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How to tell if nitrogen is here or gone

How to tell if nitrogen is here or gone
Ask the right questions to determine risk of N loss in corn fields.

How much nitrogen you may have lost if you are in one of the hard-hit areas that received far too much rain recently depends upon when you applied it and what form you applied, says Justin Petrosino. He is an agronomist for Stewart Seeds, Greensburg, and part of Monsanto's Agronomy in Action team that does plot work across the Eastern Corn Belt.

Related: How much nitrogen do you have left in the corn field?

He cites a University of Kentucky study in a recent weekly edition of his Crop Flash newsletter. If you put all of your N on upfront before planting in the first week of May, and it was urea, 75% may already be in the nitrate form and susceptible to loss, he notes.

Stay green? Will this corn stay green, or has enough nitrogen been lost that it will run out of N?

For whatever reason, likely cost and convenience, the use of urea in broadcast applications either before planting or after the crop emerged seems to be on the rise this year.

The loss in this case could be from leaching or denitrification, he says. If you applied a stabilizer with the urea, likely Agrotain, or ESN, a slow-release fertilizer, the rate of conversion to nitrate, which can be lost more easily, may occur at a slower rate.

The same University of Kentucky study indicates that if you applied anhydrous ammonia upfront, again in early May, 65% or more may be in the nitrate form by now. If you used N-serve as a nitrogen stabilizer for this spring application, data says only about 50% may be in the nitrate form.

Related: Get a handle on possible nitrogen loss in corn

In comparison, if you sidedressed with liquid 28% about June 1, around 60% of the N may be in the nitrate form. However, if you sidedressed with anhydrous ammonia, only about 20% might be in the nitrate form- the form most susceptible to loss.

Petrosino's conclusion is that if you have applied all of your N by now, about 50% or more is likely in the nitrate form. That doesn't necessarily result in big losses. But the more that is in nitrate form earlier, and if soils are waterlogged, the higher the odds for losses.

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