Growing Canola – Crop Nutrition 101

What soil type, pH and climate does canola prefer?

Canola performs well at soil pH values between 5.5 and 8.5 and grows well in cool, shorter season environments like that of western Canada.

• Soil type: Canola prefers well-drained soils with good water-holding capacity. Ideal soil types include loam and clay loam soils that provide adequate aeration and moisture retention. Sandy loam soils can also be suitable if they are well-managed to prevent excessive drought stress.
• pH: Canola thrives in slightly acidic to basic soils (5.5 and 8.5), ideal for optimal nutrient availability and root development. It is considered relatively tolerant to pH variations but can suffer from nutrient deficiencies or toxicities if the pH is outside this optimal range.
• Moisture: adequate moisture is crucial, particularly during germination, early growth stages, and flowering. Canola typically requires about 40-60 cm (16-24 inches) of rainfall during the growing season. Both drought and waterlogging can adversely affect yield.
• Climate: Canola grows best in temperatures ranging from 10°C to 30°C (50°F to 86°F). Ideal conditions include cooler temperatures during the growing season, particularly during the early stages of development and flowering. Extreme heat can negatively impact flowering and seed set. While Canola is somewhat frost-tolerant, especially during the seedling stage, late spring frosts or early fall frosts can damage flowering plants and reduce yield.

Key Nutrients: 

Achieving high yields and quality often depends on balanced nutrition. The major three macronutrients, nitrogen (N), phosphorus (P), and potassium (K) are in high demand along with sulfur (S), with nitrogen being the most limiting nutrient. Due to canola’s rapid growth and high biomass production, insufficient nitrogen can significantly reduce yield and quality.

• High-demand nutrients are nitrogen, phosphorus, potassium and sulfur
• Secondary and micronutrient imbalances or deficiencies can negatively impact quality and yield
• Sulfur is particularly important as canola has a higher sulfur requirement compared to other crops. Sulfur deficiency can lead to poor plant growth and reduced seed quality and stand count.

Nutrient Overview

• Nitrogen (N): Promotes vegetative growth, chlorophyll production, and overall yield.
• Phosphorus (P): Supports root development, energy transfer, flowering, and seed formation.
• Potassium (K): Enhances plant health, water regulation, disease resistance, and seed quality.
• Sulfur (S): Crucial for amino acid synthesis, protein formation, chlorophyll production, and nitrogen utilization.

Other essential nutrients for canola include micronutrients such as boron (B) and zinc (Zn).

Nutrient Requirements: 

Nutrient balance is key to quality yields.

N lb/acre = 100-120

P lb/acre = 15-25

K lb/acre = 60-120

S lb/acre = 20-25

Ca lb/acre = 40-60

Mg lb/acre = 12-18

Nutrient uptake values are estimated for a 35 bu/acre canola crop. Source: Canola Council of Canada (https://www.canolacouncil.org/canola-encyclopedia/fertility/basic-plant-nutrition/)

Role of Nutrients:  

Different nutrients can influence your harvest quality and yield.

+ = improving

– = decreasing

+/- = different results, depending on the rate of nutrient applied

Yield: N++, P+, K+, S++, Ca+, Mg+

Seed oil concentration: N +/-, S +

Nutrient Impact on Canola

Nitrogen: Nitrogen promotes vigorous growth, higher leaf area, and greater biomass. It significantly influences yield potential and seed quality. Insufficient nitrogen can lead to stunted growth, pale leaves, and reduced yield.

Phosphorus: Adequate phosphorus ensures strong root systems, early plant development, and improved flowering and seed set. Phosphorus deficiency can result in poor root growth, delayed maturity, and lower seed yield.

Potassium: Sufficient potassium improves overall plant health, drought tolerance, and resistance to diseases. It also enhances seed quality and oil content. Deficiency symptoms include leaf chlorosis, poor root development, and increased susceptibility to stress.

Sulfur: Sulfur has a high sulfur requirement and is particularly important for quality yields. Adequate sulfur improves protein synthesis, oil content, and overall plant health. Deficiency symptoms include yellowing of younger leaves (similar to nitrogen deficiency but starting from the newer leaves), stunted growth, and reduced yield.

Challenges and Solutions for Canola Growers

• Canola seeds are sensitive to fertilizer injury, and a high seeding rate is often required to encourage adequate stand counts and harvests. Seed-safe fertilizers are key for high-yielding harvest. By using gradual-release fertilizers with a low salt index (like Polysulphate), seeding rates may be able to be reduced, and stand counts improved.
• Ensuring adequate and balanced nutrient supply, especially nitrogen and sulfur, is critical. Over- or under-application of fertilizers can lead to poor crop performance and environmental issues such as nutrient loss. Taking an integrated approach to nutrient management can help ensure that a balanced supply of nutrients is readily available at key times in the season.
• Canola often has a short growing season, with cold early-season temperatures. Leveraging starter fertilizers and biostimulants can make the difference between an average yield and an outstanding yield.