I stand corrected! Thanks again Ray.

I never prewet.
I just either water or fertilize.

As long as the fertilizer is mixed correctly, root burn is not a concern.
Pouring powdered form on the root might do damage, but I don't see any reasoning behind harming the roots by pouring very much diluted solution on them.

You might be damaging the roots by drying them too much.
Oncidiums in barks need to be watered very good, especially if your watering interval is not frequent enough and the roots and the potting mix dry up too much.
You want to run water like crazy for a while, which is a waste to me of a valuable natural resource, or soak the pot for good ten minutes (I go for a long time. half an hour or more, although it's not necessary).

If you pour water over the pot with bark mix, plants do not get much to drink. most of the bark will not even get wet.

So, adjust the watering, or change the potting mix.
Promix kind of stuff works really well for oncidium types.

I'm going to go back to some of the earlier postings in this thread.

You distinctly admitted to watering your Oncidium only once a week, when another member, (cbuchman), had mentioned that she had to water her thin rooted Oncs rather frequently.

I underlined and bold faced the sections I wanted to stress.

I currently have a similar experience.

Let's run with this a bit before we move on to pre-wetting and all that other stuff...

I have an Oncidium species that is incredibly difficult to keep up with in the watering department. I have to literally water this orchid everyday, year-round, and quite frankly, I don't always have the energy to do so. So as you can imagine, this particular Oncidium is in rather poor condition, full of stunted growths with "accordion leaves", with a few pseudobulbs dropping leaves prematurely. And, yes, this Oncidium is grown in medium grade bark, just like yours is.

I honestly don't think you're over fertilizing, I suspect you may not be watering enough.

…Food for thought… ;)

Ray, you have convinced me. I will no longer prewater.

I don't know why people get so upset over this subject. I've seen award quality orchids grown by people who never pre-water and by people who always pre-water. Personally I don't think there's a nickles worth of difference, but don't jump on my statement, it's only a personal opinion. Bill Thoms, who has won more AOS culture awards than anyone else, says you should always water first before fertilizing. Dr. Martin Motes, who has lots of AOS awards also, says never water before fertilizing. Personally, I water before fertilizing. I hope no one feels like they need to come down here and break my knee caps for doing it. I think everyone needs to chill out about this subject. Sorry, just my opinion.

I might want to come visit, but not to see your knee caps, but to see your orchids!

Hahah yes. I am afraid i cld be too heavy handed on the mixing n rather not burn roots n delicate buds. Hence I too water b4 fertiliser. Am just clumsy n rather be safe than sorry.

I'm going to start watering my Oncidiums more.

What gets me frustrated is seeing comments like 'I fertilize at quarter strength'. Quarter strength of what? The recommended dose on the label? How is that a reliable measure? Do you seriously think that all the fertilizer companies get together and establish a single perfect dosage for their products?

Go back to basics and calculate the ppm of Nitrogen that you've been feeding with. Then calculate how much you need for 25-30 ppm. Ray, maybe you should put the link to your fertilizer calculator in your signature.

I use the Grow More "Urea-Free 20-10-20" at a quarter teaspoon per gallon of water, every other week.

I use this mix on most of my orchids biweekly and water weekly-
except for the miltoniopses in medium/fine bark which get watered twice per week, still fertilized every other week.

This thread is convincing me that I need to water my oncidiums and miltonias more than once a week or soak better...However, the oncidiums get a chronic "curl" to the edge of their leaves immediately after being watered. I was under the impression that was a reaction to being over-watered?

I had all my orchids repotted in bark at a place that heavily favors bark for everything. The nursery does not pre-soak (another debate)...A lot of my oncidiums and miltonias seem less than thrilled about the change for months afterward. Many of the miltoniopses have chronically droopy leaves after being potted in bark.