Do starter and pop-up fertilizers make a significant impact on soybean performance compared to just broadcasting the crops’ nutrient needs?
That’s a question Ontario Ministry of Agriculture, Food and Rural Affairs soybean specialist Horst Bohner has been asked by many growers during the winter months. He says when soybeans first entered Ontario in the 1960s, and through to the 1990s, researchers saw little response to using a starter or a pop-up. A better understanding of the oilseed’s yield potential, however, now has the soybean researcher and growers looking for ways to better feed the crop and drive higher yield.
On this episode of the RealAgriculture Soybean School, Bohner shares research, theories and thoughts on nitrogen, phosphorus, potassium and sulphur, whether they belong in pop-up or starter, and what we we know about effective rates.
To explore the topics, Bohner notes it’s important to define some terms. He describes pop-up as fertilizer placed in-furrow, close to touching the seed; he says most people would describe a starter as some form of a 2 x 2 band with variable fertilizer rates — it could be as high as half the rate of crop removal. (Story continues after the video.)
Before growers make the choice to feed soybeans pop-up or in-furrow, Bohner says it’s critical to understand the risks of placing fertilizer with or near the seed. “Generally, in the soybean world, we say that you should have no potassium at all in-furrow because of that salt index,” says Bohner. “So when we talk about in-furrow, we talk about a little bit of N and P being okay because we want that growth to get going, but we keep K right out of it.” Both in-furrow and bands have limits based on soil type and growing conditions, he adds.
Where sulphur fits in early-season fertility is a question still up for debate. U.S. research indicates it could play a role in optimizing soybean production when planting early, but Bohner says he hasn’t seen evidence of that in Ontario. He’s planning research trials this year to gain a clearer picture.
When it comes to nitrogen, the goal is to support fast, early-season growth and help close the canopy as quickly as possible to take advantage of better quality July light. But Bohner says trial data has only identified a 2.3 bu/ac advantage for starter nitrogen and he questions whether that provides a worthwhile return for growers.
When it comes to phosphorus, Bohner notes the tremendous impact the nutrient can have on root growth. Soybeans, however use very little phosphorus early in the season compared to other crops. “Wheat uses 15 pounds, corn four pounds and soybeans only one pound per acre in the first 30 days of life.”
Logically, soybeans shouldn’t need as much phosphorus and Bohner has the data to support the claim. “We’ve done these trials. We applied 50 pounds of MAP in-furrow, and on average, our response across 16 sites was only 1.4 bushels.”
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