Rapeseed, scientifically known as Brassica napus var. napus, is an annual oilseed crop belonging to the Brassicaceae family. Often referred to simply as rape or oilseed rape, it shares botanical kinship with familiar vegetables like mustard, cabbage, broccoli, cauliflower, and turnip. Characterized by its vibrant yellow flowers with four petals, the rapeseed plant typically grows to a height of three to five feet. Its root system is composed of a deep taproot complemented by a fibrous network near the soil surface.
A common point of confusion arises when differentiating between rapeseed and canola, as canola is indeed derived from the same Brassica napus species. Historically, “rapeseed” served as the overarching term for oilseed crops within the Brassicaceae family. However, this group is now categorized into two distinct types: industrial rapeseed and canola. While visually indistinguishable in seed form, the defining difference lies in their fatty acid profiles and glucosinolate content. Today, the term “rapeseed,” or more specifically “industrial rapeseed,” denotes varieties with a high erucic acid content in their oil, typically 45 percent or greater. “Canola,” a name registered in Canada in 1979, designates the edible oil crop bred to contain low erucic acid (less than 2 percent) and low glucosinolate levels. Given the shared cultivation practices, canola is often referenced in discussions about rapeseed, but this article will primarily focus on industrial rapeseed. For information on canola, please refer to the canola profile available on this website.
The primary economic driver for rapeseed cultivation is its oil content. With seeds containing over 40 percent oil, rapeseed can offer a more lucrative oil yield compared to soybeans, which contain approximately 18 percent oil. However, a significant challenge for rapeseed profitability is the limited market and applications for the seed meal byproduct remaining after oil extraction. Beyond oil production, rapeseed also demonstrates value as a cover crop and annual forage. Its dense growth provides excellent winter soil cover, preventing erosion. It generates substantial biomass, effectively suppresses weeds, and its root system can improve soil structure.
Certain summer annual rape cultivars are specifically bred for grazing purposes. These are particularly beneficial for finishing lambs, flushing ewes, and for feeding dairy cows and pastured sows. Forage rape reaches grazing maturity within 80 to 90 days after planting. Winter rapeseed varieties can also be grazed by livestock during their fall growth period.
Rapeseed Production and Agronomic Practices
In the United States, rapeseed cultivation has seen fluctuations. Harvested acreage decreased from 200,000 acres in 2008 to a low of 10,100 acres in 2020. However, in 2020, total rapeseed production exceeded 19.9 million pounds, with a market value of $4.4 million. A slight recovery was observed in 2021, with acreage increasing to 15,500 acres. Rapeseed has a history of over 40 years of cultivation in the Pacific Northwest and was also grown in the Southern U.S. in the late 1980s and early 1990s. Currently, the Pacific Northwest and southeastern regions of the USA represent the areas with the most significant rapeseed production. The average rapeseed yield in 2020 was 1,971 pounds per acre. Rapeseed exhibits adaptability to a wide range of well-drained soils, thriving in pH levels between 5.5 and 8.3, and demonstrating moderate tolerance to saline conditions.
A key limitation in expanding rapeseed utilization lies in the limited applications for the seed meal after oil extraction. The presence of glucosinolates in the meal restricts its use in livestock feed due to their antinutritional and negative physiological effects. This factor significantly impacts the overall economic viability of rapeseed production.
Management Strategies for Rapeseed Cultivation
Managing rapeseed for industrial oilseed production shares many similarities with canola management. Rapeseed varieties are available in both spring and winter types. Planting schedules for these types should align with the typical planting dates for spring or winter wheat in a given region, respectively. The equipment required for rapeseed production is comparable to that used for other small-seeded grain or oilseed crops, including a tractor, drill or broadcast seeder, sprayer, combine harvester, and transport wagons.
Fertilizer requirements are site-specific and depend on the yield potential of the production area, considering both soil fertility and rainfall patterns. Nitrogen needs typically range from 100 to 150 pounds per acre. Phosphorus (P2O5) and potassium (K2O) fertility needs are determined by soil test levels. Recommended P2O5 rates range from 0 to 80 pounds per acre, while K2O rates range from 0 to 140 pounds per acre. Sulfur is also a critical nutrient for achieving profitable rapeseed and canola seed production, with recommended rates ranging from 10 to 30 pounds per acre.
Seed shattering at harvest poses a potential challenge. To mitigate this, rapeseed is commonly swathed prior to combining when seed moisture content is around 35%. This practice allows for more uniform drying and reduces harvest losses.
Marketing and Industrial Applications of Rapeseed
Rapeseed production primarily targets two main markets: birdseed and industrial oil. The oil derived from rapeseed, often termed high-erucic-acid rapeseed (HEAR) oil, is particularly valued for industrial applications demanding high heat stability. A significant market segment for HEAR oils is the production of erucamide. Erucamide, favored for its processing properties over cheaper alternatives, has been used for decades by plastic film manufacturers in products like bread wrappers and garbage bags. HEAR oil also has applications in biodiesel production, contributing to the renewable energy sector.
While the market for industrial rapeseed is considered relatively mature, the increasing global emphasis on renewable resources and biodegradable materials presents potential for renewed interest in raw materials like high erucic oil rapeseed. However, given the current market landscape, it is generally advisable to grow industrial rapeseed under contract to ensure a market outlet.
On-farm biodiesel production from rapeseed or canola is technically feasible. However, economic analyses, such as those conducted by economists at the University of Tennessee, have indicated that while canola-based biodiesel production can be financially viable, rapeseed-based production may not be due to the limited market for the byproduct seed meal. Similarly, research at Oregon State University has pointed to potential financial losses associated with producing biodiesel from canola/rapeseed.
The meal derived from HEAR rapeseed varieties typically contains high glucosinolate levels, rendering it unsuitable for animal feed applications. This byproduct challenge remains a key factor in the overall economics of industrial rapeseed production.
Financial Considerations in Rapeseed Farming
The cost of rapeseed production is generally comparable to that of canola. However, a potential cost advantage for rapeseed lies in seed costs, as rapeseed varieties currently lack transgenic traits, which can make transgenic canola seeds more expensive. Weed control costs may also vary, as herbicide-resistant rapeseed varieties are not available.
Production budgets for canola and rapeseed are publicly available from agricultural extension services in various regions, including North Dakota, Pennsylvania, Maine, and Georgia. These resources provide valuable insights into the financial aspects of rapeseed and canola production in different geographical contexts.
