'New era' for N Management

Last year, MFA took on a major field study to evaluate sidedress application of nitrogen on corn and some new nitrogen rate decision tools. Now that the results are in, I have been speaking about it regularly at many of our training meetings. Whenever I bring up the topic of sidedressing—especially when I talk about waiting until plants are knee-high to do it—a murmur starts somewhere in the back of the room and sweeps forward. I see people shifting nervously in their seats, anxious about the big “what if?” What if I don’t get the N on in time? What if the corn gets too tall? What if I stress the corn by waiting that long to sidedress?

Even with the big “what ifs,” our 2016 study gives us a big reason to re-evaluate the way we manage N for our corn crop.

The amount of N we need to raise a corn crop varies tremendously from year to year and from one end of the field to the other. In my presentations, I refer to a couple of university studies that show variations of 100 pounds per acre in rates needed for optimum yield. In early July, if you were to walk through fields that have a flat rate of 160 pounds of nitrogen applied, you’d likely find sections showing nitrogen stress that probably never had the potential to yield 140 bushels per acre. You’d see other areas that are dark green and beautiful that will end up yielding 200-plus bushels per acre.

Why do we have such variations? Really, it comes down to two things: water and soil. Nitrogen loss is controlled by the amount and timing of the water we receive from the time N is applied until corn takes it up. Soil properties control how much N our organic matter will provide and the predominant pathways for N loss. Rainfall fluctuates from year to year and drives our overall N rate variation, while the soil affects the in-field variability.

In the past, it has been difficult to quantify and predict these changes, so we’ve used the “better safe than sorry” rule. Based on local conditions and experience, we’ve learned that if we apply “X” amount of nitrogen (insert your favorite rate here), everything will be OK. This works great 80 percent of the time. We have plenty of N, and we make a good crop. However, that also means many years we apply more N than we really needed, and sometimes we run out of N at a critical time and yields suffer.

Research and development into N management is starting to pay off. Today, several services are available to better define our N needs. During the 2016 season, MFA compared three different nitrogen management tools (NVisionAg, Climate FieldView Pro and Adapt-N) head-to-head on 1,700 acres across our trade territory. The results were surprising. Overall these tools performed admirably well, with yield differences among all the programs and the check strip falling well within the margin of error.

All three programs recommended N rates much lower than I was comfortable with, but I was astonished at the results. One field made 240 bushels per acre on a 160-pound average N rate. But we must consider that many areas had almost perfect conditions for nitrogen last year. Early-season weather was warm and dry, which encouraged mineralization and minimized losses. Then we had moisture late in the season when the crop needed it. Overall the tools we tested were able to recognize the low N need, and when we applied accordingly, we were able to see a significant savings in our N costs.

I don’t expect those savings every year. In fact, we’re more likely to make money with the programs by improving our yields when we have a wet spring and have seen large N losses.

However, there is a catch with these programs. They all work better the farther we get into the season because water plays such a big part in determining how much N we need. The more we know about the seasonal rainfall pattern, the better the tools can predict what we need in post application. In last year’s study, we targeted corn at the V8 growth stage for sidedress application, which put us right at the edge of rapid plant uptake of N.

We also have to leave room for the tools to save us money, which means using low rates in pre-emergent applications. In our trials, we applied no more than 100 pounds of N before sidedress. This can lead to a tense June if weather conditions don’t allow for sidedressing, but high-clearance spreaders and airplanes are available in many areas to help extend the season.

Is it worth the risk? I think there are opportunities to save money and increase yield with these tools. With their performance last year, I am convinced we are on the brink of a new era for N management.

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