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Root Health - Rockwool vs Perlite


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Old 07-25-2010, 05:28 PM
omerizm omerizm is offline
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Default Root Health - Rockwool vs Perlite

I have different types of lettuce growing in my DIY NFT system. As a medium, I used rockwool cubes and cups filled with perlite.

The roots of those grown in rockwool cubes don't look healty. The part that remains above the solution is yellow. Down below, the part that is in contact with the solution is white.

The roots of those grown in perlite filled cups seem to be ok. They are all white. Note that the cups are suspended above the water level as well, so the upper part of the roots are not in contact with the solution.

Please see photos below.

What is the reason of this? Should I let the rockwool cubes sit on the bottom of the gully?










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Old 07-25-2010, 08:09 PM
GpsFrontier GpsFrontier is offline
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Is this a flood and drain system, or NFT system? I'm not sure if anything is really wrong, some root discoloration (yellow, or light brown) is not necessarily bad. But is usually either on older roots, or roots stained by the color of the nutrients. Although from the pictures it looks like the plants in the cups hang down farther. That is ,that the bottom of the rockwool cubes is higher than the bottom of the cups. Therefore it's not nearly as noticeable on the plants in the cups, simply because their roots are closer to the water level.

P.S. Just curious, is that vinyl fence post tubing? I'm needing some 4 inch square tubing, but vinyl fence post tubing is too expensive for what I need to do.
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Last edited by GpsFrontier; 07-25-2010 at 08:12 PM.
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Old 07-26-2010, 03:54 AM
omerizm omerizm is offline
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It is an NFT system. It is true that the plants in the cups sit closer to the water. All Plants seem to be ok for now, the leaves look good and they are growing. I just want to understand why this is happening. The difference is really obvious.

The gullies are 2.8 inches deep. The rockwool cube is 1.5 inches. So it is suspended high. It is not moist. Is this ok? Should it sit at the bottom of the gully? How can I do it?

I used rectengular rain water pipes that are used to run the collected water from the roof the the ground. They are 2.8 inches high, 4 inches wide and 13.1 Feet long, made of PVC.

Köşeli İniş Borusu - Ege Plast - Plastik Boru
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Old 07-26-2010, 05:42 AM
GpsFrontier GpsFrontier is offline
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The discoloration is just due to being exposed to the air, because that part of the roots are continuously exposed to the air, and there is probably a lack of humidity in the tube that would keep that part of the root moist. The rockwool shouldn't be dry, but it shouldn't be soaked either, just moist. The roots are not wicking up enough water to keep it moist. If the plants are doing OK, then I don't know if there is any real problem. But If you want to try and lower the rockwool cubes that would help get more moisture to that part of the root system, and hopefully wick up some moisture into the rockwool cubes.

Going by the pictures, I think the easiest way to lower the rockwool cubes is to simply use the same white cups you are using for the other plants, then cut holes in the bottoms of them to place the rockwool cubes into. Personally I would experiment and make some low enough that the cubes just touched the water, and some that were just above the water level. I have seen setups that the cubes were sitting on the bottom (in the flow of water), but that will constantly saturate the rockwool cubes with water. But either way they will probably do fine. Now that I think about it, I don't think lettuce plants mind wet feet much.

P.S. Thanks for the info on the tubing, they looked square in the pictures. The rectangular rain gutter downspouts are common and easy to get here also, although for the design I have in mind I need true square 4x4 tubing or it wont work. I have found square rain gutter downspout tubing, but unfortunately not 4 inch wide.
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Old 07-27-2010, 12:05 AM
Anianna Anianna is offline
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GpsFrontier, just thinking out loud here since this isn't something I have actually tried, but I know some crafters who build molds with plywood and nails and then heat pvc with a heat gun, bending it into the shape of the mold. Perhaps you could use 2x4s to press a round pipe to square it. It would probably take a lot of pressure and I would think the corners would be somewhat rounded. I'm not sure if that would suit your needs, but it might be something to try.
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Old 07-27-2010, 02:52 AM
GpsFrontier GpsFrontier is offline
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Quote:
Originally Posted by Anianna View Post
GpsFrontier, just thinking out loud here since this isn't something I have actually tried, but I know some crafters who build molds with plywood and nails and then heat pvc with a heat gun, bending it into the shape of the mold. Perhaps you could use 2x4s to press a round pipe to square it. It would probably take a lot of pressure and I would think the corners would be somewhat rounded. I'm not sure if that would suit your needs, but it might be something to try.
Thanks for the thoughts Anianna, that is a possibility although it would be quite an involved process to do right, and costly I'm sure. The design is for 20, 10 foot long tubes. I would need to build a press that would shape it, then find a way to heat the whole tube at the same time to the right temp, in order to re-mold it without melting it. I would also need to do some trial and error to fine tune it I'm sure. Then comes the hard part. I also need 40 end caps for the tubing. As well as about 20 couplers to connect more than one piece of tubing to another, in order for easy disconnecting for cleaning and maintenance, depending on if I can get the end caps to very tight, not just water tight but resist yanking and pulling (yet removable).

P.S. Just to give you an idea what I am planing I attached a couple of pictures of a small scale setup of the design. I designed the small scale system to hold 4, 5-6 foot square tubes (holds 64 plants). I plan the large scale project to have 20, 10-12 foot long tubes (depending on the length of the tubes I can get), that system should hold a minimum of 640 plants (likely about 700). The vinyl fence post tubing would run me about $1000 to do ($650+tax for just tubing, then I need end caps and couplers). But to keep on budget, I need the cost to under $500 total.
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Old 07-27-2010, 10:03 AM
omerizm omerizm is offline
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This is an interesting idea GpsFrointier. But do you really need the gullies to be rectangular? Why don't you use 4 or 6 inch circular pipes?
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Old 07-27-2010, 02:37 PM
Anianna Anianna is offline
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Those are nifty. I can see where molding the pipes on that scale could be a problem.

I wonder if pillar molds could be waterproofed for that sort of long-term liquid exposure. I'm sure you could find 4" square pillar molds and you could cut them to whatever lengths you need pretty easily. You would still have to come up with some way to seal the ends, though.
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Old 07-28-2010, 02:43 AM
GpsFrontier GpsFrontier is offline
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Quote:
Originally Posted by omerizm View Post
This is an interesting idea GpsFrointier. But do you really need the gullies to be rectangular? Why don't you use 4 or 6 inch circular pipes?
Not rectangular, Square. Square is equal on all sides, rectangular isn't. Well the reason is the placement of the holes. I plan to grow strawberry's in this system, so I need 9-10 inches between plants (holes). If you look closely at the holes in the tube, there are two rows of holes in each tube. They are offset, and facing opposite directions. That allows me to have the same 9-10 inch spacing, but also have two rows of plants in one tube when it's turned on its edge like in the pictures. Instead of one row of plants straight up in round tubing.

I can use round tubing, I have before on another system, but then I would need 40 tubes instead of 20 for the same amount of plants. That would also take up twice as much space in the back yard. Also the system is planed as a flood and drain system, so 40 tubes would take twice as much nutrient solution to fill for the same amount of plants. I am already looking at about a 200 gallon reservoir. In round tubing the offset holes would be two low to flood the tube sufficiently without leaking out the holes.

The round tubing would be OK if I ran it as a NFT system, but I have never really been a fan of the NFT system. I believe I can better control the moisture to the plants entire root systems running it as a flood and drain system. Although, I do have it designed so the water level inside the tubes is completely adjustable, that will also allow me to run it as a NFT if I wanted to.

Thanks Anianna,
I may look into using the pillar tubes, although I cant say I can ever remember seeing square ones before. Also with all the extra fabrication I'm not sure it would be cost effective. My plan right now is to contact (e-mail) as many rain gutter manufacturers as I can, asking if they make plastic 4 inch square downspout tubs. After that, I'm not really sure where to go next (and still be reasonably priced).
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Old 07-28-2010, 06:24 AM
omerizm omerizm is offline
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My opinion is, you could still use a circular cross section and put 2 rows of holes in each tube as you plan to do with 4*4 pipe.

Like this:



If you use a pipe about 5 inches in diameter, the holes could be high enough for your application. Or you could try 6 inches. The amount of water to flood the pipes will increase of course, that is a disadvantage. But the setup will approximately require the same amount of space.

I am not saying that this is better than 4*4, but it could do the trick if you can not find 4*4 pipes.
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Old 07-28-2010, 11:17 PM
GpsFrontier GpsFrontier is offline
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Thanks omerizm,
For me it wouldn't be cost effective to use a 6 inch round tube (PVC anyway). The 6 inch tube runs $1.78 a foot x10= $17.80 + tax, and the end caps run $11.98 +tax ea. That would run me about $45 a tube. I can get the 4 inch vinyl fence post tubing with end caps for about that, probably less. I haven't checked prices for 5 inch PVC tubing and caps, but I don't think it would be much different in price. Not to mention the added operational costs like needing a reservoir at least twice the size. That would also likely double the cost of the nutrients I would go through.


It would only be economical for me to use round tubing if I used the 4 inch ADS irrigation tubing that I have used before. It runs $8 for a 10 foot tube, and $2 for each end cap, and coupler. Total $14 for a complete 10 foot tube, including a coupler piece for the center of the tube. I think I will get another ADS tube to do some testing with to see if I can get the water level high enough. But because of the angles, preliminary testing seem to show that only about 1/4 to 1/2 inch of the bottom of the basket would get wet at full flooding (before threat of overflowing out the holes). I wanted a full inch to get saturated when fully flooded.

P.S. Just for the heck of it I attached a few pictures of the ADS tubing. Notice that I gut the tube in half in order to pull out the roots and clean the inside before I reuse it. That's what I needed the coupler for, to reconnect both halves again. I also attached an updated version of the drawing of my intended design. Don't pay to much attention to the black ports sticking out the end and bottom for the inlet and overflow, I have an update but didn't want to redraw the whole thing. I just did some copy and pasting of my original design to give you an idea how I plan to have it setup. The two rows are raised so I can walk underneath them, and still be able to reach all the plants for picking and maintenance.
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Old 07-29-2010, 07:44 AM
omerizm omerizm is offline
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Interesting design! And in the second photo the root mat next to the tube is huge
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Old 07-29-2010, 07:16 PM
GpsFrontier GpsFrontier is offline
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Quote:
Originally Posted by omerizm View Post
Interesting design! And in the second photo the root mat next to the tube is huge
Ya, they weren't small plants, that root mass was from the side of the tube with my snow peas. They grew over 6 feet tall, and 4 feet wide before I cut them down. I didn't take any pictures just before I did because they were turning yellow and looking ratty. I attached a couple of the last pictures I did take of them, but they got almost twice as big as what is in the picture (the tall ones, snow peas). They grew all the way to one foot from the top of that frame I built you see in the picture. The other regular peas (the small ones in the picture) wound up getting as big as the snow peas are now in the picture.

P.S. I found another picture (third picture) when they were a little taller, I added it so you can see how tall the frame I built actually was.
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Old 08-25-2010, 01:36 PM
NorEastFla NorEastFla is offline
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Hey GpsFrontier, I do love that tube based E&F system you've developed! Your snow pea plants look awesome in it!

I'm curious about your design for the square tubing. I wonder if the total square inches of grow-holes is needed in relation to the total square inches of stems that will come from them.

When full grown, what is the diameter of each stem of the strawberry plants you intend to grow in them? How many plants would fit into a 2" opening?

The reason I'm asking is that the opposing holes may not be necessary and if eliminated, would give you additional fill height in the 4" round tubing to allow for a deeper fill depth and thus wet more area on your net cups.

If rockwool were used, it's wicking action might also eliminate the need for the maximum fill.

The suction resulting from the vacuum created by the draining cycle would pull in oxygen through the top of the net baskets and assist in the more complete draining of the rockwool on each cycle.

This would provide both oxygen for the roots and prevent any problems associated with over-wetness of the rockwool near the stems.

If the total stem mass exceeds that of spaced holes in the 4" round tubing, then a router could be used to cut a 2" continuous gap in the top of the round tubing with intermittent structural segments left intact about each foot or so. This would radically increase the stem area allowance without having to cut your grow-holes lower in the tubing.

Whatcha think? I'm just throwing out some ideas. This is exactly what I intend to do with your idea, except for the type of plants I'll be growing.

I'm designing a salad system. One small area of hydroponic plants that will provide a family of four all the salad ingredients they can use.

I've been studying, designing and using hydroponic gardening for slightly over 30 years. I have my own site, but it would be decidedly uncool to promote it on this fine site. Mine is brand new and has no traffic yet. That's why I'm here on this site posting. After my own site kicks off and becomes busy, I may be too busy to come here.

I've been observing this site for quite some time now. I've always loved the photos of the various systems here. The adaptations of the 11 plant system are fascinating and show some real ingenuity.
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Old 08-26-2010, 03:52 AM
GpsFrontier GpsFrontier is offline
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Hello NorEastFla,
I could use smaller 2 inch net pots, the crown (where the strawberry plant comes out of) is not likely to be more than 1.5 inches. But I don't see that as much of an advantage. It's the angle (45 degrees) that makes the difference. Weather it's a 2,3 or 4 inch net pot, the 45 degree angle will only allow the same percentage of the net pot to be submerged at full flooding. Less than a 45 degree angle and the plant design is compromised. With the round surface (of the tube) the the opening is not flush, making the holes lower (to maintain the same 45 degree angle). With square tubing, each side of the tube is a 45 degree angle, and the pots will sit flush with the tube, raising the water level somewhat without compromising the 45 degree angle. I attached a couple of pictures to help explain what I mean.

The reason for staggering the the plants from the right to left side is to allow the plants to reach full size without crowding. Also allowing air circulation between plants. So sticking two plants in the same pot would defeat the purpose of that. Rockwoll does have a good wicking action (so does coco chips that I intend to use) but unless it's long enough, and is bent at a 45 degree angle downward, I cant see any advantage.
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Old 08-26-2010, 01:38 PM
NorEastFla NorEastFla is offline
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It will be interesting to see the outcome of your design.

Good luck!

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