By Shannon Chant, MSc., PAg., Regional Crops Specialist, Southwest Regional Services Branch
Canola requires a lot of fertilizer for optimal production. For every bushel of crop, 1.3 to 1.5 pounds of P2O5 is taken up and the crop removes 0.9 to 1.1 pounds of P2O5 from the field. For example, a canola crop that yields 30 bushels per acre takes up 45 pounds of P2O5 and removes 30 pounds from the field. Unfortunately, the maximum recommended safe rate of seed placed monoammonium phosphate (MAP) for canola in Saskatchewan is 25 pounds per acre. This rate may limit yield on soils with low phosphorus levels and makes it difficult to replace the phosphorus used by previous crops and that will be used in the growing season. Recent research has shown that hybrid Brassica napus canola varieties are more tolerant of seed-placed fertilizers than other Brassica species. In laboratory conditions, Brassica napus hybrids were not injured by 27 to 36 pounds per acre of P2O5.
In 2015, Wheatland Conservation Area conducted an ADOPT (Agriculture Demonstration of Practices and Technologies) project just outside of Swift Current, looking at the differences between side-banding and seed-placing P2O5 at 18, 36, 53, 71 and 89 pounds per acre P2O5 with L130 hybrid canola. Seeding took place on May 14 into cool soil to increase the chance of a response to phosphorus.
The start of the growing season was dry and plant emergence counts were conducted approximately two, three and four weeks after seeding. Canola emergence rates decreased as the rate of P2O5 placed with the seed increased. All treatments where fertilizer was seed-placed had fewer plants emerge than all treatments where fertilizer was side-banded. Little response was seen when side-banded rates were increased. Dry conditions continued for the early part of the growing season. When the site received rain, growing conditions were ideal and the hybrid canola branched out a lot.
Because phosphorus is very immobile in the soil and will only move less than an inch from where it is placed, the crop had better access to the seed-placed fertilizer than the side-banded fertilizer. Yield increased as rates of seed-placed fertilizer increased, but there was no yield response to increasing levels of side-banded P2O5. For the full project report visit the Wheatland Conservation Area website.
According to Canola Council of Canada’s online Canola Encyclopedia, research in Manitoba has shown that canola can compensate for seedling injury if populations are not reduced below critical levels. Yield potential can be maintained if plant counts are five plants per square foot or more. If they are below this level, yield is reduced and maturity is delayed.
For more information on safe rates of fertilizer placed with seed, visit “Guidelines for Safe Rates of Fertilizer Placed with the Seed”.
For assistance with planning fertilizer application rates and forms, contact your Regional Saskatchewan Agriculture crops specialist or your local agronomist.