Aeroganics: Where the Old World Meets the New

It seems those who have been successful with aeroponic gardens have been really successful. However for the commercial and hobby grower alike, the consistency from one crop to the next is often lacking. In some respects this may be due to the growers increased comfort level with the system, and the level of attention to detail may suffer. Typically aeroponic systems have been very unforgiving as they lack any media around the root zone to buffer from environmental stresses such as warmer temperatures, salt residues (from fertilizer accumulation), irregularities in moisture levels, and pH and TDS fluctuations. Also, many aeroponic systems are susceptible to re-occurring pathogenetic outbreaks. Several growers report that their aeroponic gardens were producing in abundance and that after one mild outbreak of root disease, successive crops were also infected even after great measures had been taken to prevent any re-occurrence. Some recent developments in aeroponic construction materials incorporate coatings to prevent the penetration of pathogenetic spores into the growing system root chambers. However, it is agreed by most that although temperamental, aeroponic gardens are capable of producing otherwise unachievable levels of results while reducing cropping time.

Across the field, organic growers typically enjoy lower maintenance gardens, enlisting beneficial microbial life to help manage crop nutrition and improve resistance to pests, diseases, and environmental stresses. Although many organic gardens produce abundant yields, changes in nutrient regimens are slower to appear. Although this lends itself well to ease of management, growers who are using organic production methods to grow premium quality crops become limited from boosting production with intensive nutrient management.

In the mid-1980s, Hillel Soffer and David W. Burger conducted experiments at the University of California, Davis to determine the effects of oxygen concentrations in aero-hydroponics on the formation and growth of adventitious roots. In short, the results of their experiment determined that in the root formation of chrysanthemums that over 4X more roots formed in an Ein Gedi System (EGS) versus roots formed in an unstirred system. Total root length development was over 10X greater in the EGS aeroponic system. The study is posted on a number of websites on the internet.

So what is an Ein Gedi system? It is an aeroponic system that was developed and refined in Isreal by Dr. Soffer and Levinger in the 1980s. The system was developed in an area where reliability and efficiency are a must. As the region had a limited supply of water, excessive moisture could not be lost to from transpiration from the media (a key factor in fertilizer salt accumulation). This is important to indoor growers, as excess moisture from growing medias can contribute to excessive humidity leading to diseases. Since the system was developed to operate commercially in a very warm and arid environment, the design is of further benefit to the indoor grower.

Most hobby aeroponic systems operate with roots enclosed in channels or pipes, with net cups or collars providing mechanical support for the stem. The roots hang suspended in the channels (typically 5 to 8” diameter) and are intermittently misted with a hydroponic nutrient solution. As the roots hang bare and are sprayed with a relatively sterile solution usually either of two things will happen: 1) the roots will thrive, and the plant can produce past most growers wildest dreams; or 2) the roots will suffer from excessive heat and salt residue in the channels while the nutrient is not cycled and become subject to an outbreak of root disease that may resurface time again.

Root disease most often occurs in anaerobic conditions (lacking oxygen) which are associated with warm pooling moisture in the root zone. Unfriendly microbes from spores occurring in water supplies and ambient air will colonize the roots, slowly digesting the precious root system that you count on to supply water and nutrients to your crop. These types of problems can be avoided by chilling the nutrient solution and cycling frequently. However, cooling coils require vast and wasteful volumes of very cold water or gas charged water coolers require intensive power consumption.

It was determined through experimentation under very tough conditions that the solution was in the solution. It is a basic principle that larger volumes of water take longer to increase or decrease in temperature thereby insulating the root system and providing further stability to dissolved oxygen, pH, and TDS levels. It was determined that a larger volume of solution per plant (approx. two gal/4 L per tomato plant) with a continuous flow rate would provide stability to the root environment and alleviate the problems associated with warmer growing environments. However, through previous experimentations, it was realized that production could be largely increased relative to dissolved and ambient oxygen levels in contact with the plant roots. The simplest and most effective way to accomplish this task is to increase the surface area of the solution exposed as it passes through ambient air and penetrates back into solution, decreasing the surface tension. This allows the nutrient solution to become super-saturated with dissolved oxygen (DO). In the event of mechanical or electrical failure, the significant volume of solution saturated with DO would be able to sustain the crop for a significant period without significantly increasing the incidence of root disease.

Initially jet-type pumps were used to deliver the nutrient solution at significant P.S.I. (pressure) levels required for the misting nozzles installed in the root zone. An improvement in delivering high volume, high surface area mists to the plant’s root system was the incorporation of a centrifugal sprayer. The sprayer is installed centrally in each growing block. The construction of the sprayer will dictate how large of an area will be covered. Centrifugal sprayers in North America (Vortex) typically operate with a power consumption of only 25W, but provide a spray pattern up to six inches in diameter. This comfortably allows for a growing system footprint of 4’ X 4’. A hollow cone sits immersed in the nutrient solution, surrounded by planting sites (baskets). A motor (sitting outside of the root zone) spins the specially designed cone. The nutrient solution is drawn up the cone and is dispersed at significant velocity as a fine spray in a 360° pattern. The mist is delivered to the roots and re-enters the nutrient solution, dissolving oxygen into the solution surrounding the roots. The mist also helps to cool the root zone. The rotating action of the cone immersed in the solution also stirs the solution, keeping heavier materials from settling and further helps to increase DO levels by drawing air into the solution. The only limitation of centrifugal sprayers is that large plants to be grown to maturity in the system should be arranged so that the roots are in line with the spray patterns. Much like an HID lamp must have plants arranged around it to maximize light evenly. The mist is delivered at enough velocity that it bounces off solid materials such as the net baskets, tray lid and walls and is re-directed several times before finally contacting plant roots or re-entering the solution (saturating the solution with dissolved oxygen). An additional benefit of the sprayer’s design and construction is that it will allow us to take the leap into “aeroganics” because the sprayer does not clog and will not heat up the solution if it runs continuously. In fact, the solution actually stays cooler as the continuous misting provides some cooling effect in the root zone.

In the past, even with the best hydroponic solutions and the best mist head nozzles clogging would occur. Of course Murphy’s Law dictated that this would not happen until the roots were well established in the system. A great deal of damage can be done to an otherwise healthy root system by having to dig in there to unscrew mist nozzles for cleaning. Some aeroponic systems use micro-sprayers connected to micro-tubing inserted in the channels that can be more easily removed for routine maintenance and cleaning. Without the centrifugal sprayer it is not nearly as feasible to apply organic based nutrient solutions as a mist.

Featured in this article is a pictorial regarding the construction of a prototype “aeroganic” system. Note the access port in one of the four corners. The vessel is of a new design and at the time of this writing has not yet been fully introduced into the marketplace. The centre cut out is four inch (3-7/8” is ideal) in diameter, the correct size for supporting the centrifugal sprayer. The 12 planting sites were cut with a hole-saw to snuggly support six inch net baskets in an octagonal arrangement. One of the best circular cut-outs from the six inch basket sites was retained. In one of the four corners, a hole was cut to support a five inch net basket that will stay covered and serve as an access port. The cut-out from this site was also retained. The two cut-outs were secured together with a stainless steel carriage bolt and nut. The bolt also served as an easy to spot handle for the access port. This port is where a small submersible pump may be located to pump-out spent solution during changes and may serve as a mixing pump for water and nutrients while replenishing the system. The port also allows for access for monitoring equipment and for visual inspection of the root system. The tray used has an area in the center for a pressure fit of perforated pipe. The perforated pipe stands vertically, and protects the cone from ensnaring the vigorously developing root system but allows the solution to be funneled up and sprayed. A couple of salt-water air stones will bubble the solution delivered by a 3.0 psi air pump run on a circuit separate from the centrifugal sprayer. This will help protect the root system in the event that the centrifugal pump fails or loses power.

The purpose of this experimental system is to determine the feasibility of growing 100% certifiably organic crops using Dr. Soffer’s aeroponic principles. Microbial life is essential in organic growing, and as friendly microbes require aerobic conditions (presence of oxygen), it is my hope that these microbes can be “supercharged” in an aeroponic environment; hence “aeroganics.” However most beneficial microbes have evolved in soils, so may not thrive in an aqueous environment. That is why larger diameter baskets with organic based inert materials will not only provide mechanical support for the plants, but ideally provide a place to colonize supercharged microbes around the root zone. Seeds or cuttings will be propagated in an organic compost based soilless mix. This will likely occur in 1020 propagation trays with domes under continuous fluorescent lighting. As opposed to planting directly in the system, starting many more plants than are required to fill the system will allow for only the most vigorous and robust to be selected for transplant. Healthy crops start with healthy transplants. Once a small root system has been established, the seedlings/cuttings will be transferred into coconut fiber growing blocks (CoCo Tek). This growing media is 100% organic with lots of macro pore space. The fiber is very durable and may be reused. It should provide mechanical support for the plant and enough airspace for microbial colonization even when sprayed continuously. The coconut blocks will be covered (and anchored) with LECCA pellets (gro rocks) and the net baskets will be lined with coconut basket liners if available, to prevent rocks from falling into the system and provide additional airspace for microbial growth.

The system will be drained and re-filled weekly using an OMRI certified liquid nutrient program. It is important to keep the system topped-up with fresh water between changes. Although the centrifugal sprayer is resistant to clogging, it is very important that if using an organic solution that it is as free from organic debris and residues as possible (not “chunky”). If the solution is too thick, the size of the spray droplets may not be as fine, thereby decreasing the surface area of the spray available for maximum DO levels. For this aeroganic system to prove successful, it will be essential that the liquid organic nutrients being applied are able to provide a complete and adjustable balance of all macro and micro elements required for plant growth. Good quality organic solutions also provide a very complex array of sugars for microbial growth, sub-micro elements, naturally occurring hormones, amino acids, humic acids, fulvic acids, and a spectrum of beneficial vitamins.

It would be of significant value to growers if this “aeroganic” prototype produces up to it’s expectations. If the system becomes colonized with beneficial microbial life, the crops resistance to environmental stresses such as temperature, insects and disease should increase. Overall maintenance should be greatly reduced as the system runs continuously with a significant volume of solution which acts as a buffer to changes in temperature, DO levels, EC, pH, etc. Production rates should be fairly high in proportion to increased dissolved oxygen levels while allowing for changes in the nutrient regimen to push crops to their maximum. Crops grown organically tend to be of premium quality most noticeably in colour, taste, and smell and often fetch a premium price; even in a buyer’s market. An additional benefit is that the shelf life of many organically grown crops tends to be significantly higher than their inorganic fed counterparts.

Crop turn-around time in this system can be very quick. Once the crop is harvested, the media in the net baskets can be shredded and composted, simplifying disposal and improving the aeration of the compost pile

The net baskets, centrifugal sprayer, and lid can be sterilized with a mild bleach or anti-microbial solution and be re-used near indefinitely.

The system can be replanted within a matter of hours, requiring only a very small quantity of growing media to be replaced.

Hopefully by next addition we will have some results and images to share with the Maximum Yield readership.