LED Grow Light Forum

Well, imho, the very low pH explains most if not all of it.

I know you've all seen the chart before but...


With pH that low it can lock out N, P, Ca and Mg (RKY was on the right track) which explains the, yellowing, burning and spotting. Also plants with low N are more susceptible to that fungus you linked.


I'd switch soils (assuming commercial soils) and add dolomite to your soil systems in the future...or consider trying hydro.

hey SME<

can you explain what is going on if 6.7 water is going in and 5.4 is what's coming out? what does that mean? and how do you fix it?

i saw you recommend dolomite lime. what does that do for the soil? help it buffer pH better?

thanks, RKY

It means that the soil is even lower that what's coming out. Also backed up by his 4.8 soil test results. His soil pH is so low that it lowers the water pH from 6.7 to 5.4 quickly.

That's exactly right; it helps to buffer the pH better when the soil pH is too acidic, it also adds Mg and Ca to the soil.

The soil ph thing is incredibly complex and mysterious. Measuring soil runoff is totally dubious.

I'll tell you this. I measured 5.4 runoff consistently. At first this lined up with a 4.8 reading off the soil probe meter I use, an Accurate 8 which is widely considered one of the better ones.
http://www.amazon.com/Control-Wizard-Ac ... accurate+8

These numbers got my attention and I responded with flushing water and top dressing Dolomite lime. Since then my Accurate 8 readings have tended around 6.2 but the runoff numbers are still 5.4. I wish it weren't so. I'd prefer a hard and fast conclusion. What I'm left with is: the Accurate 8 isn't so accurate or measuring soil runoff is not a valid test. Some say if you run 6.5 through the soil and get 5.5 runoff it implies soil ph 4.5. The 4.8 was close.

I'd like to see data showing that soil ph confirmed using a soil probe meter, water runoff, and by slurry test. I think ph is a moving target. You can measure your tap water out of the tap and get a different reading 3 days later same water.

Better if it never gets too far out of range.

I had the same problem a while back with autos that i grew... i was able to recuperate them to a point but they suffered pretty harsh damage. What i found was i top dressed lime to recover them. What i went on to figure out tho is the soil its self . I was using Sunshine #4 mix and personally i will never use it again. Now iam not a long time grower. However out of all the types of soil i have used. I still think that Pro-Mix Hp still seems the best. Holds a Ph level from start to end. Never had a problem with it....... yet..

Xylem wrote:

asuekim1 wrote:Calmg?? nutes,boron?manganese? all produce spotty leaves, none I have seen so severe. Appears they recovered decent. Nice grow.., I have had issues with the proximity of the light, so 8-12 inches is the closest I let it get, When they were in veg 2 of 3 got really green and I had all kind of nute issues, so I dropped to plain water (DWC) and feed them every other day adding approx 100 ppm tds GH nutes and calmag. My R/O auto adds Calmg and the light really is signifigant, I think with the 440 less is more, .

Sorry, man. I don't know the hydro lingo. What does R/O auto adds Calmag mean? You have a reverse osmosis machine that automatically adds calmag?

Yeah, the plants were hit pretty hard by something. I can't imagine I precipitated it even given a lack of experience growing this species. It started barely a week in. I am interested in your comment about the light, less is more. Think it can burn? And on that note why do you think at this stage the tops are totally burnt, still some foliage lower down? (I'd like to come away with some piece of knowledge from this struggle)

Yeah sorry, my R/O- reverse osmosis, adds approx 060 ppms, of calcium and magnesium. Needed for severe water conditions here. The addition of the LED/DWC(Deep Water Culture), versus cfl T5 bubbler fed system, for me, requires less nutes, promotes lusher growth and increased lower flowering. So Its worked out that less is more.More Light, More growth, less heat, less food... GL

nineandfive wrote:I had the same problem a while back with autos that i grew... i was able to recuperate them to a point but they suffered pretty harsh damage. What i found was i top dressed lime to recover them. What i went on to figure out tho is the soil its self . I was using Sunshine #4 mix and personally i will never use it again. Now iam not a long time grower. However out of all the types of soil i have used. I still think that Pro-Mix Hp still seems the best. Holds a Ph level from start to end. Never had a problem with it....... yet..

Funny you say that. I was going to use #4 next grow. I've heard mostly good things. What happened with yours?

The best way I could explain it. Is it wouldn't hold any kind of PH level. I do have a soil pH pen and I would keep checking periodically and re testing the pen to make sure it was working ok. But in the end my plants just suffered dramatically it seemed like they ran the complete gambit on anything that was possible to have a deficiency on. I am still 100% for sure it was Molybdenum deficiency that did them in. I got rid of the #4 and been using Pro-Mix ever since. And I can really say I've had no problems.

Now yes it could of very well been bad soil to. However where its mixed and made is actually only 2 hours away from my place. So I am going to guess that it was a lot newer stuff them most. However. If you actually seem the facility for your self. Its kind of a shit hole really. It might work well for you however. I am not going to say not use it. I am just saying its not for me.