Canola Fertilizer Recommendations
Proper plant nutrition plays a major role in the winter survival of canola, seed production, and oil quality. To develop an effective fertilization program for the crop, the farmer should perform a soil analysis to determine the soil characteristics and the type and amount of nutrients already in the soil. Among other information, this test will show the soil pH and lime requirement, soil organic matter, plant available nitrogen, phosphorus, potassium, and sulfate-sulfur. Since canola is sensitive to boron and zinc deficiency, testing their availability in the upper 50 cm (19.7 in) of soil is recommended. To take a representative and appropriate soil sample, follow the instructions of your laboratory.
Canola can survive in soils with a pH that ranges from 5.5 to 8.3. However, for optimum growth, the plants prefer a more neutral pH (6-7). As a result, in acidic soils (pH lower than 5.8), applying and incorporating lime with tillage might be necessary. The amounts added should be half in no-tillage systems.
Except for the information given by the soil analysis, it is essential to know the crop nutrient removal and the periods of plants’ peak need for specific nutrients.
Nitrogen (N) and Sulfur (S)
Canola, like wheat, benefits greatly from fertilization. Nitrogen is the most important element needed in high amounts (25-30% more than wheat). The general N requirements range from 100 to 150 lb per acre (112-168 kg/ha), but the dose should be increased (by 25-30 lb per acre, or 28-34 kg per hectare) for:
- sandy soils,
- fields with irrigation (or large amounts of rainfall),
- in dense plant populations and,
- for high yield goal (more than 2.5-3 tons per hectare) (1).
On the other hand, when canola is sown in a field after legumes, the total amount of nitrogen can be reduced by 20-30%.
Sulfur is also essential in canola cultivation to maximize seed production and quality. More specifically, the recommended sulfur fertilizer rates range from 10 to 30 lb per acre (11.2-33.6 kg/ha) (2, 3, 4). Deficiency of either nutrient (N and S) can lead to canola plants with reduced height, poor branching, pod set, and leaf discoloration (purple, yellow-red). The simultaneous lack of adequate soil moisture will worsen the symptoms (1, 5).
Phosphorus (P) and Potassium (K)
Like other oil seed crops, canola demands and removes large amounts of phosphorus (P) and potassium (K) through the seeds. More specifically, with each bushel of seeds (50 lbs or 23 kg), 0.9 lb of P and 0.45 lb of K (0.4 kg of P and 0.2 kg of K) are removed from the soil. Depending on the soil P and K stored, the generally recommended rates may vary from 0 to 80 lb per acre (0-90 kg/ha) and from 0 to 60-140 lb per acre (0 to 67-157 kg/ha), respectively (3, 6).
Note: In the case of canola, 1 bushel corresponds to 50 pounds of seeds.
To ensure a good canola yield, the farmer may also need to apply Boron (B), Zinc (Zn), Calcium oxide (CaO), and Magnesium oxide (MgO). Among them, Boron is considered the most important, and nutrient deficiency can negatively affect the pod set.
Fertilizer Planning for Canola
When is it best to apply each nutrient?
Applying the total amount of P, K, and S pre-planting is recommended. The fertilizers can be broadcasted or banded and incorporated with the last tillage. Be careful not to bring the fertilizers in direct contact with the seeds to avoid damaging them. The N is usually applied in 2 doses. This is more important for the winter-type canola, where the farmer should not apply more than 1/3 of the total N during the fall. Otherwise, the plants' winter survival decreases. The farmer can add the rest of the nitrogen in early spring (7, 8). For immediate results, the farmer can apply sulfur, Boron, magnesium, and manganese by foliar fertilization from fall until the stem elongation stage in spring.
However, these are just general recommendations that should not be followed without doing your own research. Every field is different and has different needs. Adjust the type and amount of fertilizers depending on your soil analysis results (pH, soil type, available nutrients, etc.) and the amount of water your field receives (irrigation or rainfalls). You must consult your local licensed agronomist.
References
- https://www.dalrrd.gov.za/Portals/0/Brochures%20and%20Production%20guidelines/Canola%20-%20Production%20Guideline.pdf
- https://extension.missouri.edu/publications/g4162
- https://www.agmrc.org/commodities-products/grains-oilseeds/canola-profile
- https://extension.psu.edu/canola-or-rapeseed-production-in-pennsylvania
- http://canola.okstate.edu/cropproduction/fertility
- https://bookstore.ksre.ksu.edu/pubs/MF2734.pdf
- https://extension.okstate.edu/fact-sheets/winter-canola-planting-guide-for-the-southern-great-plains.html
- https://www.extension.iastate.edu/alternativeag/cropproduction/pdf/canola_crop_guide.pdf
Further reading
- History, Uses, and Nutritional value of oilseed rape (Canola)
- Canola Planting Guide: Soil Requirements, Seeding Rates, and Best Planting Time
- Plant Information and Variety Selection of Rapeseed
- Canola Irrigation and Water Needs
- Canola Fertilization Guide: Key Nutrients, Rates, and Application Timing
- Canola Pest and Disease Management
- Canola Weed Management
- Yield, Harvest, and Storage of Canola