Soybean harvest in Ontario is wrapping up as growers roll through a 2021 crop that won’t break any records but will deliver solid yields.
The province’s corn crop, however, appears poised to smash the average per-acre yield and be one for the record books. As combines continue to soldier on through November, growers are turning their attention to next year. With fertilizer prices soaring into the stratosphere, many are wondering what will be the most economic 2022 soybean fertilizer strategy as they consider booking their nutrient needs.
On this episode of RealAgriculture’s Soybean School, we contemplate this input cost conundrum with help from Dave Hooker, professor at University of Guelph. He kicks off the conversation by emphasizing the the importance of soil tests in making 2022 nutrient plans for the oilseed crop.
Hooker says growers who have built up background soil test levels to moderate or high levels may be able to ratchet back fertilizer rates and draw on the fertilizer bank they have built. With soybeans following big corn yields in many fields, he notes that it’s important to take a close look at nutrient removal rates when determining phosphorous and potassium application rates.
Based on general guidelines, soil test P drops one part per million (ppm) for every 30 lbs removed per acre. For K, soil test levels drops 1 ppm for every 15 lbs removed. So what happens when a grower harvests 250 bu/ac corn off the field in 2021? If no fertilizer is added, P will drop 3 ppm and K will see a 5 ppm reduction. (Story continues after the video.)
“If you already have your soil test P and K levels fairly high, in the moderate category, perhaps you can afford to drop three or five parts per million,” says Hooker. “But if your soil test P and K levels are fairly low in the first place you just can’t afford to not apply fertilizer.” In this case, growers need to at least apply fertilizer based on OMAFRA recommended rates. “You really need to know soil test levels and apply fertilizer accordingly,” adds Hooker.
In the video, Hooker also taps into long-term P and K trials at Ridgetown College to offer advice on fertilizer sufficiency strategies for soybeans. Again, growers need to look closely at soil tests. When soil test results are low for P and K, Hooker’s data shows a 6-28-28 starter fertilizer (at 90 – 100 lbs/ac) can increase yield by up to 5 bu/ac, but in moderate testing soils there is little to no response.
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