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Seeding canola at low rates

Some canola growers are thinking about seeding rates in terms 
of plants per acre rather than pounds of seed per acre

Successfully seeding and establishing hybrid canola can be achieved at lower seeding rates by carefully selecting the canola variety, choosing the right equipment, and paying attention to machinery settings and operation.

Other steps to successful canola seeding are:

  • Targeting final plant stands according to seed size.
  • Handling the canola in the most efficient and gentle manner possible.
  • Placing the seed in exactly the correct spot in the seedbed.

Some canola growers are starting to contemplate optimum seeding rates in terms of final plants per acre (PPA), rather than pounds of seed per acre.

Farmers working on lowering seeding rates tend to aim for between 250,000 and 300,000 PPA with some trial work at the 200,000 PPA level to check where the consistent bottom end is. Right now there isn’t enough evidence to verify that rates as low as 200,000 PPA can be successful in all soil and climate conditions and with differing genetics.

The Canola Council of Canada recommends seven canola plants per square foot — 304,920 PPA.

Focus on number of viable plants

Seed planted don’t equal viable plants per acre. Some current seeding methods have seed mortality rates as high as 50 per cent. With high vigour seed, gentle handling, precision seed placement, and good seedbed conditions, seedling mortality rates of 10 per cent can be achieved.

The size of canola seed greatly effects how the seed will be metered. Treated canola seed size can vary from 6.0 grams/1,000 seeds (75,000 seeds/lb.) to 3.8 grams/1,000 seeds (112,500 seeds/lb.).

If a 90 per cent survival rate can be achieved this would translate to seeding 3.7 lb./acre (with seed at 75,000 seeds/lb) to 2.47 lb./acre (with seed at 112,500 seeds/lb.) to achieve a 250,000 final plant stand.

This is a significant difference in seeding rates. If a large seed size of 75,000 seeds per pound were planted at 2.47 lb./acre, final stand would only be 166,725 PPA, assuming 90 per cent survival.

Especially at low seeding rates it’s important that meters can deliver precisely the number of seeds per acre, and distribute them evenly across the field. Uneven metering that distributes bunches of seed or leaves unseeded patches will lead to reduced yield.

Ensure undamaged seed

In the air distribution system too much air volume or too much air velocity can damage seed and reduce your final number of plants per acre.

One simple method to check if there is enough air volume is to remove a hose from an opener and point the hose straight up. Then hand crank some seed into the air stream to see how high the seed goes over the top of the hose. If the air carries the seed six to eight inches up over the edge of the hose, there is enough air. If the seed is propelled two to three feet up past the end of the hose, the air volume needs to be reduced. If a single fan feeds the seed air stream, this is as simple as dialling the fan back. If the fan services both the seed and fertilizer air streams, baffles will need to be adjusted to concentrate most of the air to the fertilizer stream.

Rough edges and contact points inside the air delivery system need to be reduced or eliminated. Tower lids need to be cushioned or spiralled to give the seed gentle turns at the top of the towers. On very wide drills that require large air volumes to get to the outside edges of the wings, seed brakes might be contemplated to eliminate the possibility of seed bounce at the bottom of the trench.

Knowing your seedbed helps manage mortality

One of the biggest challenges to reducing seed mortality is the exact placement of seed in a warm, moist seedbed. If your seedbed is freezing cold, saturated, covered with a two-inch crust, or hard as a rock do not attempt to seed at low rates. You will be flirting with disaster.

Low rate canola seeding machines must have parallel linkages on each row for precise depth control. Without individual row depth control, seed depth cannot be controlled accurately enough to give consistent results. Consistent seed placement at one-quarter to one half an inch into firm, moist, warm soil has shown to give the best results. Accurate seeding depth is best achieved (in order of accuracy) by double disc, single disc and knife style opener systems that are individually depth controlled.

Watch your openers

Opener closing systems are also extremely important. Gentle packing without excessive pressure assures the seed a good home to germinate from.

Opener performance in heavy residue can be an obstacle to maintaining proper seed depth. Conditioning and evenly distributing residue will improve seeding accuracy. Opener depth adjustments are required to compensate for a half-inch layer of chopped cereal straw.

Double disc and single disc precision drills are required for zero tilling canola into heavy residues such as corn, sunflower or stripper header combined cereals and flax. These heavy residues require the additional clearance of disc drills to maintain seeding accuracy without plugging.

With careful attention to detail, precision air seeding systems can give uniform high yielding stands. †

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