Robert Mullen Nitrogen Quotations

One reason is that the system assumes the soil is a blank medium and devoid of natural nitrogen. We know that's not true. And the problem we run into is that we don't know exactly how much nitrogen is in the soil and how much will be available to the crop. The release of nitrogen is dependent on the weather, so there's always a possibility of adding more or less nitrogen to the soil than is needed.

Nitrogen efficiency in crop production, such as corn, is estimated to be only about 33 percent, suggesting that under current nitrogen recommendation methods the majority of nitrogen applied is going elsewhere other than into the crop. On top of that, it's becoming more of an economic penalty to over-apply nitrogen.

It is intuitive that higher corn yields will result in greater nitrogen demand from the soil, but does that translate into higher nitrogen demand? Investigation of nitrogen rate studies conducted over several years reveals that there is not a strong relationship between maximum yield potential and the amount of nitrogen needed to achieve maximum yield.

Current nitrogen recommendations assume four things: yield potential doesn't vary year after year, the yield level the soil will support without supplemental nitrogen is negligible, pre-plant nitrogen will be available throughout the growing season, and soil uniformity produces similar yield results across the field. Growers know that none of these assumptions are entirely accurate, and they can potentially be avoided using optical sensors.

Farmers may not yet be 100 percent comfortable with the changes, but they understand why it's being done and can see the value in it. All land-grant universities in the North Central region are moving toward a similar basis for generating nitrogen recommendations.

Is it always economical to shoot for maximum yield? Research has shown that it's not. It may take the same amount of nitrogen to reach 179 bushels per acre as it does to only reach 170 bushels per acre. It's impossible to determine at what point the nitrogen level is reached to where it is no longer a benefit to gain more yield without a nitrogen rate trial in every field.

Additionally, how successful a cover crop is established also determines how much nitrogen is captured.

So, utilizing yield potential to dictate nitrogen recommendations may not be the most effective method, especially when nitrogen costs are high. Historically, we've treated excess nitrogen as cheap crop insurance. While it was then, that's not the case anymore.