Developing a fertilizer plan for your farm is never a straightforward task. There’s a lot to take into account when planning — so where do you start?
A good starting place is reviewing last year’s fertilizer rates, crop yields, and target yields. Knowing that information will help you to assess what worked, what didn’t, and why things went the way they did, giving you a start on what to do (or not do) again.
Another key piece to solving this agronomic puzzle is soil testing. Review your fall soil tests and look at future crop sequences. For canola specifically, it’s important to ensure macronutrients required to achieve your target yield are made available for your upcoming crop. Once those are in balance, you can start determining what you’ll need based on the previous information.
Nutrient Uptake and Removal #
The main focus of the 4R Nutrient Stewardship plan for canola is to optimize fertilizer applications to increase yields and to increase nutrient use efficacy.
Two to 3 lb. of nitrogen are required per bushel of seed yield. Of the nitrogen taken up by a plant, 70% of it is removed with the seed, leaving 30% of it in the field as residue. Through soil testing and the previous year’s yield data, you can utilize nutrient uptake and removal rates to generate your fertilizer rates for this year.
A recent study done by the University of Lethbridge and funded by the Canola Council of Canada looked into the factors affecting nutrient and water use efficiencies. Their findings highlight the importance of nitrogen applications applied in the spring and controlled release products help minimize losses and keep nitrogen available for the crop to use.
“Canola growers in Western Canada utilize a lot of practices that help increase nitrogen use efficiency already,” said Justine Cornelsen, BrettYoung’s Agronomic and Regulatory Services Manager. “Split applications can also be beneficial to help spoon feed nitrogen to the crop when it’s needed.”
Cornelsen added that this practice is not common right now as it’s high risk for timing, requires another application, and so takes some more planning to achieve.
For every bushel of canola seed yield, 2.5 lb of potassium are required. Potassium is a more plentiful nutrient found across Western Canada and remains in the canola plant biomass, not the seed. It’s less mobile in the soil than nitrogen, so placement near the rooting zone is key. Due to the high salt index of potassium fertilizer, it’s best to sideband the potash fertilizer than place it within the seed row.
Canola requires 0.5 to 0.7 lb of sulphur per bushel of seed yield. Sulphur levels can be extremely variable across a field, and it’s recommended you place at least 10 to 20 lb/ac – but higher rates may be required to reach yield targets. A spring application of ammonium sulphate away from the seed will help meet canola’s sulphur needs in the year of application, whereas elemental sulphur won’t be available for uptake in the year it’s applied, but it remains a good option for long-term nutrient building.
Sulphur deficiency is one of the easier deficiencies to identify in canola. The plants will have small, narrow leaves that are pale in colour if not yellow. The symptoms will be patchy across a field with a sulphur deficiency and are more likely to be seen in sandy soils with low organic matter. Cornelsen said a tissue sample will confirm the deficiency. If deficiency symptoms are detected early, a sulphur top-dressing application at bolting will help save your yield.
Seed-placed Fertilizer #
Proximity to the canola seed for all applied fertilizers is something to be considerate of and when placing fertilizer next to seed, you need to further think about seedbed utilization. This captures the amount of seedbed over which fertilizer is spread. The percent of seedbed utilization is calculated by the width of spread and row spacing – the higher the seedbed utilization, the more fertilizer that can be placed safely with the seed with heavier soils (clay) allowing for higher rates than light soils (sandy loam).
Soil moisture drastically changes what can safely be placed with the seed. For canola, you can safely place 15 to 20 lb/acre of phosphorus with the seed through products like MAP, which has a low salt index and a low toxicity to seed.
“Phosphorus is immobile in the soil so having phosphorus fertilizer near the seed allows for seedlings to pop out of the ground stronger,” said Cornelsen. “Some soils are low in phosphorus across the Prairies, so growers should be looking to build amounts of the nutrient. In the low phosphorus soils, canola will respond well to starter phosphorus.”
Canola removes around 1 lb. of phosphorus for every bushel of canola seed produced — that’s usually higher than what can be safely placed with the seed. You should build phosphorus in the off years of your canola crop, so the levels don’t become depleted. Cornelsen added that adequate precipitation can suppress the effects of both high and low fertilizer amounts as it’s the most critical input of them all.
