early- (heads fully emerged) and normal-cut (soft dough) barley silage versus barley grain production
• Materials and Methods
• • add 1/2 rates of wild oat herbicide to silage production systems
  • Conduct experiments at same site each year: assess wild oat population dynamics after several years in the silage or grain system

Treatment List

• 1. Barley grain - no herbicide
• 2. Early-cut barley silage - no herbicide
• 3. Normal-cut barley silage - no herbicide
• 4. Barley grain - Assert (1/2)
• 5. Barley grain - Assert (1)
• 6. Barley grain - Achieve (1/2)
• 7. Barley grain - Achieve (1)
• 8. Early-cut barley silage - Assert (1/2)
• 9. Early-cut barley silage - Achieve (1/2)
• 10. Normal-cut barley silage - Assert (1/2)
• 11. Normal-cut barley silage - Achieve (1/2)

97 Wild Oat Emergence (#/m²)

98 Wild Oat Emergence (#/m²)

Summary

• Extended Rotations with extra Diversity
• Fall Harrowing - volunteers
• Good Agronomics
• Early-cut silage for weed management