Deficiency? Brown spot.

[gturmindright]

Mephisto chemdogging, day 38, hempy bucket,100% perlite, jacks 321, 3.5gal ro water to .5ga tap to make ph 5.3-5.5, sometimes varying anywhere from 5.3-5.8. Runoff coming out at 6.2. Watering every other day. Temp 75, rh 55, plenty of airflow, spots only on old growth. First grow, started poorly, recovered great, just noticed my first possible issue since. Any help appreciated.

 

[namvet25]

Why are you using all perlite?very hard to control ph and nutes.

 

[gturmindright]

Good answer!

 

[Waira]

-- do you have a TDS/EC reading on your nute solution?.... it looks K related, but K defc. and K toxicity can look a alot alike initially, same browning on tips and margin teeth,...

 

[gturmindright]

TDS 760 using RO water and Jacks 321. They seem to commonly appear on older leaves.

 

[Waira]

I'm not familiar with that nute line,... No other signs of nute burn, so the ppm's are OK,... check the run-off ppm's too next time,... odd that it's rising,....

 

[GeorgeCloney]

If we reverse engineer the issue.
Set initial EC with 250ppm of calmag, then raise EC back to 760 as this is what the plant likes.
So here is the problem with this kind of solution.excess calmag will cause nute def'c elsewhere.
In theory, the theory is good, in practice it is not.

 

[Waira]

... hence why I like to see what that current run-off is for ppm's! We see quite a bit of antagonistic uptake issues here, not quite toxicity/burn, but close and often pretty specific to what exactly is overloaded... The general recommendations for extra Ca-Mg use can be ill advised at times, much depends on the nute themselves and if soil, how much coco (if any) is in it,... but some folks just keep pouring it in, and cumulatively it becomes a problem,....

 

[gturmindright]

I don't have any calmag I use calcium nitrate and magnesium sulfate. I think it could have been a pH issue I got a couple new pH pens that were measuring quite different from the one I had. Can low pH cause something like that? What pH measurement device do you all use?

 

[Waira]

that's fine then, but the carbonate based stuff can help buffer and stabilize you pH,...
pH meters are delicate devices, and if not cared for they go off calibration fast... proper storage solution, rinsing between each and every use with RO/Di water, and frequent calibration checks using a pH standard soln. 7.0 at least, better still to include 4.0 as well for a 2-point calibration...