Light stress without taco leaf?

[Animatey]

That is the prettiest display of a potassium problem I have seen. The problem with potassium is a deficiency looks just like a toxic reaction?

View attachment 1211254

IMPO Light burn looks more like brown crispy edges and bleached out bud tips.

Hey MOG, Wonder where these charts come from? Is it a Cannabis specific book maybe or just for plants in general.

I've been reading a bit about K Ca and Mg and have seen a few different ratios suggested but nothing Cannabis specific.

 

[Mañ'O'Green]

Hey MOG, Wonder where these charts come from? Is it a Cannabis specific book maybe or just for plants in general.

I've been reading a bit about K Ca and Mg and have seen a few different ratios suggested but nothing Cannabis specific.

IMPO every plant from seed has different nutrient needs. It is not a one ratio fits all scenario. Just some basic observations for calcium additions:

If you run LEDs add 50 PPMs to your regular nutrients, If you run in coco add 100 PPMs to your regular nutrients. Never feed a single nutrient always feed a balanced fertilizer.

 

[Animatey]

IMPO every plant from seed has different nutrient needs. It is not a one ratio fits all scenario. Just some basic observations for calcium additions:

If you run LEDs add 50 PPMs to your regular nutrients, If you run in coco add 100 PPMs to your regular nutrients. Never feed a single nutrient always feed a balanced fertilizer.

I'm also starting to wonder about irrigation frequency leading to toxicities.

I'm seeing some dark green and clawing as well as what you suggested could be a K tox even at low EC, but I've read a couple places now that high irrigation frequency might require reduced NH4, and possibly K.

As far as I understand, NH4 will basically increase in the medium as the time between irrigations is reduced. This could lead to N tox which would explain the dark green leaves and clawing even at low EC:

https://www.ishs.org/ishs-article/627_10

Time-dependent processes such as nitrification reduce the temporal NH4 concentrations in the rhizosphere and hence, the actual NH4 concentrations increase as the time interval between consecutive fertigations is reduced. Adjustment of the NH4/NO3 ratio at high irrigation frequencies is recommended, in order to diminish the risks of NH4 toxicity in sensitive crops.

This article suggests that immobile elements such as P and K can be reduced with more frequent irrigation. So I'm wondering if not reducing them could lead to a toxicity

High fertigation frequency: the effects on uptake of nutrients, water and plant growth on JSTOR

A. Silber, G. Xu, I. Levkovitch, S. Soriano, A. Bilu, R. Wallach, High fertigation frequency: the effects on uptake of nutrients, water and plant growth, Plant and Soil, Vol. 253, No. 2 (June (II) 2003), pp. 467-477

www.jstor.org

These plants were watered 7 times a day in 4 inch rockwool cubes (run to waste):

This plant was fertigated every 15 minutes in hydroton (recirculating):

Notice how much worse the problem is...


Still just a theory, but I've had this problem since I switched away from 6 inch rockwool cubes to mediums that required me to fertigate more frequently.