PH rising in 3x3x4 RockWool Cubes?

VapeIt · Jan 30, 2011

I took some clones, after they rooted, I put them in 3x3 RW cubes. They are @ 2 weeks into the RW and vegging. I am hand watering them every day or 2. I just hand dip them into a bucket of nutes I mixed up. I am using H&G. I am vegging in these cubes until they are ready to go into my Ebb & Grow buckets with Hydroton.

I checked the runoff of my 3x3 RW cubes by giving them a little squeeze into a cup and measured the PH - It was @ 7.
I am very careful to check the water PH before feeding with a calibrated PH meter. I have been feeding at 5.5-5.8 PH.

My plants are getting crispy and browning leaves. Why is the PH so high in the run off? Yesterday I mixed up some RO water and Clearex at @ 5.0 PH and ran a quart of this through each block. The runoff is down to 6.2-6.4 PH now. Should I keep doing this flush until runoff is 5.8?

I have been feeding with an EC of .8-1.0. That is 400-500PPM on the .5 scale.

Also, how often should I be watering by hand? More than once a day?

Thanks for any help on this.

Mr. Greenthum · Jan 30, 2011

Check and make sure ur cubes are moist but fairly dry. if your rock wool is to wet when u water ur plant it could be increasing ur ph with the old water u poured in a day or two ago..
Did u pre-soak your Rock Wool?

what kind o water r u using? Osmosis, city water, well water? you should check ur waters ppms and ph WITHOUT nutrients just plain water so u can see ur starting point.

Yodas Master · Jan 30, 2011

Sounds like you didnt presoak the rockwool with 5.5 ph water..Also let the rockwool almost dry out until you water it again..Dont let the plants sag but im sure your watering to much if more than once a day..I wouldnt recomend watering with anything under 5.5..

VapeIt · Jan 30, 2011

I use RO water from a water store.
I did presoak the rockwool in PH 5.5 water for 30+ minutes.
The starting point of my RO water is almost unreadable on the PPMs, and @ 7PH.
I ad nutes and PH to 5.5 before watering. I calibrate my PH meter weekly.

Am I not feeding a high enough PPM? Too high PPM?

I don't know how I could be watering too much when it is only every day or 2. Don't people usually do like 3 floods a day?

What is an ok runoff PH if I am feeding at 5.5? 6? Higher? My plants are losing leaves pretty fast and I think I need to get the PH down in the RW asap. Should I keep flushing with Clearex? What PH?

Thank you.

Mr. Greenthum · Jan 30, 2011

VapeIt said:
I use RO water from a water store.
I did presoak the rockwool in PH 5.5 water for 30+ minutes.
The starting point of my RO water is almost unreadable on the PPMs, and @ 7PH.
I ad nutes and PH to 5.5 before watering. I calibrate my PH meter weekly.

Am I not feeding a high enough PPM? Too high PPM?

I don't know how I could be watering too much when it is only every day or 2. Don't people usually do like 3 floods a day?

What is an ok runoff PH if I am feeding at 5.5? 6? Higher? My plants are losing leaves pretty fast and I think I need to get the PH down in the RW asap. Should I keep flushing with Clearex? What PH?

Thank you.

I would stop ClearX. Alternate straight water with nute water. The straight water will flush out the cubes in between nute waterings and should bring Ph down. Flush it out with water instead of ClearX.

What do ur ppms read?

Make sure to water into the container and NEVER water the tops of the Rockwool cubes. Let the plants pull nutes and water up through the roots. Encourage root growth down. Pouring over the top will make shallow roots and the nutes will build up in the Rockwool.

VapeIt · Jan 30, 2011

Greenthum,
I had been hand dipping them into the nute mix - 1/2-3/4 way up the RW. I had not been letting the tops get wet until yesterday. I could think of no other way to flush out the high PH. I only used Clearex yesterday as a flush to bring the PH down.
What PH should clear water be to flush these down to a reasonable PH runoff? Runoff seems to be down to 6.2-6.4 now from 7+ a couple of days ago.

I have been feeding with PH'd RO water at 5.5 and PPMs of 500 - 1.0 EC. The runoff before yesterdays flush was @ 1.0-1.2EC (500-600ppm). They are a couple of weeks into the larger RW blocks. About 6" tall.

VapeIt · Jan 30, 2011

Garden of Dreams,
It's too late to presoak my RW cubes. Plants have been in them for 2 weeks now.
I did pre-soak, but I guess not long enough.
What can I do now to bring the runoff PH down to 5.5-5.8?
Let them sit in a 5.0 plain water bath for an hour?
Thank you.

mittenmedgrow · Jan 30, 2011

Rockwool is kinda tricky. Not presoaking is deff your problem. If I was u I would flush them heavily with a 5.3 -5.5. Its easy to overshoot rockwools ph. As with coco runoff can be decieving and unless you understand the ph of rockwool is hard to accuratly tell whats going on. I use a large syringe and suck a sample right out the cube. Rockwool is all about adjusting your nute ph properly to mantain slab or cube ph.

VapeIt · Jan 30, 2011

Mitten,
I did pre-soak in 5.5 for 30 mins like the package said. Now it looks like people suggest 24 hours. Too late for that now. I will not be doing the RW cubes for veg again after this. After this run I will just put clones in netpots of Hydroton until ready to go into the E&G.

So, the question is - what is an acceptable PH inside the RW block? I did flush heavily yesterday and the runoff went from 7+ down to @ 6.4? Is 6.4 acceptable? Or should I flush again tomorrow and get it closer to 5.8??

Thank you.

Mr. Greenthum · Jan 30, 2011

Flush again where u have it now is okay but u want to make sure u can get it a little under 6.0

VapeIt · Jan 30, 2011

Thanks everyone. I will let them dry today and flush once more tomorrow.

Thanks for the help in my time of panic.

mittenmedgrow · Jan 30, 2011

Not science but an example is if your putting ph.6.0.in and 7.0 is coming out that means that your ph would be alot higher than 7.0 to change that much. .If 5.8.goes in and 6.0 comes out you drop ph a little on next watering. See wat im sayin. I never got that far off with rockwool so I cant really help to much now. presoak is key. I presoak a couple hours and add ph down untill it hits 5.5 The ph of my soak water has got to be around 3.0 ph. If your runoff is so high I might even water in a below 5.0 ph but I have never tried it so not sure. I hope it works out for you wish I had better advice.

PH rising in 3x3x4 RockWool Cubes?

PH rising in 3x3x4 RockWool Cubes?

VapeIt

Mr. Greenthum

Yodas Master

VapeIt

Mr. Greenthum

VapeIt

VapeIt

mittenmedgrow

VapeIt

Mr. Greenthum

VapeIt

mittenmedgrow

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