Seedlings in a DWC

richardoinvicApril 14, 2014

Hello,

Background:

I have a DWC system. I started 15 lettuce and basil seeds in prepared rockwool cubes under a humidity dome on a heat mat. Once the seeds sprouted and reached 1", I placed them in 3" net cups with a single layer of prepared hydrocorn in the bottom, placed the rw cubes on top and filled around the sides with hydrocorn. I have a 4 tube T5 lights on for 18 hrs and off for 6. the pH is 6 and TDS is 800ppm. The water in the DWC is just touching the bottom of the net cup and is at 68F deg.

In 2 weeks the lettuce has not done much...maybe a 1/2" taller and a little fuller and the basil has not done a thing. no noticeable roots can be seen on either.

Is this how it should be or should there be more growth by now?

cheers, Richard

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kkamm

Hey Richard,

In DWC, you want the water level to be just under the net pots. The bubbler should produce tiny bubbles which pop on top of the water. This small amount of water bursting under the pots is sufficient to provide nutrients and water to the roots in the pot. If you have the water too high, the roots may be subject to root rot. You dont want the initial roots from the seedlings sitting in water.

    Bookmark   April 14, 2014 at 4:09PM
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richardoinvic

Thanks kkamm....yes I'm sure the not pots are at or just below the water level, With the hydrocorn layer in the bottom of the net pots, the rockwool cubes sit approx. 3/4" above the water level. My concern was that I have not seen much growth over the past 2 weeks an was wondering if this is normal.

cheers, Richard

    Bookmark   April 14, 2014 at 6:26PM
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Rio_Grande

Richard did you check your ppm on your water before mixing? I ask because I have 250-300 ppm water. The first time I did a system I added nutrient to get to the 800 ppm stage. My plants diddnt do much. I learned here that I needed to test before mixing then subtract the original ppm from my later readings to determine the true reading. We have since gone to rain water but that comes with ph challenges, but ppm is like 3 as opposed to 250-300

Also while I don't disagree with the advice above I would ask can you feel any moisture in your rockwool? It shouldn't be wet, but should be able to tell there is water there.
I ask because I tried originally to put hydro ton in the bottom of my cups and placed ripples in the troughs on my nft system, almost all my plants started dying. I had 6 or so where I ran out of hydro ton and they were fine. I raised the water level in the toughs to where the hydro ton was soaked, the ones without it started to die, they were too wet and the ones with recovered. Just my experience.

    Bookmark   April 14, 2014 at 6:52PM
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richardoinvic

Rio_Grande, my ppm before I added the nutrient was 26...so that is not the issue and adjusted as you mentioned....I just now checked it again and its at 790.....down just 10ppm. Perhaps I'm impatient on the expectations.

The water level is just at the bottom edge of the net pot....and as you mentioned the bubbles are keeping the hydrocorn damp and the rock wool cube is moist.

    Bookmark   April 14, 2014 at 9:02PM
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Rio_Grande

Sounds like it aught to work

    Bookmark   April 14, 2014 at 9:48PM
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richardoinvic

view of DWC

    Bookmark   April 15, 2014 at 11:30AM
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richardoinvic

view of DWC

    Bookmark   April 15, 2014 at 11:31AM
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PupillaCharites(FL 9a)

That's a nice and neat looking set-up. I would have guessed along with Rio that the rockwool was likely too saturated. How high above the plants are the T5 bulbs? The second guess would have been: too high. I'd say preferably 6" above the leaves, 12" if the ventilation isn't so good, would be about right, but others could advise you better on this distance since I've been growing oudoors.

    Bookmark   April 15, 2014 at 1:49PM
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richardoinvic

PupillaCharites, thanks for the reply...you may be right about the rockwool being too wet. the cube sits on a bed on hydrocorn so I'd say about 1" or so above the water. The bubbling action does keep the hydrocorn wet and in turn the rockwool may have become to wet.

I had the light originally 8" above and just this morning raised to to 12" above. What I did notice this morning was a few of the plants had produced roots several inches long...I think that's a good sign.

cheers, Richard

    Bookmark   April 15, 2014 at 4:45PM
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PupillaCharites(FL 9a)

I'm glad to hear it's working out. I'm sure everyone has their own anecdotal way of saying what works in their circumstances, but let me tell you what works for me to give you more info on what others are doing (and I certainly don't know if I have the right answer which generally works, all I know is it works for me outside).

I look at the hydrocorn and if the upper surface of it is wet, I am too close to the water and get more plant disease. If I lift up (NOT right after cutting strawberries I bought in the supermarket ;-), the top ball of hydrocorn, it is somewhat dry on the underside, but the pieces below it are water-dampened, which you can see in the clay as the water turns it wet looking like a leaky ceiling vs. bright wall. I have usually around 50-65% humidity after the Sun burns off the 98% we wake up with, and it is breezy usually, but this general thing pretty much works for me at least outside, to be sure the upper root mass has access to oxygen isn't getting waterlogged down.
Cheers and good luck to you too!

    Bookmark   April 15, 2014 at 6:12PM
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Rio_Grande

Based on your reply to pupilla I wonder if your plants are just in that stage where they put most of their energy into growing roots?

    Bookmark   April 15, 2014 at 8:05PM
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