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Root rot? Too much watering in rock wool ebb & flow


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Old 12-21-2014, 08:47 AM
daytonajim00 daytonajim00 is offline
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Default Root rot? Too much watering in rock wool ebb & flow

I could have early stages of root rot but not sure. This is my first try at Hydroponics. I was told I may be watering WAY too much for my young plants (4 weeks old.)

I started seeds in 1.5" Rockwool cubes and after two weeks moved the seedlings into my newly built hydroponic system (Lettuce & Basil in one system, Broccoli & Cabbage in another). This is my first grow.

The (2) flood tables are filled with Sun Leaves Rocks. The small plants sit in rockwool-in 2" net cups-in the medium which I was flooding 4 times a day under 12/12 T5 HO lights. I keep the nutrients at the following:
Lettuce/Herb system @ 1.0 EC
Broc./Cabbage @ 1.4 EC
Reservoir temps have been around 70 degrees F.

Well my Broccoli which is 4" tall with about 6-8 leaves, have started to bend over half way up the stem. The stem at the base of the medium looks a little thinner and looks a little light purplish brown. Is this root rot? 3 out of 10 of these young plants display this. Perhaps I can catch it while it's early?

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Old 12-21-2014, 10:10 AM
daytonajim00 daytonajim00 is offline
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Here's a picture of my flood tables. They are 2 separate systems (one @ 1.0 EC, one @ 1.4 EC).


Here's a picture of one of the suspect Broccoli's. The discolored new stem growth is very faint. All stems look like this but only 2 of 10 of the plants fell over.
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Old 12-21-2014, 11:00 PM
GpsFrontier GpsFrontier is offline
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Hello daytonajim00,
I can see a few possible issues. But first you say you flood the system 4 times a day, but didn't say for how long. It's not how many times you water them, it's the total amount of time the roots are completely submerged that would suffocate them withough't enough dissolved oxygen and air bubbles. You can water 15 times a day with no problems depending on the type of growing media, and as long as the roots aren't submerged too long each time.

With that said, it's likely the plants can be suffering from stem rot. Stem rot and root rot are different. From the pictures it looks like the roockwool cubes are saturated with moisture. The rockwool cubes hold much more moisture than the rocks, and the rockwool cubes touch the base of the plant stems. Constant moisture on the stems can easily lead to stem rot. That's why you want your water level in the system to be about two inches below the top of the growing media. You want the root ball to get moisture, but you want the top of the growing media to be dry.

Another possible contributing issue is the light source. While the leaves look like they have good shape and color. Plants often have skinny elongated stems and leaves as they try and reach as high as they can, as quickly as they can to reach up to the light source when using florescent lighting. Long skinny stems simply can't support the weight of the plant as they get bigger. Florescent lighting is a low intensity light source and really works best for low light requirement plants.

Third problem I see doesn't have anything to do with your post, but I was wondering if you had a plan of what your going to do when those plants get bigger? One broccoli plant can easily grow 4 feet wide as well as tall. If you try to transplant them into another system, how do you plan to do that without tearing and damaging the roots?
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Last edited by GpsFrontier; 12-21-2014 at 11:02 PM.
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Old 12-22-2014, 01:30 PM
daytonajim00 daytonajim00 is offline
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It's 15 minutes per. So I went from 4 to 2 waterings and was thinking of dropping it down to 1. That's my timers minimum increments.

My fixture is rated @ 20,000 lumens putting it @ 2,500 lumens a square foot. I know lumens isn't the proper measurement for photosynthesis measureplment but I thought it might be a way to ball park my lighting capability. It's also why I'm sticking to vegging crops for inside. The cool thing about my system, I have 2 more reservoirs available should I want to expand and perhaps route one feeding outside tables.

Also, I was unaware of the flood needing to be 2" below grade. I'm currently flooding right up to grade. So I should drop the level? It's about 4-5 inches of rock medium.

Thanks for the input!
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Old 12-22-2014, 10:06 PM
daytonajim00 daytonajim00 is offline
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Default also to note:

I was only running my lights 12/12 but increased today to 15/9. The only other factor that has changed recently is it's been warmer here in central Florida. This unit is running in the garage and for the previous 2 weeks, the garage was 60's/50's. This week it's mid 70's. I have a 1/3 chiller laying around and will eventually plumb up my closed-loops design for temp. control in all reserviors.

With warmer temps perhaps, the basil is growing faster. Lettuce seems some signs of toxicity @ .8 EC on the new leaves. The cabbage in particular and not the broccoli, shows the limp bottom stem.

I carefully pulled back the rocks on those particular plants, and the roots look a shiny white with very fine hairs streaming off. Their EC is 1.4.
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Old 01-03-2015, 07:19 PM
GpsFrontier GpsFrontier is offline
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Quote:
My fixture is rated @ 20,000 lumens putting it @ 2,500 lumens a square foot. I know lumens isn't the proper measurement for photosynthesis measureplment but I thought it might be a way to ball park my lighting capability.
Lumins are a perfectly fine measurement of light ought-put for comparison. However you can't compare the lumen output of HID to that of florescent lighting, because the lumen drop off is far greater with florescent lights than it is with HID. The lumen rating is what the lumen output is at the bulbs surface. the farther away from the bulb you get the less lumin output your actually getting. That number drops significantly faster with florescent lights. It works the same using par for measuring light output. Par drops significantly faster with florescent lights as well.

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