SESSION 1: Introduction to Hydroponics
Hydroponics, by definition, means 'water-working'. In practical use, it means growing plants in a water and nutrient solution, without soil. Hydroponics allows a gardener to grow plants in a more efficient and productive manner with less labor and time required.
The science of hydroponics proves that soil isn't required for plant growth but the elements, minerals and nutrients that soil contains are. Soil is simply the holder of the nutrients, a place where the plant roots traditionally live and a base of support for the plant structure.
In hydroponics you provide the exact nutrients your plants need, so they can develop and grow. The hydroponic nutrients are fed directly at the root base, never stressing the plant due to lack of nutrients or water.
Virtually any plant will grow hydroponically, but some will do better than others. Hydroponic growing is ideal for fruit bearing crops such as tomatoes, cucumbers and peppers, leafy crops, like lettuce and herbs and flowing plants. Most hobby hydroponic gardeners plant crops similar to what they would grow in a soil garden.
Most commercial hydroponic growers combine hydroponic technology with a controlled environment to achieve the highest quality produce. Within a greenhouse structure you can control the ambient temperature, humidity and grow light levels allowing you to grow on a year round basis.
Advantages of Hydroponic Growing
There are many advantages of hydroponic growing. These include:
Most hobby hydroponic gardens are less work than soil gardens because you do not have soil to till or weeds to pull.
- By eliminating the soil in a garden, you eliminate all soil borne disease.
- A hydroponic system uses a fraction of the water that a soil garden does because no water is wasted or consumed by weeds.
- In hydroponics, plant spacing can be intensive, allowing you to grow more plants in a given space than soil grown produce.
- A small hydroponic garden can be set up almost anywhere.
- By providing the exact nutrients your plants need, they will grow more rapidly and produce bigger yields.
- In studies it has been proven that hydroponic produce is higher in nutritional value than field grown crops.
- Hydroponic produce generally tastes better than field-grown produce.
- If you are growing indoors in a grow tent, grow box, or in a greenhouse, you can grow your hydroponic plants on a year-round basis.
Six Common Types of Hydroponic Systems
In a soil garden, plants are rooted in the soil and draw nutrients from it. In hydroponics, a nutrient rich solution is fed directly to the plant roots. In some hydroponic growing systems an inert growing medium, such as rockwool is used in place of soil. These growing mediums are porous and absorb the nutrient solution, allowing the plants to use it as needed.
In other hydroponic systems, like the NFT system, no growing medium is used and the plant roots are suspended in a grow channel.
THE WICK SYSTEM: The Wick system is by far the simplest type of hydroponic system. This is a passive system, which means there are no moving parts. The nutrient solution is drawn into the growing medium from the reservoir with a wick. This system can use a variety of growing medium. Perlite, Vermiculite, Pro-Mis and Coconut Fiber are among the most popular.
The biggest drawback of this system is that plants that are large or use large amounts of water may use up the nutrient solution faster than the wick(s) can supply it.
WATER CULTURE SYSTEM: The water culture system is the simplest of all active hydroponic systems.
The platform that holds the plants is usually made of Styrofoam and floats directly on the nutrient solution. An air pump supplies air to the air stone that bubbles the nutrient solution and supplies oxygen to the roots of the plants.
Water culture is the system of choice for growing leaf lettuce, which are fast growing water loving plants, making them an ideal choice for this type of hydroponic system. Very few plants other than lettuce will do well in this type of system. This type of hydroponic system is great for the classroom and is popular with teachers.
A very inexpensive system can be made out of an old aquarium or other water tight container. The biggest draw back of this kind of system is that it doesn't work well with large plants or with long-term plants.
NUTRIENT FILM TECHNIQUE (also known as NFT): With the Nutrient Film Technique the plants are grown in channels which the nutrient solution is pumped through. The plant roots are flooded by the nutrient solution as it passes by. Ideally, the bottom of the roots are exposed to the nutrient solution, while the top of the roots are exposed to air. Most NFT systems are fed on a very frequent timed cycle. For instance, 10 minutes of nutrient solution flow, followed by 5 minutes of nutrient solution drain. Since the plant roots are not in a growing medium, it is crucial that they are flushed often to keep them moist.
NFT is ideal for lettuces, leafy crops and herbs, all of which are short term crops. Larger NFT channels can be used long term crops as long as some form of plant support is provided..
EBB AND FLOW: The Ebb and Flow (also know as flood and drain) method of hydroponic gardening simply allows all the plants in the garden to be fed the same amount of nutrient solution at the same time.
The plant grow bed, which contains plant pots filled with a growing medium, is flooded with the nutrient solution for a set period of time and then allowed to drain for a set period of time. This allows the growing medium and plant roots to stay moist while bringing fresh oxygen to the root base each time the nutrient solution drains away.
Most Ebb and Flow systems will flood the grow bed for 10 or 15 minutes of every hour or two In an Ebb and Flow system, the plant roots are most commonly grown in a medium of perlite, rockwool or expanded clay pebbles.
An Ebb and Flow system, popular with many home hydroponic gardeners, is ideal for growing a broad variety of crops since both long and short term crops do well in this system.
AEROPONICS SYSTEM: The aeroponic system is probably the most high-tech type of hydroponic gardening. Like the NFT system below the growing medium is primarily air. The roots hang in the air and are misted with nutrient solution.
The mistings are usually done every few minutes. Because the roots are exposed to the air like the NFT system, the roots will dry out rapidly if the misting cycles are interrupted.
A timer controls the nutrient pump much like other types of hydroponic systems, except the aeroponic system needs a short cycle timer that runs the pump for a few seconds every couple of minutes.
DRIP SYSTEM: In a Drip system, the nutrient solution is delivered to the plants through drip emitters on a timed system. The timed cycle flushes the growing medium, providing the plants with fresh nutrients, water and oxygen as the emitter is dripping.
The emitters are usually scheduled to run for approximately 5-10 minutes of every
hour. In a drip system, the plant roots are most commonly grown in a medium of
perlite, grow rocks or rockwool. The drip system is often used in commercial
hydroponic facilities that grow long term crops like tomatoes, cucumbers and
Hydroponic Growing Media
In a traditional garden, plant roots are in the soil. They support the plant and search for food and water. In hydroponics, we often use a growing medium in place of soil. The roots of a hydroponic plant do not work as hard as those of a plant grown in soil because their needs are readily met by the nutrient solution we feed them.
Ideal mediums are chemically inert, porous, clean and able to drain freely.
Many materials have been used as hydroponic growing media. These include: vermiculite, saw dust, sand, peat moss and, more recently, rockwool, perlite and expanded clay pebbles. Today's popular growing mediums, perlite, rockwool and expanded clay pebbles are described below.
Perlite is derived from volcanic rock which has been heated to extremely high temperatures. It then explodes like popcorn, resulting in the porous, white medium we use in hydroponics. Perlite can be used loose, in pots or bagged in thin plastics sleeves, referred to as "grow bags" because the plants are grown right in the bags. Plants in perlite grow bags are usually set up on a drip feed system. Perlite grow bags usually hold 3 or 4 long-term plants.
Perlite is also used in many commercial potting soil mixes.
Rockwool is derived from basalt rock. It too is heated to high temperatures but then is spun into fibers resembling insulation. These fibers are spun into cubes and slabs for hydroponic production. The cubes are commonly used for plant propagation and the slabs are used similarly to the perlite grow bags. A plant is set onto the rockwool slab and grown there. The plant roots grow down into the slab. Rockwool slabs usually hold 3 or 4 long term plants.
Expanded Clay Pebbles / Growrocks: Many hobby hydroponic gardeners use expanded clay pebbles for their growing medium. Expanded clay pebbles have a neutral pH and excellent capillary action. Often Ebb and Flow systems use expanded clay pebbles in the grow pots as the growing medium.
to Session 2: Hydroponic Lighting