Index | Search | Home

---

---

Canola (Rapeseed)

E.S. Oplinger¹, L.L. Hardman², E.T. Gritton¹, J.D. Doll¹, and K.A. Kelling¹

I. History:

Canola is a name applied to edible oilseed rape. This plant belongs to the mustard family along with 3,000 other species. Close relatives of this crop have been cultivated for food since the earliest recordings of man. Rapeseed has been important to Europe since the 13th century as a source of food and oil for fuel. Rapeseed production became popular in North America during World War II as a source of lubricants. Its oil has the property of adhering well to moist metal, making it an ideal lubricant for marine engines.

The name "canola" was registered in 1979 by the Western Canadian Oilseed Crushers Association to describe "double-low" varieties. Double low indicates that the processed oil contains less than 2% erucic acid and the meal less than 3 mg/g of glucosinolates. Erucic acid is a fatty acid that has been related to heart disease. Glucosinolates have breakdown products that are toxic to animals. Both characteristics make rapeseed products poor candidates for animal consumption.

In the early 1960s, Canadian plant breeders isolated single lines free of erucic acid and began programs to develop double low varieties.

Today annual worldwide production of canola is approximately 7.5 million tons on 4 million acres. Canada accounts for 15% of the world production and the European Economic Community for nearly 17%. The United States produces less than 1% of the world production. Minnesota and North Dakota are the major U.S. production states with about 20,000 acres. Canola ranks 5th in production among the world's oilseed crops following soybeans, sunflowers, peanuts and cottonseed.

II. Uses:

A. Oil and Protein:

Like soybean, canola contains both high oil content as well as high protein content. It contains about 40% oil and 23% protein compared to 20 and 40%, respectively, for soybean. Like soybean, when the oil is crushed out, it leaves a high quality, high protein (37%) feed concentrate which is highly palatable to livestock. Commercial varieties of canola were developed from two species; Brassica napus (Argentine type) and Brassica campestris (Polish type). Both species of canola produce seed that is high in polyunsaturated fatty acids (oleic, linoleic, and linolenic).

B. Forages:

Another potential for canola is as an annual forage. Historically, it was used as a forage for field-raised swine and poultry. Canola can produce 1.0 to 2.0 tons of dry matter per acre in a single season. A study conducted in Kansas found winter rapeseed forage to have crude protein of 21-33%, compared to 24% for winter wheat foliage.

III. Growth Habits:

Both fall and spring seeded types of canola are available. Canola growth is characterized by six main growth stages. Much of the management of this crop is related to the length of time and plant characteristics within each of these stages. Stage 0 is preemergence. The germinating seedling may take from 4 to 10 days to emerge. During this time it is susceptible to many soil borne pathogens. In Canada, seed protectant fungicides are often used on spring types, however effective materials have not been registered for use in the U.S. Speed of emergence depends on soil temperature and moisture, seed soil contact, and depth of planting. Stage I is the seedling stage where the very young plant has just emerged from the soil. Cotyledons are pushed through the soil surface by an active hypocotyl. At this stage, the seedling is still vulnerable to many soil pathogens, and to flea beetle infestation. Both pests are detrimental to stand establishment. Since the early canola crop is a poor competitor, it is extremely important to get a good stand.

Stage 2 is the rosette stage characterized by an increasing leaf area index. Spring canola will remain in this vegetative stage for several weeks. Winter canola also stays in this stage for several weeks in the spring. Near the end of Stage 2, the crop is nearing its maximum leaf area index and at that point is a much better competitor. Increasing day length and temperatures initiate bolting and the beginning of Stage 3, the bud stage. The plants reach their maximum leaf area index at this time along with 30 to 60% of its total dry matter. A large accumulation of foliage is required to provide adequate sugars during flowering and pod fill.

Flowering begins Stage 4 and continues for 14 to 21 days. Three to five flowers open per day and 40 to 55% of the flowers that open will develop pods. Ripening, or Stage 5, begins when the petals fall from the last formed flower on the main stem. Pod fill is complete 35 to 45 days after flower initiation, and the seeds contain about 40% moisture at this point. The crop is considered ripe and ready for swathing when 30 to 40% of the seed from pods on the main stem have turned color. Spring varieties of B. napus mature 74 to 140 days after seeding and B. campestris in 66 to 111 days.

IV. Environment Requirements:

A. Climate:

Canola is widely adapted, particularly to the cool extremes of the temperate zones.¹ Minimum temperatures for growth have been reported to be near 32°F. The crop will germinate and emerge with soil temperatures at 41°F but the optimum is 50°F. Winter annual varieties are grown where adequate snow covers or mild winters are common. The crop has been produced successfully in Michigan without benefit of snow cover. Planting date has a dramatic effect on survival however.

B. Soil:

Canola does best on medium textured, well drained soils. The crop is tolerant of a soil pH as low as 5.5 and saline conditions. Because of its tolerance to salinity, canola has been used as the first crop on newly drained dikes in the Netherlands. Canola requires approximately 16 to 18 inches of water through its growing season, with 8 to 8.3 inches used by annual varieties in July near flower and pod fill.

V. Cultural Practices:

A. Seedbed Preparation:

Stand establishment is very important with canola because of its lack of early competitiveness. Seeding into a smooth, firm seedbed helps maintain a uniform seeding depth and even emergence. Seedbed preparation is usually done with a shallow (4-5 inch) tillage operation. Recent research, however, has shown some success establishing canola with reduced tillage.

B. Seeding Date:

Canola can be seeded in either the fall or the spring depending on the type of variety. Fall dates need to be timed to achieve about 6 true leaves and good root reserves before a killing frost. Planting between August 15 and September 1 should accomplish this in most areas of Wisconsin and Minnesota.² Spring planting should begin as early as soil is dry and weather permits. Like spring small grains, spring canola generally yields the best with early planting. At Arlington, WI canola seeded the last week of April averaged 1325 lb/a compared to 1150 lb/a when seeded three weeks later on May 20.

C. Method and Rate of Seeding:

Canola is usually seeded with the small seed attachment of a grain drill to a depth of 1/2 to 1 inch. Rows should be spaced 7 inches or less. Research has shown highest yields with 3-inch row spacings. Canola should be seeded at 4-5 lb/a if drilled and 7-8 lb/a if broadcast depending on seed size and soil texture. Stands should be around 6-8 plants per square foot for highest yields. Canola stands of this density can withstand up to a 2/3 kill before reseeding is more profitable than maintaining the existing crop.

D. Fertility and Lime Requirements:

Little information is available on the responsiveness of canola to lime applications or soil pH. Most current canola production areas tend to be on soils which are slightly acid to alkaline, however this does not mean that more acid soils necessarily need to be limed to these levels.

Some states recommend that P and K should be applied on the basis of soil test recommendations for winter wheat. Table 1 shows the nutrient removals for typical wheat, barley and canola yields. For Wisconsin and Minnesota this means that when soil tests are in the medium range about 20-30 lbs Of P₂O₅ and 20 lbs of K₂O should be applied per acre. At lower soil tests these rates should be increased. Because canola is sensitive to direct seed contact with fertilizer, applications should be banded at least 2 inches to the side and below the seed or broadcast.

Canola responds well to nitrogen fertilizer, with optimum yields occurring around 80-100 lbs N/acre. For spring canola, it should be broadcast and incorporated at seeding time along with the P and K. For winter canola, nitrogen may be best applied as a split application using starter nitrogen application of about 10-20 lbs/acre, followed by the remainder in the spring prior to regrowth.

As shown in Table 1, canola is a heavy user of sulfur. Soils most likely to respond to S additions are light colored, sandy soils, in northwestern Wisconsin and northern Minnesota which have not been manured within the past two years.

E. Variety Selection:

There are several varieties of oilseed rape available particularly from Canadian sources. Recently released varieties which meet the qualifications to be called canola are:

Andor—Released by University of Alberta in 1981 with distribution rights to Can-Alta Seeds Ltd., Red Deer, Alberta.

Global—Developed by Svalof A. B., Plant Breeding Station, Sweden. Distributed by Bonis and Company Ltd., Lindsay, Ontario, Canada.

Hyola 70—Hybrid developed by Contiseed Ltd. (Canada) to be marketed in U.S. in 1988, by Contiseed, Huron, SD.

OAC Triton—Tolerant of triazine (Sencor, Lexone, atrazine, etc.) herbicides. Originated by University of Guelph, Ontario. Licensed in 1984.

Regent—Originated by University of Manitoba. Licensed in 1977.

Topas—Reported to have moderate resistance to Sclerotinia. Developed by Svalof A. B., Plant Breeding Station, Sweden. Distributed by Bonis and Company Ltd., Lindsay, Ontario, Canada.

Tower—Originated by University of Manitoba. Licensed in 1974.

Tribute—Tolerant of triazine herbicides (Sencor, Lexone, atrazine, etc.). Better oil quality than OAC Triton but much lower seed yield than Westar. Originated by Agriculture Canada, Saskatoon, and University of Guelph, Ontario. Licensed in 1985.

Westar—Originated by Agriculture Canada, Saskatoon. Licensed in 1982. Production of certified seed limited to Canada.

Candle—Originated by Agriculture Canada, Saskatoon. Licensed in 1977.

Tobin—Originated by Agriculture Canada, Saskatoon. Licensed in 1981. Production of certified seed limited to Canada.

Characteristics of spring seeded canola varieties in Minnesota tests are shown in Table 2. (from Varietal Trials of Farm Crops-Minnesota Report 24)

F. Weed Control:

The best weed control practices are tillage, establishment of a good stand, and weed control in previous crops. Cruciferous weeds (wild radish, wild mustard, pennycress and shepherd's purse) are nearly impossible to control in the crop.

1. Cultural: As with small grains, the weed control in canola is primarily from the crop itself. Follow all recommended cultural practices to assure a dense vigorous crop that competes well with weeds. Select fields with minimal weed pressure and try to avoid those with weeds in the mustard family.
2. Mechanical control measures cannot be used in canola. A rotary hoe would kill many crop plants and row cultivation is not feasible because of the narrow row spacing.
3. Chemical: Treflan is the only herbicide registered in the United states for use in canola. Treflan and Poast are registered in Canada. Treflan is applied preplant incorporated and gives good annual grass control, but misses ragweed, mustard, and lady's thumb smartweed. Poast is used for postemergence control of annual grasses, quackgrass and volunteer cereals.

G. Diseases and their Control:

White mold (Sclerotinia stem rot) can be a serious disease after flowering in seasons with cool, moist growing conditions. Infection occurs when dropped petals contact the stem and spores germinate on the dead petals. Bleached stem lesions occur around the initial infection, then white mold and black fungal bodies grow inside and outside the stem. Sudden wilting and premature dying of individual plants are usually the first noticeable symptoms. Since white mold is a problem in several other crops, its occurrence in canola must be carefully monitored. Avoid planting canola following such crops as soybeans and dry edible beans or sunflower.

H. Insects and Other Predators and their Control:

Many insects may infest canola at various stages of its growth. Probably the greatest problem is caused by the flea beetle, a shiny black beetle about 10 to 15 mm long which attacks canola particularly at emergence, although it can be a problem later as well. Hot, sunny weather promotes feeding damage. Most growers control flea beetles with a granular insecticide mixed with the seed, but other seed-applied formulations and postemergence insecticides are also available. Seed-applied insecticides provide protection for about half as long as the granular materials. Flea beetle has not been a problem with winter canola types.

Diamondback moth larvae can be a problem in dry years. The larvae are pale yellow to light green, 11 to 13 mm in length, and frequently hang by a spun thread. Larvae eat flowers and young pods, and peel older tissue. Seeds under peeled pods often fail to develop properly. Spraying with one of the recommended insecticides can be justified in situations where there are over 20 larvae per plant.³

I. Harvesting:

Timely harvest of canola is critical to prevent shattering. When pods first begin to yellow, the crop needs to be checked on a 3 to 4 day schedule. Harvest maturity can only be determined by observing the color of the seed. In canola that stands well, 30 to 40% of the seed on the main stem needs to be brownish-red in color prior to swathing. This corresponds to about 30 to 35% seed moisture. Canola does have a tendency to lodge, particularly with over-fertilization of susceptible varieties. In severely lodged canola, swathing should be done when 40 to 50% of the seed in exposed pods has turned color.

Shattering can account for significant crop losses, therefore harvesting must not be delayed. Canola should be cut high on the stem and lightly pushed into the stubble with a windrower to prevent blowing. The crop is combined when it has dried to near 10% moisture. Direct combining with the use of a desiccant is possible in canola that is standing well, but determining application time is difficult and field losses are higher. The cylinder speed should be set at 450-1000 RPM and the cylinder concave clearance at 3/16 to 1/2 inch. Losses should be evaluated for further refinement of these adjustments. Canola that is to be stored for six months or more must be dried to near 8% moisture.

J. Drying and Storage:

Rapeseed must be handled and stored carefully. Tight storage bins are required. Seed can sweat in storage even at 9 to 20% moisture content. Inspection is required to prevent heating and spoilage in the bin. The small seed restricts air flow, so thin layers are necessary for drying wet seed. If much straw is present a scalper should be used to clean the crop.

VI. Yield Potential and Performance Results:

Yields of canola in the upper Midwest have been extremely variable in recent studies. In Minnesota, yields have ranged from 150 to 2500 lb/a with oil ranging from 39 to 47%. A test weight of 52 lb/bu is generally used for canola.

Studies conducted at several locations in Wisconsin have found yields of spring types ranging from 250 to 2300 lb/a, while winter types frequently have not survived the Wisconsin winters. Recent Wisconsin yields are summarized in Table 3 and Minnesota yields in Table 4.