Coco is a high cation exchange capacity medium. These cation sites are naturally loaded with sodium and potassium if the coco is not buffered. When unbuffered coco is feed nutrient water it will pull the calcium and magnesium out of the feed and attach to these cation sites, basically robbing the plant of available calcium and magnesium.
"Before you use coco, it should be properly rinsed, buffered and mixed with perlite. Be sure to see our video and tutorial for “
How to Prepare and Buffer Coco Coir”. The buffering process is crucial to prepare the coco for plants, and especially seedlings.
As I explain in the article, “
Why You Need Cal/Mag in Coco”, the coco itself has cation exchange sites that need to be filled with calcium or magnesium. Buffering the coco allows you to satisfy the majority of the cation exchange sites. However, during the grow, more cation exchange sites are continuously exposed, which require additional CalMag. The coco will take its share of the calcium and magnesium before the plant has a chance, so if you do not provide enough, the plant will suffer.
Calcium and magnesium deficiencies are common problems with plants grown in coco. It is especially difficult to deal with CalMag problems during the seedling stage. This is because the coco is taking the Ca and Mg from the nutrient solution. However, you cannot simply increase the dose. You are limited in the amount of CalMag that you can provide to seedlings because they cannot tolerate a solution with high Electrical Conductivity (EC). CalMag has a strong impact on EC so when seedlings do suffer Ca or Mg deficiencies, they can be tough to correct. If you do encounter problems with Ca or Mg deficiency during the seedling stage, we have
suggestions for you below. However, it is best to avoid the problems in the first place by properly preparing your coco."
