Fertilizers and Applications

[Windy]

What brand of 20-20-20 fertilizer does the best job? I've found some on line, but it seems only the 20-10-20 actually says it's urea free (at least, from the few searches I've done).

I'm new and have been reading a bunch (lots of great info on OB), but I'm getting confused about how to apply fertilizer. Most say to add it to water when soaking. But, I've also read others mist it on. Which is best?

If I mist fertilizer, do I only do the roots? I'm very careful to avoid getting the leaves wet except to remove dust (then, I dry them).

Right now, I'm using Better-Gro's fertilizer (20-14-13) in every other a soak. I also have their bloom booster (11-35-15), but haven't tried using it yet. This brand is the only one locally available.

I'm so confused....

[King_of_orchid_growing:)]

Orchid fertilizers are usually in a concentrated crystalized form. You can't just put the fertilizer on the orchid's roots and water them. The fertilizer must be dissolved in water and diluted to the proper concentration to spray onto the orchid's growing media.

The directions on the label should give you an idea of how much to use per how many liters or gallons of water. However, this is not a strict rule. Some orchids can handle more fertilization, others will literally die if too much fertilizer is provided.

Here are some examples of what I'm talking about.

Vandas like heavy fertilization. They can handle stronger concentrations of fertilizer dissolved in their water than most orchids can. It doesn't mean any one should go overboard, however.

Disas are notorious for not tolerating much fertilization at all. It is much more advantageous to use fertilizer as sparingly as possible and with as low a concentration as possible when dealing with Disas.

Some people here like using the MSU formula of fertilizers. I personally am using the G&B Orchid brand which is urea free, and works very well too.

[King_of_orchid_growing:)]

Maybe Ray can give you more insight to fertilizers. What I've given you are the basics.

I've found that brand names don't matter. What matters are the nitrogen/phosphorous/potassium ratio and the urea free nitrogen source. Whether the nitrogen source is ammoniacal or nitrogenous doesn't matter too much, although from what I understand, the more bioavailable type of nitrogen source is the nitrogenous one.

So far, according to research, the only orchid currently known to be able to directly absorb urea based nitrogen is Phalaenopsis. You don't have to take my word for it, you can google scholar this, there's an article about it on the web.

[Ray]

"King" has given some good advice.

Rather than filling up space here, let me point you to a number of related articles in the "Feeding your plants" section of First Rays' Free Info

King - reading that article, they stated that the urea was not hydrolyzed, but if it's in solution, it MUST be!

[King_of_orchid_growing:)]

Originally Posted by Ray

King - reading that article, they stated that the urea was not hydrolyzed, but if it's in solution, it MUST be!

Can you please explain, I don't understand what this means.

Thank you.

[Ray]

Maybe I'm misinterpreting or missing something in their treatise, but when you put a salt into solution, it ionizes - separates down into individual sub-molecules having an unbalanced charge - by connecting to the complimentary OH- or H+ from water, i.e., it hydrolyzes. It is that hydrolyzed molecule that is absorbed by the plant.

Urea readily hydrolyzes in water, to form ammonia and carbon dioxide:

(NH2)2CO + H2O = 2NH3 + CO2 (Actually, they exist in solution as the hydrolyzed species NH4OH and H2CO3)

The study claimed that chemical analysis showed that the urea was not hydrolyzed in the media, but it is my understanding that a plant can only absorb hydrolyzed chemical species, which suggests to me that the urea is hydrolyzing somewhere - maybe with water inside the velamen.

Just because the velamen absorbs it, there is nothing that says the plant can actually use it! Don't forget that the velamen is just a spongy layer of dead cells, not an active part of the plant's nutrient uptake mechanism. You can put rocks in your mouth too, but that doesn't mean you'll be able to digest them!

Maybe this study refutes the long-time accepted notion that the reason "orchids cannot use urea" is because there are no soil-borne microorganisms to break it down, but to my thinking, it certainly doesn't prove they can use it directly.

[King_of_orchid_growing:)]

Awesome point. Learn something new everyday.

You might be right. I have no idea what they meant either. I'm not a chemist nor did I go in depth into the study of chemistry on my own time.

Thank you.