Dry conditions impact fall fertilizer applications

GENESEO, Ill. — Moderate to severe drought conditions across the Corn Belt provided ideal conditions for fast harvest, but it also draws questions about fall fertilizer strategies and tillage if the weather trend continues.

Eric Wilson and Jared Goplen, Wyffels agronomy managers, said the dry fall can impact the ability to seal anhydrous in the ground and cause ineffective tillage. Here’s what they had to say.

On Tillage

Goplen: There has been a fair amount of tillage done, especially starting a month ago when some of the soybean fields started coming off, and even back then there was a lot of large clods. The soils have been fairly dry.

Make sure when you are considering fall tillage that you’re going to be able to knock those clods down in the spring.

There will be some fields we will have to hit twice in the spring, and if you’re fine with that, that’s fine. I realize that tillage needs to get done in some places.

Do whatever you can to keep those clods to a minimum so we’re not dealing with basketball-size clods next spring.

On Anhydrous

Goplen: We’ll definitely emphasize on 50-degree soil temperature and decreasing for applying anhydrous. We’re going to have plenty of time to get this done — even if we get two inches of rain, hopefully, it’s still going to soak in and dry up quick enough. I think we’ll be able to get most of the fall anhydrous and tillage done before freeze-up basically.

I’m not too disappointed that there’s been some anhydrous applied, at least just to see how things are going to work, see if that soil is going to seal.

That gas will either leak out or it will basically stay in the soil and look for water. It needs enough water to bind to and convert into ammonium.

That’s the form we want that ammonium to stay into through the rest of the fall season and ideally until next spring after we plant corn so that nitrogen isn’t moving around and is a little more protected in that ammonium form.

I guess the best way to tell whether or not it’s working is to put the rig in the ground and go out after a couple of minutes and see if you smell it. If you smell it, that gas is seeping out. If you don’t smell it, it’s staying in the soil.

It’s has been working fairly well on the loamier ground. In the little bit heavier clay, if you’re doing tillage it’s causing some basketball-size chunks to come out of the ground.

There’s just too big of cracks and that gas is not being able to seal very well. Sandier soils would be in the same boat where there’s a lot less water sticking around and it’s more likely to seep out, as well.

Wilson: I’ve seen fall applications in some previous years in northern Iowa where we didn’t get the anhydrous band sealed up well, it creeped up, and I was seeing root injury the next spring from fall-applied ammonia. That can be significant.

If it takes off those initial roots, that seedling root system, it really sets those plants back. A lot of times they do pull through, they do make it, but they end up being runt-like plants before they can get the nodal root system established.

On Nitrogen Deficiency

Goplen: One of the other conversations I’ve had a lot this year around nitrogen. It was incredibly wet early. Being incredibly wet early, how much of that nitrogen stuck around?

There are some areas where maybe corn yields were a little disappointing. You maybe do a basal stalk nitrate test or something like that just to see. Nitrogen was deficient, severely deficient in some cases.

I’ve had a lot of conversations leading up to this, even before dry soils, about your nitrogen system and how you can make that more resilient. Let’s say not every acre of your ground is going to take that anhydrous perfectly this fall.

You’re going to lose a little bit. Some of it is going to leak out as gas. Maybe there’s a way next spring you can change your system a little bit, to add a little bit of nitrogen next spring.

An easy target is with a pre. If you’re putting 10, 15 gallons of water on with your pre, maybe use 32% or 28% with that.

So, you can maybe pull back a little bit on your fall nitrogen rate and rely a little more on that spring application. It will even things out and gives you a little more resiliency. It’s kind of like hedging your risk a little bit.

I’ve encouraged guys to think about their system and what makes sense logistically. Logistics will trump agronomy every time.

But if there are ways logistically you can work in a little diversity in your system without adding a bunch of extra headaches or other field passes, I encourage guys to think about that.

Wilson: We spent a tremendous amount of time this summer talking about nitrogen, what we lost and what we were seeing. There were a lot who did supplemental applications.

They decided to split some things up. They made extra applications. They used inhibitors. They used nitrogen stabilizers.

When we get a year like that, the more of those tools or diversity you add to your nitrogen program, the more likely you’re going to be successful when we have a year with above-normal leaching and losses.

If it make sense logistically and you can split nitrogen applications up a little bit, especially if we’re going into the fall, I highly encourage using nitrogen inhibitors, nitrogen stabilizers.

I know they cost money and it might not seem like much, but they add up and they can matter in a year with Mother Nature doesn’t play in our favor to keep the nitrogen in the ground where we need it.

Goplen: I feel like this shouldn’t have to be said, but we’re going to say it anyway — fall urea is always a bad idea. There’s been a handful, not a lot, a couple of fields that I dealt with this summer and fall that did not yield well and it was 100% fall-applied urea.

The problem with that is it converts, it’s in nitrate form really quickly, and that’s just prone to loss. So, we lose a lot more nitrogen with that fall urea. That’s really why I don’t like that practice, no matter where you’re at.

Wilson: It’s near impossible to stabilize urea. When you put urease inhibitors on urea, that’s all they’re inhibiting. They’re inhibiting volatilization. That’s essentially half the urea.

On Dry Fertilizer

Goplen: Unfortunately, the fertilizer quotes have not come down quite as much as we’d like, especially phosphorous — that still seems to have a little higher price tag than what we’d like.

Wilson: Let’s assume 250-bushel corn is what you hauled off this year. This would just be in grain removal. If you take a MAP price of $770 a ton, that would equal 168 pounds of MAP that you would need to put back just for removing 250-bushel corn, which comes out to $65 an acre.

If you also include the potash removal, that would be 105 pounds of potash at $450 a ton and $24 an acre. So, we’re right at $90 an acre, not including application, just for 250-bushel corn removal, which is significant.

You and I know how this goes. Corn prices are down, guys want to make cuts somewhere. I fully understand that process.

Goplen: Hopefully, when prices were good, guys were maybe putting a little more fertilizer out the last few years, thinking of fertility as a bank account to some level.

For the most part up here, phosphorous is out of line a little bit. In most soils, if you’ve done a good job of managing fertility, we could probably pull back a little on the phosphorous rate and we’ll be OK.

If you are trying to trim on the fertilizer bill, maybe trim a little on the phosphorous rate, but keep the potassium rate a little closer to what you were planning. Over the last several years, I’ve seen a lot more potassium deficiency than phosphorous deficiency.

I think most of our soils probably have reasonable levels of phosphorous in soils that are in that optimum or high category and you’re still putting something out there, those you probably can trim a little on the phosphorous rate and be just fine. We tend to see potassium deficiency in dry conditions.

Wilson: Potash — in particular, potassium — is really critical to mitigating a lot of plant stress. When we have stalk integrity issues, when we have dry soil conditions or drought issues, potassium is really important to help that crop get through that situation from a physiological standpoint. It’s not something I want to be short on.

It’s not that phosphate is less important. That’s not what we’re saying here at all. It’s just that phosphate tends to come back in a lot better shape on the soil test that we have been looking at broadly.

Having up-to-date soil tests is going to let you be a lot more dangerous in what you can do in terms of dry fertilizer rates. But if we’re just throwing a dart at a blank board and trying to make a guess, my guess is your phosphate is probably OK and your potash is probably quite low.