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Snypie

How to water and feed a 4" RW cube?

Hello,

 

I need some help to grow some healthy plants in rockwool. I tried it several times and there was always a lot of problems. I want to prepare them for NFT.

I germinated the seeds then put them into 1” RW. I used RO water with nutes to 0.3 EC (or 150 ppm on 0.5 scale). Then every day I put the cubes halfway into the nute solution. I do this until there is plenty roots coming from the bottom of the RW. This is around 10-14 days from sprouting.

Then I translplanted them to 4” RW cube. I soaked the cubes in 0.5 EC nute solution PH’d to 5.5 overnight. And from this point when thing going worse. My opinion is my mistakes are watering and feeding. As I mentioned I start feeding them in 4” cube with 0.5 EC then upped to 0.8 and 1.0. I was watering them when the cubes were about half weight then the soaked weight (so every 3-4 days). I top watered them with plenty of runoff. I measured the runoff PH and the EC and it was high. PH over 7.0 and EC over 1.5-2.0, so i needed to water more. In other word every watering was a huge flush to push that numbers down to an acceptable range. I can’t decide if I should water more often but i am afraid of overwatering. And i am sure i was overfeeding them too.

So  my questions are:

1. How do you water the 4” cubes? From the bottom or the top? How much water? Do you water them every day?

2.     What kind of EC do you use?

Edited by Snypie

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Rockwool is very easy to overwater and is most likely the problem, I gave up using it years ago because of the issues you are having.

There are people who grow NFT but I couldn't get on with it so can't help you there...

good luck

 

:oldtoker:

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When I used to do nft, as soon as the roots had popped out, into the big cubes and on to the spreader mat. Pump on and away I would go. Gradually increasing the ppm as I went.

Why aren't your rw cubes on the spreader mat yet?

I can't think why you are experiencing such issues. And I never suffered from overwatering yet the pump was on constantly so the RW cubes always soaked. Tbh, I thought it was difficult to overwater in RW. Anyway, I've moved to coir but still admire the nft technique for its simplicity and excellent results. Just got fed up of disposing the cubes.

Anyway, many nft experts here so hopefully someone can advise you better. Sorry I can't be of more help.....

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If your using RO water and feeding at an EC of 0.8 to 1.0 this is WAY to high imo.

 

Your taking your water down to 0.0 the adding pure purpose made nutrients to the water, then watering the roots directly in an inert medium, your going to scorch them, or in the early stages just kill them off.

 

To give you some idea of what I mean....

 

large.5db5d70fdef29_OGKZ2.JPG.75310991e7

 

 

This was my OGKZ about 3 or 4 weeks ago. At this stage I was feeding 0.7-0.8 EC into a 70% RO 30 Tap water solution.

 

This is the same plant TODAY.

 

large.5dd3e5d661b8b_ogkz3.JPG.d2fda18627

 

 

 

I have NEVER gone above 1.0 EC during the entire grow. And I'm not using 100% RO water either. 

 

 

I'm going to assume your using soft water nutrients if your RO, which will mean even more "potency" in your nutrients.

 

At the early stages if your using pure RO your'll need about 0.2 EC of a good quality Cal/Mag and another 0.2-0.3 max of base grow nutrients and that is all until your into your res or tray etc. :yep: 

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Dear @GreenVision,

 

thank you for your reply. I will use a dry base nutes + dry Calcium nitrate + Magnesium sulphate. It will not higher than 0.5 EC. OK.

But what about watering the 4" RW cubes? I was buying some RW cubes today and the seller said it is not necessary soak the cube just put into the 1" RW and water lightly at the base of the plant around 100 ml of water. In this way you can water every day and the RW is not more waterlogged. But i can see everywhere on the internet you must soaking the RW before planting and after that you must water to runoff. Which one is the truth?

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2 hours ago, Snypie said:

Dear @GreenVision,

 

thank you for your reply. I will use a dry base nutes + dry Calcium nitrate + Magnesium sulphate. It will not higher than 0.5 EC. OK.

But what about watering the 4" RW cubes? I was buying some RW cubes today and the seller said it is not necessary soak the cube just put into the 1" RW and water lightly at the base of the plant around 100 ml of water. In this way you can water every day and the RW is not more waterlogged. But i can see everywhere on the internet you must soaking the RW before planting and after that you must water to runoff. Which one is the truth?

Watering lightly with no runoff will cause the nutrients to build up because of natural evaporation and the young plant wont take up all of it. Watering frequently to runoff will replenish the air in the cube, remove the excess salts and restore the target nutrient balance and moisture level. If you follow pamplemousses suggestion of putting it straight onto the spreader mat after the roots pop out and putting it in the 4 incher there will be constant fresh nutrient solution and air running through the bottom of the cube which the root will reach down for. The block will soak up off the mat and there will be a decreasing gradient of moisture up from the bottom of the block. Also note Green visions advice about EC levels.

Edited by catweazle1
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@Snypie  everyone has they're own way, find what works for you.

 

To start with I always pre-soak my cubes in pH'd water, but then my tap water us pH 8 so I kinda have to... Seeds / clones in starter cubes, when they're settled rooting out move them into the 4" cube..

 

I usually pop 4 small plastic golf tees in the bottom of the cube to keep it off the ground, the cube itself kept in an old micro-meal tray to catch any drips. I feed pH'd plain water for the first couple of days then start with something like Formulex or Shogun Start, half strength for a couple of days then move up to full strength.

 

To water I take my cube out and pop it in the sink usually, then water carefully untill runoff and then a bit more. Pick the cube up and bounce it gently on a corner to remove any excess water then back into the prop cab it goes.

 

Once there's a good few roots popping out the bottom of the cube it's good to plug onto an nft tray or drop into a dwc system :yep:

 

Don't get too hung up on numbers either, your plants tell you what to feed once you learn how to read them. I check EC so I don't burn them but couldn't tell you what EC I fed my seedlings at - it's whatever they need. Light green / yellowing, they're probably hungry, feed a bit more. Dark dark green, leaves curling, burnt tips, probably over fed, take it down a notch.

Simples.

 

 

Edited by Ranec
Spellingz
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@Ranec love the use of golf tees..... That's what I love about forums. There is always someone who has thought of a novel and simple solution.....:smokin:

And good advice re the feeding. The plant will usually tell you it's needs. It's just a matter of experience to be able to interpret correctly and react accordingly.j

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Okay, thanks to all for your reply. No i am seeing my mistakes. Feeding too strong, not watering enough and not putting the cubes on the tray.

I will germinate some seeds tomorrow and will be opening a new diary.

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7 hours ago, Snypie said:

Okay, thanks to all for your reply. No i am seeing my mistakes. Feeding too strong, not watering enough and not putting the cubes on the tray.

I will germinate some seeds tomorrow and will be opening a new diary.

You do prep the cubes first, dont you? Wash through under the tap then soak overnight in pH5.5 water.

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Yes of course i will soak the 1" starter cubes in Ph'd water.

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I have a new question about the nutes.

So i want to use still RO water but not with dry salts. I want to try out the GHE flora series. It has 3 bottles: Grow + Micro + Bloom. The Micro is available in soft water and in hard water format. It says you must use the soft water formulation if the water source contains less than 70ppm calcium.

From the website:

To ensure the best results in your area, Flora Series is available in both hard water and soft water versions: (more than 70 mg/L calcium, use FloraMicro hard water formulation, with less (or if using reverse osmosis, use FloraMicro soft water).

 

But i have read that some people still use a CalMag product with the soft water micro if using pure RO water. What is your opinion?

Edited by Snypie

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