WHAT IS HYDROPONICS? HYDROPONICS 101

Hydroponics research at Disney World’s Epcot in Orlando, Florida.

What is hydroponics?

According to the dictionary, the answer is:

The process of growing plants in sand, gravel, or liquid, with added nutrients but without soil.

Luckily, we’re sticklers for detail here, and we’re going to cover the subject in a little more depth.

How Plants Work

Hydroponics is the process of growing plants not in soil, but in a different growth medium. This allows for more control in what the plant does and does not receive.

There are 4 main things a plant needs to live: water, light, nutrients, and CO2.

Plants breathe in CO2, and split it into Carbon and Oxygen molecules. Small amounts of the oxygen are used, and the rest is released into the atmosphere (which paved the way for Oxygen-breathing organism, such as you and me!).

Using sunlight, the plant combines this carbon with water (H2O) to make a sugar molecule. This process is known as photosynthesis.

This sugar molecule can then be combined with nutrients found in the soil to form plant tissue, so the plant can maintain itself, grow, and reproduce.

If a plant doesn’t receive these four inputs in the right amounts, the plant cannot grow optimally. At worst, it can die. Hydroponics allows for the delivery of these inputs in precise amounts, opening the door to maximizing a plants potential.

HYDROPONIC TECHNIQUES

This subject is covered in greater detail in this article, an introduction to general hydroponic systems, but here is a summary of the different hydroponic techniques used today.

Solution Culture

In a solution culture, there is no soil medium. The roots are placed directly into some form of nutrient solution. There are 3 ways this is commonly done:

Static Solution: This is where plants are grown in a container filled with a nutrient solution. These systems are generally the easiest to set up, and can be as simple as a plant growing in a glass jar filled with hydroponic fertilizer.

Continuous Flow Solution: This is where a nutrient solution continuously flows past the plant roots. These systems are generally the easiest to automate, as the temperature, nutrient levels, pH, etc of a nutrient solution can be controlled within a separate storage tank before being released.

Aeroponics: This is where plant roots are exposed to a mist or aerosol of nutrient solution. This method allows for excellent aeration (air flow).

An example of continuous flow solution culture at work.

Medium Culture

In a medium culture, there is a solid medium for the roots to be contained in. The material used is inert (doesn’t supply nutrients to the soil) and is simply used as a solid structure for the roots to live in. Some common materials used in medium culture hydroponics:

Rockwool: Often used in drip irrigation systems. It is excellent at retaining water, and good at holding air.

Oasis Cubes: These are small cubes, good for starting seeds or cuttings. They are pH neutral, retain water, and can easily be placed in the soil or into a hydroponic system.

A 50/50 Perlite and Vermiculite Mix: These two mined materials complement each other nicely. Perlite is great for aeration and soil drainage. Vermiculite is great at holding onto water. A balanced mix of the two results in a great medium for plant growth.

Coconut Fibre: One of the top performing growth mediums. Contains hormones that stimulate roots and helps protect against disease and fungus infestation. A 50/50 mix of coconut fibre and expanded clay pellets in an extremely effective growth medium.

Now, we will take a look at the 4 essentials to plant growth, and how we can control and regulate them through hydroponics.

SUPPLYING WATER THROUGH HYDROPONICS

In a hydroponic system, water is delivered directly to the plant roots through the process known as irrigation. In both a solution culture and a medium culture, water can be delivered in one of two ways: traditional irrigation (where the water is delivered from above) or sub-irrigation (where the water is delivered from below, hitting the roots directly).

To learn more about the process, check out What Is Irrigation?

SUPPLYING LIGHT THROUGH HYDROPONICS

Artificial lighting is used in most hydroponic systems. While it delivers an imperfect light spectrum in comparison to the sun, it allows a grower to control variables such as intensity, how long a plant receives light, and what kind of light it receives.

Photosynthesis uses light from the visible light spectrum, mostly red and blue.

Types of lamps commonly used:

High-Intensity Discharge Lamps (HID): These deliver a high lumens/watt ratio (a lot of light for the energy used). They are great for the vegetating/flowering/fruiting phases of a plant.

Metal Halide types produce a more blue light, which is good for vegetative growth and shorter, denser plants.

High pressure sodium lamps produce a more red light, better for flowering and fruiting phases.

There are also blended lights available that give you a more balanced light spectrum.

Fluorescent Lamps: These are less luminous, and should be used for plants with lower light intensity needs (seedlings, herbs, lettuce, orchids, etc). A plus is that they generate less heat than HIDs. They also come in blue or red light forms.

A couple other items needed in setting up a hydroponic light system:

A Ballast: This will regulate the current of electricity received by the lamp.

A Shade or Reflector: These help direct light towards the plant.

Calculating the Cost of Power per Day in a Hydroponic system:

To calculate how much a system will cost you per day in energy costs, apply this simple formula:

Price of power/kilowatt (this can be found on your power bill. Let’s use $0.15/kW for our example)

X Total Kilowatts Used (ie 3 500 watt lamps would be 1.5kW)

X Hours/Day the lights will be used (ie if you run your lights for 8 hours, this number is 8).

So: $0.15 X 1.5 X 8 = $1.80 per day in electricity costs, or $657 per year.

SUPPLYING NUTRIENTS THROUGH HYDROPONICS

Hydroponics offers a big advantage when it comes to supplying a plant with nutrients. They can be supplied in the right amount at the right times, optimizing the process. Regular soil is often deficient in nutrients, due to poor conditions or excess planting. Plants in such a soil must put energy into growing out their roots to find the needed resources. This takes away from vegetation and flower growth. A plant in a good hydroponics system has no such problems.

There are 13 essential nutrients a plant needs to survive and thrive:

Primary Nutrients (needed in large amounts): Nitrogen (N), Phosphorous (P), Potassium (K)

Secondary Nutrients (needed in smaller amounts): Sulfur (S), Calcium (Ca), Magnesium (Mg)

Micronutrients (needed in trace amounts): Zinc (Zn), Iron (Fe), Copper (Cu), Manganese (Mn), Boron (B), Molybdenum (Mo), Chlorine (Cl)

A good hydroponic growing solution or fertilizer will contain all of these nutrients in correct proportions, creating a superior growing environment than can be found in most soils.

Hydroponic fertilizers come in organic and synthetic forms.

SUPPLYING CO2 THROUGH HYDROPONICS

Our last input needed is CO2. In most cases, the CO2 contained in the atmosphere is enough for optimal plant growth. In cases where all 3 other inputs are supplied at very high levels, CO2 can be added to the air of the growing environment to supercharge your plant growth.

pH BALANCE IN HYDROPONIC GROWING SOLUTIONS

Another advantage of hydroponic systems is that the pH balance of the growing environment can be precisely controlled. This can be used to both create an ideal growing environment for a plant type to grow, and to create an ideal environment for certain nutrients to be absorbed.

pH Levels Needed for Different Hydroponic Crops

Here’s a brief guide to the pH levels needed for certain hydroponic crops. A 1 on the pH scale is very acidic, a 7 is neutral, and a 14 is extremely alkaline.

Keep in mind these numbers will differ when plants are grown in soil.

Tomato plants being grown hydroponically.

Pineapple: 5.0 -5.5

Pumpkin: 5.0 – 6.5

Strawberries, Tomatoes: 5.5 – 6.5

Cucumbers: 5.8 – 6.0

Carrots: 5.8 – 6.4

Beans, Broccoli, Chives, Garlic, Lettuce, Peas: 6.0 – 6.5

Cantaloupe, Onions: 6.5 – 7.0

Cabbage: 6.5 – 7.5

As you can see, most plants prefer a slightly acidic soil.

pH Levels Needed for Nutrient Availability

Some nutrients are available for absorption at some pH levels, and not at others. Here’s a brief guide:

Nitrogen: Available at all but the most extreme pH levels.

Potassium: Available at all but the most extreme pH levels.

Phosphorous: Available at most pH levels, but starts to drop off at pH 7.5 and up.

Calcium: Easily available at ph 6-9. Availability drops off dramatically as the soil gets more acidic.

Magnesium: Somewhat available in acidic soils, easily available at neutral soils.

Iron: Easily available in acidic soils, starts to drop off after 6 and is hardly available in even slightly alkaline soils.

Manganese: similar to Iron in availability.

Boron: fairly available at most pH levels, optimal at 5.5.

Checking pH levels

There are 3 ways to check pH levels:

  1. Paper test strips (cheap but not precise)
  2. Liquid pH test kits (most common, accurate and easier to read)
  3. Digital Meters (the high-tech, more expensive way. Effective… but they have a reputation for breaking down)

Adjusting pH Levels in Growing Solutions

To lower the pH level, add diluted phosphoric acid to the solution.

To raise the pH level, add diluted potassium hydroxide to the solution.

Always add your nutrient solution or fertilizer first, as they will lower the pH level naturally. Test, and if adjustment is needed add small amounts of adjuster and check the pH (it’s easy to overshoot and go too far, especially with concentrated adjusting chemicals).

FOR RELATED ARTICLES, CHECK OUT AN INTRODUCTION TO GENERAL HYDROPONIC SYSTEMS, HOW TO MAKE YOUR OWN HYDROPONIC SYSTEM, AND HOW TO MAKE YOUR OWN HYDROPONIC NUTRIENT SOLUTION

Good luck and stay prepared!

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Comments

  1. NFT is the best system I have used its easy to manage and because it is continuous you don’t have to go every day to check them. In fact you only have to put food in once every 7 days, and the ph stays quite stable if you use a big water tank, well at least in winter. this is the best system I have used up to date and easy to clean and the most productive.

  2. Thanks for the information. Beginners might want to search out “5 gallon bucket DWC” if they want to get started growing for less than $30

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