Soil test, soil test, soil test!
A canola fertilizer program should be based on yield goals, the 4Rs of nutrient stewardship (right source, right
right time, right place), and current soil nutrient levels. The best practice when making fertility plans is to rely
soil test recommendations for fertilizer inputs. If time or conditions do not allow soil testing in the fall, then it
can be completed in the spring. Spring soil testing can often be more accurate when following a drought year, such as
Nitrogen (N) Only about half of the N on a fall soil test result is available to the following
Mineralization of N in organic matter will release N to the crop throughout the growing season and is important to
consider when making N fertilization plans. However, mineralization rates can vary widely with soil type and moisture
levels and are limited in the early season when soils are cool and wet. Therefore, in-soil banding, and preferably
banding, of N in the spring or late fall is advised to supply the N needed for early crop growth.1,2 If a
application is the only option, spring is the best time to help minimize losses, and consider using a
Phosphorus (P) Fertilize according to soil test recommendations. When high rates are needed, side
banding of P
fertilizer in the spring is safer for the crop than seed-placed P, which can burn canola seedlings.1
Sulfur (S) Soil tests are important for assessing overall S reserves, but S can be highly variable
throughout a field;
therefore, even if a soil test shows moderate to high levels of S, some additional S might be needed to alleviate
For more detailed information on nutrient inputs for canola, refer to the following articles from the Canola Council
Canada: Canola Watch How much fertilizer does canola need? and Choose the right placement for nitrogen and phosphorus fertilizer applications.
Fertility management after a challenging growing season
The severe drought in June through July 2021 decimated canola yields, which were down by 40.2% from yields in 2020,
despite a larger harvested area due to optimistic spring projections.3 Low yields may leave soil nutrient
higher than expected. With some farmers realizing only around half of their expected yields in 2021, the question for
the following growing season becomes: What nutrient credits may remain in the soil from last year?
A soil test is particularly important after an “off” year, when typical crop nutrient removal rates are unreliable.
soil tests were not completed last fall, consider testing in early spring. This can help allow for more distribution
previously applied nutrients in the soil and result in more accurate tests after a dry year.
Another option is to estimate nutrient removal based on canola yield. While this method is not ideal, it can be used
nutrient maintenance when a soil test is not available. Important caveats are that crop removal rates vary by variety
(for example, high-performance hybrid canola varieties have higher yield potential than open-pollinated traditional
varieties at the same applied nutrient rate4), climate/region, and soil type. This method also does not
losses due to erosion, leaching, etc. Below is a chart with typical nutrient removal rates in western Canada. Refer
crop nutrient removal estimates from your region and last year’s yields to estimate fertilizer inputs.
Table 1. Nutrient removal rates for canola2
|Removal (lb/bu of seed yield)
Also, keep in mind what the previous crop was on a field intended for canola. Fall soil tests have shown higher
year-over-year residual levels of nutrients following one crop versus another. For example, residual N levels in the
fall were higher in wheat stubble versus barley stubble on a year-over-year basis.5
Where can I lower input cost and where should I use a full fertilizer rate?
The simple, less-technical approach to lowering fertilizer inputs is to dial down fertilizer rates in typically
low-yielding sections of the field, such as hilltops and low-lying areas, particularly after a hot, dry year like
where leaching and crop nutrient removal was likely limited.
The opposite strategy applies to high-yielding areas of the field. Vigorously growing, healthy plants take up more
nutrients; therefore, growers may want to increase fertilizer inputs in these field zones. Additionally, average
fertilizer rates used in Canada may not be adequate to keep up with the demand of newer, high-yielding canola
and over time soil reserves may be depleted if fertility is not targeted to yield potential.
Alternatively, farmers may opt to even out nutrient variation in the field by dialing back fertilizer inputs in
high-production areas and increasing it in low-production areas. This helps to synchronize crop growth and maturity
order to simplify fungicide applications and harvest.
How can variable rate technologies help improve nitrogen use efficiency in canola?
Variable rate technologies can help farmers optimize their inputs based on the variation in their
potential, but with much greater accuracy. With the Climate FieldView™ platform, canola farmers can build
management zones throughout their field based on biomass production maps (called scouting layers in
farmers manually set a prescription for N fertilizer depending on what the management zones call for, which is based
their goal, such as maximizing yield potential in their most productive zones or leveling out nutrient variation in
field. Talk to your representative for more information on how FieldView™ can help improve your farming
For more information about manual fertility scripting with FieldView™, please visit
https://support.climate.com/kt#/kA04z000000oPd0CAE/en_CA to learn more.
1 Canola Council of Canada. Choose the right placement for nitrogen and phosphorus fertilizer
Research Hub. https://www.canolacouncil.org/research-blog/choose-the-right-placement-for-nitrogen-and-phosphorus-fertilizer-applications/.
2 Canola Council of Canada. How much fertilizer does canola need? Canola Watch.
3 Statistics Canada. 2021. Production of principal field crops, November 2021.
4 Karamanos, R.E., Goh, T.B., and Poisson, D.P. 2006. Nitrogen, phosphorus, and sulfur fertility of
hybrid canola. Journal
of Plant Nutrition. Vol. 28-7.
5 Agvise Laboratories.
Services and products offered by The Climate Corporation are subject to the customer agreeing to our Terms of
Our services provide estimates or recommendations based on models. These do not guarantee results. Before making
financial, risk management and farming decisions, agronomists, commodities brokers and other service professionals
should be consulted. More information at https://climatefieldview.ca/legal/disclaimer. FieldView® is a registered
trademark of The Climate Corporation. Used under license. Performance may vary from location to location and from
to year, as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple
and years whenever possible and should consider the impacts of these conditions on the grower’s fields.
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