Talk to me about edema

This is my worst season for pepper edema.  The main difference from past seasons is the addition of a second 400-watt HPS light, and a bigger fan.  Plants are in a basement which is pretty warm with the second HPS.  As far as edema is concerned, is it good, bad, or neutral to have a plant catching the fan's direct breeze?  Now that I think of it, this is my first season using coir as a portion of my soil mix.  Does it retain water longer than peat moss?  Is this even relevant to edema?  Thanks.
 
Edema is just the excretion of salts true the cells in the leaves. It's a combination of factors, mostly watering, container size and nutes (salts).

If your plant uses up X volume of water per day and you use a small pot, the soil will be very moist/wet. If you put the same water in a large container, the cappilair effect will distribute the water more evenly. This usually also gives a better grow rate.

As for the fan, it has multiple uses;

A. It moves air around, thus blowing away humid air > reduced chance of soil born pests like gnats, and fungus.

B. As it moves humid air away from the plant, evaporation from the leaf pores/mouths increases. If there's sufficient moisture in the soil, the pores stay open. The roots need to take up moisture to replace the evaporated water and by doing so the plants take up nutes. This also helps with the Edema as the cells don't burst. Proper lighting is necessary, as you need a lot of photosynthesis to use up those nutes.

C. It is said it strengthens your stems, but I honestly can't say I've ever noticed a difference between my ventilated and non ventilated peppers.

And than you have the nutes. You want to use weak solutions of liquid nutes regularly opposed to a weekly dose of high PPM of nutes. A mature plant can handle high PPM quite well, but small plants can't handle the salts. Edema is relatively harmless, but it's still damage. As leaves sometimes curl up there's also significantly less photosynthesis, limiting growth.

So in short;

Larger containers (if possible)

No need to hit them with the fan, just make sure air in the room is moving.

Provide lighting

Go easy on the nutes






Ps. Coir holds up a lot more water than peat and doesn't distribute it as well imho. It has good capillair use, but most water descents to the bottom of the container if you water just a bit too much. It gives Edema much faster, that's exactly why I don't use coir. When repotting, make sure to mix some perlite in the bottom half of the container. 5-10% should be enough.
 
There's nothing wrong with coir though, it's just a different medium. You can get great results with all mediums if you use them properly. Most people just mix it in their soil, easily getting it waterlodged. I prefer a very easily draining soil + peat mix with 5-10% perlite due to the wet climate we have here. If your climate requires moisture retaining traits, add fibrous material like coir to soil. Just make sure you don't water to much before they can go outside.
 
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