Corn School: 4Rs drive side-dress nitrogen application


It’s been dry and cool in Ontario for most of this spring and those growing conditions impact everything from planting, to weed control, and even nitrogen application.

On this episode of the RealAgriculture Corn School, Ontario Ministry of Agriculture, Food and Rural Affairs soil fertility specialist Colin Elgie shares nitrogen strategy tips for growers as the crop progresses into the side-dress application period.

For Elgie, nitrogen application is driven by the 4Rs — the right source, time, place and rate. When it comes to source, most growers are using UAN, either 28% or 32%, or top-dressing with urea. When choosing the source, it’s really a matter of identifying what works best with the operation, he says.

That choice will also impact the potential for nitrogen loss, and growers really have to understand the source they’re applying, Elgie adds. “Urea especially is very prone to losses from volatilization and if you’ve got urea sitting on the surface, you can lose a lot of that to the atmosphere pretty quick.” UAN, however, is less than half urea so when it sits on the surface, the potential for volatilization is much less. (Story continues after the video.)

Effectively timing application is critical because nitrogen use efficiency can be optimized when growers match availability with the corn crop’s uptake curve. “We know that later on in the season, that crop can pull a lot more nitrogen out of the soil than it can earlier on,” says Elgie. Growers who apply later, closer to the 8-leaf stage, are generally applying more nitrogen when the crop is capable of taking up the nutrient more quickly.

When it comes to placing nitrogen in the soil, Elgie says soil type is a huge consideration. “In real sandy soil, you’ve got a lot higher chance of losses from volatilization as well as leaching.” Heavy clay soils, on the other hand, are a lot more prone to denitrification because these soils, when they get wet, tend to sit for long periods without draining.

Elgie says it’s also important for growers to pay attention to soil pH when planning nitrogen applications. “In high ph soils — high sevens and eights — you can really run into some rapid losses just from the conversion and availability of that nitrogen to turn to ammonia.”

In the video, Elgie discusses various application methods, from knifing in UAN to using Y-drop style applicators to dribble nutrient in the row. He discussed placement depth and the benefits of placing nitrogen along the row versus in the middle of the row, and also digs into the value of using nitrogen stabilizers in a dry year.

How do growers choose the right nitrogen rate? Elgie says source, timing, and placement all play a role in choosing the best rate. Profitability is also a key consideration. “The rate that you’re trying to choose is the most profitable one and that can change from year to year based on economics,” he says, stressing the importance of factoring both nitrogen price and yield potential into the rate decision.

Click here for more Corn School videos.

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