Nitrogen as Ammonia vs Urea

[turnyface]

For those using chemical fertilizers and 100% inorganic soil.

Does it matter if the nitrogen comes from ammonia versus urea? I've read on here that it takes time for the urea to breakdown (days) into usable nitrogen and if watering daily, which I do in the summer, the urea based nitrogen would simply wash out before becoming usable. Essentially, I'm not getting the nitrogen amount from Miracle-Gro I think I'm giving my trees.

One comment here, but I've seen this around the site in other places as well:

Post in thread 'Best Fertilizer For Growth?'

Jan 14, 2019

One other thing I consider when looking at ferts is the amount of nitrogen available as ammonia or ammonium salts, vs nitrogen as urea. Urea needs to break down to become available for plants but ammonia does not. With my mostly inorganic soil mix I'm assuming my fertilizer doesn't hang around all that long, and the urea may not get a chance to break down.. So, I prefer nitrogen as ammonia rather than urea.

• BrianBay9

Would it make sense to use orchid fertilizer where there is no urea based nitrogen? Or maybe switch to organic fertilizer instead?

Orchid Plus

Better-Gro® Orchid Plus® plant food is a urea-free, professionally formulated plant food, containing fast-acting nitrate nitrogen – the key component to enhancing vigorous growth in orchids.

www.better-gro.com

 

[Glaucus]

Urea causes pH fluctuations. So the general idea is that when growing in substrate, to not use urea. This because soilless media cannot buffer those fluctuations as well as potted plants in soil. Urea is ideal for full ground. It is also the cheapest nitrogen form, I believe.
Urea is also ideal for foliar feeding, but I forgot why. Nitrate is usually considered as the easiest form of nitrogen to take up for potted plants. Many chemical fertilizers are nitrate only, no ammonia. Ammonia acidifies the soil while nitrate does the opposite. I believe nitrate is also easier to leach out of the soil. Ammonia hangs around a tad bit longer. All forms of nitrogen go back to the atmosphere eventually. While PK stay in the soil.

 

[nuttiest]

I use humic coated urea twice a year and it definitely seems to have advantage over ammonium, even in pumice in training pots. Results in 3 days means it doesn't take that long. I don't use it when there is daily water required, so I don't know how long it would last.

 

[turnyface]

I think I'm going with this "orchid" fertilizer alone with some homemade Espoma planttone organic cakes.

Amazon.com : msu orchid fertilizer 13-3-15

 

[Deep Sea Diver]

Honestly, we’ve tried a number of organic and inorganic fertilizers over the years. Spent a good deal of time poring over ingredients and their effects.

In the past year and a half at the museum we are even testing Ryan Neal’s fertilization plan. While at home we are using a mix of organic and inorganic fertilizers and supplements.

The biggest issues we’ve discovered is the organic fertilizers, both solid and liquid, tend to gunk up the media fairly quickly compared to inorganic fertilizers. Thus soji or surface preparation is required more frequently than when using inorganic alone.

Organic fertilizers can also be deficient in trace elements, causing interesting effects…also attract varmints and gunk up hard surfaces, making these slippery.

Inorganic fertilizers can damage the roots if one doesn’t have the quantities dialed in. We use the effects on our finest rooted plants, azaleas, as a guide to acceptable quantities and timing for liquid fertilization. Solid fertilizer quantities and timing is by tree group. One could say this is simplistic and I would agree, yet it works really well in practice.

Red tinged tips on azalea leaves. Normally one would see this with hotter, sunnier weather. Over fertilization often looks darker. However slight over fertilization might look similar.

Imho The issue with azaleas is there are quite a number of cultivars. Thousands. Each cultivar group can react differently, while sports within a group also vary, yet normally less. However the experts say the newer cultivars tend to be weaker overall. Not sure we’ve seen this, yet differ to the experts on this one.

Cheers
DSD sends

 

[Glaucus]

Are you growing orchids? Is there a special issue with orchids and urea? @Leo in N E Illinois should know even more about this.

Seems both are good chemical fertilizers to use. But make sure to keep the dosage appropriately low. Better to apply it at a low safe dose several times.


Ah yeah there is also a possible issue with urea that it doesn't bind to substrate particles because it has no charge. A lot of fertilizer could immediately wash out from substrate, even if it is charged. But with urea not being charged, that could be even more significant. But I am not sure. In horticulture they usually recycle the runoff and use it again, so they wouldn't care that much about this aspect of urea. But more about the pH effect.
Plants can and will take up urea directly, though. How much urea gets taken up directly or how much in HN4+ after being broken down, I have nu clue. When applying urea to farm fields, they even add an unease-inhibitor to prevent breakdown into HN4+ and prevent ammonia pollution. Urea is also not measured by an EC meter. So for ppm determination though electric conductivity, the urea is ignored. But it does have an osmotic potential on the roots.

So yes, urea fertilizers should be avoided for bonsai.

 

[Glaucus]

Another thing is that fertilizers high in ammonium can make it harder for the plants to take up other positively charged ions, like calcium or potassium. Nitrate is the easy fast food of fertilizers. So growing bonsai in substrate, a high nitrate fertilizer is fine. And many high end water soluble fertilizers are very high in nitrate. As you can see one of your labels has a small ammonium percentage when compared to nitrate. This is not uncommon.

Note, that for bonsai you want to provide just enough nitrogen. This gives more hardy durable shorter shoots/leaves/needles growing plants. In development when you want to grow long shoots, you want to give plenty of nitrogen. But when in refinement, you want to give less. If you give a lot of nitrogen, the plant could grow very long shoots that are quite susceptible to stress or disease.

 

[turnyface]

Are you growing orchids? Is there a special issue with orchids and urea? @Leo in N E Illinois should know even more about this.

Seems both are good chemical fertilizers to use. But make sure to keep the dosage appropriately low. Better to apply it at a low safe dose several times.


Ah yeah there is also a possible issue with urea that it doesn't bind to substrate particles because it has no charge. A lot of fertilizer could immediately wash out from substrate, even if it is charged. But with urea not being charged, that could be even more significant. But I am not sure. In horticulture they usually recycle the runoff and use it again, so they wouldn't care that much about this aspect of urea. But more about the pH effect.
Plants can and will take up urea directly, though. How much urea gets taken up directly or how much in HN4+ after being broken down, I have nu clue. When applying urea to farm fields, they even add an unease-inhibitor to prevent breakdown into HN4+ and prevent ammonia pollution. Urea is also not measured by an EC meter. So for ppm determination though electric conductivity, the urea is ignored. But it does have an osmotic potential on the roots.

So yes, urea fertilizers should be avoided for bonsai.

Orchids are grown in bark and like our bonsai, don’t hold onto the urea before it’s washed out and/or the soil can break it down into usable nitrogen. At least that’s my understanding.

 

[Glaucus]

This article has all the details, but may not answer your questions directly.

Urea application in soil: processes, losses, and alternatives—a review - Discover Agriculture

Urea is the most used fertilizer because of its significance on world food security but it is also the toughest fertilizer to manage. It is readily available to the plant and it is vulnerable to loss in various ways, causing environmental pollution and huge economic losses. Urea application...

link.springer.com

But yeah don't use urea fertilizers for bonsai or orchids. Nitrate also easily leaches from a soil, substrate or pine bark medium.
Only ammonia is really sticky and hangs around for a longer time.
How much nitrate flushes out immediately vs how many urea, with say a pine medium, I have no idea. I wouldn't worry about this too much.

 

[turnyface]

Honestly, we’ve tried a number of organic and inorganic fertilizers over the years. Spent a good deal of time poring over ingredients and their effects.

In the past year and a half at the museum we are even testing Ryan Neal’s fertilization plan. While at home we are using a mix of organic and inorganic fertilizers and supplements.

The biggest issues we’ve discovered is the organic fertilizers, both solid and liquid, tend to gunk up the media fairly quickly compared to inorganic fertilizers. Thus soji or surface preparation is required more frequently than when using inorganic alone.

Organic fertilizers can also be deficient in trace elements, causing interesting effects…also attract varmints and gunk up hard surfaces, making these slippery.

Inorganic fertilizers can damage the roots if one doesn’t have the quantities dialed in. We use the effects on our finest rooted plants, azaleas, as a guide to acceptable quantities and timing for liquid fertilization. Solid fertilizer quantities and timing is by tree group. One could say this is simplistic and I would agree, yet it works really well in practice.

Red tinged tips on azalea leaves. Normally one would see this with hotter, sunnier weather. Over fertilization often looks darker. However slight over fertilization might look similar.

Imho The issue with azaleas is there are quite a number of cultivars. Thousands. Each cultivar group can react differently, while sports within a group also vary, yet normally less. However the experts say the newer cultivars tend to be weaker overall. Not sure we’ve seen this, yet differ to the experts on this one.

Cheers
DSD sends

Do you skip organic altogether?

What would/do you use for “slow release” fertilizer? Osmocote?

 

[Deep Sea Diver]

Presently we use a base fertilizer of Osmocote Plus… varying the quantity for different plants and ages. Mostly full strength except sensitive roots species.

For liquid fertilization in the spring we use 1/2 strength fish emulsion plus 1/2 strength humic acid/kelp plus yucca, eventually trading off the fish emulsion for Miracid about 1/2 strength with full strength humic acid/kelp plus yucca.

The latter ingredients cut down the gunking up the media a bit, but issues remain - slicks on the pavement unless it’s washed off soonest. Not an issue if one has all bonsai over crushed rock or grass etc.

Next year we are going to test Todd Schfler’s (see First Branch Bonsai site) with the RAW bloom and grow routine posted on the site continuing Osmocote Plus as a base. The former is more of a hydro blend…. from the short trial this year the gunk issue is much less.

That said, soji/soil prep has to be done eventually in any case….due to sky fall….but much less frequently.

Cheers
DSD sends

 

[turnyface]

Are you growing orchids? Is there a special issue with orchids and urea? @Leo in N E Illinois should know even more about this.

Seems both are good chemical fertilizers to use. But make sure to keep the dosage appropriately low. Better to apply it at a low safe dose several times.


Ah yeah there is also a possible issue with urea that it doesn't bind to substrate particles because it has no charge. A lot of fertilizer could immediately wash out from substrate, even if it is charged. But with urea not being charged, that could be even more significant. But I am not sure. In horticulture they usually recycle the runoff and use it again, so they wouldn't care that much about this aspect of urea. But more about the pH effect.
Plants can and will take up urea directly, though. How much urea gets taken up directly or how much in HN4+ after being broken down, I have nu clue. When applying urea to farm fields, they even add an unease-inhibitor to prevent breakdown into HN4+ and prevent ammonia pollution. Urea is also not measured by an EC meter. So for ppm determination though electric conductivity, the urea is ignored. But it does have an osmotic potential on the roots.

So yes, urea fertilizers should be avoided for bonsai.

I have a lot of young pre-bonsai I'm trying to push and grow. That's why I was thinking of using 3x the dose (1 TBSP vs. 1 tsp) once a week. My trees are in 80% perlite and 20% coco coir.

 

[Deep Sea Diver]

Here’s my position after a number of years experimenting with dosage levels.

Thinking 3x the normal dose of any fertilizer or additive is over the top.

Many of us have tried the same route and backed off.

Plants can only transpire and photosynthesize so fast. As a result, the roots can only take up and use so many nutrients.

After that the remainder is a waste of resources or, at worst, harmful… damaging the rhizosphere, clogging up the media lowering the H2O:O2 balance and/ or damaging the roots.

Even Water Pall wrote me when I asked about the overfertilization methods he’d advocated that he’s changed his ideas about over fertilizing.

It in the end, these are your trees. so your choice!

Best
DSD sends

 

[Lorax7]

Urea can kill a potted tree in APL mix quickly (depending on the species and other factors). Lost 2 spruce that I had because I didn’t read the fertilizer label carefully enough (I thought I was buying the same thing I’d bought previously, but it wasn’t - the packaging just looked really similar).

 

[Leo in N E Illinois]

Nitrogen is a necessary nutrient, It can be absorbed as Ammonia, or ammonium ion, as an amino acid, as nitrate, as nitrite, but not as urea. Urea must be broken down by soil bacteria in the soil water film to release ammonium ions. Then the root tips can absorb the ammonium ions directly. A large percentage of the ammonium released are converted by the same bacteria to nitrate, which is also used by plants. However, there is a metabolic cost to plants in absorbing nitrate.

Ammonium, ammonia, and ammino acids can be absorbed by plant roots with no metabolic costs. These compounds simply move across the cell walls into the vascular system.

Nitrates, must be metabolically processed by the plant to move into the cells, and this costs energy. A significant percentage of daily photosynthesis can get consumed in the processing nitrate for absorption. I am fuzzy on details, I've been retired for more than 15 years, and I had never really learned all the chemistry. @Glaucus

Also remember inorganic substrates do not support the diverse soil microbiome that one would find in vegetable garden soil.

So for bonsai in inorganic soil, it is preferable to use fertilizers that will release nitrogen as ammonia, ammonium or ammino acids. Fish Lysates are excellent sources of ammino acids.. All other nitrate and nitrite sources require either metabolic expense from the tree or intervention from soil bacteria which may not exist in sufficient abundance in an inorganic soil;.

Rape seed, cotton seed and other seed meal cakes do require micro-organisms to break down and release the nitrogen, which usually comes off as ammonium and ammino acids.

I have on rare occasions used household ammonia (4% active) the brand intended for household cleaning as a nitrogen source. The dose was low, but I forget the dose I used. You will have to do your own parts per millions calculations, (ppm)

Since I got out of orchids, and downsized by orchids from over 1000 plants to less than 20, I am not doing these calculations anymore.

Fish Lysate, and Seaweed emulsion with a little humic and fulvic acid are the only fertilizers I use these days, for the last 4 years.

 

[Glaucus]

Yes, plants need to add energy to go from nitrate back to ammonium ions. This because of the oxidation state of the nitrogen atom. Nitrate needs to be reduced back to ammonium to be incorporated into organic molecules, through the Glutamine synthetase pathway. But it seems that scientific studies do not show that plants therefore prefer ammonium over nitrate. Theoretically, not giving nitrate but ammonium should give the plants an enemy boost, by saving them some sugars. But in practice in experiments growth & yield is for nitrate or ammonium fertilizers are basically the same. Because of easy nitrate bioavailability, nitrate is often considered to be the superior nitrogen form. Despite the energy the plant needs to spend to form amino acids from it. People are trying to figure out nitrate/ammonium ratios for important foodcrops, but that seems to be hard to do.

Plants are able to take up urea directly through passive transport through the leaves. And then use urease enzyme in the leaves to break it down to ammonium. But plants also have an active transporter named DUR3, which is probably found in the roots. But there is no complete info on this yet, it seems, based on a quick google scholar search. So it is true that traditionally it is said that most urea is broken down by bacteria in through hydrolysis the soil into ammonia.

There is a lot of science here, but the main takeaway is that plants have spend 700 years evolving to take up nitrogen from the soil without being fertilized by humans. The main mistakes bonsai people make is either not fertilizing enough, or fertilizing too much. And not so much the exact type of fertilizer. Bonsai people like to use specialized bonsai fertilizer. But fertilizer is fertilizer. Biogold, fish lysate, fermented chicken manure, blood meal, seaweed extract, high protein plant waste, or chemical fertilizer; plants can all use it. Even if they are bonsai.

As for the soil microbiology, while it is true that organic fertilizer is much more of a food source, chemical fertilizer can still be used by some microbes in some circumstances. But that would be mostly for specialized bacteria. Generally when people talk about the soil microbiology, they want more fungi. And they got those by adding organic matter high in cellulose aka carbon. But organic fertilizers are usually high in nitrogen, low in carbon. And they feed bacteria more than fungi. Which might create a less desirable soil microbiology. But we are really talking soils now, not bonsai bot substrates.

Theoretically, it might be best to fertilize with individual amino acids. But this is almost never done.

Not sure what Walter Pall opinion specifically was referred to, but I understood that in his Youtube series he readily admitted that almost all fertilizer he applied was flushed out again by watering.

 

[Carol 83]

Since I got out of orchids, and downsized by orchids from over 1000 plants to less than 20, I am not doing these calculations anymore

How come? Just too much work?

 

[PastryBaker]

I think I'm going with this "orchid" fertilizer alone with some homemade Espoma planttone organic cakes.

Amazon.com : msu orchid fertilizer 13-3-15

View attachment 571694

Glad I found this. I wondered about this for bonsai. I use it on my orchids and I think it is the one developed by Michigan State University.

 

[Applicative]

Yes, plants need to add energy to go from nitrate back to ammonium ions. This because of the oxidation state of the nitrogen atom. Nitrate needs to be reduced back to ammonium to be incorporated into organic molecules, through the Glutamine synthetase pathway. But it seems that scientific studies do not show that plants therefore prefer ammonium over nitrate. Theoretically, not giving nitrate but ammonium should give the plants an enemy boost, by saving them some sugars. But in practice in experiments growth & yield is for nitrate or ammonium fertilizers are basically the same. Because of easy nitrate bioavailability, nitrate is often considered to be the superior nitrogen form. Despite the energy the plant needs to spend to form amino acids from it. People are trying to figure out nitrate/ammonium ratios for important foodcrops, but that seems to be hard to do.

Plants are able to take up urea directly through passive transport through the leaves. And then use urease enzyme in the leaves to break it down to ammonium. But plants also have an active transporter named DUR3, which is probably found in the roots. But there is no complete info on this yet, it seems, based on a quick google scholar search. So it is true that traditionally it is said that most urea is broken down by bacteria in through hydrolysis the soil into ammonia.

There is a lot of science here, but the main takeaway is that plants have spend 700 years evolving to take up nitrogen from the soil without being fertilized by humans. The main mistakes bonsai people make is either not fertilizing enough, or fertilizing too much. And not so much the exact type of fertilizer. Bonsai people like to use specialized bonsai fertilizer. But fertilizer is fertilizer. Biogold, fish lysate, fermented chicken manure, blood meal, seaweed extract, high protein plant waste, or chemical fertilizer; plants can all use it. Even if they are bonsai.

As for the soil microbiology, while it is true that organic fertilizer is much more of a food source, chemical fertilizer can still be used by some microbes in some circumstances. But that would be mostly for specialized bacteria. Generally when people talk about the soil microbiology, they want more fungi. And they got those by adding organic matter high in cellulose aka carbon. But organic fertilizers are usually high in nitrogen, low in carbon. And they feed bacteria more than fungi. Which might create a less desirable soil microbiology. But we are really talking soils now, not bonsai bot substrates.

Theoretically, it might be best to fertilize with individual amino acids. But this is almost never done.

Not sure what Walter Pall opinion specifically was referred to, but I understood that in his Youtube series he readily admitted that almost all fertilizer he applied was flushed out again by watering.

this is very interesting and I should spend my time reading the research more.

I have been using aminos as I've read they increase calcium uptake, I would be interested in the mechanism. Also use humic / leardinite / fulvic at 5:2 ratio, but your comment regarding carbon being from cellulose (makes sense like browns in compost) makes me wonder if another carbon source is required for fungi.

I believe the source for those are plant based proteins.


also following Todd's schedule with a base of Holly tone for acid loving plants. Not sure the ph of the npk raw products but dont want to mess with trying to buffer down the water.

 

[Glaucus]

Amino acids can act like chelating agents, keeping certain metal ions bioavailable. But they aren't as good as EDTA or EDDHA.
Of course, the amino acids themselves can also be taken up. Probably acting as a carbon source, nitrogen source, and energy source.
But purified amino acids are way more expensive than other types of fertilizer. So they are rarely used as a product.
Yeah the NPK Raw people probably have them. But I am not sure when these products are worth the money.

The thing with carbon and the soil microbiology is that bacteria are bad at breaking down cellulose. And fungi are much better at this. Which is why you get a succession of plants. Where bare newly disturbed grounds get a certain type of annual weeds. Which go hand in hand with a soil high in microbes and low in fungi. Then, when grasses move in, maybe the next season, then it shifts a little bit. Once you have a full season where grasses have grown, these choke out most of the annual weeds. And you get biannuals that can compete with grasses. And then after that, perennials and shrubs. This shades out the grasses as well. And both the grasses and now the shrubs produce plant material much higher in cellulose. So you get more fungi. And then finally, you get actual trees like oaks. And then finally the most mature forests would be coniferous forests. This is the end stage in succession and now the soils will have more fungi than bacteria.

And the idea is that plants take up dead bacteria and fungi more than they take up the raw minerals. And that at the same time, plants feed the soil microbes with sugars that only the plants are able to produce, because they do photosynthesis, and in this way plants 'farm the soil'.


This video explains it fairly well.

How this translated to bonsai culture, no idea actually.