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Get ready to apply lots of N soon

After a long and cold winter, it feels good to know its mid-March. We all recall last year’s “Mayday snowstorm,” a reminder that spring is a pretty unpredictable season. In agriculture, we have to head into it with plans, backup plans and backups to the backups. I’ll share a few things to think about while we are chomping at the bit getting ready to hit the fields.

Get ready to apply lots of N soon

After a long and cold winter, it feels good to know its mid-March. We all recall last year’s “Mayday snowstorm,” a reminder that spring is a pretty unpredictable season. In agriculture, we have to head into it with plans, backup plans and backups to the backups. I’ll share a few things to think about while we are chomping at the bit getting ready to hit the fields.

A concern right now is getting the rest of our nitrogen applied this spring. We had some good fall NH3 seasons recently; probably averaged getting 50% to 70% of our total N applied in the fall over the last decade or so. Much like last spring, fall 2013 wasn’t so agreeable, and we didn’t get nearly as much work done as we counted on. Now we’re faced with putting a much larger portion of our N on in the spring than we’ve had to do in years.

We’ll need a great early spring to get the N applied in good shape. If we get too many rainy and muddy days, we’ll face many challenges. Pushing the limits with spring NH3 and wet soils can lead to issues like soil compaction, N losses if the knife track doesn’t seal well, and ammonia burn to corn seedlings. This is easier said than done, and is advice coming from a guy who consistently struggles with this attribute: Try to exercise patience and not get the season started off on the wrong foot by pushing to get spring NH3 applied.

We can try to shift to liquid 28% or 32% N sources or dry N sources if NH3 doesn’t work out, but there are significant challenges for those as well:

Price. Dry and liquid N are typically more expensive than NH3. On top of that, if growers prepaid NH3 and end up having to switch, there can be financial penalties on top of just the normal price differences.

Logistics. NH3 is 82% nitrogen, so transport and storage is inherently more efficient than dry (46%) or liquid (28% to 32%). Dry and liquid take more trucks and labor to get them delivered, a potential challenge in a short spring season. As a former retailer, running low or out of N fertilizer in spring (even for just a few hours) was a nightmare for both us and our customers. Retailers do everything in their power to keep inventories full and schedule deliveries, but sometimes there just aren’t enough trucks and trailers.

Availability. If the season is short, pipelines and terminals can be maxed out, leading to shortages of N similar to what we saw with propane this fall and winter. So, while there are alternatives to spring NH3, getting ahold of them may or may not be a challenge. If you can, have a quick discussion about your availability and pricing options on alternative forms of N with your fertilizer dealer ASAP.

Alternative: spring-applied N

Another alternative is to apply N after planting is done. There are several ways to do that if you have to, or you can even plan on it. As we get past the spring rush, often N product shortages are alleviated. While you have a smaller application window, the good news is you may have more flexibility on N products.

In the article below, I explain various spring and sidedress N options, which have pros and cons. I don’t mean to make planning for spring or sidedress application to sound like a bad thing; we just haven’t had to get this much N on in the spring in a long time. If weather cooperates, it will be no big deal. I also don’t want to make it sound like we should always apply as much N as we can in the fall to alleviate this sort of pressure in spring. Fall NH3 certainly has its own set of benefits, challenges and risks as well.

Having been on both sides of the fence, the keys will be communication, cooperation, patience and flexibility. Talk through multiple plans with your fertilizer dealer now so everyone is on the same page later as far as N sources, pricing, availability, ability to switch, application options, equipment and the rest of the long list of details.

McGrath is an ISU Extension field agronomist at Harlan in western Iowa. Contact him at


CSI: Iowa

Application options for spring-applied N

You can spray liquid N mixed with residual herbicides after planting but before the corn comes up. Iowa farmers do a lot of this each year, but sometimes run into challenges. If corn starts emerging before you get the N and herbicides on, talk to your agronomist. Odds are you’ll be shifting gears, since you can have significant crop injury with most herbicides mixed with typical rates of liquid N applied on emerged corn.

I’ve gotten caught on that a time or two; lesson learned. I’ve also learned the hard way that if we don’t get a nice quarter-inch to half-inch rain soon after application, we can lose some of the N — not to mention we need rain for the herbicides, too. Adding a urease inhibitor can slow urea conversion, which provides more time for rainfall to move urea into the soil.

Sidedressing NH3 is another option. While time-consuming, it is one of the most “efficient” ways to supply corn with N. What I mean by efficient is it’s injected into soil so we don’t worry about volatile losses that sometimes occur with surface-applied N. It’s also applied closer to when the corn plant is starting to demand more N, so risk of N loss to denitrification and leaching is reduced.

Sidedress injection of liquid N is also very efficient, but keep in mind that N costs per pound are higher than for NH3. On the other hand, some farmers point out they can handle and inject liquid N faster and easier than NH3, so that can narrow the efficiency gap depending on equipment you have access to use.

In the region of Iowa where I work most of the time, areas where long, straight rows are few and far between, you must carefully weigh the amount of time sidedress N can take compared to the small window you have for application. I don’t want to oversell the glory of sidedress and then have farmers irked as they’re dialing for a high-clearance rig, plane or helicopter to get their N on. I learned that lesson the hard way in 1993.

You can also “dribble” liquid N on rather than inject it during sidedress time, if you can access the equipment. While risk of volatile loss is lower than broadcast liquid N, there is still some risk, and we still need rain to get the N into the root zone.

A dry idea

Another option, one that’s becoming more common each year, is broadcasting dry N over emerged corn. There are three forms I see used: ammonium sulfate, ammonium nitrate (getting very hard to source) and urea. The most popular is probably urea with one of the urease inhibitors. Ammonium sulfate isn’t prone to volatile loss, but is usually more expensive per pound of N than urea.

You can lose significant amounts of N if urea doesn’t get that quarter-inch to half-inch of rain to move it into the soil profile; that explains the popularity of urease inhibitors. They aren’t a cure-all, but can buy you some time. A big advantage to post-applied dry N is many retailers have equipment to do it, either dry carts you can use (in small corn) or custom application with a row-crop rig with a dry box on it that can run in fairly tall corn depending on the setup. It’s relatively fast and opens the window a little wider than injection.

But no matter what dry N source you use, you need a rain to get it to the corn.

— Clarke McGrath

This article published in the March, 2014 edition of WALLACES FARMER.

All rights reserved. Copyright Farm Progress Cos. 2014.

Nutrient Management

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