150w HPS DWC GH Lucas Formula - Nutrient Level Adjustment?

sneekymofo

Member
I have a DWC system under a 150w HPS and I have been using the Lucas Formula. Do I need to adjust the nutrient PPM down since I am using a "smaller than normal" light?

I'm in my 5th week of flower in a ScrOG, temps are between 72 - 80 deg in the cabinet (+0-8 deg over ambient), and pH is between 5.5 - 6.0. I use a five gallon bucket, but after hydroton and roots, only about 3 gallons actually fit in the reservoir. I'm showing beginning signs of nute burn (necrosis, crisping leaves, tips, etc.). I have done Clearex flush and have temporarily adjusted nutes to 75% of where they were, but my "top-end" PPM was only 1260. I'm now sitting at 910 (using 75% of the Lucas 0-8-16). I top off daily with pH adjusted H2O, and adjust to an add-back at half-week to bring PPM's back up to the starting point. I dump the reservoir each week. Light is about 6-8 inches from the tops, and my hand is comfortable underneath the light.

The strain reminds me of a White Rhino, but it is of "unknown origin." I burnt the piss out of it the first two runs at this strain, so I switched to Lucas to avoid the problem. (Like a dumb-ass I tried to use GH's suggested nutrient levels....burnt 'em so bad they almost burst into flames!) I'm using GH nutes, and should have tons of O2 in the root-zone. Pic below is hard to see the burn, but it is definately there.....

Do "smaller" wattage lights require less nutrients than those suggested by the 0-8-16 formula? Should I switch back to the 0-5-10 regimen (which the plants did awesome in under the veg stage)? Inquiring minds want to know.....thanks to anyone with any insight!

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