To survive and thrive, plants need: 1) physical support, 2) water, 3) nutrients, 4) light, and 5) oxygen. Soil provides the physical support for the plants, along with nutrients. However with time, nutrients are depleted and plants no longer grow to their maximum potential.
In hydroponics, the soil is replaced with an inert material to provide support, and nutrients are provided in water that is directly applied to the plant roots. In this way an optimal amount and combination of nutrients are provided to the plant constantly, resulting in optimal growth.
Benefits and Disadvantages of Hydroponic Gardens
The benefits of hydroponic gardening over traditional soil gardening are as follows:
- Due to the provision of optimal nutrient levels, plants grow quicker and have higher yields.
- Crop turn-around time is quicker because there is no need to prepare soil.
- The fact that plants aren’t in contact with soil means that soil-borne pests and diseases can’t attack your plants.
- Since weeds grow from the soil, they do not typically grow in hydroponic systems.
- Reduced use of water.
The disadvantages of hydroponic gardening are:
- The cost to build or buy a hydroponic garden.
- The cost to maintain the hydroponic garden (mainly nutrient solutions).
- The requirement to regularly manage water, nutrient, and pH levels.
- Electricity costs to run water pumps, if these are a part of your garden.
- The possibility of plants drying out if there is a pump or electricity failure, again only relevant to gardens using a water pump.
Types of Hydroponics Systems
Successful hydroponic gardening is achieved by providing nutrients, oxygen, and physical support to your plants. There are a number of ways in which this can be achieved, and this leads to the different hydroponics “systems” that will be discussed here. Each has its advantages and disadvantages, and plants may prefer certain systems over others.
Water culture hydroponics is the simplest form of a hydroponic garden (See Figure 1). Plants are contained in vessels that float on a bath of hydroponic nutrient solution. Oxygen is supplied by an aquarium air stone that runs continuously. A water culture system can easily be set up using an aquarium (where you can watch the roots develop) or a plastic box and a polystyrene sheet that will float on the nutrient solution and hold the plants. Since plants are continuously in contact with the nutrient solution, there is no danger of damage to plants should a power or air pump failure occur. Lettuce, strawberries, and herbs grow particularly well in this system.
With drip hydroponic systems (see Figure 2), there are at least two containers, one on top or higher than the other. Plants are located in the top container, while the nutrient solution is in the bottom container. The nutrient solution is pumped up to drips located by the stem of each plant with a water pump, and an aquarium air stone is used to oxygenate the water. The nutrients filter down to the plant roots and are passed back to the bottom container. Typically both the water and air pumps run continuously with this type of system. A crop of almost any plant will grow well with this system. Plants with large root balls are particularly suited to drip systems.
Ebb and Flow Systems
Ebb and flow systems (Figure 3) are another inexpensive type of hydroponic setup. The setup is very similar to the drip system, where there are two containers, the one on top containing the plants, and the one on the bottom containing the nutrient solution. Rather than the nutrient solution being passed slowly to drippers at the stem of each plant, the nutrients are pumped in large volumes into the top container, flooding the container. An overflow pipe determines the height of the nutrients, typically to where the roots begin at the base of the stem, with excess liquid being recirculated through the overflow pipe back to the bottom container. With ebb and flow systems, the pump is switched on and off intermittently (perhaps 30 mins on, 15 mins off), to flood the grow tray periodically. When the pump is switched off, all of the nutrients are syphoned out of the grow tray via the pump line. The emptying period allows for oxygen to reach the roots, and for this reason an air stone is not absolutely required for ebb and flow systems. As with drip systems, almost any plant will grow well with this type of system. Plants with large root balls are also particularly suited to eff and flow systems.
The Nutrient Film Technique
The nutrient film technique (see Figure 4) is designed to run highly oxygenated nutrients continuously over the roots of plants, typically grown in baskets hanging in a PVC pipe. The nutrient solution is continuously recycled. In a “classical” nutrient film technique setup as shown in Figure 4, should the pump stop running, all of the nutrients would run out of the pipe and the plants would dry out in a matter of hours. It is possible to make the angle of the pipe smaller and add an overflow pipe similar to what’s in an eff and flow system. This would serve to provide a reservoir of nutrients that would remain in the event of a power or pump failure. Because of the confined space of a PVC pipe and the requirement for nutrients to continuously flow over the roots, the nutrient film technique is particularly well suited to plants that have small root balls such as lettuce, strawberries, and herbs.
An aeroponics design (see Figure 5) is the most advanced of all hydroponic garden setups. Plant roots hang into a container and are sprayed continuously or in short bursts with nutrient solution (e.g. one minute on, one minute off). The system can be designed so that nutrients fall to the bottom of the container as shown in Figure 5 or drain to another container. The advantage of aeroponics is that as the nutrient solution is sprayed out of sprayers, it is becomes highly oxygenated, delivering a high level of oxygen to the roots. Power and pump failure is disastrous while the plants are young and their roots do not reach the nutrient solution reservoir, however once they do they are quite safe. Aeroponics is particularly suited to plants with small to medium-sized root balls such as lettuce, herbs, tomatoes, and peas.
A number of textbook hydroponic garden systems have been described here and further explanations can be found at hydroponic warehouse. Obviously each type of system has its pros and cons. It is possible to design a system that contains features of more than one of the systems above, to overcome some of the disadvantages, or to add some advantages. For example, the first system I made was a combination of the aeroponics and nutrient film technique systems. I set up the system with PVC pipes and sprayers that sprayed nutrients directly onto the plant roots. The nutrients then flowed down the PVC pipe in a nutrient film technique style to be recycled. I also made the angle of the pipe very small so that a reservoir of nutrient solution always remained at the bottom of the pipe, which serves to keep the plant roots moist should the power or pump fail, or an individual sprayer become blocked. A photo of it is shown in Figure 6. In considering the type of hydroponic garden you would like to buy or build, first of all consider the type of plants you want to grow and the size of their root systems. This will narrow down the number of systems that are ideal for your purpose. Then consider how much money you want to spend in setting it up, and whether you want to invest in a pump.
*Images from Brooke L.L. “Getting started everything you need to know – hydroponics”.