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The best defence is the right depth

Avoid disease and delayed emergence by choosing the right depth and following these five steps to uniformity

If agronomist Doug Moisey doesn’t see any canola seed on the ground when inspecting a freshly sown field he worries. This might seem like an unconventional cause for concern, but as Moisey explains, “In normal seeding you’ll get some seeds bounce out of the furrow and that’s fine.” If no seeds are visible on the surface Moisey suspects that the furrows may have been too deep.

Ideal seeding depth

Ideal canola seeding depth is one-half to one inch below the press wheel furrow, says Moisey, who covers north-central Alberta for Pioneer Hi-Bred. Below this level, seedlings have a long way to grow before they see sunlight.

“Once (the plant) starts producing chlorophyll it will help it beat the disease factor,” says Moisey. The canola plant also produces a wax to protect the hypocotyl — the part of the plant that is above the seed, but below the cotyledons — but this wax is only produced once the seedling emerges. Until then, the young canola plant relies on the fungicide and insecticide present in the seed treatment. The protective value of these products may be depleted before a deep-seeded plant reaches the surface. Seeds can decay in the ground before emergence and seedling diseases like wire-stem and insect pests like flea beetle can quickly destroy a young seedling, thinning the plant stand.

Along with seedling death and non-emergence, delayed emergence can haunt canola growers throughout the growing season. Some deep-seeded plants may survive, but they will be behind shallower seeded plants. When it comes to making time-sensitive fungicide applications for later season disease like sclerotinia, it is important to have a stand of plants that are at similar growth stages. As well, farmers may have tough choices to make at harvest if they have an uneven plant stand.

Ensuring uniformity

There are several things farmers can do before and during seeding to ensure uniformity of seeding depth.

1. Visual inspection. Whether a grower is using the same drill he had last year or a new one from the factory, it is important to do a visual inspection of the seeding tool.

“If you’ve been noticing that you’re getting variable emergence make sure your drill is level front to back and side to side,” says Moisey. He suggests that farmers get out the laser level when the drill is in the yard and make sure each opener is at the right height.

2. Check tire pressure. “Make sure your tire pressure is right,” says Moisey. “A couple of pounds of air pressure on one side and you’ll have a drill that’s on the angle.” In the field, make the time out of the tractor count by ensuring that seed depth is checked at the appropriate place.

“Checking right behind the drill isn’t the best place to look,” says Canola Council agromonist Keith Gabert. “Go check back a pass because you’ll see how you were operating at field speed.”

3. Check across width of the drill. Avoid checking on the headlands where the soil has a different consistency than the rest of the field and check across the width of the drill, not just one or two openers, says Moisey.

4. Check every field. Gabert reminds farmers to repeat the process on subsequent fields. “You set the depth in one field and when you move to a field where the ground is a little mellower or a little harder then you’re not getting the same depth.”

5. Consider slowing down. Seeding speed also affects seed placement. While there is always pressure to get the crop planted in the spring, the time saved by seeding a mile faster may be lost if a farmer has to wait for an uneven plant stand to mature in the fall. Different soil and equipment types respond differently to excess seeding speed. Heavy soil may rip into large clods producing poor seed to soil contact. Seeding too fast in sandy soil will throw too much dirt. Producers with double-shoot system on their drill need to make sure seed does not roll into the fertilizer trench.

Five miles per hour or slower is general guideline for canola seeding speed, but as Moisey points out, “There is no optimal speed. The ideal seeding speed is whatever places the most amount of seed at the right depth.” †

About the author

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Sarah Weigum

Sarah Weigum grows pedigreed seed and writes at Three Hills, Alta.

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