Canola, a contraction of “Canadian oil, low acid,” is a variety of rapeseed developed in the 1970s to improve its nutritional profile. It belongs to the Brassica plant family, which includes crops like mustard, cabbage, and broccoli. The plant is cultivated for its small, dark seeds, which contain approximately 45% oil. Crushing the seeds yields one of the world’s leading sources of edible vegetable oil, prized for its low saturated fat content, and a high-protein meal used for livestock feed. Successful production requires careful management from planting through harvest.
Preparation and Seeding Requirements
Successful canola cultivation begins with careful consideration of the field and planting mechanics. The crop performs best in well-drained soils, with clay-loam textures often preferred, as the plant is sensitive to waterlogging. While canola tolerates a wide soil pH range (5.5 to 8.3), acidic soils below 5.5 should be avoided to ensure nutrient availability.
A well-prepared seedbed is necessary for optimal seed-to-soil contact, which ensures uniform and rapid emergence. Farmers incorporate crop rotation, avoiding planting canola in the same field more than once every three or four years. This practice disrupts disease cycles and manages soil-borne diseases like blackleg, maintaining soil health.
The timing of seeding depends on the variety, as canola is grown as both spring and winter annuals. Spring canola must be planted early, typically when soil temperatures reach 45 to 50 degrees Fahrenheit, to ensure maturity before late-season wet periods. Seeding depth is controlled, ideally ranging from one-half to one inch, because the small seeds have limited energy reserves. Seeding rates are adjusted to achieve an optimal final stand of five to eight healthy plants per square foot.
Management During the Growing Season
Once established, intensive crop management supports the plant through its vegetative and reproductive phases. Canola has a high demand for specific nutrients, particularly nitrogen and sulfur, to maximize yield and oil content. Nitrogen application is often split: a third is applied at or before planting, and the remainder is top-dressed in the spring before the rapid bolting stage. Sulfur is also a limiting nutrient; a soil test determines precise needs, and application often occurs with the initial fertilizer blend.
Weed control is necessary because canola seedlings are highly susceptible to competition, requiring timely herbicide applications, usually at the two- to four-leaf stage. Insect pests, such as flea beetles, are addressed early, often using insecticide seed treatments to protect vulnerable cotyledons and young leaves. Scouting monitors for later-season pests, like the diamondback moth and cabbage seedpod weevil, with foliar insecticides applied only when economic thresholds are reached.
Disease prevention uses integrated strategies, targeting blackleg and Sclerotinia stem rot. Planting certified, disease-free seed and using resistant cultivars are primary defenses against blackleg. For Sclerotinia, which thrives in cool, moist flowering conditions, a fungicide application at the early-flowering stage is a strategy used in high-risk years. The crop requires consistent moisture, especially during the late vegetative and flowering stages, as water stress leads to significant yield loss.
Harvesting and Yield
Determining the precise moment for harvest minimizes seed loss from shattering, as the canola plant easily drops its seed once ripe. The optimal time is signaled by a change in seed color and moisture content, not by calendar date. Canola is ready for final harvest when the seed moisture content is between 8% and 10%.
Farmers use two primary methods: swathing or direct combining. Swathing involves specialized equipment cutting the crop and laying it in a windrow on the stubble. This is done when 40% to 60% of the seeds on the main stem have started changing color from green to brown. Swathing accelerates drying, allowing the crop to be combined seven to ten days earlier and reducing weather-related losses.
Direct combining, where the crop is harvested while standing, is increasingly viable due to shatter-resistant varieties. This method is preferred in warmer, drier regions or with uniformly mature fields. Specialized headers on the combine are necessary to handle the small seeds and reduce losses. Yields are typically measured in bushels per acre or tons per hectare, averaging 500 to 2,000 pounds per acre globally.