Why is top fed not effective after roots go below waterline in a DWC?

[BrokrnEyes]

When I first started Hydro growing, I read this on another site and took it at face value and planned for it in my build. I've now come across a situation where knowing the reason this is the case may be helpful. Could someone explain why once the roots are below the waterline in a DWC the Top fed part is often considered not as effective as it was? Does it have to do with oxygenation of the roots? If so what about the roots above the water line? Would lowering the water level to its bare minimum anf increasing the void for the Top fed be more beneficial than a deeper DWC?

 

[LiveAndLetGro]

Interesting question. I don't know the answer but someone who does will be along shortly, I'm sure. I'm going to follow this post so I can hear the answers as well. Happy Growing!

 

[Scientific]

After roots get established in the reservoir, top feed isn't as effective simply because it really isn't needed anymore. Very quickly the mass of roots in the reservoir far exceeds what's in the pot so you don't need to water the pot.

Hydroton balls will actually wick water up from the reservoir to the top of the pot (try it!), so top feed isn't actually even needed if you start with the reservoir level high enough to reach the bottom of the pot. You can lower the reservoir level after roots emerge from the pot if you want. Again, very quickly the percentage of roots in the reservoir far exceeds whats in the pot or exposed to air, so the quality of the reservoir water is what really matters (oxygen level, temperature, and circulation--a little in-aquarium circulation pump from the pet store is a big help once you have a giant root mass in your reservoir).

I always have to add my favorite photo to discussions like this:

 

[Chris Scorpio]

After roots get established in the reservoir, top feed isn't as effective simply because it really isn't needed anymore. Very quickly the mass of roots in the reservoir far exceeds what's in the pot so you don't need to water the pot.

Hydroton balls will actually wick water up from the reservoir to the top of the pot (try it!), so top feed isn't actually even needed if you start with the reservoir level high enough to reach the bottom of the pot. You can lower the reservoir level after roots emerge from the pot if you want. Again, very quickly the percentage of roots in the reservoir far exceeds whats in the pot or exposed to air, so the quality of the reservoir water is what really matters (oxygen level, temperature, and circulation--a little in-aquarium circulation pump from the pet store is a big help once you have a giant root mass in your reservoir).

I always have to add my favorite photo to discussions like this:

Wow Scientific....she really needs a good perm or something

Now THAT'S some roots

 

[Scientific]

Now THAT'S some roots

Thanks CS. Hydroponics is kind of a pain what with schlepping all that water for three months and having to constantly fuss with the pH and PPMs, but those roots kinda say it all. Hydroponics is awesome!

 

[BrokrnEyes]

After roots get established in the reservoir, top feed isn't as effective simply because it really isn't needed anymore. Very quickly the mass of roots in the reservoir far exceeds what's in the pot so you don't need to water the pot.

Hydroton balls will actually wick water up from the reservoir to the top of the pot (try it!), so top feed isn't actually even needed if you start with the reservoir level high enough to reach the bottom of the pot. You can lower the reservoir level after roots emerge from the pot if you want. Again, very quickly the percentage of roots in the reservoir far exceeds whats in the pot or exposed to air, so the quality of the reservoir water is what really matters (oxygen level, temperature, and circulation--a little in-aquarium circulation pump from the pet store is a big help once you have a giant root mass in your reservoir).

I always have to add my favorite photo to discussions like this:

I think this does answer my question, and it's somewhat unfortunate in my situation as it sounds like I have to stop a part of my experiment, although it is useful bit of information for later.

During this past grow, I was finally able to incorporate fog into my system, making it into a FOG/Too Fed DWC/Brings Bubble system.

I started with a four hour cycle after the roots were coming out of the baskets, 1 hf fog to 3 hours Top Fed with the Top fed on constantly at night to provide moisture. Gradually I transitioned this to a 3 hours fog on to 1 hour DWC and during that transition thr plants were growing beautifully on a 10% nutrient to 1 gal water ratio, and even showing signs of nutrient burn! However, as soon as the transition into flower (they are auto flowers) I noticed yellowing of the bottom most leaves. Because there are other flowers, I went with low stress training and assumed that these low level leaves were simply dying off because of lack of exposure to light, which they were iin completeshadow. Yesterday I checked on the plans to see that a not insignificant number of the leaves have turned yellow, I upped the nutrient level to30% but I have a strong suspicion now that there is more route mass below the waterline then there is above and because of that the plant is becoming nutrients starved due to insufficient nutrient levels for it's now a parent default to the DEC Rather than fog if what you're saying is in fact what is going on with my situation. It's worth noting that the container the plants are sitting in it is a 15 gallon Rubbermaid with no more than 2 gallons of water at the bottom with a pair of air stones to provide oxygenation of the border as well circulation of the fog in the container.

Hope that all came out right.

Over at GWE, I found a thread in which someone claimed that the flow of water from a Top fed trains the roots to naturally go downward, anf that they had had rootball up close to the stem when they hadn't used a Top Ded, if that's the case I'll have to use the Top fed more sparingly (timing when it comes on and for how long, likely not more than five minutes, just enough to wet the grow media and the rest of the time let the fog run to avoid letting the roots get to the water.

 

[Scientific]

I think there are a lot of ways to successfully grow cannabis hydroponically. My idea about just getting rid of top feed was in an effort to get the same results with the least amount of effort and equipment.

I suspect that yellowing bottom leaves means a nutrient deficiency, not a light deficiency. I think what happens is that in the absence of needed nutrients, the mobile nutrients move from the oldest leaves to the newest. I would also guess that what you have is a nitrogen deficiency (and possibly some others). The fix, happily enough, is just to pour more fertilizer in the reservoir.

 

[BrokrnEyes]

Yeah im sure thats what i need to doand currently in the process, i wonder if the dial up i went with is enough or if i should just dial it up all the way, gradually of course, to nutrients regular for DWC.

 

[Scientific]

Yeah im sure thats what i need to doand currently in the process, i wonder if the dial up i went with is enough or if i should just dial it up all the way, gradually of course, to nutrients regular for DWC.

If by "nutrients regular to DWC" you mean the manufacturer's recommended level, I think experience has shown that half that is the better bet for a starting point.

 

[Icemann420]

Exactly

 

[Icemann420]

I think there are a lot of ways to successfully grow cannabis hydroponically. My idea about just getting rid of top feed was in an effort to get the same results with the least amount of effort and equipment.

I suspect that yellowing bottom leaves means a nutrient deficiency, not a light deficiency. I think what happens is that in the absence of needed nutrients, the mobile nutrients move from the oldest leaves to the newest. I would also guess that what you have is a nitrogen deficiency (and possibly some others). The fix, happily enough, is just to pour more fertilizer in the reservoir.

I have a mobility chart for you

IMG_0655.PNG

• Icemann420
• Mar 9, 2018

Mobility chart

 

[The Germinator]

Thanks CS. Hydroponics is kind of a pain what with schlepping all that water for three months and having to constantly fuss with the pH and PPMs, but those roots kinda say it all. Hydroponics is awesome!

Perspective. I love the daily chores involving dwc. Can't get enough of it.