Rockwool PH and other challenges... Automated Top Feed Drip...Crop Steering

Hey all....first post. Been growing for years and have switched from promix to Rockwool cubes (Grodan)...and went to top drip automated using Growlink with crop steering method up next...and would love any other Rockwool growers to chime in with any tips. Anything that is unique to rockwool would be great. Here are some of the challenges that I have come up against...and then figured out. At least figured out and has worked for me...Im sure there are lots of suggestions and experience here so post it up!

1- PH buffering the blocks (dont follow factory directions!)...trial and error brought me to an overnight at 4.0 water...then second soak with nutes (Jacks) at 4.5. I Usually end up at 5.4-5.6 stable.

2- Dont squeeze the blocks ever...it will ruin the integrity and create salt channels

3- I made the mistake initially of keeping the blocks to wet at a young plant age...I learned to let them dry back at least 50% of volume or weight until healthy roots established into whatever size block they were in at the time

4- Sometimes less is more...I have found that the need for anything but jacks is not really necessary. If Temp, RH, VPD, PH at the roots, EC, light PAR, proper drybacks, etc...are all dialed in correctly... then the plants literally have everything they need to thrive...eliminating the need for any supplements.

5- Dont move smaller block to the next size until well populated with roots first...also make sure that the EC is lower on the new block than the rooted block. Sprinkle with Mykos...or the like

That's enough out of me...looking forward to the communities tips, experience, suggestions, and workarounds with rockwool......good growing!!

Have you tried the new grodan cubes? You're only supposed to soak them for less than 2 minutes. I just started using them. They have some sort of wetting technology incorporated into them so that the moisture content stays consistent within the whole cube. I was using flora flex cubes that they ended up discontinuing and they were horrible..

Hey been out of commission for a bit... No I am using the older version. There is definitely lime dust that needs to be rinsed though or spikes happen. At least for me. Being the first run in RW...I'm in the learning curve. I have my second set in 4" and have learned to let them dry back very well to get them rooted. Even if PH is off or deficiencies are showing...let them dry back...don't keep trying to flush the corrections into the block without good dry back and root mass. I'm coming out of Promix, switched from Botanicare to Jack's, and also have gone to automated drip using Growlink....so like an idiot, I changed everything LMAO. Anyway...I am going to try a run in Coco this go round, or at least half the room. (4 light flower room)

soaking in ph below 5 will begin to break down the block. not suggested.
soak above 5.5ph using ph'd and filtered water.
Ive found anything over an hour pre-soak is unneeded.
never had an issue with any lime or ph in several years of 6x block growing.(hugo's and pargro's)
IMO 4x blocks are too small, not enough volume for the roots.

Hey thanks Rocket...didnt know below 5.5 could do that, so I will adjust. I will use the 6x6's next for sure, as they seem to be just the right substrate volume for 9 per ight with auto drip. I made some fundamental mistakes early on in my first run which I chased the whole time. Short version is...unhealthy and underdeveloped root zone. I was talked into 8x8's by Grodan rep. Way too much block. So I'm using up the couple cases I have and cut them in half. I have a tool to cut out an insert for the 4x4 (which are actually 2.5x4x4) to set in so that I can get an even feed and or flush through.... with the intent of roots populating out sideways as well (we will see)...
A few pics of Veg room and transplants into 4x8x8 with cutout.

Veg room hand fed for now.
Flower room automated.

Rocket or anyone else....do you find spikes in PH when first letting roots establish in RW during longer dry backs? I'm using Jacks (salts).... I'm wondering if salts can cause this, if there is no regular runoff early on during root establishment? That being said...I am making sure that I have well populated root zones before pushing the feed through...would love any input on this for sure.

Question for anyone using Jacks or salts with RW and top feed drip... Jacks says use full strength (2.4 EC) from early veg right through Flower. Should this be dialed way back with automated top feed in RW?

Thanks in advance for any input! ..... I'll try to stay more involved here and post up pics along the way

Current gear, nutes, environment,etc

Gear
Fluence Spyder X Plus
Grow link automated drip
DAP mini constant pressure pump
Chiller
Recirc pump
Air stones
C02
Filters, fans, etc

Nutes Inventory
Jack 321
TPS Silica
Recharge
Kelp
Fulvic
Mamouth P
Roots accelerator
CalMag
Superthrive
Molasses
Mycos
Cleanse - athena
Clearex
P Booster
K Booster




Veg environment
80 degree
72-75 RH
325-425 ppfd
5.5-5.8 Ph
EC-1.5 until I can go to automated drip with run off










Recirc pump

If you overwater a cube, a good way to drain it is sitting it on top of another piece of rockwool. It works really well. I usually do this when I'm transplanting the seedling so that the cube isn't too wet.

setting the block on a folded towel works as well.
good for 150-300ml drain.

thanks for the tip with the draining and I will use it... I stood my 4x8x8's on end and let them drain some after soak and nute prep...
Do you think I am on the right track with a first really good dryback after transplanting?
Test plant (2.5x4x4 flush inserted into 4x8x took 5-6 days to dryback to just before wilt.

Qsound said:

thanks for the tip with the draining and I will use it... I stood my 4x8x8's on end and let them drain some after soak and nute prep...
Do you think I am on the right track with a first really good dryback after transplanting?
Test plant (2.5x4x4 flush inserted into 4x8x took 5-6 days to dryback to just before wilt.

Click to expand...

That's a long dryback, but if they look okay then it should be fine. Make sure to flush them out. I've had issues of EC spikes when the rockwool dried too much.

Oh...I baled on the coco run because my teens are in 4"rw and figured that would be bad transplanting cubes into coco. My thought process was that the cube would stay wet and potentially rot the stalk while the coco dries back quicker than the block. So thats why I am using up my 8x8's cut in half. looking forward to trying 6x6 as well

lusidghost said:

That's a long dryback, but if they look okay then it should be fine. Make sure to flush them out. I've had issues of EC spikes when the rockwool dried too much.

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Thanks for the help....The 5-6 days is the very first dry back after transplant...I have noticed the same with EC spikes after dry backs....so I went in a little light on the EC when prepping block for the 4x4 insert...and then plan to flush when I'm not so paranoid of drowning the roots like I did the first RW run. I run 36 plants at a time so I don't want to have to drain out a flush or saturated block with a towel or the like for so many...so I rely on the root zone for the dry back after flush if that make sense. The test plant I did looked pretty good after the 5-6 days with a few roots poking out the sides of the 8x8x4,. Showing very small nute def, but fairly confident the flush and bumped EC will take care of it tomorrows feeding...

Qsound said:

Oh...I baled on the coco run because my teens are in 4"rw and figured that would be bad transplanting cubes into coco. My thought process was that the cube would stay wet and potentially rot the stalk while the coco dries back quicker than the block. So thats why I am using up my 8x8's cut in half. looking forward to trying 6x6 as well

Click to expand...

I ran that same setup (4" cubes in 3 gallon pots) for about 5 years and it worked really well. Just make sure to bury the cubes deep enough and then top off the pot once the water packs down the coco enough to expose the cube.

Things look nice! I run 4" cubes that I ultimately put onto unislabs, and I drain to waste with MegaCrop.

I've been using RW for 30+ years, and yeah, I think you are quickly seeing the pros and cons. The first 3 weeks or so is the most challenging, or at least as long as it takes to get your root mass started. If you let things dry back too much, you do get massive ph and EC spikes. Keep it too wet and your roots don't really have any reason to go on the hunt. So it's a delicate balancing act, and the whole thing is probably most dependent on our unique environmental conditions.

It's trial and error, but as others have mentioned there are ways to dry out your blocks if they are staying too soggy. Full disclosure, I've never used the 6" or Hugos but I'd imagine they would be that much harder to get the root system established. But in my system, I've had better luck with hitting my blocks real hard with solution almost daily. When I say real hard, I pick my blocks up and literally pour nute solution through them until it flowing freely out the bottom. I'm accomplishing 2 things by this - a wholesale replacement of the nutes in the block with properly ph'd and ec'd nutes, and just as importantly, I'm bringing in fresh oxygen into the block. And that's what you need to grow in these things. So that's what works for me. Once they've filled out the 4" blocks I put them on the unislabs and the auto watering system.

One final thing that might be transferable to your grow, once I have one set of leaves I feed them pretty much at the same EC the entire grow. Good luck!

I usually buy 4x2.5" cubes because the regular 4" kind stay too wet early on.

Qsound said:

do you find spikes in PH when first letting roots establish in RW during longer dry backs? I'm using Jacks (salts).... I'm wondering if salts can cause this, if there is no regular runoff early on during root establishment?

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Your ph rises from the Rockwool not from the nutrients. Even the ph on the new blocks rise.

Qsound said:

Question for anyone using Jacks or salts with RW and top feed drip... Jacks says use full strength (2.4 EC) from early veg right through Flower. Should this be dialed way back with automated top feed in RW?

Click to expand...

Just use whatever EC works for you, what have you used in the past? I feel like I can feed higher in coco vs Rockwool. Jacks says some things that don't really make sense so I've stopped paying attention to what cute companies say, they still follow some older beliefs that have been proven wrong in modern times.

Triplefastaction said:

Things look nice! I run 4" cubes that I ultimately put onto unislabs, and I drain to waste with Mega Crop.

I've been using RW for 30+ years, and yeah, I think you are quickly seeing the pros and cons. The first 3 weeks or so is the most challenging, or at least as long as it takes to get your root mass started. If you let things dry back too much, you do get massive ph and EC spikes. Keep it too wet and your roots don't really have any reason to go on the hunt. So it's a delicate balancing act, and the whole thing is probably most dependent on our unique environmental conditions.

It's trial and error, but as others have mentioned there are ways to dry out your blocks if they are staying too soggy. Full disclosure, I've never used the 6" or Hugos but I'd imagine they would be that much harder to get the root system established. But in my system, I've had better luck with hitting my blocks real hard with solution almost daily. When I say real hard, I pick my blocks up and literally pour nute solution through them until it flowing freely out the bottom. I'm accomplishing 2 things by this - a wholesale replacement of the nutes in the block with properly ph'd and ec'd nutes, and just as importantly, I'm bringing in fresh oxygen into the block. And that's what you need to grow in these things. So that's what works for me. Once they've filled out the 4" blocks I put them on the unislabs and the auto watering system.

One final thing that might be transferable to your grow, once I have one set of leaves I feed them pretty much at the same EC the entire grow. Good luck!

Click to expand...

Hey all...thanks so much for the great info and input...yes it would seem the first few weeks with RW are the most challenging and sets the stage for the rest of the grow. So I just transplanted 2 days ago from rooted 2.5x4x4 into 4x8x8 that I made from 8x8's.

You can see the deficiencies, tip issues, lower leave, serrated, leathery beginnings, etc. Running 4 strains, total 40 plants and some less affected than others. Mostly all of the yellowing and def's are lower on the plant....overall dark green which I would call high N, but am second guessing everything at this point.

You will see one of the plants is quite leathery....

They have roots starting out the bottom and I took some run off samples by syringe this morning ....

PH=5.8 EC=1.2-1.5
Jacks 321 - Roots Acel .5ml P/G - 1/4 tsp P/G Superthrive - and Fulvic

They are about 50% dried back from initial transplant...what would your next move? My move would be to let dry back another day perhaps and then flush through with 2.0 EC (Jacks) at 5.5 PH...then put them all on towels for a 250 mill pull. (ran a test on one and pulled about 8-9 liquid oz)

I'm not confident on the EC strength side of this because of my lack of experience with RW, vs the signs that are showing on the fans. So would love all of your input...thanks again and happy growing!

Your numbers look pretty good, so I'm not sure. I generally approach these things as deficiencies caused by lockout, which leads me to a good flush with lower nutes and allows me to basically start from scratch. That's something the soil guys can't do.

I will say, that based on the size of your plants, *in my system*, I'd be feeding multiple times a day to runoff at about 1.0 EC and I'd be past the point of thinking of drybacks other than the rudimentary crop steering I try to do. Even if I had to do a flush, I'd hit them up with my normal multi day feeds beginning immediately. But again, that's the way my system works.

Probably repeating myself, but is so important to remember that the only real way to get good oxygen to your roots is by having your nute solution pull it in - either through top feeding or during the drain phase of a flood/drain setup. So if we just dump a bunch of solution in our rockwool and let it sit there for days, we could be suffocating the roots, and then burning them as our rockwool goes into the high EC and PH problematic phase.

You've got a lot of plants, try some different things and don't get discouraged. I recently changed grow spaces and it took me 3 runs to figure things out, despite my first grow being over 30 years ago. So much of what we are discussing is a result of environmental factors and there's really no one size fits all. But once you get it down, watch out. Clean, easy, fast growth that you can't achieve any other way.

Thanks Tripplefast!... I was thinking the same regarding lockout/def...and I am going to flush as you recommend. I had just put my well rooted 4x4 into the 4x8x8, so thats the reason for the size of the plant and the dry back. So I think I get it, and contrary to Jack's tech line... If ya dont mind a couple straight questions since you have some great experience with RW...

Do you run the typical 5.5 - 5.9 or so in RW?
Would you say that the multiple feed in a day is the reason for the lower EC?
Which would give them a new fresh balanced set of nutes every hour at lower EC, rather than a higher EC sitting for a few days like I had done previously in 5 gallon/Promix?
So in turn...the frequent feed to run off will keep salts flushed and PH consistent?

Thanks again for the help and sharing your knowledge

Qsound said:

Do you run the typical 5.5 - 5.9 or so in RW?
Would you say that the multiple feed in a day is the reason for the lower EC?
Which would give them a new fresh balanced set of nutes every hour at lower EC, rather than a higher EC sitting for a few days like I had done previously in 5 gallon/Promix?
So in turn...the frequent feed to run off will keep salts flushed and PH consistent?

Click to expand...

#1 - PH, yes I'm happy in that 5.7-5.8 range. Bumping up to the 6.0 level occasionally can sometimes be helpful if in flower, but I've had lots of happy plants just hanging around 5.8.

#2 - You might think that would be the case, but no, not really. The plant is going to take what it takes/needs as long as you give it the appropriate environment at the root level. I've just found that 1-1.2 EC is all I need to bring *my* typical plants to the finish line. That really depends on the size of your plants. But if you aren't feeding them enough, that'll manifest as overall yellowing/lightening of leaves, versus the spotting and burning you are seeing. But my plants, my system, I can run that EC from a 3" plant to a 30" plant without problems.

#3. Yes, absolutely. If you haven't set up an auto watering system you need to think hard on your plans. Once they get to flower those cubes are going to be drying out real fast. Again, the only way we can grow plants in water is to make sure we are introducing an appropriate level of oxygen. And that happens via feedings. I'm not saying you can't probably grow in RW by just soaking your plants once a day. But you'll likely experience problems similar to what you are seeing, and the further into flower you get the worse it'll be.

#4. Yes. This is the basic concept of growing in rockwool. Out with the old, in with the new! Good luck!

Edit - you don't need to feed every hour. I typically feed maybe 4x day in veg and 6-8x/day in flower. I don't typically feed at night during the flower stage (keeping humidity down) unless the plants absolutely demand it. Then you start up your crop steering fertigations when lights come on.

I'm getting verbose here, but one more comment regarding drybacks - they are important, especially in flower. There's lots of info out there about crop steering with rockwool which basically comes down to keep them pretty saturated during veg and allow more dryback during flower.

BUT - the saturation/dryback cycles, whatever you settle on, should all occur within each 24 hour period. If you aren't getting enough overnight dryback during flower, for example, you need to lower your shot sizes leading up to dark so the plant enters the night cycle a little less saturated. Grodan does sell a several thousand dollar monitoring solution to this problem, but most of us are forced to trial/error it.
And my experience is keeping them pretty saturated in veg gives me best results. I just feed every 4 or 6 hours or whatever.