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The earliest aeroponic system that comes to mind was described as being constructed from wooden barrels suspending bare rooted plants, where inside an irrigation mister/sprinkler delivered solution from a manure tea brewer via a pump. While being of rudimentary construction, the early aeroponic pioneers discovered that the plants grew exceptionally fast and they witnessed first hand how the root environment they created helped to accelerate plant growth.
Today, we know that the increased dissolved oxygen levels, greater root surface area available for water/nutrient absorption and exclusion of growing medias offered by performance aeroponic systems help growers push plants to new heights. What was once a technology reserved for intensive plant researchers and elite commercial growers is now available to the growing public.
There are many variations on what are termed “aeroponic” growing systems, and in this article, we are going to have a closer look at the different design and construction types of some of the systems currently available.
We will also have a look at how to properly manage these types of systems. While having become much friendlier, they can still be temperamental and perhaps intimidating for less experienced growers. The types of nutrients, additives and beneficials used and at what rates and timing are also very important. The nutritional management of plants grown aeroponically will differ from soilless and hydroponic growing systems.
Firstly, aeroponics is often described as a plant growing method where bare plant roots are suspended and bathed continuously or intermittently with a nutrient rich mist or spray. Where this differs from “hydroponics” is that there is no growing medium used around the roots, but may be present in very small quantities to provide mechanical support. Also the roots are often misted or sprayed with a nutrient rich mist, where in hydroponics roots are often submersed or the nutrient is delivered as more of a drench, rather than a fine spray or micro-droplets.
The main advantage of aeroponics over hydroponics is the amount of dissolved and ambient oxygen that surrounds the rootzone. Sprays and finer droplets will have a greater surface area for picking-up and delivering increased amounts of dissolved oxygen (DO) versus nutrients that are applied as drenches or through sub-irrigation methods such as ebb and flow. The root systems of aeroponically grown plants often have more surface area available for the absorption of water, nutrients and dissolved oxygen; furthering the potential growth rates of healthy plants.
Also, by virtually eliminating the growing medium surrounding the roots, there is nothing to buffer nutrients, minerals, vitamins, carbohydrates, amino acids, etc from absorption by the crop. For growers with a good working knowledge of the nutritional requirements of their crop this can offer an advantage; as all elements have the potential for immediate absorption and transport by the plant. The fact that there is little or no growing medium to sterilize or replace between crops is also of significant advantage, offering fast turn-over rates between crop plantings. Aeroponic systems conserve moisture, there is little or no growing medium exposed for moisture to be lost from. All water and nutrients are supplied directly to bare roots which are often contained in a “sealed” root environment, increasing the efficiency use of water and nutrients for the grower.
To date, there are three basic nutrient delivery systems which have proved to be reliable for delivering enough water and nutrients to crops while fulfilling the criteria of an “aeroponic” system (maximum root surface area exposed, maximum dissolved oxygen).These are:
- micro sprayers/micro misters
- centrifugal sprayers
- modified spray delivery systems
Micro Sprayers and Micro Misters
These are the most widely used components in constructing aeroponic systems and most often supply individual planting sites through a manifold system. Many of us have seen the overhead misting nozzles above our produce at the grocer’s.Every so often a very fine and low volume spray is delivered to keep our vegetables looking their best. Now imagine this spray is infused with exacting nutrients and is delivered via timers directly to the bare roots of your favourite plants. This is the basic principle.
The misters at the grocers likely operate directly from municipal water supplies via a solenoid and timer. While being simple and effective, this does not afford growers the opportunity to supply nutrients along with the fine mist. City and municipal water supplies opperate at significantly higher pressures compared to nutrient delivery systems in hydroponic gardens with various pumps. So the grower requires a larger output pump and well built manifolds to supply micro-misters. The high pump output requirement means that a large amount of power must be used. Typically a 1HP rating associated with the pump is required, meaning that the pump will draw near 750W of electricity when operating. Also, almost all pumps will heat the nutrient solution, increasing the need to lower nutrient temperatures to 65° F. Larger pumps will tend to generate more heat.
Note that inline/centrifugal pumps will heat nutrient solutions less than submersible pumps.
Once the pump output required for the manifold and micro mister system is achieved, the focus becomes the micro-misters themselves. Typically, micro-misters are spaced between every planting, unless high densities of very short-term plants are used for cropping. Misters vary in quality; those that have been especially manufactured for aeroponic applications are preferred. Misters that can deliver fine mists while being resistant to clogging may be difficult to find. The misters should also be accessible for cleaning even while there is a crop growing. Occasionally, the mico-misters WILL NEED TO BE REMOVED FOR UN-CLOGGING, as clogging is common. Clogged misters diminish the crop’s output potential as they either restrict or completely inhibit individual plants ability to absorb water and nutrients. Using a high quality inline-filter with a mesh screen rating comparable to the misters specifications (i.e 100 microns) will also be necessary to help lessen the need to clean and occasionally replace micro-emitters in the system. Keeping nutrient salt residue to a minimum also helps to prevent the micro-misters from blocking up.
Some growers opt for a slight step down in terms of the advantages of aeroponics for something more trouble free. There are micro sprinklers that can be installed that spin 360° and deliver very fine droplets of water, although not creating a true “mist”.
Micro-sprayers as discussed previously, will not create a true “mist” if the pump output and pressure in the manifold is not substantial. Under powered micro misters make more of a weak “water cone” shape rather than a mist. However this shape of nutrient emission still delivers increased dissolved oxygen and offers a good degree of surface area for nutrient and water delivery to the root system.
Ein-Gedi/Centrifugal Sprayers
This patented technology is innovative and highly effective. It is surprising that this nutrient delivery method has not been more widely adapted to North-American style hydroponic/aeroponic systems.
A small, low-wattage motor sits outside of the growing system, while within the growing system, a small plastic cone with a protruding circular disk spins 360°. Your household humidifier may contain this type of mechanism. This small inert cone draws up the nutrient solution and spins it off as a very fine mist traveling with significant, but gentle velocity. While the mist is not ultra-fine, it is a true mist and offers several advantages when compared to more conventional aeroponic nutrient delivery systems. Firstly, the cone units cannot clog, greatly reducing the amount of maintenance and frequency of service as with micro-sprayers. The cone also provides a “stirring” effect of the nutrient solution. In this type of system, the plant’s root system is essentially growing within the nutrient reservoir. Typically, several litres of nutrient solution surround the lower portion of the root system. The upper roots feed on the fine oxygen infused spray while lower roots are constantly bathed in a highly oxygenated and nutrient rich solution. The volume of solution surrounding the root system helps to protect against increasing temperatures, salt build-up and power outages. As an additional benefit, the motor never comes into contact with the nutrient solution, so it does not add any additional heat to the root environment, reducing cooling requirements to maintain 65°F nutrient solution temperatures. This type of system usually operates the centrifugal sprayer constant, 24/7.s
While this type of delivery system offers several key advantages, there are some limitations. The spray pattern, while large, originates from one central point in the middle of the circular and horizontal spray pattern. So for larger root systems, the individual plant sites need to be aligned within the spray pattern in such a fashion that one plating site is not blocking another from receiving the spray directly. Also, only one side or portion of the root system will be able to receive direct contact with the spray, as the spray originates from a central point in a circular pattern. Several sprayer units could be installed to overlap spray delivery to fewer but larger planting sites. Each sprayer unit requires it’s own power source or supply cable or cord. While not a large drawback, additional consideration and materials for wiring will be required.
Modified Spray Delivery Systems
Some popular types of aeroponic systems available to home gardeners can be described as “hybrid” aeroponic systems. Instead of using internal mist nozzles, sprinklers, or centrifugal sprayers these systems deliver fine jets of nutrient solution from internal supply lines that are run under high pressures. The very fine jet-stream of nutrient solution turns into a fine mist when it contacts the hard internal surfaces of the growing chamber, net cups or depth of nutrient solution below. The spray typically emanates from between each of the planting sites (see photos). When the pressurized stream of nutrient solution penetrates the depth of solution maintained in the growing chamber, it greatly reduces the surface tension in the nutrient solution where bare roots of plants are immersed; increasing the plants ability to absorb water and nutrients through the roots. The solution depth then flows back into the reservoir, which further helps to aerate the root environment.
This system follows the basic principles of aeroponics: increased surface area of roots available for nutrient absorption AND saturation of the root environment/nutrient solution with dissolved and ambient oxygen. This modified spray delivery system is easier to maintain than manifolds using micro-spray nozzles. However, the orifices in the internal line may clog if a good quality inline filter is not installed and properly maintained. These internal lines are difficult to clean and maintain once plants are established in the system, so prevention becomes especially important in keeping the nutrient delivery system with this method “clog-free’. While the growing chambers for the roots are smaller in size when compared to conventional aeroponic systems, the depth and continuous flow of highly aerated nutrient solution across the root system keeps the plant roots well supplied with highly aerated nutrient solution.
Tips and Tricks for Aeroponic Growing Systems
Temperature
Besides clogged nozzles, this is the number one reason a grower may achieve poor results using aeroponic technologies. If temperatures in the root zone AND the nutrient solution are not maintained between 65-70°F, dissolved oxygen levels may drop dramatically. The ability for water to hold oxygen greatly decreases with rising temperatures. If oxygen levels in the root zone are lacking due to warmer temperatures, not only will the crop’s growth potential (and yield) be limited, but the root system may contract a disease. Pythium is often present in most growing situations. However, it does not infect or take hold of the plants unless anaerobic (lacking oxygen) conditions prevail. Pythium can wipe out your crop in a very short period if left un-checked. In most growing situations, a water-chiller will be required to maintain the nutrient solution and temperatures in the root zone optimal. If your growing environment operates at greater than 70°F (which most do), it will be necessary to invest in a reservoir chiller if you are to harness all the benefits of operating an aeroponic system. Not only are well managed root temperatures required to reap the benefits, but they will help to prevent root diseases which can devastate your crop and significantly lower production levels. If you can afford to run a performance aero system, you can afford to buy a chiller!
Spray Nozzles, Emitters, Nutrient Orifices, etc
Make sure that any emitter, sprayers, orifices, etc that deliver nutrient solution to the bare roots are accessible for cleaning and maintenance without disturbing the roots. The bare roots in aeroponic systems are sensitive, they should not be rubbed against, handled, exposed to light, etc. Inspect nozzles, emitters, etc frequently when operating to ensure that they remain un-clogged. Clogged or restricted nozzles, etc can starve your crop of water and nutrients, reducing results or even leading to crop failure.
To help keep emitters, nozzles, orifices, etc operating trouble free make sure to keep you nutrient solution as “clean” as possible. Use a good quality inline filter and maintain it often. Use nutrients, additives, and beneficials that are not “chunky” and dissolve into the solution readily. A fine-meshed tea bag (50-100 microns) can be suspended in the reservoir for any additives, products, etc which do not quickly dissolve or have a nature of creating debris in the solution. Harder to dissolve ingredients can be mixed separately in a bucket containing water and there poured through a filer into the reservoir.
Using a high quality surfactant or “wetting agent” will also help to keep your emitters, sprayer orifices, etc free from nutrient salt build-up which often create clogs and restrict flow. Non ionic surfactants with a mid HLB rating (hydrophilic lipophilic balance) are preferred and also help to increase nutrient availability and lessen the incidence of root disease.
Compressed air can be blasted through the manifold and emitters to remove clogs and maintain flow rates. Be careful not to damage roots or introduce oils from industrial air compressors onto the bare roots.
Pump Filters and Inline Filters
Filters will need to be cleaned and inspected at least twice per week. Remove filters and rinse them out under hot water. Compressed air can also be used to blast filters clean. Installing a bio-filter in the reservoir will help contain beneficial microbes. Remember that well run aeroponic systems are rich in oxygen so this provides an ideal environment for many beneficial fungi and bacteria to colonize both the growing systems and plant roots.
Size and Plant Spacing
Plants grown aeroponically are often planted at higher densities and of much smaller stature. The reproductive/flowering phase should be initiated sooner for the overall size of the plant versus conventional and hydroponic growing methods. A finely tuned aeroponic system will grow the plants much larger and faster; reducing the time required in the vegetative cycle required for the plants to achieve the desired height, branching, etc at harvest time. In most aeroponic systems, plants are harvested at less than 2’ (65 cm) in height. Shorter plant heights with higher planting densities make more efficient use of artificial lighting sources helping to increase yields and plant quality.
Nutrients, Additives and Beneficials
Nutrients have the potential to be highly available to plants in aeroponic systems. Regard your aeroponic system as a high performance automobile or racing motorcycle. You wouldn’t fill either of these with low-grade fuels, so make sure to use the highest quality nutrient available to get the most out of your aeroponic system. There are some ultra premium two part bloom fertilizers available that are capable of pushing plants beyond conventional cropping expectations. With a fine-tuned aeroponic system, a dialed-in specialty nutrient program and a reservoir chiller, growers may achieve yields and crop quality they previously had not thought possible. Yields per light can be astounding versus soil or conventional growing methods.
Many growers report that in aeroponic systems nitrogen becomes disproportionately more available to crops than the other nutrient ions in the solution. If using a three-part base nutrient, it may be necessary to reduce the amount of the “micro” formulation used while supplementing with a Calcium-Magnesium solution that contains a full spectrum of trace elements. Note that most Calcium-Magnesium supplements contain some nitrogen, but they proportionately contain significantly higher amounts of Calcium-Magnesium.
Make the most out of the increased dissolved oxygen levels in your system by including beneficial fungi and bacteria in your feeding program. These beneficial microbes can quickly colonize the roots, significantly increasing the root’s surface area available for nutrient and water absorption while dramatically increasing the health, vitality and growth rate of your favourite crop. Because the well managed rootzone and highly aerated nutrient solution create an oxygen intensive environment, you can add slightly less than the recommended rate of most inoculants, as recommendations on the label are based on conventional soil/soilless gardens. In fact, it may be wise to reduce the concentration of all nutrients, additives and beneficials by 25% and gradually increase levels until the crop’s threshold for absorption has been determined (slight tip burn on the ends of the leaves).
Some benefical inoculants are supplied with an inert carrier powder, as the active ingredients are microscopic in size. These carriers may not dissolve completely. Powdered beneficial inoculants can be placed in a “tea bag” using a fine and inert mesh. This will release the active ingredients into the solution, while keeping any debris that can clog emitters out of the system. Benefical microbes can become “super-charged” in aeroponic systems.
The addition of products to load the plant with carbohydrates helps to nourish beneficial microbes and gives the plants more energy for growth, yields and essential oil production. A thick, slimy whitish substance may appear on pump filters, etc. If the system is aerobic (containing oxygen) this substance will flourish and is beneficial to the crop. However, it should be rinsed from pump filters (during weekly maintenance) or wiped off the sides of the reservoir (if applicable) between reservoir changes. Remember that it is vital to keep debris from entering the nutrient manifold where it may plug emitter, sprayer, orifices, etc. As long as this beneficial substance is contained within the reservoir and root environment it can be beneficial or un-problematic. If you are unable to maintain optimal reservoir and root environment temperatures, try to keep your nutrient solution as inert as possible to prevent the possibility of contamination from anaerobic conditions. Remember, you are not getting the most out of your aeroponic system if you don not keep the nutrient temperature 65-70°F and use the best quality nutrients, additives and beneficials available to you.
Running a high quality digestive enzyme through your aeroponic system once a week as a treatment between nutrient changes will help keep root zone healthy and clean. These digestive enzymes will convert any decaying organic matter such as old roots into substances that are beneficial and available to your plants.
Today, what was once a growing technology available to intensive plant researchers including NASA is available to the home gardener. If you are not a veteran grower it is not advisable to construct your own aeroponic system. Look for aeroponic systems that have proven results, are plug and play, and offer operating instructions and customer support. Some manufacturers supply nutrients with their systems. These are typically intended for growing a wide variety of plants, so shop around for a specialized feeding schedule that is formulated for your particular crop to get the most potential out of your performance growing system. If you are new to growing indoors under artificial light, it would be wise to gain some experience before investing the significant amount of time and money required to operate a modern and productive aeroponic growing system. Growers having success with aeroponics are able to achieve greater and better quality yields in less time than with soil/soilless and hydroponic growing methods. They also use less water and nutrients than with conventional methods. Turn around time between harvest and planting is greatly reduced and very little if any growing medium needs to be replaced between crops. Aeroponic systems require high quality water, so if you have marginal water quality you will need to source and install a Reverse Osmosis (RO) filter. Be prepared to spend more time monitoring and maintaining your aeroponic system versus conventional growing methods, just like you might a high performance vehicle versus a utility wagon. So for experienced and diligent growers: fuel it up with premium, step-in, turn the key and drive your crop to peak performance; the results can be exhilarating.