NFT - What Happens Before The Roots Hit The Film?

[mattstronaut]

Hi everyone, first time poster and very new to growing. I have a 10 site NFT system I built myself out of square column wrap channels. I think it's going to be great, but I just put my first plants in about 2 weeks ago and things aren't going so good. The first few days were great, lot's of growth popping out the bottom of the baskets and I was sure that the roots would hit the film in no time. Then I thought they weren't getting enough N because the leaves never really greened up and were kind of yellow, so I bumped it up a little but then got burnt tips. Then the temps got hot so I added a chiller and I think I made it too cold at 60F. Now the plants look awful but I have my EC back down to around 1.0 and nutrient temps up to around 68F. Things seems to be going better and I am back to seeing new root growth after lots of browning and die off. I can't imagine the browning was due to O2 deprivation since my O2 meter says I am hovering around 8ppm which is solid for the temps I am at. I am "feeding" 4 times a day for 3 minutes each. "Feeding" at this point consists of two streams of water squirting either side of the basket so the nutrient soaks the hydroton and trickles down onto the roots. The film is constantly running but the roots of course aren't there yet and have a ways to go. pH is steady around 5.7.

Can anyone tell me if, based on the pictures I've posted, that I was correct in my assertion that the nute temp was too low and the EC too high? It was up to 1.3 at one point. Also of note, early on, at the suggestion of a friend, I put them on 24 hour feeding which got them WAY overwatered. Then I went to 2 feedings per day for 10 minutes each and the root growth I did have dried up and died, or at least started to before I put them on their current 4x schedule.

Also, am I crazy to think this will even work? My channels are about 9 inches high so the roots have a solid 6" inches to travel before hitting the film. I had read this was desirable, but now I am not so sure. Thank you SO MUCH in advance for any advice. I am so painfully aware that as a noob I bit off more than I can chew with NFT, but here I am willing to learn and own my errors.

[bigbadbillybob]

how are you recirculating the water,is it via a pump, and is it oxygenating the water at all?
Can you also give us more details on the feed like what exactly are you feeding them. what nutrient brand, grow, bloom or what?
Its a bit difficult to guess without knowing the full story.
Give us as much detail as possible, more pics of the system for a start.

The plants dont look great, but i dont think the water temp has anything to do with it, they look overwatered and locked out to me..
The ph and ec sound about right, maybe a bit hot if anything, but if the nutrient is soaking the rockwool, to the extent that it is constantly soaking, it wont help. You want the roots to reach out to the water.

More details please
I

[mattstronaut]

how are you recirculating the water,is it via a pump, and is it oxygenating the water at all?
Can you also give us more details on the feed like what exactly are you feeding them. what nutrient brand, grow, bloom or what?
Its a bit difficult to guess without knowing the full story.
Give us as much detail as possible, more pics of the system for a start.

The plants dont look great, but i dont think the water temp has anything to do with it, they look overwatered and locked out to me..
The ph and ec sound about right, maybe a bit hot if anything, but if the nutrient is soaking the rockwool, to the extent that it is constantly soaking, it wont help. You want the roots to reach out to the water.

More details please
I

Thanks for replying! Yes circulation is done with a pump. The nutes get sprayed out of two nozzles at 60 PSI (trying to mimic the oxygenation that happens with falling water) plus a 1030 GPH air pump with three 4" round air stones. At o2 of 8 ppm it's 100% saturation at the temps I'm maintaining. The nutrient brand is Earth Juice and I'm using Grow Part A and Bloom Part B in the proportions listed on the bottle. There's also some Neptune's harvest blend in there, which I think may be the source of too much nitrogen. I drained the tank halfway and filled with fresh water which brought the EC down to its current 1.0 (my other meter says .9 and I consider it to be more reliable). The rock wool is definitely not constantly soaking. 4 times a day it gets sprayed for 3 minutes, but most of that water drips down the hydroton and never really soaks the rock wool, although it does stay damp constantly. Below I've attached a picture of the basket from inside the channel during a feeding session. You can see the two streams hitting the upper area of the basket and the nutes dripping off the roots that are dangling down.

If the issue is overwatering then what should my next step be? When I was doing two and three feedings (6 minutes each and 4 minutes each, respectively) the root tips were drying out, but the leaves were starting to perk up. Now with 4 - 3 minute feedings they look overwatered again. I suppose I could try 4 - 2 minute feedings but that seems like it would hardly even get to the rockwell behind the hydration.

[bigbadbillybob]

hmmm, im a bit stumped with this one, if im honest.
it doesnt look like too much nitrogen to be honest, more like magnesium defficiency.
if you have cal mag, then add some to the res, as per the bottle instructions. you could also spray the leaves just after lights on with it -diluted.
i know nothing about your nutrients, but noticed that they are organic, which i aint a fan of in hydro.
if you have a part A for grow and part B for bloom, then you maybe only need to give them the grow, as they are in veg. when you switch the lights to 12/12, then use the bloom. check with the nutrient manufacturer tho as some get A and B at both veg and bloom.
personally id bin the nutrients and use something non organic, like Ionic.
ionic stuiff has a simple nute for grow and a nute for bloom

if the root zone is drying out then feed them more often. as its a one off system with a bit of aeroponics thrown in i would try more feeds, but less feed durations, so say feed them 4 or 5 times during lights on for 3 minuites.
i know i said they looked over watered, but the roots shouldnt really dry out. the brown root tips look like a sign of pythium or root rot, another common thing with organic nutrients.

give it a try and let us know if it improves

i take it your temperatures and humidity are in the ballpark?
about 24-28 lites on and about 18-22 lights out?

[mattstronaut]

Temps and humidity seem to be spot on. In the root zone the humidity is 95% (I'm assuming it's actually 100% but my hygrometer doesn't go there) with a temp of 65. Nutes are 20-21. Canopy temps are around 24 lights on, 18 lights off. I will try more shorter feedings during lights on. I had been feeding them during lights off as well. Is that a faux pas or just a waste? Thank you once again for your help. I will post an update in a few days with hopefully some much happier photos.

[ggotch]

i think bbbb meant whats the humidity at leaf level,that determines wether shes drinking or no.or drinking too much or not enough etc.

not sure rh at rootzone means anything ?

might just be too baked to understand that bit.. :bzzzzz:

[bigbadbillybob]

yeah i meant at canopy level - to see if its maybe too high or low, you should be aiming for over 50% (prefferably about 60-70%) during veg.
You can feed them at lights off, but it is generally better to feed when the lights are on- especially in veg. In flower you will have no choice other than to feed lights off too, to prevent the roots drying out.
Try and get the nutrient temps down to 18-19 if possible.
cheers

[mattstronaut]

Hah, right. Sorry about that. I keep it around 50 during daylight and up to 60 at night, with a drop just before the lights go out to prevent condensation as the room cools. I use a simple ultrasonic humidifier and a mechanical timer.

[bigbadbillybob]

thats fine mate, lets see how it does with the extra feeds .
Ive just had another thought about this.
The hydroton was washed rinsed and Ph'd to 5.8 before you put it in wasnt it? By that i mean that you rinsed all the crap out of it, and soaked it over a couple of days in PH 5.8 water?
If this is the first run in the system it could be raising the Ph too high once it has gone through the hydroton.
Can you check the ph of a sample when it comes out of the bottom of the net pot?
Im not a fan of rockwool myself, it also fucks about with Ph, but next time you could use a root rior or root it cube- they are much better, aspecially as you have the hyroton to keep it in place.

[Type M]

Sorry I have no idea what your issue is, but this isn't NFT. More aeroponics maybe?