Glenn Longabaugh won’t tell you not to put zinc on crops. However, he will tell you there are likely other nutrients to look at first in your soil fertility program before worrying about zinc.

“You need to take care of the big items first,” says Longabaugh, an agronomist for WinField United. “Those include nitrogen and potassium. If you don’t have enough of those, you will really give up yield quickly. If you give up yield, you give up profit potential.”

Here are three tips from Longabaugh that could help you achieve as much profit as possible.

1. P levels tend to be satisfactory in Indiana. When agronomists pull plant samples and a lab runs tissue tests, if the sample came from Indiana, odds are it won’t be limiting in phosphorus, Longabaugh reports. Whether it’s because of the age-old practice of applying 6-24-24 for decades or some other factor, most Indiana soils have acceptable to high levels of P. This is typically reflected in adequate phosphorus levels in plants, as determined through tissue testing.

Nevertheless, there are fields that will likely respond to a phosphorus application. If phosphorus tests low in a field or part of a field, then investing in phosphorus could be important.

2. N and K are key during corn's grand growth phase. When corn is shooting from the early stages to waist-high or taller, it’s known as the grand growth stage. That's when lots of nitrogen and potash are required by the plant, Longabaugh says. If there isn’t enough N or K available, the deficiency will show up in leaf sample tests — and potentially in lower yields.

3. Zinc, sulfur and boron are still important for good yields. Longabaugh isn’t saying that there aren’t times when you should apply zinc, sulfur and even boron. In fact, he notes that plant levels of one or more of these nutrients may be lower than optimum at some point during the season. “What I am saying is that this isn’t the first place I would look if I was trying to make sure there weren’t any yield-limiting factors in my soil fertility program," he explains.

Sulfur was hardly ever limiting in the Midwest until a couple of decades ago. However, power plants have cleaned up emissions so much to comply with the Clean Air Act that sulfur can be deficient these days. It’s another secondary nutrient that is needed, especially in corn during the grand growth phase.  

Manganese is a micronutrient that corn plants also need the most during the grand growth phase, Longabaugh continues. Plants need enough zinc later in the season to reach optimum yields.

While you don’t hear much about it, copper is another nutrient corn plants need, typically around the V5 stage.

“The bottom line is very clear, however,” Longabaugh says. “When you’re in the grand growth stage and you’re tissue sampling, don’t be surprised if nitrogen is the limiting factor. It’s important to fix nitrogen first with a mid- or late-season nitrogen application.”