Any ideas as to what this is?

[gonewild]

Yes, the ammonium hydroxide that is formed from urea is a salt. Then, depending on pH, a fraction of the dissolved ammonium becomes dissolved ammonia, which is a gas that can leave the solution over time.

So then a stock tank of ready to use fertilizer would loose urea nitrogen as ammonia gas over time reducing the nitrogen content applied to the plant.
Probably not a big deal considering all the unknowns.

 

[terryros]

We use spring water that we pipe in from about 1.25 miles away, with very low TDS - generally less than 15. As you might expect it has low alkalinity, one of the reasons that a 15-5-15 CaMag is one of the components of our program. The pH of the final solution is 6.5 plus or minus 0.1 over time. We use oyster shell and coral calcium as a topdressing for a few varieties that appreciate a higher pH. Also apply ground dolomitic limestone annually to all the Cymbidiums.

In the pH battleground, there is the thought that pH at the root zone is best if around 5.8, while some information suggests that a pH of about 6.5 is better for direct foliar absorption of urea. I think to get the foliar absorption, the urea needs to be fresh in solution before it breaks down to ammonium. In my rotation with 5 different solutions, two are mostly nitrate and have a pH of 5.8. I don't spray the leaves with these solutions. With the urea-heavy solutions, I use a pH of 6.5, include a wetting agent, use the solutions within a half-hour of creation, water the media, and heavily mist all leaf surfaces to facilitate urea absorption. Yep, it may all be a crazy dance, but there is a bit of evidence behind most of it. At least I have a fun diversion; it isn't especially time-consuming or expensive, and I don't think I am hurting anything.

 

[Arne]

So then a stock tank of ready to use fertilizer would loose urea nitrogen as ammonia gas over time reducing the nitrogen content applied to the plant.
Probably not a big deal considering all the unknowns.

My point is that the fraction urea that disappears as ammonia gas is really small if the pH is pH 6.5 for instance. Don't worry about it.

 

[terryros]

My point is that the fraction urea that disappears as ammonia gas is really small if the pH is pH 6.5 for instance. Don't worry about it.

If a urea based fertilizer is in solution at a pH 6.5 or below how fast does the urea convert to ammonium?

 

[southernbelle]

Because you mentioned the cell walls are dissolving it caused me to remember something. What plant is this? Is there a chance it's genetics come from a cool or cold environments and you are growing in warm conditions?
I'm Peru I collected various species at high/cold altitudes and took them down to warm/hot conditions. Most died quickly and had similar cell destruction to your pictures. Researching why high altitude plants die at low altitudes I found out proteins in high altitude plants dissolve in warm temperatures. Literally the plants turn to mush starting out like what you have.

It's a complex paph (Elwing 'Snow Mass' x Amanda Hill 'Muir Woods HCC/AOS). The strange thing about your hypothesis is that it's been in constant growing conditions, so I don't think your hypothesis can be a factor.

 

[gonewild]

It's a complex paph (Elwing 'Snow Mass' x Amanda Hill 'Muir Woods HCC/AOS). The strange thing about your hypothesis is that it's been in constant growing conditions, so I don't think your hypothesis can be a factor.

Not even close to thinking it was a hypothesis! More ruling out possibilities.

 

[Brabantia]

What is your water supply and have you monitored the pH of your solutions(s)?

Yes I control the pH of the fertiliser solution. I ajust these using tap water ( usualy 40 to 50 ml for 1 liter) mixed with rain water. In such conditions at 65 ppm of total nitrogen using 21-7-21 fertlyser pH solution is around 6.2 an a conductivity of 450 500 µS. We have a very hard tap water 40 to 45 °F mainly calcium carbonate.

 

[Ray]

If a urea based fertilizer is in solution at a pH 6.5 or below how fast does the urea convert to ammonium?

Much to my surprise, it apparently doesn’t dissociate, but stays as a hydrolyzed urea molecule, suggesting no loss of ammonia or nitrogen.

 

[Roots]

Southern belle, I wish you good luck with the orchid. I am anxious to hear if phyton 27 did the trick.

To everyone else, thank you for all the info on urea. I have been wondering why anyone would use it if it has to be converted before up take, especially in a non organic medium situation. I would love to know more about how some orchids use it without bacterial conversion. If anyone has any resource recommendations, I would appreciate it.

 

[Tom-DE]

Here is an example of what incorporating urea into our program has achieved. Paph. Dollgoldi grew very slowly if at all for me before urea, as did all of the multifloral primaries. This summer it put on two leaves, three new growths and is wanting to flower. Great foliage color as well. Nitrate N was just not cutting it.

Are you rotating the fertilizer? What brand of urea fertilizer are you using? Although I have been using MSU for ages, I don't mind adding some urea fertilizer back to the feeding program....after all, that was what we used in the old days...

 

[kman]

Are you rotating the fertilizer? What brand of urea fertilizer are you using? Although I have been using MSU for ages, I don't mind adding some urea fertilizer back to the feeding program....after all, that was what we used in the old days...

I use a 15-5-15 CalMag at 100 PPM N, with urea added at a strength of 100 PPM N. Total 200 PPM N, constant feed. Water is > 15 PPM TDS. Once a month or so I use plain water for a day or so. I use a watering can to apply Kelpak & Foxfarm Bushdoctor Kangaroots about monthly, more for new transplants.

Here is a big difference from what many folks do: I plant entirely in clay pots, short Azalea pots or seed pans if possible, and use NZ tree fern for most Paphs up to 5". Above that and for all multifloral species and hybrids I use straight rockwool cubes. Phrags are all in 50% rockwool, 50% #4 perlite except for small seedlings which are in 100% rockwool. This and high airflow provides superior drainage and I can water with high frequency during the growing season. Paphs and Phrags love to be watered. Works for me.

 

[Tom-DE]

I use a 15-5-15 CalMag at 100 PPM N, with urea added at a strength of 100 PPM N.

Is the urea in the fertilizer(what kind)? I don't know if you can buy "pure" urea unless you make them by yourself

 

[gonewild]

Is the urea in the fertilizer(what kind)? I don't know if you can buy "pure" urea unless you make them by yourself

You can buy Urea on Amazon.

 

[kman]

Is the urea in the fertilizer(what kind)? I don't know if you can buy "pure" urea unless you make them by yourself

https://www.amazon.com/gp/product/B0C91CKH3N

 

[Tom-DE]

Thank you. I didn't know they sell it just like that...I have always used fertilizer that has already had N in it. Good to know.

 

[gonewild]

You can buy most fertilizer components on Amazon.
I've bought Urea, calcium nitrate, potassium nitrate, phosphoric acid, chelated iron.

 

[tnyr5]

All this talk of food is making my plants hungry lol.

 

[Brabantia]

We use spring water that we pipe in from about 1.25 miles away, with very low TDS - generally less than 15. As you might expect it has low alkalinity, one of the reasons that a 15-5-15 CaMag is one of the components of our program. The pH of the final solution is 6.5 plus or minus 0.1 over time. We use oyster shell and coral calcium as a topdressing for a few varieties that appreciate a higher pH. Also apply ground dolomitic limestone annually to all the Cymbidiums.

I'm curious to know how you use 15-5-15 Ca Mg fertilizer. I've also bought this fertilizer and found that when I make a solution with rainwater containing 65 mgr/L nitrogen, the pH drops to 4.5. It's a very acidic fertilizer and unusable with pure rainwater. The only solution is to add tap water, but in a quantity equal to at least 10% of the total volume... unless you use KOH to bring the pH to between 6 and 6.5.

 

[terryros]

I'm curious to know how you use 15-5-15 Ca Mg fertilizer. I've also bought this fertilizer and found that when I make a solution with rainwater containing 65 mgr/L nitrogen, the pH drops to 4.5. It's a very acidic fertilizer and unusable with pure rainwater. The only solution is to add tap water, but in a quantity equal to at least 10% of the total volume... unless you use KOH to bring the pH to between 6 and 6.5.

I have two nutrient solutions that must be made in 100% tap water to reach a pH of 6.3. Another solution needs 15-20% tap water to reach 5.8. Two other solutions must be in 100% RO to reach 6.4 and 6.0. You have to test your solutions. Most city tap water will raise the pH and perhaps add some extra nutrients (Ca, Mg, Si).

 

[Ray]

I'm curious to know how you use 15-5-15 Ca Mg fertilizer. I've also bought this fertilizer and found that when I make a solution with rainwater containing 65 mgr/L nitrogen, the pH drops to 4.5. It's a very acidic fertilizer and unusable with pure rainwater. The only solution is to add tap water, but in a quantity equal to at least 10% of the total volume... unless you use KOH to bring the pH to between 6 and 6.5.

I imagine it depends upon the specific fertilizer, but when the original MSU RO formula (13.2-3-15-8Ca-2Mg) was released, I used it in RO water at 92.5 mg/L for a 125 ppm N solution, and I saw that same, low pH level, and that freaked me out. At that time, I used KOH to bring it back up to pH=6.0.

Then I had conversations with several experienced growers that were educated and knowledgable about fertilizers, who told me that, while the solution may be acidic, it is a very weak acid, so the pH will be overrun by almost anything and that the most significant influence on the rhizosphere pH comes from the plant, the medium, and the microbes living in them, and not the pH of the applied solution at all.

I was doing my experiments with plants in semi-hydro culture, using a neutral LECA. Whether I applied a solution at pH 4.5 or at pH 6, the pH in the reservoir a few hours later was the same, at around 6.0-6.2. Even more interesting was that, depending upon the time of day - hence, where in the plants' daily process cycle was - it could swing as low as 3.5 and as high as 8.

You can prove that for yourself by running a "pour through" test and checking that pH:

1. Water your plant thoroughly with whatever solution you wish.
2. Let it stand of 60 minutes.
3. Trickle enough distilled (I suppose RO is OK) water over the surface to collect about 50 ml of drainage
4. Test that.
   
   At that point, I stopped adjusting or even measuring the pH of my fertilizer solutions.​