Aeroponic towers can grow produce faster than traditional growing with soil. This faster growth is mostly driven by (1) more efficient nutrient absorption and (2) plant roots having higher oxygen uptake in aeroponic systems vs. being buried in the ground.
Plant roots are suspended in air inside the aeroponic tower. Roots are then irrigated with a simple solution of water + nutrients on regularly scheduled intervals of say, 15 minutes every hour. Water is recycled inside the tower like a water fountain. Water is pumped to the top of the system and flows back down with gravity, watering roots along the way. This watering cycle repeats resulting in exceptional water efficiency.
Tower systems are a relatively new concept for residential gardening. Certainly most people garden the traditional way – with soil. Gardening with soil is what most of us learned in grammar school and it's very intuitive. But tower farming offers some unique advantages such as growing vertically, which takes up less space. This makes it ideal for people who don’t have yard, or those who want to grow indoors.
Hydroponics vs Aeroponics – What’s the Difference?
Many people are familiar with hydroponics, but not aeroponics. Aeroponics is actually a subset of hydroponics. An analogy would be to compare it to martial arts. In martial arts we have karate, tae kwon do, judo, jiujitsu and other styles. While each style is different, they are part of the martial arts family.
Aeroponics is part of the hydroponics family. Within hydroponics you have deep water culture, ebb and flow, nutrient film technique, aeroponics and more. Each style is different but they all have one thing in common – they use nutrient-rich water (not soil) to supply sustenance to plant roots. These growing methods are all part of the hydroponics family.
Hydroponics
Hydroponics is a method of growing plants without soil. Gardening without soil, is another way to think about what hydroponic gardening is.
The word “hydroponics” comes from Greek origin. “Hydro” means water and “ponics” which means work. So the literal translation is “waterwork.” With hydroponics – plant roots absorb their nutrients from water instead of soil.
Aeroponics
Just like hydroponics – aeroponics uses water to supply plant roots with nutrients. But a key difference is plant roots are also exposed to air. Hence the word “aero” which also comes from Greek origin.
Other hydroponic methods such as deep water culture, ebb and flow, and nutrient film technique flood or submerge plant roots in water. But with aeroponics plant roots are never submerged. When grown aeroponically plant roots are suspended in air, while nutrient-rich water is dripped or misted over the roots on an interval-based watering schedule. This intermittent watering means that plant roots have more exposure to air, than water!
Historical Context
People have been growing plants in soil since the beginning of human time. It wasn’t hard to figure out really. All you had to do was look around and you would see plants growing out of the ground. The hardest step wasn’t the growing part, but finding high quality seeds.
Surprisingly – hydroponics goes back a long way too. The Floating Gardens of the Aztecs, pictured, (1100 BC) were floating islands of plants cultivated on freshwater lakes. The Hanging Gardens of Babylon (600 BC) utilized hydroponic principles in its design. The first documented studies of hydroponics started in the 1600’s, but it wasn’t until the 1800’s when these scientific studies began in earnest.
Aeroponics is a relatively newer discovery within the hydroponics family, with its origins beginning about a 100 years ago. But the technology to create hydroponic systems came much later, with the creation of better materials and improved manufacturing.
Scientific Studies
The first studies of aeroponics dates back to 1911, when Russian botanist V.M. Artsikhovski experimented with spraying nutrients into the air, nearby surrounding plants. He wanted to see if plants could absorb nutrients from the air. He published an article, “On Air Plant Cultures” with his findings which showed plant could absorb nutrients in this manner, and that it could be used as a method for plant cultivation. Artsikhovski’s work was a key first step demonstrating that plants could absorb air-bound nutrients.
A follow-up study was performed in the years that followed, by Dutch biologist Fritz Warmolt Went in 1957. A world-renowned biologist, Dr. Went spent much of his research career at the California Institute of Technology (Caltech) in Pasadena, California. His experiment involved growing coffee plants and tomatoes, with their roots suspended in air. He took his experiment further than Artsikhovski’s, by spraying nutrients directly on to the root section of the plant. Dr. Went’s method of nutrient application directly on plant roots further demonstrated that plants could absorb nutrients in this way. He went on to create the term, “aeroponics” we use today.
Nearly three decades later an American, Richard J. Stoner, was the first person to commercialize the use of aeroponics. He developed a device called the Genesis Rooting System, for which he filed a patent in 1983. A second generation of this system would be called the Genesis Growing System, released in 1985. It was a closed-loop system with a nutrient-recycling reservoir. Principles of Stoner’s closed-loop design are still used in today’s modern aeroponic towers.
Benefits of Aeroponics
The primary benefit of aeroponics is faster growth times. Studies have measured these growth times to be 3 x faster than growing in soil. But there are other benefits as well, including higher plant nutrient efficency:
• Higher oxygen uptake. Because plant roots are suspended in air, they have higher oxygen uptake vs. plant roots growing underground in soil. Yes, plant roots need to breathe oxygen! This process is called “root respiration.”
• Direct delivery of nutrients. Nutrient-rich water is delivered direct to plant roots. This compares to the indirect delivery of nutrients when growing in soil. Since plants cannot absorb nutrients through dry soil, the soil must first be watered. Water absorbs nutrients from the soil, and then it is absorbed by plant roots.
• Precise nutrient control and efficiency. It is easier to fine-tune the exact nutrients delivered to your plants via aeroponics. This is helpful when growing certain species which require more of a particular nutrient. Nutrient use is also more efficient, requiring less nutrients to be used overall.
• Prevents root rot. When roots don’t get enough oxygen, they can rot. This is usually caused by over-watering or poor drainage, which limits the roots’ ability to breathe oxygen. Suspending roots in air virtually eliminates root rot in aeroponic systems.
• Exceptional water efficiency. Water is delivered in a closed-loop system, where water is continuously recycled. With soil gardening, only a fraction of the water used is actually absorbed by plant roots. Most of the water is lost in the ground, through runoff, or evaporation. There is a savings of 95% compared to traditional gardening.
• Vertical gardens take less space. Since these systems grow vertically, tower gardens take less space. In less than 1 square meter you can grow 24 pots (or more) of herbs, fruits and vegetables. This same yield would require several meters of horizontal land.
• No soil. Since aeroponic growing is hydroponic growing, no soil is required! This means you can bring your garden indoors with the mess.
How Does an Aeroponic Tower Work?
Let’s break down the key workings of this system:
At the base of the grow tower is a reservoir that holds the nutrient-enriched water. The solution is forced upward by a pump via pipes or tubing. Then water drips on to plant roots as the water comes back down the tower. This water returns to the reservoir for reuse after dripping down the roots and through the tower. With this closed-loop method, water waste is vastly reduced.
Compared to plants in soil or conventional hydroponic systems, the roots in the growth chambers receive a lot more oxygen since they are suspended in air. One of the main causes of the rapid and healthy growth of plants cultivated aeroponically is their enhanced intake of oxygen.
A typical aeroponic tower is made up of many vertical sections piled on top of one another. Plants are grown in these planting compartments within each tower. Usually composed of food-grade plastic, the towers are built to be strong and lightweight.
Reservoir
An aeroponic tower’s reservoir and watering system are crucial parts. For your plants to flourish, the water tank has to be big enough to accommodate adequate water. All of the plants in the tower garden should receive enough water from an effective watering system. The reservoir serves as the foundation for the nutritional solution in your tower. A well-designed and maintained reservoir is essential. The scale of your tower and the quantity of plants you plan to cultivate should be reflected in the reservoir's size. Refilling and nutrition changes are less frequent with larger reservoirs.
Water Pump
For the root systems to be watered, the water pump is a necessary component. Make sure your pump is strong yet quiet enough for aeroponic tower gardens. All of the plants in the tower garden rely on nutrients delivered by the water pump. There are two different kinds of pumps: external and submersible. Both types can be used. External pumps stay outside the reservoir, whereas submersible pumps are located right within. In consumer towers, submersible pumps are typically more common. Large-scale towers frequently utilize high-pressure pumps because they travel further from the ground.
Grow Lights
If you plan to use your tower indoors, you should find an area that gets plenty of sun. Ideally next to a south facing window (in the northern hemisphere). Otherwise – grow lights are highly recommended. LED grow lights, to be more specific. LED diodes are easy to arrange vertically so they cover the entire height of the tower. They’re also very efficient and deliver great light intensity relative to the amount of electricity they consume.
Timers
Watering and lighting cycles can be automated with timers. This “set it and forget it” approach is one of the most appealing features of aeroponic towers. Because timers are adjustable, you can increase or decrease watering times and intervals depending on the changing temperatures of the seasons. Lighting schedules can also be adjusted.
It’s important to take into consideration, the characteristics and design when choosing your aeroponic tower garden. Important considerations include reservoir size, water pump style, automated timers, sunshine access and/or LED grow lights.
Maintaining Optimal Conditions
• If using LED lights run them for 12 to 16 hours daily and position them 6 to 10 inches away from the plant canopy for best development. Look for adjustable lights which can be moved closer and further away from the tower.
• Select a nutrient solution that easily dissolves in water which will avoid fertilizer build up at the bottom of the reservoir.
• Check water and pH levels regularly to make sure there is water in your reservoir. The water pump should be completely submerged at all times. pH should be checked weekly. If pH is out of range (5.5 - 6.5 is ideal) your plants will not be able to absorb nutrients.
• The watering schedule for your aeroponic tower should run at regular intervals. A good schedule to start with is 15 minutes on, 45 minutes off for 14 - 18 hours a day if you're growing outdoors. As temperatures increase you should increase watering frequency and duration.
• The ideal temperature range for plants in a vertical garden is 65 to 78 degrees Fahrenheit and the humidity level should be kept at about 60%.
Best Plants for Aeroponic Tower Gardens
A large variety of crops may be grown in these systems because of their adaptability. Popular options include leafy greens like mustard greens, kale, and lettuce as well as herbs like parsley and basil. Aeroponic towers are also capable of growing fruits and vegetables, like tomatoes and cucumbers. However, keep in mind tomatoes and cucumbers are vining plants so a trellis will be required to support them. These towers are a great way to cultivate since plants will develop more quickly and yield more. In other words, each plant will yield more nutrient-dense, homegrown food for you and your family.
Aeroponic Applications
Residential Growing at Home
Aeroponic towers are used by consumers to grow food at home. With these systems, home growers can control the entire growth process from germination to harvest. GMO-free seeds can be used and grown without any herbicides, pesticides or other chemicals. Because food is grown at home, it reduces the carbon footprint of your produce since it is not trucked from hundreds of miles away.
These vertical gardens make it possible to grow in limited space indoors or on a balcony. This makes them ideal for urban areas, for people who live in apartments or condominiums without access to a yard. Typical towers are capable of growing 24 pots of more in less than 1 square meter of floor space.
Arid Regions
Traditional soil farming requires large amounts of land. Keeping that much land moist for plant cultivation is a huge task, requiring millions of gallons of water. The most productive farms are located in milder climates, with a fair amount of natural run-off or rain. Or at least, access to a spring or well system so water can be transported at a reasonable price.
But in arid regions of the world - the Middle East for example, there can be very little rain all year while temperatures routinely break 120 degrees Fahrenheit in the summer. Water is really at a premium In these climates, and there are very tight seasons when farmers can grow outside. Indoor aeroponic farming is a very practical method for plant cultivation in these regions. Recycling water is a huge benefit and it is fast, leading to faster crop turnarounds per year.
NASA and Growing in Space
Many concepts of aeroponics are ideal for growing plants in space. In the absence of gravity, loose soil would float around making it unpractical to use. Aeroponics does not require transportation (i.e., rocket-launch) of heavy soil, multiple plants can grow in a compact area, nutrient application is highly efficient, and its closed-loop reservoir system recycles water.
In 1997, NASA (the space agency of the United States) began work on an agriculture system which could be used in space. The eventual goal of being able to grow food on longer space flights, and future colonies on the moon and other planets. Using aeroponic systems, simultaneous tests were conducted on the space station Mir, and also back on Earth. Adzuki beans were used in the experiment. The tests showed the Adzuki seedlings grown in space, grew faster than the seedlings grown on Earth!
The success of this and other NASA experiments led to prototypes of small systems which could be used in space. One of these systems was an inflatable, enclosed aeroponic farm (pictured) which can be deflated for storage during transportation. More recent prototypes contain up to 1,000 pots and can grow 12 growing cycles per year. While the system has not yet been used in space, it shows promise for future space travel. Since most space-food comes in dehydrated packets, fresh greens and vegetables would be important for astronauts on long space missions.
