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Weed Wisdom March 2019

Consider cultural weed management

by Dr. Charles Geddes

As the snow begins to melt, growers everywhere wait eagerly to get back to the land. This is often a time to plan out the coming growing season, and secure seed, fertilizer, and chemicals, among a wide range of other organizational tasks. Growers invest a large amount of money in crop inputs, but the investment is often unsecure and subject to environmental conditions and pest pressures.

Choosing to rely solely on herbicides for weed management can result in increased selection pressure for herbicide-resistance, and potentially reduced crop tolerance to competition from weeds surviving or emerging after the herbicide application. However, investment in non-chemical weed management tools can be a difficult decision to make, economically speaking. Non-chemical weed management options often result in increased immediate investment of money or time, and potentially reduced profit margins in the short term in exchange for longer-term sustainability. However, an investment in cultural weed management can reap dividends in the long-term due to mitigation of herbicide-resistance (which is rarely assigned a monetary value in economic analyses).

Cultural weed management includes a wide range of tools used to prevent weed problems. Some examples include increased seeding rates, reduced row spacing, crop rotation, cover cropping, among many others. The decision to include cultural tools in your weed management toolbox starts before the crop is planted, and almost always before weeds are a visual or aesthetic problem in the field. It is important to consider cultural weed management options in your plans for the upcoming growing season to help reap the benefits of reduced selection pressure for herbicide-resistance.

Glyphosate-resistant kochia in a spring wheat – lentil – spring wheat – canola crop rotation using wide-row spacing and 1x seeding rates (TOP) vs. narrow-row spacing and 2x seeding rates (BOTTOM) with the same herbicide regime.