Reducing toxicity of seed-placed phosphorus fertilizer in canola
Date: March 2021
Term: 3 years
Status: Completed
Researchers: Patrick Mooleki, Alick Mulenga, Brett Mollison, Kim Stonehouse and Brian Beres, Agriculture and Agri-Food Canada, Jeff Schoenau, University of Saskatchewan and Manjula Bandara, Alberta Agriculture and Forestry
SaskCanola Investment: $218,500
Total Project Cost: $413,146.50
Funding Partners: Alberta Canola Producers Commission
Grower Benefit(s)
Researchers initiated a two-year study in 2018 to determine the maximum safe rate of seed-placed P fertilizer with different opener widths and row spacing in canola; and to develop updated seed-placed P fertilizer guidelines for producers and crop advisors to use. The study results showed that increasing the rates of seed-placed P fertilizer increased the toxic effect on canola seeds and seedlings. However, this was mitigated by increasing the width of the openers, and/or using narrow row spacing. P requirements of canola can be met through seed row placement without significant reduction in grain yield and quality as long as N and S fertilizers are not placed in the seed row.
Project Summary
For most crops, phosphorus (P) recommendations range from 30 to 50 lbs P2O5/acre. However, with the exception of cereals, these rates are too toxic and can cause damage to seed and seedlings if placed with the seed at the time of seeding. High rates of P can be applied as a sideband or mid-row band, but this is not always an option for many producers. As well, the current maximum safe rate of seed-placed P fertilizer guidelines for canola are based on only one configuration of a 1-inch opener and 9-inch row spacing. The safe rates of seed-placed P (in lb P2O5/ac) using this configuration are 15, 20 and 25 lbs P2O5/acre for Alberta, Manitoba and Saskatchewan, respectively, which are not adequate to meet P requirements of canola. Producers and crop advisors wanted to know how much P fertilizer can they apply with the seed if they are using wider openers.
Researchers initiated a two-year study in 2018 to determine the maximum safe rate of seed-placed P fertilizer with different opener widths and row spacing in canola; and to develop updated seed-placed P fertilizer guidelines for producers and crop advisors to use. This field study was conducted at five locations in 2018 and 2019, including Saskatoon, Melfort and Scott in Saskatchewan, and Brooks and Lethbridge in Alberta. The treatments included row spacing at 9- and 12-inches; opener width at 1-, 2- and 4-inches; and seed-placed P rates at 20, 35, 50 and 65 lbs P2O5/acre. In 2019 a control treatment of 0 lbs P2O5/acre was added. The treatments were applied using a custom-built drill fitted with Morris Contour 1 shanks and rollers and Dutch Universal openers with the flexibility and ease of changing opener width and type, and row spacing. All other fertilizer requirements for nitrogen (N) and sulphur (S) were side-banded.
The study results showed that increasing the rates of seed-placed P fertilizer increased the toxic effect on canola seeds and seedlings, leading to reduced plant population. However, this was mitigated by increasing the width of the openers, and/or using narrow row spacing; which increased the seedbed utilization (SBU) and reduced P fertilizer concentration near the seed. The effects of the treatment combinations on plant density in the study, averaged over the two seasons and five locations, did not translate into similar effects on biomass yield, grain yield and other canola crop characteristics. This small impact on yield and quality reflects the compensatory capability of canola under reduced plant density.
Overall, the study showed that P requirements of canola can be met through seed row placement without significant reduction in grain yield and quality as long as N and S fertilizers are not placed in the seed row. Producers seeding at 12-inch row spacing should avoid using openers less than 2 inches wide if seed-placing P fertilizer. At 12-inch row spacing, using 4 inch wide openers could help reduce toxicity of seed-placed P fertilizer. For producers using 9-inch row spacing, opener width should not exceed 2 inches, unless slower seeding speed is used. Producers who are placing N and S fertilizers away from the seed have more room to increase seed-placed P fertilizer without causing significant reduction in plant density and grain yield of canola.
Full Report PDF: Reducing toxicity of seed-placed phosphorus fertilizer in canola