Thank you for taking the time to visiting and liking my thread.
I explained (in another thread), why I think a pure Kratky system is not ideal for growing cannabis.
I did get a crop and achieved my aim of producing enough seeds to be independent. The yield was low and the plants were stunted but they made it through.
During this year, I have carried out several experiments to determine why a pure form of Kratky works so well for lettuce and microgreens but struggles to produce a satisfactory Cannabis crop.
Lettuce and microgreens are a one cycle crop and use up all of the nutrients before finally being harvested. During the growth phase, I found that the root tips barely grew more than an inch in the water at all times with the majority of root mass accumulating in the air space of the tank.
I think the air in the tank is constantly oxygenating a thin layer of water through absorption. The oxygenized layer must play a role in the plant’s ability to take up nutrients while the air-roots keep the whole plant healthy. This leads to a bountiful and tasty crop.
Cannabis is a longterm two-cycle crop (veg&bloom) and seems to require far more root exposure to nutrients than root tips in a shallow oxygenized layer can provide.
In my grow, I needed to top up each Kratky pot a few times during the veg phase changing from two-litre pots to eleven-litre square pots. On each occasion, I filled up to the 2/3 point thinking that the more roots in water would mean nutrient uptake and improved plant growth.
This proved not to be the case. The roots now in the crucial oxygenized layer were further up the root stem and the root tips were in the unoxygenated layer and could not take up nutrients.
That is the reason why my yield was low and the plants were stunted but it is also why they made it through.
I’m in week three of flowering my 2nd grow using a Kratky + air stones + 145-litre tank system and I’m confident that the addition of bubbles and agitation with an increased water surface area has increased oxygen levels and overall plant health.
Good luck with your grows and experiments.
O’whee