Rapeseed is a generic term for a number of different species which are similar in appearance, but sometimes substantially different in chemical composition or botanical origin. Rapeseeds are members of the Brassica family which also includes broccoli, cabbage, cauliflower, mustards, etc. Most rapeseed produced today is Canola, a variety of rapeseed with low glucosinolate and low erucic acid content, suitable for human consumption. However, varieties of rapeseed that contain high levels of the fatty acid erucic acid in its oil are produced as an industrial crop. Industrial uses of erucic acid include lubricants, plasticizers, coatings, surfactants, and an additive in rubber.
Seed yields show substantial regional variation, largely due to the lack of appropriate varieties. Yields have been highest in the Northwest with typical commercial yields of about 1,300 to 1,500 lbs seed/acre. Oil constitutes 40 to 45 percent of the seed weight and erucic acid is 45 to 50 percent of the oil. The meal is characterized by a high concentration of glucosinolates which decreases the palatability of the meal to livestock and can be toxic to some animals, limiting its usefulness as a livestock feed.
Commercial production of industrial rapeseed in the U.S. is limited (table 1). Most is produced in the Northwest in regulated rapeseed production districts due to the potential to cross-pollinate with other Brassica species.
Source: U.S. Department of Agriculture, National Agricultural Statistical Service
Industrial rapeseed is a cool season annual and includes both winter and spring varieties. The most common species commercially grown in the U.S. are Brassica napus (a winter variety) and Brassica campestris (a spring variety). It can be grown throughout much of the United States wherever wheat is grown, but varieties suitable for efficient commercial production are lacking for many areas. Winter varieties need to be planted early enough to reach a rosette size of 6 to 8 leaves before the first hard frost which generally occurs between mid-August and mid-September depending on geographic region (earlier in the northwest and later in the southeast). Harvest is generally in late May to early July, again depending on geographic region. Spring rapeseed is generally planted in March to April and harvested in August to September.
Rapeseed requires a firm seed bed and a relatively shallow planting depth. Fairly narrow row spacing (6 to 12 inches) is recommended. Seeding rates of 4 to 8 lbs/acre are typical if planting is by grain drill (higher rates are needed for broadcast planting). Compared to winter wheat, rapeseed is more tolerant of drought and saline conditions. Rapeseed does not tolerate wet soils. The nutrient requirements of rapeseed are similar to other small grains (e.g., 80-100 lbs N/acre, 30-40 lbs P2O5/acre, and 60-80 lbs K2O/acre). Sulfur may also be necessary, particularly in sandy soils.
Rapeseed is susceptible to pathogens that can rapidly build up in the soil and should be produced in rotation with other non-Brassica crops and planted once in a 3 or 4 year period. Production of rapeseed uses the same equipment (with some adjustments to accommodate the small seed size--90,000 to 150,000 seeds/lb) used to produce small grains (i.e., wheat, oats, barley, etc.). Production costs are similar to those of wheat.
Rapeseed is ready to harvest when the seeds have dried to 10 percent moisture. A moisture content of 8 percent is recommended for long term seed storage.