Can High Pressure Sodium Cause Plant Illness?????

[jdoyle]

I have six plants, all the same age and from the same batch of seeds. The plants are under a 400 watt MH and are around 18"-20" tall. Up until about two weeks ago the plants were all doing fantastic, nice big dark green leaves, and growing like crazy. While the plants were still doing great I decided to add my 400 watt HPS light in order to space the plants farther apart. I placed the HPS right next to the MH, they were almost touching. I had three plants under the MH and three underneath the HPS. Well what happened was this: within 2 days of installing the HPS the three plants underneath the HPS began to wilt very badly. I immediately removed the HPS and put all of the plants undernath the MH again. Since then though, the three plants that were underneath the HPS have been doing worse and worse and are probably going to die. The leaves are droopy and are very yellow, the lower fan leaves are yellowing and some have died. The three plants that were underneath the MH the whole time are doing just fine. I cannot understand what is going on. At first I thought it might just be a coincidence that the illness set in when I added the HPS, but that doesn't make sense since I have been treating all of the plants exactly the same: same size pots, same amount of fert, same kind of fert, same watering schedule, kept in the same environment. I am a somewhat experienced grower and I have taken very good care of the plants. I never overwater, I keep the temp between 75-80 degrees, I keep the humidity between 50-60%, the ph of the soil is right at 7, I use a good soil mixture of 1/3 vermiculite, 1/3 perlite, 1/3 miracle grow, I do not over fertilize, the plants have always had plenty of airflow, I bypass my water softener to get my water and am pretty sure the water is good since I have never had a problem with it b4. I have tried a few possible solutions but have had no luck, I have tried: adding epsom salts for mg, hydrated lime for ca, flushing in case of over fertilization, and I have also added fertilizer (each was done on only 1 plant at a time for testing purposes).

The only thing I can think of is that the HPS somehow caused the illness. Is this at all possible? Is it possible that the addition of the HPS caused some kind of nutrient to be used at a higher rate casuing a deficiency? Any suggestions or insights would be really appreciated. I just hope I can save the plants in time. Thanks for taking the time to read this.

Joey

[just_blaze_it]

i would think that if there was a problem using HPS lights, they wouldnt be recommended as the best all round growing light in the world. you say the temperature doesnt go higher than 80f, but what you descibed sounds very much like heat stress. make sure you keep an eye on the tempereature when/if you add the HPS. if you were using a bulb such a mercury vapour, the bulb itslef may have become volatile, thus exuding harmful radiation. altough the only reported deterioration is that of brightness at the rate of approximatley 30% every 13 months. hope this helps!
Just Blaze It.....
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[Cody3]

heat stress isnt just on the tempurature... put ur hand flat on the top of the plant and if the light starts getting too warm for ur hand then raise it up... or just try raising up the light even if its not too hot for ur hand..

[SmknVTEC]

Somehow I doubt the light would cause these problems. Have you fed the plants yet? Also, does your Miricle Grow soil have time release ferts in it?

[Dr_Dankenstein]

I've had the exact same problem. I cloned and veged my plants in a different room under a MH bulb they were a nice dark green and very healthy. I moved them to a different room under a HPS bulb to begin flowering and the plants are begining to yellow or turn a lighter green. The room has more airflow than the vegging room. The only thing that really is different is that the room is larger and the hps has more watts than the MH .

[SmknVTEC]

Not a factor Doc.
Try giving the plant a high dose of N fertilizer if you have not already. This will get them through flower.