Potassium powers soybean yield. Nitrogen and phosphorus make key contributions and then there are the micros like sulphur and boron that pitch in and help.
How much of these nutrients should growers apply in 2022 to optimize their soybean acres? How do you navigate the challenge of skyrocketing fertilizer prices and availability versus lucrative market prices for the oilseed crop?
To answer those questions, why not start with the soil test values for the intended soybean fields. That’s what Ontario Ministry of Agriculture, Food and Rural Affairs soybean specialist Horst Bohner is telling growers this spring. “It’s a great indicator of whether or not you can expect a response” to your fertilizer investment, he says.
For the past two years, Bohner has been conducting fertilizer trials to determine soybean yield response in poor soil testing fields (P= 12 ppm, K=98 ppm) and good soil testing fields (P=22 ppm, K=153 ppm). On this episode of RealAgriculture’s Soybean School, he shares his data and why he recommends growers consider not applying fertilizer this year in fields that have good fertility levels. (Story continues after the video.)
Key to Bohner’s rationale is the yield response he’s seen in his trials. Poor testing soils have shown a significant yield bump: 51.6 bu/ac for the untreated check versus 58.7 bu/ac for Aspire + MESZ +KMAG (83 lb/ac + 45 lb/ac + 100 lb). That’s a 7.1 bu/ac yield bump.
But when it comes to fertilizing the good soil testing field, the yield response to all treatments falls apart — the best response Bohner could achieve was 2.7 bu/ac.
“If I had a lot of acres to manage this year, and I had been able to build the soil to a reasonable level the last few years, I wouldn’t put down any fertilizer,” says Bohner. “Let’s focus on other stuff and make some money. We’ve got some good selling prices. Don’t spend it on fertilizer if you don’t need to if your soil test is in a good place.”
To further illustrate his point, Bohner compares the untreated checks of both poor and good testing soils. With no fertilizer applied, the poor soil average was 51.6 bu/ac compared to 63.5 bu/ac for the good soils — a whopping 12 bu/ac advantage.
Bohner also discusses the need to revamp and overhaul Ontario fertilizer recommendations, given these research insights. “To say that you should only fertilize for the [current] year is fine for nutrients like nitrogen, but for nutrients like phosphorus and potassium, it’s just not good enough.
“This year really shows that you should put on fertilizer when prices are low to build your soil… and in a year like this, do nothing. You’ll be further ahead, I’m sure of that.”
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