# Nitrogen carry over



## rjmoses (Apr 4, 2010)

In the shower this, where I do some of my better thinking, I had an idea/question.

I've been wanting to change my OG fertilizer program to see if I could get a better yield, especially on the second and third cuttings. This year, I knifed in 28% on two of my fields at 30 lbs/ac after my first cutting and was fairly pleased with the results. (I couldn't get enough AMS even though I had pre-bought it; no urea available.) Those fields did much better than the fields where I applied AMS. I made one pass with 30" centers on the knives and it was noticeable but after a while, it seemed that the 28% migrated to the fill in between knife centers.

Normally, I apply approximately 140-150 lbs urea in late February for spring green-up. I then follow up with AMS after the first cutting. Besides being tricky to get get it timed right so that the urea and AMS get rained in, I feel that my nitrogen losses due to sublimation might be significant.

So I got to thinking: What if I knifed in 28% in the fall (mid-to-late October) in two half-rate passes? A lot of people hereabouts are doing fall application of anhydrous for their corn without significant losses.

My questions are: Would the 28% carry over like anhydrous? Any ideas how to measure losses? Would 28% work the same as anhydrous? Soil type in mostly clay, so I don't think leeching would be much of a problem as long as I stay above the top hardpan layer.

Any thoughts?

Ralph


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## swall01 (Jun 10, 2018)

rjmoses said:


> In the shower this, where I do some of my better thinking, I had an idea/question.
> 
> I've been wanting to change my OG fertilizer program to see if I could get a better yield, especially on the second and third cuttings. This year, I knifed in 28% on two of my fields at 30 lbs/ac after my first cutting and was fairly pleased with the results. (I couldn't get enough AMS even though I had pre-bought it; no urea available.) Those fields did much better than the fields where I applied AMS. I made one pass with 30" centers on the knives and it was noticeable but after a while, it seemed that the 28% migrated to the fill in between knife centers.
> 
> ...


I had been seeing really poor results with broadcast urea on my coastal, switched to ammonium sulfate this year. putting out 60 units (after every cut) and getting higher yield better quality hay than using 100 units of urea in years past. i think the urea just evaporates too fast, both in the field and on the yard at the fertilizer dealer.


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## Gearclash (Nov 25, 2010)

> So I got to thinking: What if I knifed in 28% in the fall (mid-to-late October) in two half-rate passes? A lot of people hereabouts are doing fall application of anhydrous for their corn without significant losses.


One thing to consider I that corn typically grows much deeper roots than what we think of as grasses. There are many operators applying NH3 for the next year corn crop in the fall here, but there is a growing minority who put no N on in the fall and maybe not even in the early spring, preferring to side dress most or all of the N on once and sometimes twice during the growing season. If grass has shallower roots than corn would not the "spoon feeding" approach be even more beneficial?


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## VA Haymaker (Jul 1, 2014)

IMHO a good way to add fall nitrogen is with fall phosphorus application using DAP 18-46-00

Per UGA, fall nitrogen promotes tillering.

Good luck,
Bill


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## r82230 (Mar 1, 2016)

Spoon feeding as Gear mentions sounds the best.

I'm wondering if you could dribble 28%, say at 15" centers (in spring, after cutting, etc.). I be experimenting I guess. :huh: In MY area, grasses like the potash in the fall, the N during the growing season. Doesn't grass take nitrogen and carbon (from air) and convert to starches/sugars (similar to other green growing plants).

One thing is that you are not getting any sulfur with the 28% solution, might be a consideration. At least it is something that I have found that I need to be conscious of with my hay fields. YMMV

My one cent at it's best today, after all you ask for thoughts (good thing you didn't ask for smart ones, at least from me ).

Larry


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## mlappin (Jun 25, 2009)

We added AMS to our fertilizer program on the older fields that tend to be more grass than alfalfa, definitely seen an improvement over the old standard or slight deviation of 6-15-40. Whether its the extra nitrogen or the sulfur thats helping is up in the air atm.


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## vhaby (Dec 30, 2009)

Anhydrous ammonia is all ammonia (NH3) . When knifed into soil, the ammonia most often attaches to one of the hydrogens on water (HOH) to form ammonium hydroxide (NH4OH) that has a basic reaction resulting in a pH increase. The ammonia can also attach to a hydrogen on soil clay where it will exist as ammonium (NH4). Under the right conditions such as warm moist soils, bacterial will begin converting the ammonium to nitrite and then to nitrate that can be leached downward in the soil. Producers who apply anhydrous ammonia in fall and expect the nitrogen to be available for spring-planted crops need to wait to apply it until the soil becomes sufficiently cool to slow or even stop bacterial activity, thus preventing the conversion of ammonium to nitrate.

The question in the initial post was whether banded 28% liquid N in the fall would still be available for spring crops. The 28% N is a diluted version of urea ammonium nitrate (UAN, 32% N). UAN is half ammonium nitrate. The nitrate part of the ammonium nitrate is immediately leachable. So, even if the 28% N is applied to soils that are sufficiently cold to slow or prevent bacterial activity from converting the ammonium portion of the 28% UAN solution, the nitrate portion of the 28% N can be lost to leaching or even by denitrification (conversion of nitrate to a gas) during rainy winter months.

So the simple answer is that 28% N solution banded in fall will lose some of the applied nitrogen making it not all be available for crops the next spring.


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## rjmoses (Apr 4, 2010)

vhaby said:


> So the simple answer is that 28% N solution banded in fall will lose some of the applied nitrogen making it not all be available for crops the next spring.


Thank you. I hadn't thought about the conversion process.

Ralph


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