Interesting article it reminds me a lot of the work of Authors: Grace Gershuny, Joseph Smillie in their book the soul of the soil. I find much of the article very useful information though I’m not sure it all completely applies to fruit growing as much as vegetables. Kansas is unique in some aspects but in my area nitrogen is an invitation to fireblight. I found the section about zinc fascinating! Thank you for posting the article.
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Thanks for all the great comments!
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Urea needs to be quickly watered or incorporated into the soil because if it lays on the surface it can quickly convert to ammonia gas which is lost to the atmosphere. Once in the soil the ammonia quickly attaches to the CEC of soil clays and organic matter. Then after a matter of days to weeks depending mostly on soil temperature the ammonia is nitrified to nitrate by soil bacteria. Most plants take up nitrate much better than ammonia. One exception being blueberries. Ammonia doesn’t leach out of the soil because it’s attached to soil particles. Nitrate moves with the soil water so can be leached out of the root zone.
After applying anhydrous ammonia in summer the crops I’ve applied it too showed a greening within about one week indicating that at least part was already converted to nitrate.
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Fruitnut,
I have a question for you, if you don’t mind. I was always “scared” if I saw the Urea gone (without much rain) I thought I had lost the N value (to denitrification). I have since spoken w/ another grower, who goes to various seminars, and he said that’s not so. He said even under the most severe conditions here in KS/MO, the KS Extension has done tests that denitrification in the cool spring is pretty minimal (i.e. the most denitrification which could be obtained in tests in our soils was in the low double digits)
It still bothers me that I see the Urea “disappear” but as far as I can tell, the experts say it doesn’t denitrify too much. According to the table in this link, even after 10 days at 90F, the loss is only 20% (of course this wouldn’t resemble spring conditions). The next table shows significant denitrification taking place at a soil pH of 7.5 (10 days). Which is higher pH than our soil.
https://www.extension.umn.edu/agriculture/nutrient-management/nitrogen/fertilizer-urea/
My question is that if you see the Urea disappear, without the required 1/4 to 1/2 inch rain, is it gone? I’ve been told it’s not gone, but laying in the shallowest part of the soil for the next rain to water it down.
Thoughts?
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Another issue to increase denitrification is when it’s applied to mulch and not directly to soil. For peaches I overcome the issues here by using 90 day sulfur coated urea at first growth. Can’t tell how much is wasted but plenty gets to trees and it has been very helpful to sustain vigorous growth. Tends not to release N uniformly through the 90 days I’m told, and probably lets more go the first month, which is good for my purposes. In my nursery, I give one more serving of straight urea about mid-June (when it’s raining) to keep them juiced through summer. Wood is money. Surplus rain we’re having ain’t helping the brix, but my inventory is impressive- double growth this year over last for peach trees and I gave them all the N they needed for max growth.
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I had forgotten about the large effect of soil pH. That’s why we didn’t use urea in west Texas with our pH 7.5 soils.
I’d say that dew or other factors could play a part in the urea pellets melting into the soil surface. The losses aren’t as great as they might appear esp at cool temperature and low soil pH.
The surface losses are from what I’d call volatilization. The urea is split into ammonia that escapes as a gas. Denitrification is a separate process that occurs in wet soils where nitrate is converted to nitrogen gas.
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Thank you.
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I see why you like nitrogen. Pump up those nursery trees so they are worth more money. Very good plan. Then to all that excess growth on orchard trees has to come out. So that keeps you busy pruning half the yr. That’s what I’d do to in your position.
On the other hand I’m sure you realize that commercial producers would rather partition growth to fruit vs wood. That’s why they like dwarfing stock and high density plantings. Those systems are designed to maximize fruit production and minimize excess wood that is just an expense to remove. Over application of nitrogen in such systems would be a bad practice.
Most home growers would rather have smaller trees, less pruning, and more fruit. True some need to get trees above the deer. But that’s a choice people make that has considerable downside. So to be honest if we butt heads about N that’s part of where I’m coming from. You have a pretty unique operation.
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These discussions leave me a bit cold. Sure there is a need for N and other nutrients, but for every inorganic molecule there are hundreds organic molecules waiting to be freed. If you have a thriving biology in the soil, it will do it for you. I think fertilizer should be a capital investment, same for mulch. Apply it once, or twice, then the system is self supporting. Exceptions are container fruits and other relatively rare situations, I am talking field planted trees here. I have completely moved from a chemical picture of soil.
My clients don’t want small trees, most have lots of land and often it is not fenced from deer. I have to have 4’ of trunk before first branches at the majority of sites I work to set up coon and squirrel baffles and keep the fruit and leaves above the deer browse line. It has nothing to do with commercial production, but in much of the country fruit bushes don’t fill the bill for small plantings. Every place I’ve ever lived, trees are better than bushes primarily because of wildlife issues and a lack of love for electric fences.
The nitrogen I apply for established trees is at very low dose.
I like to increase my yields with a splash of quick release N in early spring (or fall), so it’s there when the cells of fruit are dividing and well nourished spur leaves do a better job of nourishing the fruit. Making bigger fruit with more cells shouldn’t reduce their sugar. Most organic N tends to arrive at precisely the wrong time to serve the fruit and serves the wood instead. I use only my own urine for my orchard trees which is one very quick release form of organic N.
The quicker a nursery tree is sized up, the sooner I can sell it and the more likely it will live to be sold. As I said, in the nursery business wood is money and money grows on trees.
I understand what you are doing and why. Big trees are stately. Little trees with a fence are ugly. There’s a place for everything.
I’ve planted home orchards at 7 locations since 1971. Every one used small closely spaced trees. I’ve never had significant deer damage. I won’t be growing fruit at ridiculously close spacings in a greenhouse without that experience. Not only that I have a fig nursery business in the 5ft alleys between my trees. And I spend very little time pruning.
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Some neighbors or mine who raise cattle say urea will go away if not worked inot the dirt or watered in. The mfa and coop dealers will coat the urea, ime not sure what the name of v the coating is, it costs almost nothing and I believe protects it for 7 to 9 days.
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sulfur. That’s the relatively cheap stuff. It protects for longer than that, I believe. In my part of the country it’s easy for home growers to just wait until rain is almost a certainty or is actually happening. The purpose of coated urea is to slow and extend the nitrogen’s affect, unless you are talking about a product I’ve never heard of. The common product corn growers use around here is 90 day.
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