Malhi: Improving Canola Yields with Balanced and Efficient Nutrition

Date: June 2001
Term: 3 years
Status: Completed
Researcher(s): Dr. S.S. Malhi, Agriculture and Agri-Food Canada, Melfort, SK
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: MCGA

Project Summary

Canola is a major cash crop of the Parkland region of the Prairies where many soils (especially Gray Wooded) are deficient or potentially deficient in plant-available sulphur (S) for canola. The objectives of this study were to assess the amount of yield loss when S deficiency on canola occurs during the growing season and to compare the effects of S fertilization at different growth stages on seed yield and quality of canola in northeastern Saskatchewan. Overall, S application at seeding appeared to be the best strategy to overcome S deficiency and optimize seed yield. A foliar application can correct S deficiencies during the growing season substantially if applied before bolting stage, and moderately as late as early flowering stage. The results of boron (B) fertilization trials showed that regardless of the site, year, canola cultivar, as well as fertilizer rate, time and method of application, B fertilization had no consistent influence on seed yield, protein content or oil content.

Canola is a major cash crop of the Parkland region of the Prairies where many soils (especially Gray Wooded) are deficient or potentially deficient in plant-available sulphur (S) for canola. More than 4 million hectares of Prairie agricultural soils are deficient in S, and substantially greater areas are potentially deficient in the surface soils due to leaching. Because canola has high requirements for S and S is immobile in plants, a deficiency at any growth stage of the crop can drastically reduce canola yield. Many farmers in the Parkland region have incurred substantial loss in seed yield due to severe S deficiency, particularly at flowering and pod formation. However, information was lacking on the relative effectiveness of S fertilization during the crop growing season.

The objectives of this study were to assess the amount of yield loss when S deficiency on canola occurs during the growing season. Researchers also wanted to determine if S deficiency on canola can be corrected and seed yield and quality of canola on S-deficient soils can be restored to its normal levels by applying sulphate-S fertilizer at different crop growth stages using different times and methods of applications.

Field experiments were conducted from 1998 to 2000 on S-deficient soils in northeastern Saskatchewan. Each plot received a blanket application of 50 kg/ha P2O5 and 25 kg/ha K2O. Potassium sulphate was applied at 15 and 30 kg/ha S rates at pre-seeding, seeding, bolting and flowering stages of canola. Various application methods of fertilizer S were compared at seeding, including incorporated prior to seeding, sidebanded and seed placed. Applications in- crop included topdressed and foliar applied at bolting and flowering. Seed yield was measured, and seed samples analyzed for oil content, protein content and total S concentration.

Table 1. Relative effectiveness of sulphate-S fertilizer applied at different growth stages on seed yield of canola

(averaged over six site-years from 1998 to 2000 in northeastern Saskatchewan)

aFor the N + S treatments, 120 kg N ha-1 was applied at seeding.

In all experiments there was a marked seed yield increase response to N + S fertilizer, small response to S alone and negative response to N alone. Oil content in canola seed was increased with N+S application compared to N alone treatments, but S application had no effect on protein content. The N+S treatments significantly increased total S concentration of canola seed, and the increase was greater with the 30 kg/ha S rate than the 15 kg/ha S rate.

Overall, S application at seeding appeared to be the best strategy to overcome S deficiency and optimize seed yield. The results suggest that S deficiency for canola can be corrected and seed yield restored with application of sulphate-S fertilizer in the growing season, moderately to substantially until bolting stage and moderately as late as early flowering stage. For correcting S deficiency within the growing season, foliar application of S was more effective than topdressing with a granular product in restoring canola seed yield in S-deficient soils.

Boron Deficiency in Canola: Rates, times and methods of B application

Researchers also conducted field trials in 1998 to 2000 in northeastern Saskatchewan on sandy soils to determine if low canola yields were due to boron (B) deficiency in soil. They also wanted to determine if canola yield and quality can be enhanced with B application, and to determine the best rate, time and method of application. Boron fertilizer was applied either by broadcast and incorporation prior to seeding, seed placement or foliar spray at 10-20% bloom stage.

Although application of B fertilizer was expected to increase seed yield and improve seed quality in some of these soils, it did not happen. The results showed that regardless of the site, year, canola cultivar, as well as fertilizer rate, time and method of application, B fertilization had no consistent influence on seed yield, protein content or oil content. The results of these experiments and field survey trials suggest that B deficiency on canola occurs rarely, if at all and may occur in small patches on sandy soils of the Carrot River area.

If canola producers suspect a B deficiency, researchers offer the following suggestions to help producers save money and optimize the use of B fertilizer:

Apply B fertilizers in test strips to find out if there is any increase in seed yield and only then consider B fertilization of whole fields on a regular basis.

If it is already planned to apply B fertilizer on canola, then leave some strips without B fertilizer in the field to compare seed yields with and without B fertilizer.

Scientific Publications

Malhi, S.S. and Gill, K.S. 2002. Effectiveness of sulphate-S fertilization at different growth stages for yield, seed quality and S uptake of canola in northeastern Saskatchewan. Can. J. Plant Sci. 82: 665-674.

Malhi, S.S. Raza, M., Schoenau, J.J., Mermut, A.R., Kutcher, R., Johnston, A.M. and Gill, K.S.

2003. Feasibility of B fertilization for yield, seed quality, and B uptake of canola in northeastern Saskatchewan. Can. J. Soil Sci. 83: 99-108.

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