Differences in Deficiency in Mg vs. N vs. K
 

I know that Magnesium, Nitrogen and Potassium are all immobile (edit: should be mobile) nutrients and deficiency in these would show problem in old growths. But, what is the difference in their appearance? Do they all look the same? like yellow, and that's all?

Actually, all three are quite mobile. Calcium is the least mobile.

I've attached a scan from Marschner Mineral Nutrition of Higher Plants that shows a few symptoms of deficiencies and toxicities.

The elements in parentheses are those that may also be part of the issue, next to the more likely candidate.

Thank you for the correction, Ray. You are right, a typo there.. should be mobile nutrients..

Anyway, these symptoms described are for all plants? They apply to orchids too?

To the best of my knowledge, it's reasonably applicable across the board.

Google charts with pics for different plants (vegetables, marijuana, etc), and you may get a better idea of how the characteristics display.

Hi Karrolhk,
An interesting article, with pictures and descriptions, of the main nutrient deficiencies written by a professional:
Identifying Nutrient Deficiency in Plants.

Thanks for posting that link.

A caveat or two, however. While those images pretty accurately portray what extreme symptoms may look like, they provide absolutely no indication of what constitutes a deficiency, and we must remember that orchids, being extremely slow growers, will rarely get that far along.

When we were first experimenting with K-Lite, with intentionally low levels of K & P, I was told specifically what to look for in their deficiencies, but in the decade since, the symptoms have never been seen by me or reported by others, suggesting that even with them being applied at 8% of the N, with that being low to start with, the demand is still being met.