URBANA, Ill. — Running out of nitrogen is often seen as the most limiting factor for corn yield. This really isn’t the case. Todd Gleason has more from the University of Illinois.
More often than not farmers worry, especially during years with wet springs, that the corn crop won’t have enough nitrogen to maximize yield. There are two problems in that scenario. The first is that maximizing yield shouldn’t be the goal. It should be optimizing the yield. In this case that’s figured economically. Secondly, if the optimal amount of nitrogen fertilizer is applied, it doesn’t generally run out says University of Illinois Agronomist Emerson Nafziger.
Nafziger: Most of the time in our field nitrogen is not the limiting factor. The problem with this idea is that the crop takes up the amount in the soil in addition to the amount of fertilizer we put on. In our better seasons, like 2016 where we never really had loss conditions in the soil, we know that our crop often had a hundred pounds of nitrogen, at least, coming from the soil. I’m not sure 2017 will be much different than that.
That’s a hundred pounds on central Illinois soils. Calculating the optimum rate, then, might take less N than expected. Farmers can find that number by searching Google for the N-Rate Calculator. Numbers can be generated for seven corn belt states.
Nafziger: If you ran the calculator for corn following soybean for fall anhydrous application in central Illinois, we be in about the 175 pound range. We also put a range in there and people should pay attention to that. It might say 175, but the most profitable range is going to given right below that number. It might say 160 to 190. And you the farmer might say, “You mean we can choose? Let’s just choose the high one.”
You could, says Nafziger, but the whole of the 30 pound range is within one-dollar of the maximum projected return per acre for the corn crop. This is because the optimal rate of nitrogen application curve is very flat at the top.
Let me say that again. The N-Rate calculator produces an application rate optimized to generate the maximum return per acre. The whole of the projected range is within a dollar of the maximum.
— Emerson Nafziger, Extension Agronomist – University of Illinois
Todd Gleason, Farm Broadcaster
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