Story Posted: October 19, 2011

Is your canola getting enough food?

Fall soil tests of fields that were in canola in 2011 will tell you how much nutrients are left, and hint at whether the crop ran out of gas. This information, along with the soil test results from fields planned for canola next year, can help set fertilizer rates for 2012.

New canola hybrids, improved management practices and better equipment can all contribute to higher canola yields over time. The key question for growers is: Has your fertility program increased over the past five years to take advantage of this higher potential?

"It pays for growers to re-evaluate their fertilizer rates at least once every three or four years," says Dan Orchard, Canola Council of Canada agronomy specialist. "The most economical fertilizer rate will vary by region and soil type, and growers have an idea what the best rates are for their farm, but those rates can and will change."

Growers may discover they can achieve higher yields and higher profits by increasing their fertilizer rates by 10% or even 25%, he says. An agronomy survey of over 1,000 producers across the Prairies in 2009 showed that growers achieving the top 40% of yields were applying 24% more nitrogen, 17% more phosphorus and 32% more sulphur, on average, than those whose canola was yielding in the bottom 40%.

Information gathered from soil nutrient analysis is an important step in setting fertility rates. Soil labs provide fertilizer rate recommendations based on several factors, including available nutrient levels from soil tests, crop rotation, soil type and historic yields. Growers can use these results to determine if the fertilizer rates they have been applying are in line with current industry recommendations, even if they don't follow them exactly.

"Growers who haven't updated their fertilizer rates for a few years may see the recommendations and be encouraged to try higher rates on some of their acres to compare yield and returns," Orchard says.

Fall is a good time to do soil tests. Growers may have an extra few hours to take samples, unlike in spring. And with results and recommendations in hand before winter, growers have more time to plan their fertilizer programs for 2012, to order fertilizer, and to take advantage of typically lower fall fertilizer prices.

The ideal time is to take samples when soil temperatures drop below 7 C. Because microbial processes in the soil slow down as temperatures cool, sampling late in the fall will provide a better indication of what nutrient levels will be next spring.

Fall soil tests can also indicate whether this year's crop had the available nutrients needed to reach its economic potential. "For example, if soil nitrogen reserves are drained in fields that were in canola in 2011, this suggests that the canola crop could have used more nitrogen and perhaps achieved higher yields and higher profits," Orchard says. If actual yields in those fields were also less than expected based on crop condition, this is another indicator that nutrient shortage may have been a factor.

As a general rule, if soil test results show available nitrate-N to be less than 10 pounds per acre, then the crop may have needed more nitrogen for a greater yield. If results are between 10 and 20 pounds, the crop probably had adequate nitrogen. And if a field ended the season with more than 20 pounds of available nitrogen per acre, excess nitrogen may have been applied in that year.

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