Aeroponics 2.0 (aka high-pressure aeroponics) is different from the aero systems that first appeared commercially in the 1990s. These systems produce a very light mist that floats around in the air and looks like fog, so the term fogponics is often used to describe this style of growing.
In a fogponics system, water and nutrients are atomized and distributed in a mist with droplets in the range of 30-80 microns. A droplet of 50 microns is the optimal size roots can uptake, as determined by NASA’s research on aeroponic potatoes in the International Space Station during the ’90s. Because most droplets in this range are lighter than air, they float around the root chamber until colliding with roots or other obstructions. The root chamber remains humid with roots dangling in air, which is why it is called an aeroponic system.
For the atomization and mist to occur, an external, high-pressure pump is needed instead of the submersible, pond-style pump that is typically used in aero systems and usually produces low pressures (under 4 psi). To produce the mist or fog, pumps must run pressure in the range of 80-100 psi. Low-pressure aeroponics uses low-pressure, high-flow pumps, whereas high-pressure aeroponics uses high-pressure, low-flow pumps. For this reason, the mist is extremely gentle and floats around like a fog in a properly tuned high-pressure, aeroponic system.
There is another kind of fogponic system that includes the use of an ultrasonic fogger, much like the kind found in humidifiers. With an ultrasonic fogger, a small ceramic plate is vibrated by an oscillator more than one million times per second and creates droplets only 3-5 microns in size. This thick fog can actually suffocate roots because it displaces available oxygen. However, if the root chamber is well-aerated and properly cooled, the roots will be under the right conditions to grow. With enough oxygen and the proper temperatures, cuttings often root faster in this type of system. However, with greater rewards come greater risks in the sense that the roots are extremely sensitive to high-temperatures and low-oxygen levels.
Using a lower dose of nutrients when using ultrasonic foggers is recommended because the salts of the nutrients can damage the equipment. In addition, the nutrient mix cannot be easily carried in a fog consisting of such small droplets. For this reason, this type of set-up is best suited for propagation and early vegetative cycles. For flowering or fruit production, nutrient-craving plants perform much better with a droplet size closer to 50 microns, which can fully support the plant’s hunger for nutrients.
Growing with High-pressure Aeroponics (HPA)
High-pressure aeroponics (HPA) is the most efficient way to grow, as NASA determined with its aeroponic potato production. When this type of efficiency is achieved, roots develop fine hairs called trichoblasts that are more efficient at taking up nutrients and can provide a higher rate of growth than roots growing in other methods. This style also happens to use the least amount of water and nutrients possible, which is what motivated NASA to give it a try, as it looked for ways to minimize cargo costs for space missions.
When cloning or germinating with HPA, it is important to provide the roots with enough humidity so they can develop a strong root system. This is done by setting timing cycles so they are almost always on, or with a shorter ON/OFF ratio than later on in the growth cycle. After roots have developed, it is good to dial back ON times and increase OFF times. This will be done continually, from the time of initial rooting until later in the growth cycle.
Trichoblasts, or “root fuzz,” are allowed to develop only in a finely tuned HPA system that doesn’t oversaturate the roots, which can grow into pom-pom-sized fuzzy masses under the right conditions. Less spray time and wetting causes more oxygenation, leaving the roots with a hyperactive surface area that can absorb more nutrients and water out of the air/vapor mix. Less is more with HPA, so the feeding solution should be closely monitored.
The same nutrient density used in early veg should also be used throughout the rest of the cycle, as far as EC/ppm levels are concerned. It is important to judge this by the amount of trichoblasts (fuzz) that have developed on the roots. If these are not present, a feeding schedule similar to typical hydroponic and aeroponic styles can be used.
On the other end of the spectrum, when trichoblasts are prevalent, plants can be burned by the higher density of the nutrients. A good rule of thumb is to reduce nutrients by about 25-50% of normal strength as the plant’s absorption rate increases.
Cleaning the HPA System
Post-harvest, it is important to keep the HPA system’s lines primed and the system running. This will prevent the lines from drying out and the nutrient solution from drying, caking and breaking off, which could eventually block the small orifices and clog the nozzles. Preven-tative maintenance is key to avoiding future failures.
This is also a good time to add a cleaning solution, such as hydrogen peroxide, to help clean and sterilize the plumbing. Before beginning another crop, the system needs to be cleaned out the same way a typical hydroponic or aeroponic system would be cleaned: with good scrubbing and sterilization methods. The plumbing lines and pump can be left intact, or if they have been running clean, they can be dismantled.
Hybrid Garden Systems
Many HPA gardeners build hybrid systems, which include equipment that runs other growing styles as a back-up plan. For example, an HPA set-up can be easily converted to an ebb and flow or recirculating deep water culture system by fitting it with removable or adjustable drains and a submersible pump hooked up to a timer that can be plugged in as needed.
In the event of extreme temperatures, or equipment failure, this can be invaluable. The trichoblasts will have been removed throughout the process of heavy watering, and will take some time to grow back, but the crop will be saved and can continue to thrive in either setting.
An adjustable system that can go between hydroponics and HPA is also an advantage when growing in the same set-up from cuttings to harvest because growers can switch it up whenever necessary. A hybrid system makes it possible to root with bubbleponics, or grow in the early vegetative cycle with hydroponics and then move towards HPA as the root system develops. This often results in stronger root systems that can support larger plants.
Finally, a hybrid system provides a fun way to learn the variances in different growing styles and how the plants react to subtle nuances in air, water and nutrient delivery. This often provides growers with an educational experience in addition to crop production alone. Often, tinkering around with the system is as therapeutic as the gardening itself.