Earlier today I watered my plants (growing in Coco) with Nutrient solution pHed to 5.8. The run off was in the mid-to-high 7's. A few of the plants show pretty clear signs of a magnesium deficiency, but other than that seem to be fairly healthy. Should I flush the Coco with pH adjusted water until the run off is where I want it? Also, I am not sure what caused the pH to get so high. Would excess salt raise or lower pH?
Coco has a natural tendency to raise the ph. Personally I don't really try for much runoff as I'm trying to conserve nutes and my space is limited. I also don't even measure my runoff. I always handwater and use fresh tapwater that has been sitting for 24 hours and with an airstone running in it. There is alot of controversy on the matter of runoff though. Here is a link to the icmag forum. There is a lot of very useful information on growing in coco coir. http://www.icmag.com/ic/forumdisplay.php?f=65577
Yea i seens lots of issues concerning this online too. Lots of people say that the coco retains cations and messes with run off readings. I've noticed lots of people who use it are actually taking a little medium(coco) with the water sample much like taking a soil sample by measuring the water with the ground medium in it. I would probably go about it that way unless someone around here with more experience with the coir could tell ya something different.
