Controlled-release nitrogen deserves a look in upper Michigan, too

Corn (silage and grain), hay and pasture, and small grains could benefit from more available later-season nitrogen (N).

The potential benefits of using controlled-release nitrogen fertilizer, such as ESN (44 percent nitrogen encapsulated in polymer), include reduced potential for nitrogen leaching in coarse-textured soils and a more uniform supply of nitrogen for developing plants throughout the entire growing season. Of course, the controlled-release product costs more, about $0.25 per pound of nitrogen.

Many livestock and dairy producers growing corn have quite different situations than cash crop producers. Most corn in upper Michigan is grown on dairy or beef farms and often receives significant applications of manure. This corn is not commonly sidedressed with nitrogen. That leads to the question, “If lots of manure is present and releasing nitrogen throughout the season, then are the benefits of more costly controlled-release nitrogen reduced?” Where nitrogen fertilizer is needed in addition to manure, controlled-release nitrogen fertilizer may reduce leaching potential and should provide a more consistent supply of N through the season. But will it pay?

Topdressing grassy hay or pasture fields with controlled-release nitrogen could result in more consistent growth throughout the season. This may be a real benefit for pastures on sandier sites, depending on the year. ESN release is based on temperature, not soil moisture. Therefore, cool years may be too cool for uniform release. However, polymer-coated N products still require water in order for the N to release. For example, if a drought situation is encountered soon after application, the nitrogen contained within the polymer-coated fertilizer prills may not release or may not release in an orderly pattern. Many grass hay fields in northern Michigan are harvested only once per year and plain urea is probably a good choice since it should maximize early grass growth at less expense.

For wheat, oats or other small grains, controlled-release nitrogen fertilizer on sandier soils makes a lot of sense. The need for nitrogen at time of grain fill coincides with the highest likelihood that urea applied earlier in the season has undergone losses from leaching or denitrification. Research has shown that split applications of spring nitrogen on wheat improves yield in certain years. Heavy rainfall early in the season favors split application. Dry conditions following the last application would work against the option of split application. Using controlled-release nitrogen could accomplish the same thing as a split application without the risks involved. Be aware that polymer-coated urea tends to “float” during heavy rains and can move with water during significant rain events. Research data indicates that the most benefit comes with incorporation of controlled-release nitrogen fertilizer.

Finally, soil type must be a big consideration. Clay soils that predominate in the eastern and western ends of the Upper Peninsula hold onto nitrogen better than sandier soils, reducing the potential benefit of controlled-release nitrogen fertilizers compared to plain urea. And of course, the improvement in yield must at least match the extra cost of controlled-release nitrogen. Only experience gained over time by farmers and researchers in northern Michigan will provide an answer for that. Michigan State University soil scientist Dr. Kurt Steinke is currently conducting experimental trials with ESN including several variables. Results will be shared as they become available.

Refer to MSU Extension’s George Silva’s earlier article “Slow release nitrogen fertilizers” for more information.

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