Spots occur on fans 1-3 nodes below new growth. First as round dots then progressing to blotches.
RDWC, 64F chilled 1.25EC nutrient solution pH’d with controller 5.8-6.0, in late flower controller adds pH at 5.6 brings to 5.9 then falls to 5.6 and repeats, veg controller adds pH at 5.8 brings to 6.2 then falls to 5.8 and repeats.(1) 12” air stone per plant 6 per 32w air pump, 5000k lights, 78-84F 50-60%rh air at 800-1200 ppm CO2.
I should mention I use RO water (3ppm). 5g/gal base, 1g/gal sweetener.
plants are one per tote, system is RDWC and therefore the water level of the tanks are constant thanks to the central reservoir.
Two weeks ago I lowered the base to 3g/gal and added 8ml/gal of sensi calmag this didn’t see any change.
Plants are right at 24-25”
This is a true RDWC not a static bucket system water flows from and returns to the reservoir at a nominal rate of 100gph.
I don’t have a par meter but based off the 5000k conversion I should be under 400Micromoles (25,000 lux x 0.0135 =337Micromoles).
I change the nutrient solution weekly I usually have added 50% of the volume back between nutrient changes (as top off), ppm are stable and I only add base for the volume being added as topoff. Since it’s RDWC the volume fluctuates a bit but total vegetive system solution volume is about 22 gallons.
To me it kinda looks like it could be a mag deficiency with the light green leaf tissue in between the veins. But I’m still learning how to diagnose plant leaves myself.
Looks like you have multiple plants in each tote? Girls are about almost 2 ft high? I have had this problem before. Just in case, how much cal mag are you using? Just curious. I do not think it is a calmag issue though. The leaves look dark enough. What color is the stem? Purple? Are the discolored areas on the fan leaves starting to dry out and turn brown to gold?
To figure out the exact problem you will need to do a process of elimination.
I would drop my ppm to below 700. I think 1200 is a bit high for the size of those plants. Maybe it is ok for 4 in one tote, but you have to make sure there is enough water. Since your temp is higher than normal and using c02, your plants will drink more because of perspiration. A day or two not having enough water and the ppm spikes, could cause this.
lower the calmag amount (because of below)
foliar feed with 2 percent epsom salt (if this fixes the problem you know specifically it is a magnesium issue)
Watch for a while and after a couple days if it seems to stabilize, then slowly up the calmag. Bring your ppms up slowly and keep h2o levels up daily. If you are using a RDWC you can easily make an epicenter with a float valve and a top off res.
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Thanks! Co2 is 800-1200 EC is 1.25 (or 625ppm not 1200) plants are one per tote, system is RDWC and therefore the water level of the tanks are constant thanks to the central reservoir.
Two weeks ago I lowered the base to 3g/gal and added 8ml/gal of sensi calmag this didn’t see any change.
If very high intensity lights and CO2 is in use makes me wonder if the TDS shouldn’t go up a bunch. Never having done a closed system I remember Rob talking about the lighting really playing hell with nutes, including calcium. Probably wouldn’t hurt to supplement with it.
I don’t have a par meter but based off the 5000k conversion I should be under 400Micromoles (25,000 lux x 0.0135 =337Micromoles).
I’ll add calmag without lowering the base this time so about 800ppm.
Looks like either a calcium or phosphorus deficiency. If I were you @tazard, I would check the pH of your leachate, it’s possible that your pH is too low.
Phosphorus could be caused by low water temp, or soil that is too compact. In addition to this, phosphorus is taken up by the plant very quickly so if you don’t feed often, there could simply be a lack there.
Calcium deficiency is mainly caused by low pH at your root zone. Other than that, if you’re growing in a media (e.g. coco) that requires calmag buffering and you have not done so, it will inhibit your plant’s ability to take up calcium, phosphorus and other important nutrients.
I have also seen that same problem with pro mix. It’s often pH at the root zone that will cause this. Watering with a higher pH, higher nute concentration, adding dolomitic lime or mycorrhizae are all ways of helping combat this problem. Some things will work better than others depending on the situation.
You might already have all the calcium in your medium that you need but if your pH is off or certain other nutrients are in excess, you can cause a lockout of calcium so you need to do some troubleshooting to see if you have a lack of calcium or if you have calcium lockout
).
