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Establishing winter canola

Look at herbicide history, soil type and planting date to get canola growing well

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Winter canola seed sales have been strong and Ontario acres in 2020 are expected to be higher than ever before.

Why it matters: While research on the crop has been limited, some recommendations are available, based on experience of the past few years and with spring canola in Ontario.

Field selection

Fields should have good drainage and low clay content. Seeds may fail to emerge with wet conditions after planting and plants will rot in wet areas in the winter and spring. Heavier soils can also cause heaving, which will kill plants or significantly reduce yield potential.

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Lower yields were often observed on clay soils in 2018-19 even when winter survival was adequate.

Winter wheat is generally better at overwintering than winter canola. If winter wheat survival is poor on a given field, canola survival will likely be worse. Some producers have had success with canola on fields that tend to dry out in summer causing other crops to suffer. The relatively dry conditions in spring and summer of 2020 were a factor in high yields this season.

Herbicide history

When selecting a field, look back at least two years in the field herbicide records. There are a number of restrictions and not all are listed here.

Infinity has a 10-month re-cropping interval to canola. Other products that have a 22-month re-cropping interval or more include imazethapyr (Pursuit, Optill), metribuzin (Sencor) and atrazine (Primextra, Marksman).

Herbicide application options before planting of winter canola are limited. The primary choices are glyphosate, glufosinate (Liberty), clopyralid (Lontrel) and trifluralin (Treflan), as well as grass control products. Eragon and 2,4-D can cause crop injury and should be avoided in pre-plant burn downs.

Consult the OMAFRA Guide to Weed Control — Publication 75 (Chapter 4, Table 4-4) for more information.

Conventional winter and spring canola (those without herbicide-tolerance traits) are the same species and have the same reactivity to herbicides, but not all herbicide labels have information on canola, or on winter canola planting time frames.

Planting date

Planting date trials have been conducted in Essex County by Dr. Eric Page, at Agriculture and Agri-Food Canada, Harrow. The most success was realized with planting in the first two weeks of September. Winterkill and yield losses increase beyond the third week of September, but in a mild or longer fall season, the losses with late planting were less extreme.

Planting in August in southern counties would likely result in bolting in the fall (moving into reproductive growth stages and stem elongation); bolted plants typically do not survive winter.

Based on observations from Page’s trials, about 600 growing degree days (GDD, base 0 C) are required for adequate growth of canola in the fall. For reference, winter wheat requires about 450 GDD in the fall.

The general recommendation is to plant winter canola seven to 10 days before the ideal winter wheat planting date for your region. Canola survives through winter on its roots, whereas winter wheat survives on the seed.

For many, this means planting in the first two weeks of September. Late August planting may be appropriate for some areas, such as Simcoe County, north Bruce and north Grey Counties. We hope to have more information about Eastern Ontario planting dates in the next two years based on trials at University of Guelph — Winchester Research Station. Winter canola is not recommended in Northern Ontario due to poor winter survival.

Before winter, plants would ideally have a tap root approaching the width of a pencil and four to eight true leaves.

Seeding rate and method

Canola can be seeded on 15-inch rows or narrower. Twin row setups on 30-inch centres or 20-inch row widths may be OK, but rows may not totally close and plants may develop large stems. Local research has not been conducted on wide rows.

Seeding can be conducted with drills, air seeders or row unit planters. Each may come with some frustrations because of the small seed and low seeding rate. Seeding rates depend on the expected level of emergence, which varies with the precision of the seeding equipment.

Seed size can vary. Small seeds can have a large impact on seeds per acre, so with canola the seeding rates are often somewhat approximated. However, seed is sold based on live seed counts and the retailer should be able to provide you with a target seeding rate in pounds to achieve the proper plant count.

Generally speaking, it is recommended that seeding rates for winter canola be lower than what we typically use for spring canola in Ontario. Winter canola plants need to be more spaced out, so they do not compete with each other and grow too tall in autumn or “goose neck” out of the ground leaving crowns exposed well above the soil surface.

Drills tend to have lower rates of emergence which should be accounted for, so aim for four pounds per acre or about 330,000 plants per acre. If it is difficult to get the seeding rate that low, bulk up the seed with elemental sulfur or MAP.

Canola plates for row unit planters are available. Growers have often reported that sensors do not read seed in the tubes so the monitor may not show how much seed is going down. Planters have higher rates of emergence and wider rows so rates can typically be reduced to three or 3.5 lb. per acre, or about 250,000 to 330,000 seeds per acre. Some producers have achieved good plant stands with as low as 2.5 lb. per acre.

Seed to a depth of one-half to one inch. Seeding deeper may result in variable or slow emergence. Broadcast seeding is not recommended because plants will be slow to grow in the fall. Other things to note are that planting into residue can also cause goose neck/high crowns, which increases risk of winterkill. Also, slugs love canola and can be abundant where there is residue. They can quickly destroy large areas of a field right after emergence. Some tillage or moving residue away from the seed row can mitigate risk of slug damage.

Fertility

In the fall, application of 30 to 40 lb. per acre of nitrogen is recommended. Lack of nitrogen early on can significantly reduce the growth rate of seedlings. Producers have had good results following up with 100 lb. per acre or more of nitrogen in the spring. After generating some yield results, in future years producers can better match their nitrogen fertilizer rates with removal rates, while also considering fertilizer cost and return on investment.

Canola also has a high sulfur demand, higher than cereals. While local research on sulfur needs in winter canola has not been conducted, deficiency symptoms have frequently been observed at later growth stages. We also know spring canola needs about 20 lb. per acre of sulfur. It is recommended that producers apply a total of up to 25 lb. per acre of sulfur in the sulphate form (elemental will not be available to the plants); at least 10 lb. per acre before seeding and another 10-15 lb. per acre in spring.

Nitrogen and sulfur are typically broadcast ahead of seeding because only very low amounts can be safely applied with the seed. A two-by-two band would be safe but is uncommon in Ontario canola. In one 2020 winter canola field, a mid-row band of nitrogen in a twin-row setup had more variable growth than an area of the field that had broadcast application. In the spring, both liquid and granular fertilizer are safe to apply in crop.

Putting some starter phosphorus with the seed promotes fast early growth. Up to 25 lb. per acre of P2O5 can be safely placed in the seed row.

Learning together

If you have any questions, contact Meghan Moran at 519-546-1725 or at [email protected].

I am interested in checking fields before winter and again in early spring to monitor winter survival and learn more about management practices that work on farms.

In the new year, I plan to post more information about assessing winter survival, spring fertilizer application, monitoring for cabbage seedpod weevil, and protecting the crop from white mould.

This article first appeared at fieldcropnews.com.

Megan Moran is a canola and edible bean specialist with OMAFRA.

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