Pros & Cons of Hydroponics, Aeroponics, Kratky, Aerogardens

Hydroponics is becoming much more popular with home gardeners and there are a number of different systems including regular hydroponics, aeroponics, kratky hydroponics and indoor hydroponic gardens such as AeroGardens and LetPot. This post will examine the differences between these systems and provide a pros and cons list for each one. Armed with this information you will be able to select the right one for your situation.

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What is Hydroponics

In simple terms hydroponics is a way of growing plants in water without soil. The systems can be very productive and are used commercially for some vegetables. The lack of soil makes them ideal for cleaner environments such as greenhouses and homes.

Each of the methods discussed here are similar in that none of them use soil and they all use hydroponic fertilizer. What makes each one different is the way in which they apply water (nutrient solution) and air to the roots. There are also differences in the way the plants are started and the support used to hold up the plants.

Here is a table summarizing some of the differences between hydroponic methods.

Feature	Traditional Hydroponics	Aeroponics	Kratky	Aerogardens
Moving nutrient solution	Yes	Yes	No	Partially
Water pump	Yes	Yes	No	Yes
Built-in lights	No	No	No	Yes
Easily scalable	Yes	Yes	No	No
Cost	High	High	Low	Medium

The Importance of Water and Air

Plant roots absorb three things: nutrients, water and air (oxygen). The air is as important as nutrients and water, but when roots are submerged in water they have difficulty getting enough oxygen. A hydroponic system must therefore provide extra air and each systems does it in a different way.

Some systems move the nutrient solution which ensures that the water sitting next to roots is saturated with air. Other systems use lower levels of liquid so that some roots are in air and others are in water. Still others spray a water mist onto roots so they remain very wet while at the same time being exposed to air.

Traditional Hydroponic Systems

I have grouped several very similar hydroponic systems into this one category because they all have the nutrient solution moving past the roots.

These systems are designed to have plant roots mostly submerged in water. The oxygen is provided by having the nutrient solution in constant movement, ensuring that oxygen rich water is always next to the roots.

Pros

• Scale up well for large commercial operations.
• Efficient use of water and nutrients.
• Monitoring nutrient concentration in the water is easy, even on large systems.
• Can be constructed as DIY systems.

Cons

• More complicated because they use either pumps or wicks.
• Not suitable as smaller in-home systems.

These systems can be divided into subcategories based on the method used to move the water.

Nutrient Film Technique (NFT)

NFT systems place the nutrient solution in large reservoirs and then pump it into small channels that are sloped so that the nutrients run along the channel and return to the reservoir using gravity, as shown in the picture below. Plants are usually held in net pots with their roots mostly dangling in the nutrient solution. The channels, which could be PVC pipes, are kept small making the system suitable for small root systems like lettuce.

Wick System

The wick system is the simplest type of traditional hydroponics because it uses no pumps or aerators. Nylon wicks are positioned around the plants and dangle into the nutrient solution. Liquid is pulled up the wicks to the roots by capillary action. Control of nutrient concentration is more difficult with wicks than with pumps and these systems are more suited for small gardens.

Deep Water Culture (DWC)

Deep water culture places the roots directly in the nutrient solution so that most of the roots are covered. Rather than move the water past the roots, a diffuser or air stone increases the level of oxygen in the water to ensure roots get enough. The downside to this method is that the nutrient solution can become dirty and root diseases are more prone.

Aeroponics

In aeroponics the plants are suspended mostly in air and nozzles are positioned beside the plants to provide a continual fine mist. These nozzles spray the nutrient solution onto the roots providing both a moist environment as well as lots of oxygen. Excess liquid falls down into a reservoir where the pump can pick it up.

The reservoirs are deeper than in other hydroponic systems but they use less solution than other systems.

Pros

• Plants grow well because they have good access to both nutrients and air.
• Uses very little water.

Cons

• Requires a pump.
• Reservoirs are larger than in other systems.
• Spray nozzles tend to clog.

Kratky Method

This method was developed by B.A. Kratky from the University of Hawaii. It is similar to deep water culture except that there is no pump, which makes it a very simple system.

Plants are inserted in the nutrient solution using a reservoir that could be a mason jar, pail, milk jug, or countless other items. As the plants grow they use up the water and the level drops forming an “air gap” between the top of the water and the lid. As the air gap gets larger, more and more of the roots are exposed to air, but the tip of the roots remain in the nutrient solution.

In essence, Kratky starts out as a pumpless Deep Water Culture system. It is claimed that you can set up this system and forget it. Plants are left to do their own thing until harvest time.

Pros

• No pumps or electricity.
• Don’t have to change nutrient solution.
• Can be ignored for many weeks.
• Smaller containers can be used; one per plant.
• Low cost.

Cons

• Not suitable for a large number of plants.

Aerogardens

Aerogardens are also called indoor hydroponic gardens and the term was coined by the first commercial small counter top garden developed by AeroGarden. Since its introduction, many competitors have released similar systems, including LetPot, InBloom, Click & Grow and iDoo.

These systems are similar to Deep Water Culture systems in that roots are mostly submerged in water. They tend to have pumps but most are only run for a few minutes a day to keep nutrient solutions mixed and fresh.

What is unique about these systems is that they are self contained and include a built-in light so that they can sit on a kitchen counter. Several systems now let you control the whole device from a phone app and some even have automated control over the addition of fertilizer and topping up the liquid level.

Most brands recommend doing a deep clean every three to four months which involves taking out all the plants and scrubbing everything down. A deep clean keeps plants healthy and the system running smoothly.

Pros

• Self contained system, including the light.
• Decorative, suitable for use in living areas.
• No knowledge of hydroponics needed.

Cons

• Expensive compared to the amount of food it produces.
• Needs regular cleaning.
• Grows very few mature plants at one time.