Winter canola planting considerations

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Winter canola cultivars exist today that make production possible across much of Kansas. When a winter-hardy cultivar is planted at the right time into good soil moisture, plant development is optimized and the crop will have the best chance at surviving the extremes of the Kansas climate.
 

The planting window for winter canola arrives in Kansas by early September. Here are some key points to ensure a successful start to the 2020-2021 growing season.

Variety Selection

• Variety selection should be based on the following traits: winter survival, yield, oil content, herbicide tolerance, disease resistance, maturity, lodging susceptibility, and shatter tolerance.
• Producers also have the option of selecting either open-pollinated varieties or hybrids.
• Winter hardiness should be the number one consideration if the crop is being grown in a new area.
• The majority of the varieties grown in the southern Great Plains are open pollinated. These varieties consistently overwinter and have considerable yield potential. Roundup Ready herbicide tolerance is available in open-pollinated varieties.
• More hybrids are being grown in the region. Hybrids tend to have larger seed size for easier seed metering, vigorous fall and spring growth, and greater yield potential in non-limiting environments. Clearfield herbicide tolerance is available in hybrids.
• Varieties with tolerance to carryover of sulfonylurea (SU) herbicides applied to a previous crop (e.g. Finesse) can be planted in the fall to avoid the long plant-back restrictions these herbicides have for canola.
• Consider selecting two or more varieties with differing relative maturities to spread out harvest operations and reduce risk.

Site Selection

• Although canola grows over a wide range of soil textures, well-drained, medium-textured soils are best. Soils where water stands for several days or those prone to waterlogging are poor choices.
• The soil pH should be between 5.5 and 7.0. Soil pH correction with lime should be considered when growing canola in soil with low pH (less than 5.5).
• Be mindful when planting canola following crops like sunflower, soybean, alfalfa, or cotton. These crops share similar diseases with canola. Planting canola continuously is not recommended and it is not insurable. Plant canola after grass crops such as wheat or corn because these crops do not share diseases with canola.
• Canola will perform best when adequate time is given after the preceding crop to allow for soil moisture recharge and weed control, and where there is adequate time to get the canola planted early enough to help the plants survive over winter.
• Avoid fields with heavy winter broadleaf weed pressure if possible. If planting where heavy broadleaf weed pressure exists, consider planting a Roundup Ready cultivar.
• Grassy winter annual weeds are easily controlled by using herbicides that are labelled for conventional, Roundup Ready, or Clearfield canola.
• Make sure you are aware of the herbicide history of potential sites. Winter canola cultivars are sensitive to SU and triazine herbicide carryover. These products have long plant back restrictions (often 18 months or greater). Be especially cautious about herbicide carryover restrictions when following corn.

Seedbed Preparation

• Weeds must be controlled chemically, mechanically, or with a combination of both methods prior to planting because canola seedlings are not competitive with weeds.
• Open-pollinated varieties typically range from 100,000 to 125,000 seeds per pound and hybrids range from 70,000 to 100,000 seeds per pound. Because of its small seed size, a properly prepared seedbed is critical for successful canola establishment.
• A level, firm seedbed with adequate moisture within the top inch is preferred. A seedbed with many large clumps results in poor seed placement and seed-to-soil contact. An overworked seedbed may be depleted of moisture and will crust easily, potentially inhibiting emergence. In addition, this could promote deep placement of the seed.
• No-till planting is an option, and some long-term no-till producers have produced canola successfully. With proper settings, no-till planting usually results in very good stands. However, maintaining stands over the winter can be difficult with low disturbance in heavy residue cover. This problem has been overcome by burning surface residue immediately before planting or by using a more aggressive residue manager that removes residue from the seed row. Research in south central Kansas indicates that even with good winter survival, no-till canola yields under heavy residue were lower than where residue was burned or where tillage has been performed.
• No-till producers should ensure that drills and planters are properly set and consider using a setup that creates a more disturbed seed row. Using a high-disturbance opener (such as a coulter, residue manager, or hoe-type opener) in no-till can improve winter survival and result in yields comparable to those obtained in tilled fields.
• If using tillage, perform the most aggressive tillage as early as possible, with each succeeding tillage operation being shallower than the last. Incorporate fertilizer and herbicide with the last tillage operation. Some producers perform one aggressive tillage operation as early as possible and then control newly emerged weeds chemically. Planting into this “stale” seedbed will help ensure adequate moisture for establishment.

Seeding Date, Rate, Depth and Row Spacing

• The general rule is to plant canola six weeks before the average date of the first killing frost (28 degrees F) in central and south central Kansas, or six to eight weeks for southwest and northern Kansas. This allows adequate time for plant canopy development and root growth to improve winter survival. Planting too late will result in small plants with inadequate reserves to maximize winter survival. Planting too early may result in excessive growth that can deplete soil moisture. Excessive growth may also elevate the growing point or crown too far above the soil surface, increasing the chance of winterkill. This can be a problem when heavy residue remains in the seed row without correct management.
• In northern Kansas, winter canola should be planted by September 15 and in central Kansas by September 25. In far south central Kansas (Barber, Harper, and Sumner counties), winter canola should be planted by October 1 and in southwest Kansas by September 15 to avoid problems with winterkill.
• The most recent 3-month outlook from NOAA projects an increased chance of warmer-than-normal temperatures through November. The precipitation outlook is for below-normal precipitation across the state.
• Winter canola will compensate for a poor plant stand; however, it is important to obtain as uniform a stand as possible to facilitate optimum plant development, winter survival, weed control, and uniform plant maturity. A seeding rate of 3.5 to 5 pounds per acre (approximately 350,000 to 500,000 seeds per acre at a 100,000 seeds per lb seed size) is recommended for open-pollinated varieties in narrow row spacing. Because of the higher seed costs of hybrids, it is recommended to plant them on a pure live seed basis. The recommended seeding rate is 250,000 to 300,000 pure live seeds per acre in narrow rows.
• More producers are experimenting with canola planted in 30-inch rows. Producers are able to obtain more accurate depth control, precision seed metering, and residue removal from the seed row with row crop planters. Generally, yields may be slightly reduced moving from 15 inches to 30 inches under dryland conditions. However, producers are able to reduce their seeding rate to 1.5 to 3.0 lb per acre (about 135,000 to 270,000 pure live seeds per acre at a 90,000 seed per lb seed weight). Planting an open-pollinated variety or hybrid with prolific branching will also increase the profitability of canola planted in 30-inch rows.
• It is important to check drill calibration. Some drills may require a speed reduction kit to obtain the optimum rate without damaging seed. Some producers planting on 7.5-inch spacing will plug every other row unit and plant on 15-inch spacing so the drill does not have to be slowed as much.
• Seed placement is critical for successful germination, emergence, and stand establishment. Optimal germination occurs with seed placed ½ to 1 inch deep. Under drier conditions, canola may be planted deeper (not greater than 1.5 inches), but delayed emergence and reduced vigor may occur. Soil crusting following a heavy rain can result in a poor stand. Canola emergence can be greatly reduced when using a deep furrow opener followed by a heavy rain prior to emergence, since soil can fill in the furrow, resulting in a deeper than intended seeding depth.
• To ensure proper seeding depth, producers must plant slower than when planting wheat (preferably 5 mph or slower). Finally, it is important to check seeding depth in each field.
• Rows spaced between 7.5 and 15 inches allow for rapid canopy closure (improved light interception) and weed control. Yields are similar with row spacings in this range.
• Plant-to-plant uniformity at emergence is critical for optimum plant development, overwintering, and weed control.

Plant Nutrition and Soil Fertility

• Soil testing, including a profile sample for nitrogen (N) and sulfur (S), is an important tool in determining fertilizer needs. If you have questions, contact your local Extension office. All nutrient applications should be made based on soil test recommendations. Canola fertility recommendation programs can be found at: http://www.agronomy.ksu.edu/soiltesting/

• Fertility needs are similar to winter wheat; however, canola needs slightly higher N and S levels.
• Applying high rates of fertilizer in-row at planting is not recommended because canola is sensitive to ammonia and salt damage (phytotoxic effects). However, research by Oklahoma State indicates that a low rate of DAP or MAP (30 to 40 lb/acre of product) is beneficial and not detrimental to yield. The best management practice for banding fertilizer should separate the fertilizer from the seed by two inches to avoid direct contact. Pre-plant broadcast application is also acceptable.
• Lime: Apply lime so that pH is in the range of 5.5-7.0 and early enough so the lime has time to react.
• Phosphorus (P) and Potassium (K): No added P is required if the P soil test is above 30 ppm. Additional K should be applied if soil test levels are less than 125 ppm.
• Sulfur (S): Canola requires more S than wheat because of its high content of sulfur-containing proteins. Sulfur deficiencies are most common on coarse-textured and low-organic-matter soils. Sulfur can be applied at any time from pre-plant until the canola plant breaks dormancy in late winter. Apply S based on the soil test recommendation. Sulfate-sulfur (SO₄-S) soil tests should be above 10 ppm or fertilizer should be applied. If no soil test is available, an application of 20 lb/acre S is recommended.
• Nitrogen (N): Pre-plant N applications must be carefully balanced, as too little or too much fall-applied N may negatively affect winter survival. One-third to one-half of total N (based on expected yield) should be fall-applied. At least 30 lb/acre but no more than 80 lb/acre of actual N is the general rule for fall applications. Winter survival, plant vigor, and yield potential can decrease without applying fall N.

Weed Management

• A clean seedbed is critical to establishing winter canola. Small canola seedlings compete poorly with established weeds. However, once a good stand and canopy are established, canola suppresses and outcompetes most winter annual weeds.
• No matter what herbicide program you use, the most important thing to remember is to control weeds early in the fall.
• Trifluralin and ethalfluralin are effective at controlling many problem winter annual weeds pre-plant, but each requires mechanical incorporation.
• Grass herbicides such as Select Max, Assure II, and Poast are labeled for cool-season grass control in canola.
• Roundup Ready (glyphosate tolerant) canola varieties are available, providing excellent control of many problem weeds. Glyphosate is not labeled for application once the plant has bolted after dormancy.
• Clearfield canola varieties are available and provide another herbicide resistance option for controlling winter annual grasses.
• Before applying any herbicides, care must be taken to ensure there are no traces of problem herbicides, such as sulfonylurea herbicides, in the sprayer equipment.

Insect Management

• An insecticide seed treatment is highly recommended for control of green peach aphids and turnip aphids through fall and early winter.
• Monitor canola stands for the following fall insect pests: grasshoppers, diamondback moth larvae, flea beetles, aphids, and root maggots. Several products are labeled and provide good to excellent control.

Disease Management

• The best control of canola diseases is achieved through careful rotation. Canola should not be planted on the same field more than once every three years and should never be planted continuously.
• Blackleg (Leptosphaeria maculans) is the most serious disease threat to canola. Maintaining proper rotation intervals, planting disease-free seed, and using fungicide seed treatments are important management practices to slow the spread of blackleg.
• Damping-off of young seedlings, which resembles the pinching of the stem at or just below the soil line, is caused by several fungi including Pythium, Fusarium, and Rhizoctonia. A fungicide seed treatment can lessen the effects of these soil-borne diseases.

 

For further information, see the Great Plains Canola Production Handbook. Contact your local Extension office for a copy or download it online: https://www.bookstore.ksre.ksu.edu/pubs/mf2734.pdf.

Also see the Canola Growth and Development poster, available on the web at: https://www.bookstore.ksre.ksu.edu/pubs/MF3236.pdf.

 

Mike Stamm, Canola Breeder
mjstamm@ksu.edu

Ignacio Ciampitti, Crop Production and Cropping Systems Specialist
ciampitti@ksu.edu

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