@ chrissy1gardener, If several kinds as tomatoes, herbs, or lettuces would be grown together in the same setup, why would they possibly taste "terrible" ?

As for the spacing in an aeroponics system, I guess there is no rules or formulas. The fact that nutrition uptake is even more optimized, roots will generally extend less and you can plant very narrow. The rest is a matter of testing and experience. Some systems may even come with their proper (and preset) plant spacing. I is circumstantial, so to speak, and you have to figure it out by yourself somehow, by watching several systems closer and how it is done with every and each of them.

The key with preventing spraying nozzles from clogging is lower nutrient concentration. Fortunately this is typical for aeroponics, as you actually need lower nutrient concentration "by nature". Obviously good filtering is recommended as well.

Nozzle clogging issues are negligable if you filter to 1 micron and use drain to waste.
Root space will depend on the life cycle of the plant you are growing, a tomato needs more space than a lettuce as its in the system for a much longer period and naturally grows a more extensive root system.

Root size is also dependent on the type of aero.
If you use low pressure with sprinkler type nozzles the roots will head straight down and then spread out on the floor of the chamber. Not dissimilar to nft,they follow the water flow into the drain and ultimately end up in your res if its a recirculating system.
If you use high pressure with fogging nozzles, the roots still head for the floor and spread out but as there is very little run-off to follow they will generally ignore the drain, and instead begin to climb up the walls in an attempt to reach the nozzles.. they realise where the mist is coming from and head towards it.
The roots that initially dropped straight down will reach out sideways into void to capture the mist. This type of root structure will fill up all the available space and eventually obstruct your nozzles.

Although, all of what you describe here sounds plausible somehow and is not wrong, root expansion- or in research called shot vs, root growth, is strongly related to nutrient composition, balance and uptake. Plants indeed extend their root system acording to plant size, but if the nutrients you provide are optimal and perfectly balanced, plants would mainly focus on vegetative growth and considerably limit root expansion. If using both, a real areoponic system and optimal nutrients, it may happen that roots will not follow any anticipations of yours ;-). You can observe such tendency already with tomato plants grown in "real" NFT channels. Btw: Depending on flow rate of one's NFT system, roots expand very little and even a few go "upstream".

If talking about aeroponics, I am actually talking about high pressure spraying and related. Well some people may call a low pressure sprinkler system aeroponics as well, but I guess it's about time for an official terminological differentiation here. There is very little air involved with sprinklers, right?

Same as some people "falsely accuse" their actual NST (nutrient stream technology) in simple PVC tubes, being an NFT. I am certainly not a maniac, Buddha beware, but then again I can observe more and more confusion and misunderstandings, due to inappropriate terminology, that eventually needs to get differentiated ... ;-)

Hi Lucas,
Some people do consider aeroponics to be a lawn sprinkler attached to a 3psi pond pump, its akin to NFT in my book as the feed regime and results are quite similar.
The aeroponics i refer to uses 100psi and

Sorry hex2006, I can't see any contradiction with what I said earlier.

Bottom line: I simply can't fully agree with your detailed "root behavior description" as it seems to me that it will depend a lot on nutrition (and other params) as well. I am pro pluralistic of course, and fully aware of the fact that different people mean different things when talking hydroponics and using specific terms. I am just differentiating and pointing out possible confusion with general and vague terminology, which (as a matter of facts) is most probably due to colloquialism and thus isn't addressed to you personally ;-)

Hi Lucas,
Everyone is entitled to their opinion/view..no problem with that :)
Most aeroponics systems use relatively long misting durations of at least 3-5 seconds from a multitude of nozzles in a relatively small chamber.Aeroponic myths appear to stem from those that overwet the roots.
If too much liquid is delivered, regardless of the droplet size, the roots will be too wet and the structure will be different.
If you`ve ever uprooted a plant in the garden, and found some of the roots have grown into worm holes in the soil you will have noticed the structural difference of those roots compared to the ones surrounded by soil. A truely aeroponic plant should possess exactly the same root structure (the chamber acts like a large worm hole),if it doesn`t then its too wet.

Nutrition is related to environment, these roots don`t need and indeed cannot cope with normal EC levels as very little water is delivered in the mist.
Its not the easiest way to grow a plant but its interesting.

Ok, I read all this and a WHOLE LOT MORE but have still not found what I really need. I have been using a form of aero but wish to go to a root tunnel that has misters and air circulation so the fog permiates (misters alone create a fog that sinks). What I need is similar to a plant spacing recommendation on seed packs, but because I control the roots completely I need a "root space" recommendation. How wide and how deep does a rectangular root tunnel (fully drained--no liquid area) for a pepper plant (my test run) that will be 3 to 4 feet dia.? The plant and root cannot exceed 6 feet tall as the greenhouse is short. I have managed to seal it and will be using CO2 enrichment. I have been thinking 2 foot wide and 18" deep (as this has to be 6" off floor for drainage, the "above ground" part cannot exceed 4 foot tall) but have heard that a plant this size may only have a root ball the size of a 2 liter bottle. Is this true? That would require only 12" wide and 18" deep, allowing for air circulation, making the root trays smaller then the tops. Construction will be much easier if this is true. Can anyone help me with this information?

oldnew,

First, unless you have become very proficient at using aero, I would not delve into foggers. More expensive, harder to build, etc., etc., etc.

AS for how much area per plant, it's not so much the root area as the canopy you need to worry about. You can space tomato plants six inches apart and six inches between rows and deliver all the nuits they need. But... will the plants have not only room to grow the foliage they need to support photosynthesis but to absorb light. I have read where one can grow determinates 10" apart in 12" rows if you don't mind trimming leaves so the plants can get some air. That's my intent, though I may end up going with 11", depending on the exact amount of room I have.

Mike