Tillage for weed control

October 3, 2012 - Issue 31

Tillage may not be a best practice in dry regions this fall. Dry soils will be difficult to penetrate, and tillage will destroy standing stubble and its snow-catching capability. We can’t predict winter weather, but this extra moisture may be valuable next spring.

Growers who decide to till may also experience:

—A heavy flush of weeds from long buried seeds that have lost their dormancy and will germinate when moved closer to the surface.
— Burial of weed seeds and shattered canola seed will increase their longevity in the soil. Burial protects the seed from predation by birds and small ground dwelling rodents and insects, as well as placing seeds in a more stable moisture and temperature regime in the soil that places seeds into a type of suspended animation, extending their survival. This deep seed bank could remain preserved for many years until disturbed again.

Canola crops leave an average of 2-3 bushels per acre of seed in the field, or at least 20 times the seeding rate. Swaths flipped and rolled by heavy winds can increase this number significantly. Leaving seeds undisturbed so they germinate in the fall or get eaten by birds and insects is a good way to reduce the volunteer seedbank. (Note: A hot and dry fall can induce secondary dormancy, with or without tillage. This has probably already happened to some extent this fall.)

The clubroot angle: Tillage also creates additional opportunities for equipment to carry soil infested with clubroot spores to neighbouring fields, and can facilitate spread of infested soil through increased soil erosion.

For more: Is that tillage really helping?

Canola Watch