Canola Planting Guide: Soil Requirements, Seeding Rates, and Best Planting Time

Wikifarmer

Editorial team

5 min read
16/12/2024
Canola Planting Guide: Soil Requirements, Seeding Rates, and Best Planting Time

Canola Soil Preparation, Soil and Seeding Requirements

To successfully cultivate canola and help the plants reach their yield potential, the farmer needs to know and control the factors affecting seed germination and crop establishment. 

Planting time and Soil requirements of Canola

Canola grows well on a wide variety of soils, given that they have good drainage since it is pretty sensitive to water lodging. However, it thrives in non-compacted clay-loam soils that do not crust. Sandy soils should be avoided, especially in regions with a high drought and heat stress risk. Canola can grow successfully with a pH ranging from 5.5 to 8.3. Acidic soils (below pH 5.5) should be avoided or adapted to ensure nutrient availability and root health. 

The crop is tolerant of saline soils, which makes it a good choice for planting on newly drained dikes (12). Due to the deep and extended root system (up to 1-1.20 m or 3.3-4 ft), deep soils should be generally preferred. Canola is very sensitive to some widely used broad-leaf herbicides (like sulfonylurea, ALS-inhibitor herbicides, etc.) used in crops like corn and wheat. If you plan to sow canola in a field, avoid using such products in the previous crop, especially if they have an extended residual life (3). Finally, if possible, avoid planting canola in fields where winter legumes, canola, or other Brassica species have been cultivated for the past 2-3 years to reduce the disease and pest build-up. 

When to plant canola? 

It is a cool-season crop but is not as cold-resistant as small grains. As a result, the moment of planting, especially for the winter-type canola, is crucial and can affect the plant's productivity and survival through the winter. The same is true for spring-type canola, regarding the high summer temperature and the early fall frosts. The plants are quite sensitive to -2 to -3 oC (-28 to -26 oF) from germination to the rosette formation stage. The seeds can germinate when the temperature exceeds 5 oC (41 oF), with the optimum being 10 oC (50 oF). Rosettes are generally resistant to low temperatures (up to -15 oC or 5 oF). For this reason, the farmer's goal should be to plant around the end of summer or early fall so his/her plants have reached the rosette stage before the first killing frost (less than -3.8 oC or 25 °F) (42). Moreover, plants with a big and well-formed crown (6-8 true leaves and 6-10 in or 15-25.5 cm canopy height) have better chances of withstanding extreme temperatures through the cold season (53). However, too early planting (e.g., July for the northern hemisphere) may lead to the flowering of the plants before winter, which will cause crop failure (low resistance of the plants to frost at that stage). Respectively, the spring canola produced higher yields when planted in early-mid spring (end of March, start of April in the northern hemisphere) compared to late spring. 

Soil preparation and planting

Canola can be grown in no-till or conventional tillage systems as well as conventionally tilled systems. In a conventional tillage system, the farmer may plow the field 2-3 times before planting, followed by laddering. To reduce the soil disturbance, the grower can apply one shallow tillage (4-5 in or 10-13 cm) as a preferred alternative. Conservation tillage methods, such as minimum tillage, help retain soil moisture and reduce erosion. These methods are particularly advantageous in areas with poor drainage or high organic matter, as excessive tillage can lead to soil compaction and moisture loss. Spring tillage should focus on warming and drying the soil in colder climates while avoiding residue removal that could lead to erosion risks.

Farmers are advised not to enter the field when it is still too wet, but it is also recommended not to plant in a very dry seedbed (irrigate if needed). Due to the seed's small size, the seedbed should be fine, without clods. Avoid shredding the soil too much, especially before rainfall, because it can lead to the formation of soil crust and, as a result, failure of plant emergence (67). 

Canola seed rate and planting density

The seeding rate guidelines differ depending on the seed viability, germination rate, planting strategy (in rows or broadcasted), and variety type (hybrid or open-pollinated). 

Generally, the recommended seeding rate is:

  • 3 to 6 lb per acre or 3.4-6.7 kg/ha (up to 600,000 seeds per acre or 1,482,000 seeds/ha) when planting in rows (drilling) and 
  • 6.5 to 8 lb per acre for broadcast seeding (7.3-9 kg/ha)

Argentina-type canola has a higher seeding rate than Polish-type canola. 

Keep in mind that the seeds of open-pollinated varieties are generally smaller than hybrids (100,000-150,000 seeds per pound vs. 60,000 to 100,000 seeds per pound, respectively or 220,000-330,000 seeds per kg vs. 132,000-220,000 seeds per kg, respectively) (8). 

Take this into account and adjust the seeding rate correspondingly when necessary. Hybrids can give economically acceptable yields, even when planted at lower seeding rates, 175,000-250,000 seeds per acre (or 432,250-617,000 seeds/ha). On the contrary, a seeding rate below 225,000 plants per acre (495,000 plants/ha) for open-pollinated varieties will decrease the final yield significantly. Except for sowing, in some regions, transplanting of seedlings (8-12 days old) is preferred. In this case, the farmer opens small planting pits with 6 in (15 cm) diameter and 8-10 in (20.3-25.4 cm) depth and plant distances of 30*30 cm up to 75x75 cm (or 11.8x11.8 in up to 30x30 in) (6).

For a good yield, 5-12 plants per ft2 (54-130 plants/m2) are needed to grow throughout the season. However, acceptable seed production may be obtained even with 2-5 plants per ft2 (22-54 plants/ m2) that can benefit from the extra space and compensate for the yield lost. As a result, it is advised to carefully evaluate your plants' population after a damaging event (e.g., frost) before destroying it (98). 

Farmers usually plant seeds at a depth of 0.5-1 inch (2-2.5 cm) in a firm, moist seedbed. Additionally, since sowing is usually performed with a grain drill, an intra-row spacing (distance between rows) between 6 and 14 inches is acceptable (or 15.5-35.5 cm). At the same time, many farmers prefer closer distances (18-25.5 cm or 7-10 in) (105). A planting speed of 5 miles per hour is considered optimum. Under favorable conditions, a seedling will emerge 4-10 days after planting. In some cases, thinning may be needed 3-4 weeks after sowing to maintain a population below 15 plants per ft2 (or 162 plants/ m2) (11). 

References

  1. https://www.agmrc.org/commodities-products/grains-oilseeds/canola-profile
  2. https://hort.purdue.edu/newcrop/afcm/canola.html
  3. https://efotg.sc.egov.usda.gov/references/public/NM/energy3a_GreatPlainsCanolaProductionHandbook.pdf
  4. https://www.lima-europe.eu/rapeseed/
  5. https://extension.missouri.edu/publications/g4162
  6. http://sri.ciifad.cornell.edu/aboutsri/othercrops/otherSCI/In_SMImustard_Pradan.pdf
  7. https://www.ag.ndsu.edu/publications/crops/canola-production-field-guide#section-12
  8. https://bookstore.ksre.ksu.edu/pubs/MF2734.pdf
  9. https://extension.okstate.edu/fact-sheets/winter-canola-planting-guide-for-the-southern-great-plains.html
  10. https://www.uky.edu/ccd/sites/www.uky.edu.ccd/files/canola.pdf
  11. http://www.kiran.nic.in/pdf/farmers_corner/pamphlets/Cultivation_of_Rapeseed_and_Mustard.pdf

Further reading