Biobizz nutrients

even coco can becomem hydrophobic. any solid substrate can. It occurs as microbes die and leave an "oily" film coating particles over time... if you buy the cheap coco bricks (10 $ for 5kg type thing), it is untreated and will be extremely hydrophobic... same with untreated sphagnum peat moss. you do want the top layer to dry before irrigating again or you grow mold and stuff on surface of soil. Like ezjay said, if it is a serious problem you can add a wetting agent. in general, you should not need to add this during a typical grow as long as you avoid the untreated substrate options.. that expect you to do it, hence the cheaper price. The salt content of those 5kg bricks is off the charts. they are not washed even if they claim to be. the mother earth 5kg brick nearly killed 2 grows and was a bitch to water, because it was never treated wtih a wetting agent. Same with the raw sphagnum peat. whereas something like promix applies wetting agents and puts a 1ec charge into the peat... or the loose coco optiosn out there are often treated / washed thoroughly.... if not stop buying those brands.

I'll flip the perspective a bit here. The problem isn't overwatering, but a lack of oxygen in the root zone. The roots breath, and the root tips drink. +1 to the Yucca Extract suggestion, but would recommend NEVER letting it dry out to the point you'll require using it.

If the hydrophobic conditions are your issue - look up wetting agents. For situations like that I’ve used a natural one that contains yucca extract. The specific one I used was safergro natural wet.. just add a bit to your feeds/watering