Constant nute burn @ Low EC

Hey guys. So I'm doing my second grow now and there's something odd occurring, that happened last grow too. My plants seem to be getting nute burn at low PPM's. They're currently 10 days old @ 220 ppm. The tap water is 120 ppm so that's 100ppm of nutes (~1/4 strength). The same thing happened during my last grow. The plants ended up being okay though but it's still quite worrying. The EC also seems to gradually rise, along with the pH, instead of dropping up until much later in vegetative growth. It might not seem bad but I'm a perfectionist and I want things to run 100% smoothly. I am growing hydro for that reason - to be able to modulate and regulate my environment to produce perfect crop.

My specifications are as follows:
10 gallon res
6 plants per res (AK47 from RQS)
2 80mm air stones
Air pump (35gal/min)
pH'd @ 5.6 (swings about 0.15 every day)
Ambient temps during day : 77-83F
Res temps : 68-70F
Humidity : 45-65%
Nutrients used : Greenhouse Feeding (N-P-K-Mg: 24+6+12+(1.2))

In the photos below you should be able to see the slightly burnt tips as well as some odd deformities. Some input would be greatly appreciated.

I will say your root temps are too warm. Lower your ambient until the temps at the bottom of your pots average around 72, or figure out a way to cool off the root zone without adjusting the ambient. Plus cover up that rockwool or you will get a green sludgy mess

I would also put something reflective white on top of those totes to keep some of the light heat out of the totes

Thanks for the advice man. I literally just ran to cover up the rock wool. Will put some white coating on the top of the totes in a second. Do you mind elaborating on why a warm ambient temperature would cause or promote nutrient burn?

I stay in a pretty hot area. Summer days average between 80-86 degrees, so I do my best to keep the environment cool. Currently running an air conditioner in the tent set to 66. Manages quite well but obviously struggles to maintain the penetrative heat directly under the lights.

discodance said:

Thanks for the advice man. I literally just ran to cover up the rock wool. Will put some white coating on the top of the totes in a second. Do you mind elaborating on why a warm ambient temperature would cause or promote nutrient burn?

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your ambient temp will transfer into your root zone and your roots will be too hot. A great way to think of growing anything really is that you are not growing the green bits on top, you are growing the white bits underneath. If the roots are ideal everything else will work itself out (within reason). Growing is an exercise in compromise, ideally, in a perfect system, your co2 is 2000 ppm your leaf surface temp is 96F your root temp is 71 F and your humidity is dead on the VPD chart. This is obviously not possible so we have to compromise one value to help another value. This being said the most important values are the ones that affect the roots.

I guess ideally you could use something like a space blanket as a top cover, this would get rid of the worst of the radiant heat. Like one of those little foil survival blankets

Uncle Reefer said:

I guess ideally you could use something like a space blanket as a top cover, this would get rid of the worst of the radiant heat. Like one of those little foil survival blankets

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Very difficult to work with.

I'd just use some aluminum foil. Pull a lid, put the aluminum foil on it, poke your holes out, done in 20 seconds.

TacoMac said:

Very difficult to work with.

I'd just use some aluminum foil. Pull a lid, put the aluminum foil on it, poke your holes out, done in 20 seconds.

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I've heard some bad things about aluminum foil, though; especially that it reflects too much heat. You sure it would be an optimal solution?

Reflects heat? Umm...that's what you want it to do to keep it out of the tub.

Space blankets are more efficient at reflecting, but they're very thin, very flimsy, very difficult to cut and you'd have to use spray adhesive to mount it to the lids.

go buy a cheap laser thermometer and go point it at everything, take notes try with and without foil , do it for science. This will teach you a ton

TacoMac said:

Reflects heat? Umm...that's what you want it to do to keep it out of the tub.

Space blankets are more efficient at reflecting, but they're very thin, very flimsy, very difficult to cut and you'd have to use spray adhesive to mount it to the lids.

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Yeah yeah, I feel you but won't that reflect too much heat upwards into my leaves?

White craft paper will work as well. Anything other than black would be a big step in the right direction.

And no, it wont. Your leaves are sitting right above a pitch black furnace right now.

Just simple flat white paint will be your best option and bn probably the most cost effective!

shawnery said:

Just simple flat white paint will be your best option and bn probably the most cost effective!

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He'd half to leave the lids off to cure for 48 hours.

That would be the death of his plants.

TacoMac said:

He'd half to leave the lids off to cure for 48 hours.

That would be the death of his plants.

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Yeah. In retrospect I should've probably done all this shit before I decided to grow again. Oh well, will make a plan.

discodance said:

Yeah. In retrospect I should've probably done all this shit before I decided to grow again. Oh well, will make a plan.

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Just lay some white sheets of craft paper over them. It doesn't have to be perfect. You're just trying to cover up all that black that's absorbing all that heat.

Hell, paper towels would help.

I'm new so I could be way off.

Unless I missed it I didn't hear what kind of light you are using. If it's to much you could not only get heat stress but light burn and nute burn as well from increased nutrient absorption or am I way off?