Can anyone explain, or link me to, a complete/thorough description of the "salt build-up" problem I so often hear?

[Smoke]

That’s why gypsum should be in everyone’s bonsai mix. There’s a reason farmers till tons into their farms soil.

http://homeguides.sfgate.com/effect-applying-gypsum-soil-70933.html

About a teaspoon per gallon of soil. Thoroughly mixed

 

[hemmy]

how bad would you consider my water in terms of EC?

I wouldn’t think that it is that high. Your TDS is relatively low. There are online conversion charts, but they make a lot of assumptions since it based on the minerals/salts present.

Your water has fairly high Alkalinity and Hardness, but Ca and Mg aren’t very high, possibly pointing to high Carbonates and Bicarbonates (which could affect nutrient availability). Do you acifidy or do you get cholorsis?

For all this handwringing and if you are that interested, you could send a water sample out to an Ag lab and just get their recommendation on water treatment and fertilizing.

 

[MichaelS]

Wow thank you! That's been copied into my pH/CEC document (am writing my own book/notes as I go!), will need to read this a couple times (spaced apart) to really absorb it...how bad would you consider my water in terms of EC?
View attachment 188570
They don't list it but can it be calculated based off the TDS? Also, do you think it'd be overkill/unnecessary to get an EC meter?

I don't think 280 ppm is a problem. You can work out the ec but it would take time as different salts give different ec readings so you would need to do them all separately etc. Not worth the trouble. Aren't there lots of orchid nurseries in Tampa? If they use the water successfully then you don't have a problem. The pH is a bit high so use acidifying fertilizers now and then. No need for a meter. Use your experience and observations to judge fertilizer concentrations.

I don't allow the medium to dry too-much between waterings (I actually worry that some of my trees have a problem regulating temperature, I'll have stuff starting to wilt in the midday sun even if it got watered 3-4hrs prior, and I mean hose-watered canopy/trunk/substrate....I thought it was poor substrate but I've since re-boxed a couple of the trees in question and put them with ~20% organics and into bigger boxes- no detectable difference, still fast wilting)

If they're wilting when wet it means that they are transpiring faster tan they can take up water. If the roots are healthy with plenty of white tips, then your only option is to cover with shade cloth to reduce temp and air movement. It's the latter that removes water more than heat in my experience.

Good stuff, precisely what I was hoping to hear What do you consider low CEC? For instance, lately I've been making tropical (bougainvillea) mixes with ~40% diatomite(8822), 25% perlite, 20% scoria/lava (1-5mm), and 15% organics (mostly pine-bark chunks, some sphagnum moss and a pinch of peat on the top / as top dressing), am thinking that this is still well within the realm of 'low cec' right? Max CEC would be epiphytic mixes for orchids if I'm understanding correctly..

Thanks for such a great reply I really appreciate it!!

The CEC of that mix would be medium to low. That's not necessarily a problem, you just need to feed a bit more often. Eg; you can grow plants in a zero cec medium with continuous feeding as in hydroponics. If you want to dramatically increase CEC add zeolite. CEC will also increase as the bark is slowly converted to humus. Sphag has a high CEC but I'm not sure if you are using it on the surface or in the mix.

 

[hemmy]

I'll have stuff starting to wilt in the midday sun even if it got watered 3-4hrs prior

What is your particle size? Maybe you need to go slightly smaller to increase saturation and lower your air filled porosity.