May 22, 2022

High costs spotlight nitrogen quandary

BLOOMINGTON, Ill. — Nitrogen provides the fuel to feed the corn plant’s engine and meeting that need efficiently is at the forefront, particularly this year with price spikes and supply concerns.

Nitrogen application timing, rate and source during the current cost and supply challenges were among the topics covered by Emerson Nafziger, University of Illinois professor emeritus, in an Illinois Fertilizer and Chemical Association-hosted webinar.

Here’s what the crop production specialist had to say about nitrogen management.

On MRTN

A maximum return to nitrogen calculator is available on the IFCA website, www.ifca.com. The current price for natural gas — primary feed stock for ammonia production — is about twice what it was a year ago.

Supply chain issues are making prices and availability more uncertain than usual. The 2022 corn price is currently projected at $5 per bushel, down from the $5.25 average for all of 2021.

We do know that the MRTN calculator value that we use is not perfect. Perfect would mean when you put that amount on you’re absolutely certain that it’s exactly the right amount for that field.

The conundrum we’re in with MRTN is anything that’s based on previous data is never going to be perfect because every field would have to act just like this field or that field. It’s tough to predict the nitrogen need of the crop and we can predict the soil N supply.

No two N rate trials are exactly alike, so having the MRTN based on data from previous trials means that it can’t give a perfect prediction for a given field in a given year.

It is, though, the best guess we have. And I would put that statement up against anybody that wants to come up with a better way to do it.

Our approach is let’s get a bunch of trials together and see what they say we would have needed, knowing at the time that it’s never going to be a perfect prediction.

On Fall Versus Spring

The uncertainty about prices is a real issue, but those uncertainties are not going to develop next spring. They’re already here.

Dan Schaefer, IFCA director of nutrient stewardship, did 17 trials comparing fall and spring applied anhydrous at the same set of rates. The timings were side-by-side and rates were the main plot and here are his findings:

• Yields at the optimum rate were identical — 237.7 bushels per acre for fall applied and 237.8 bushels per acre for spring-applied N.

• The optimum N rate was 211 pounds per acre for fall-applied and 194 pounds per acre for spring-applied N.

• The difference — 17 pounds of N — is in the vicinity of what has been found in tile-drainage comparisons; more loss from fall- than spring-applied. We think much of 17 pounds is probably accounted for by what came out the tile lines from fall application compared to spring.

So, it’s a good source, obviously, we can get yields from fall-applied nitrogen, it probably is going to take more nitrogen to get that, not very much more, but still don’t get wild and put on 40 more pounds on in the fall.

There are going to be years when the difference is larger and there will probably be years when it’s smaller, depending on how the fall, winter and early spring go.

On Fall N Application

There is anhydrous available, but the consistency of supply as applications gets underway is not known. Anhydrous prices continue to rise, which should decrease the application rate some.

Applications should be done under drier conditions. Mudding-in anhydrous in the fall is not advised.

Soil temperatures need to get to 50 degrees and headed down at the time of application to keep most of the N in ammonium form through early spring.

It is recommended to use a nitrification inhibitor when nitrogen is applied in the fall.

If anhydrous ammonia cannot be applied this fall, applying next spring remains a viable option, but that may mean more uncertainty in nitrogen supply and price.

We got almost no anhydrous put on in the fall of 2009. We don’t like that. Suppliers don’t like that. Nobody likes that. It’s a problem logistically in the spring, but we can get it done.

On Partial Rates In Fall

Applying half or so of the full rate in the fall is a way to limit potential loss, but carries extra costs — applications, labeled rates of nitrification inhibitor.

It might be a reasonable option for a partial application of N, if done properly, if there’s supply this fall, but not for sure — time, amount or form — next spring. If we can put 100 pounds on the fall should we do that? I think if the opportunity exists and we signed up for nitrogen at a reasonable price.

A fall application does more or less commit the field to grow corn for next spring.

Tom Doran

Tom Doran

Field Editor