Spring and Winter Canola: Fertility Management

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Pub 811: Agronomy Guide > Spring and Winter Canola > Fertility Management

Excerpt from Agronomy Guide for Field Crops
Order OMAFRA Publication 811: Agronomy Guide for Field Crops

• Placement and Timing
  • Table 6-4. Spring Nitrogen Requirements for Winter Canola
• Nitrogen
• Winter Canola
  • Table 6-5. Phosphate and Potash Recommendations for Canola Based on OMAFRA-Accredited Soil Tests
• Phosphate and Potash
• Nutrient Deficiencies

Placement and Timing

Most fertilizer for canola is broadcast. The high rates of nitrogen required and the seeding methods used work against the use of fertilizers banded with the seed. There may be occasions, particularly where phosphorus soil-test levels are low, when phosphorus application with the seed would be advantageous. Take care not to exceed safe rates.

The rate of nitrogen fertilizer placed with the seed must not exceed 11 kg/ha (10 lb/acre). Place only superphosphate or monoammonium phosphate (MAP) with the seed.

100 kg/ha = 90 lb/acre

¹ To use this table, the price of canola must be known or estimated. Canola at $450/t and nitrogen at $1.50/kg results in a price ratio of 3.3 (1.50/0.45). At these prices and an expected yield of 3.0 t/ha, use 170 kg/ha of nitrogen.
² 1 t/ha = 893 lb/acre.
³ Where manure is applied, reduce the fertilizer according to the amount and quality of manure (Manure).

Nitrogen

Spring Canola

Canola has a great demand for nitrogen. The nitrogen fertilizer recommendations for canola in Table 6-3, Nitrogen Recommendations for Spring Canola, this page, are based on the price ratio between canola and nitrogen fertilizer. Rates should be adjusted downward if manure was applied or if the previous crop contained legumes such as alfalfa (see Table 9-7, Adjustment of Nitrogen Requirement, Where Crops Containing Legumes Are Plowed Down, and Table 9-8, Typical Amounts of Available Nitrogen, Phosphate and Potash From Different Types of Organic Nutrient Sources). Excessive nitrogen in the soil has been linked to green seed problems.

Winter Canola

Fall Application

Apply up to 40 kg/ha (36 lb/acre) of nitrogen in the fall. If the land was fallowed for one or more months before planting or if forage legumes were plowed down or manure applied before planting, no nitrogen fertilizer should be applied.

Spring Application

The rate for spring application of nitrogen is based on the expected yield and on the price ratio between canola and nitrogen fertilizer. See Table 6-4, Spring Nitrogen Requirements for Winter Canola.

100 kg/ha = 90 lb/acre

¹ HR, MR, LR, RR, and NR denote, respectively, high, medium, low, rare and no probabilities of profitable crop response to applied nutrient. Profitable response to applied nutrients occurs when the increase in crop value, from increased yield or quality, is greater than the cost of the applied nutrient.

² A rating of "NR" may mean reduced yield or quality of the crop if fertilizer is applied.

Phosphate and Potash

Phosphate and potash recommendations for canola are given in Table 6-5, Phosphate and Potash Recommendations for Canola Based on OMAFRA-Accredited Soil Tests. For information on the use of this table or if a soil test is unavailable, see Fertilizer Recommendations.

The phosphorus requirement for canola is greater than for cereals, due to the higher protein content of the seed. A 2.5 t/ha (1 ton/acre) canola crop will remove an average 66 kg/ha (59 lb/acre) of phosphate fertilizer (P₂O₅). During germination and emergence, canola is sensitive to fertilizer salts. Salt injury can substantially reduce stands. Canadian research suppots an initial 11-17 kg/ha (10-15 lb/acre) of starter phosphate. The highest response can be expected when planting into cool soil conditions on soils with low-to-medium fertility levels.

Nutrient Deficiencies

Sulphur

Canola requires twice as much sulphur compared to cereal crops. Soils in Southern and Northeastern Ontario generally have adequate sulphur for optimum yields, either as native soil sulphur or from atmospheric deposition. Trials have shown no consistent response to sulphur containing fertilizers in Southern or Northeastern Ontario. There have been scattered instances of sulphur-deficient soils with low organic matter in Northwestern Ontario. Deficiency symptoms are a general yellowing of the entire plant, mottling of leaf surface, purple underside of leaves and small, pale yellow flowers (Plate 30).

Plate 30. Sulphur deficiency in canola results in mottling of the leaf surface, purple underside of leaves and small pale yellow flowers.

Soil testing is not a reliable way to assess sulphur availabilty to crops, since sulphur content changes rapidly. Plant tissue testing can be useful where sulphur deficiency is suspected. Where required, sulphur can be supplied by replacing some urea with ammonium sulphate to supply the same amount of N. Elemental sulphur is not available to plants until it has oxidized to the sulphate form, a process that can take 12-18 months.

Boron

Boron deficiencies are rare in canola, although there have been some plots that have shown positive yield responses to foliar applications of boron. Symptoms include seed abortion, misshapen pods and narrow, strap-like leaves. It is rarely seen, but when it occurs, it can significantly reduce yields. Boron deficiency can be corrected with either foliar or soil applications of soluble boron fertilizers.