If the worry is certain salts building up that could burn the roots, perhaps more specific fertilisers are needed. Talking in terms of "salts" doesnt make sense there either. If theyre becoming insoluble and are unable to be dislodged... who cares! I suppose salts that *dont get used* like chlorides and so on can build up, but if you are using low salt water like rainwater I dont see how that would happen, just dont add as much fertiliser!

Clawhammer - you raise an excellent point regarding the use of minimal but still adequate fertilizer. It may be even more important than ever to use the 1/4 to 1/2 amounts of fertilizers to reduce the salt load that apparently is difficult to deal with. Thank you.

here is a question i have been mulling.

if the salts and minerals are deposited on the media and they are so well stuck on/in there that they cannot be flushed out, then who cares if they are there or not? if they arent going to release into the water what negative effect is there to them being present?

basically, if they are so stuck on the media what harm do they present to the plant?

Claw - 800 plants? Wow just wow! Congratulations.

ROBB

But they DO release back into the solutions applied to the plants. It's all a matter of degree.

In my earlier sponge analogy, we were immersing a "contaminated" sponge in plain water. Consider that sponge again.

If you soak a sponge in colored water, then let it dry, upon rewetting some (not all) of the dye will redissolve and go back into solution, making that solution a bit stronger.

If every time you immerse it, it is back into the same concentration of dyed water, more and more of the dye with be deposited in the sponge, and more and more of it will come out with each subsequent immersion.

If the "dye" was fertilizer salts - and let's not forget that fertilizer are a blend of several, each with its own solubility characteristics - that concentration creeps toward toxicity over time.

Ray, thank you for explaining that! The light bulb just clicked on. I never thought of it that way, but it all makes sense now. And I suppose the toxicity level will vary from orchid to orchid. So something like your k-lite fertilizer would possibly slow the inevitable build up to toxicity? Great science lesson for the day. I will be the first to admit when I flush, it is very randomly and our water is hard (still trying to figure out how I find the TDS in my water, report doesn't show it). That being said, with most of my 200+ orchids I haven't noticed any adverse effects. But I'm also very diligent on keeping an eye on my potting media and repotting with fresh before it breaks down, and I probably don't fertilize as often as I should. Very interesting topic!

TDS isn’t a required reporting statistic so some municipalities don’t add it to their published reports. If you can call and talk to someone at the water district and explain that you’re looking for a more detailed report, they’ll probably send you one.

Thank you, Dimples!

If you are potting in organic media like bark then this probably won’t be of much concern to you. The general consensus seems to be that the bark will break down before the fertilizer toxicity reaches a level that matters, and broken down bark will do far more damage then fertilizer toxicity ever will.

Ray and Fred. My understanding of how plants work is that they are entirely passive about what enters their root tissues. By that I mean they have no mechanism to select one chemical other another. If they are exposed to both the good elements of fertilizer and the bad ‘salts’ in a fertilising event, then don’t they take both into their roots indiscriminately. Isn’t the problem then simply too much fertilizer? Get the quantity of fertilizer right and there won’t be any ‘salts’ hanging around building up their toxicity?

There are several factors that control the buildup rate, and concentration of the applied solution is probably the most significant. That's one reason that frequent, dilute fertilizer applications are better than infrequent, stronger ones.

Other factors include how absorbent the medium, and how rapidly the medium dries.

K-Lite was designed to keep the potassium and phosphorus levels low, as the plants don't need a steady, heavy supply, as they store them in excess and because N, Ca, K, and Mg can compete for uptake in plants. If the concentration of particular ions in the applied solutions is raised by design, by buildup in the medium, or stored to excess within the plant, it can result in deficiencies of the others.

But yes, for the same nitrogen loading, K-Lite is likely to build up slower to most other fertilizers.