Calling all RDWC & Undercurrent Pros

[budshoteyes]

Then the only question....is the one hose feeding or circulating or both?

 

[cyat]

Then the only question....is the one hose feeding or circulating or both?

I would say both and oxygenating the water as it runs thru the rocks.
Having a 1.5 in return helps to make it work with no blockages, oh and having a powerful pump about 250 gph or more per bucket. I ran a 1800 in flower for 4 tubs and a 1200 in veg for 4 smaller tubs.

 

[desertsquirrel]

The DO is mentally flawed, how it's replenished isn't understood properly. Atmospheric pressure is needed.

I find it odd that you mentioned how easily plants extract oxygen from water, but then mention how it's best to have the bubbles directly in contact with roots? But why? Bubbles contacting roots do nothing, roots take no oxygen from the bubbles, the bubbles provide no oxygen to the water. The only thing the bubble does is agitate the water as it rises so as to stir it up.

Plants use o2 for several purposes. Their extraction of it directly from the water is for tissue synthesis/photosynthesis. But O2 is also needed to be present (though not up-taken) for the process of osmosis to happen at all.

So though not directly used the bubbles have a direct effect on how much solution can be uptaken. Interestingly the UC's are famous for explosive rates of evapotranspiration.

 

[desertsquirrel]

Hey bro,

FWIW, you're correct, in that plants can do fine with low DO, ex., ~4 ppm, but they do better when water is saturated with O2 (ex, 9-10 ppm), but not super-saturated with O2 (ex., > 10 ppm).



P.S. I've been using Google SketchUp (3D design tool) to develop my DFT setup (a hybrid from ebb/flow table, but water will be ~4-6" deep at roots) with only air used to move water and increase DO (no water pumps). I will be using my new system this grow starting next month, for the first time. If you like, I could e-mail you my Google Sketchup work so you can check it out. I think my DFT will out yield and out grow other hydro methods like NFT, UC, aero, etc. Granted, I have not used it yet or even built it yet, but the science is very sound (ex,. level of DO2, water flow rate, 'air roots', etc.

Sure, id love to see your design.

 

[PoopyTeaBags]

Poopyteabags
If one takes a closer look at Heath's top feed it is only for circulation and not to feed the roots at all. The one hose outlet cannot feed a root that is the with of the pot,at best it can only wet one quarter of the top root. He does not use a dripper or flow ring to spread the water out evenly for feeding purposes. Also notice that he cannot use any if little pressure on the flow especially when the roots are packed full in the pots.....circulation is way slower! Heath plays with water levels during the growth stages of the plant and has no choice but to lower levels and or pressure or risk flooding in later stages!
( Heath showed us two cad drawings of his system )

I don't think Heath showed us his veg system which I believe is the bottom drain type as that would be how he would feed those roots,playing with water levels till the veg is mature and then transplanting to the flower pots with the top drain system to prevent flooding...no need to feed the top roots as the bottom roots are doing their job of nutrient uptake!

I wish Heath would pop in to clarify....could I be wrong?
Right or wrong I'm sure we'd both be honored to see him here!

Aerators ....keepalive.net

not sure what threads you read. but he said what i said almost verbatim. if he was using it just for recirculating purposed he could have hooked it up to just recirculate in the bucket instead he chose to top feed over the hydroton and spicified it was so he didnt get cord roots.

 

[Scrogerman]

The stuff i read on this subject blows my mind! not even scratched the Surface tension!

http://www.google.co.uk/#hl=en&pq=effects%20of%20dissolved%20oxygen%20tension%20and%20mechanical%20forces%20on%20plant%20roots&xhr=t&q=effects+of+dissolved+oxygen+on+plant+roots+in+hydroponics&cp=57&pf=p&sclient=psy&rlz=1R2PCTC_enGB348&source=hp&aq=f&aqi=&aql=&oq=effects+of+dissolved+oxygen+on+plant+roots+in+hydroponics&pbx=1&fp=1&biw=1069&bih=691&bav=on.2,or.r_gc.r_pw.&cad=b

 

[spurr]

The stuff i read on this subject blows my mind! not even scratched the Surface!

http://www.google.co.uk/#hl=en&pq=e...biw=1069&bih=691&bav=on.2,or.r_gc.r_pw.&cad=b

Here ya go buddy, for science try these searches, you'll more legit results that way, less .com sites, etc (using the same key words you used):

SCIRUS:
http://scirus.com/srsapp/search?q=e...n+plant+roots+in+hydroponics&t=all&sort=0&g=s

Google Scholar:
http://scholar.google.com/scholar?h...=on.2,or.r_gc.r_pw.&um=1&ie=UTF-8&sa=N&tab=ws


Here is a decent study on tomato (note: mg L−1 = ppm):

"An upper limit for elevated root zone dissolved oxygen concentration for tomato"
Youbin Zheng, Linping Wanga and Mike Dixon
Scientia Horticulturae, Volume 113, Issue 2, 26 June 2007, Pages 162-165
http://www.sciencedirect.com/science/article/pii/S0304423807001203

Abstract

It is well understood that insufficient oxygen within plant root zones can greatly diminish plant productivity. However, little is known about the effect of elevated root zone oxygen concentrations. Tomato (Lycopersicon lycopersicum Mill., cv. Trust) seedlings were grown in nutrient solutions containing dissolved oxygen (DO) concentration ranging from 5.3 to 40 mg L−1 for 4 weeks. There were no visible symptoms observed on the leaves or stems in any of the treatments. Leaf chlorophyll content was higher in the 40 mg L−1 treatment than with 20 and 30 mg L−1 DO treatments.

Two weeks from the start of the experiment, roots in the 40 mg L−1 treatment exhibited stunted growth, became thicker, and had fewer side and fine roots compared to roots in the lower levels of DO treatment. Almost all the measured growth parameters (fresh and dry weights of root, stem, and leaf, leaf area, stem diameter) were significantly reduced in plants grown in the 40 mg L−1 treatment compared to plants in the lower level of DO treatments, except that the plant height increased with the increasing DO concentration. Root respiration increased linearly with increasing DO concentration; however, there was no effect on leaf net CO2 exchange rate.

It is suggested that it was safe to enrich root zone DO to as high as 30 mg L−1, although the growth benefit was minor by increasing DO from ambient air saturated level (

8.5 mg L−1) to 30 mg L−1. Higher than 30 mg L−1 could cause reduction in tomato plant growth.

 

[quantic_soul]

Spurr, i'd love to see your sketchup design. I have been trying to design some sort of ebb flow type design myself to test in a grow tent. I also really wanted to get your adblock scripts you wrote for this site. I had asked you to PM it to me a long time ago but I realized I don't have those privileges yet on this site.

If you want to I'd be very grateful if you sent me both of those

 

[spurr]

@ quantic soul,

Yea, I can send you both, I have your e-mail now, in case you want to edit your post to remove your e-mail.

 

[Scrogerman]

Thanks for the Links/advice Spurr, ill get right into them. Cheers!¬)

 

[Cameltoejoe]

Re: Calling all RDWC & Undercurrent Pros

Being a tester for undercurrent i have been doing side by sides and testing many aspects of RDWC. In my testing i have found the whole DO mentality to be flawed.

Plants have no problem extracting oxygen directly from water, they split the H2O molecule during photosynthesis. This being said, they do need FREE o2 for the process of osmosis, where by roots uptake any solution at all.

Bubbles in direct contact with the rhizosphere is what we shoot for in our systems.

What testing did you do to figure this out?. What data did you collect?

 

[Verdure]

I believe Heath's root pots were full of cord roots till they hit water level which was above the root pots bottoms hence only feeder roots were seen in his root pics. I believe that the cord roots he disdained were the huge ones that would form upon hitting air zones between the root pot bottom and the water level if spaced apart!

I was there when Heath started his thread but never thought to ask to see a root pic plus stem out of his pots....I was and still am so totally in awe of his grows!

A few 5 gallon rwdc growers have told me they lower water level as the grow progresses,that it pushes the plants to grow and feed better and faster. Makes me think of the low level krusty buckets.

In September I hope to be running a micro pore aerator in my Rez....though using airstones at the moment I'm still not sold on the water fall method yet!

you dont air stones, the water moving and from the big pump recirculates the water and causes massive DO. A very efficient method.

 

[Verdure]

Just as done by sqydro

https://www.icmag.com/ic/showthread.php?t=233006