Hydroponics is the science of growing plants without soil. Instead, plants receive all the essential minerals they need from a nutrient-rich water solution. Because of this, hydroponics allows growers to control every aspect of plant nutrition, which often leads to faster growth and higher yields.

This method is becoming increasingly popular. For example, you will see it used in living walls, rooftop gardens, and urban grow rooms where soil is too heavy, impractical, or simply unavailable.

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What Can Be Grown Hydroponically?

In theory, any plant can be grown hydroponically. However, the method is especially effective for greenhouse crops like:

• Tomatoes
• Cucumbers
• Peppers
• Roses and other cut flowers

Every plant root needs three things: oxygen, moisture, and nutrients. Therefore, a hydroponic system must keep the root zone nutrient-rich and moist, while also ensuring excellent aeration. Without oxygen, roots suffocate quickly.

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Types of Hydroponic Systems

Hydroponics can be divided into two main types.

1. Substrate systems (hydroculture): Roots grow in an inert medium such as perlite or rockwool.
2. Aggregate-free systems: Roots grow directly in flowing nutrient solution, such as in Nutrient Film Technique (NFT).

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Substrate (Aggregate) Systems

At its simplest, hydroponics can be a plant in perlite or another medium, watered with a nutrient solution often enough to stay moist. Because air spaces exist between particles, the roots receive oxygen and avoid suffocation.

However, most growers use automated drip irrigation systems. Nutrient solution is pumped from a stock tank and delivered to the plants. The solution can either:

• Run to waste, which is simple but costly and less eco-friendly, or
• Recirculate, which is cheaper and reduces pollution.

For example, commercial tomato growers often use rockwool slabs drip-fed with nutrients. The excess drains into a trough and is reused. Another common setup is ebb and flow, where pots are periodically flooded and then drained back to the tank.

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Managing Nutrient Solutions

Success in hydroponics depends on the nutrient mix. A proper solution contains:

• Macronutrients: Nitrogen, Phosphorus, Potassium, Magnesium, and Sulphur
• Micronutrients: Iron, Copper, Manganese, Boron, Zinc, and Molybdenum

In addition, two key factors must be monitored:

• pH: Aim for 5.8–6.2. Use citric acid to lower pH or baking soda to raise it.
• Electrical Conductivity (EC): This measures nutrient strength. If the solution becomes too salty, dilute it with water.

Because nutrient ratios change over time, you should replace the solution every two weeks. As a bonus, you can reuse discarded solution on garden soil as fertiliser.

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Aggregate-Free Systems (NFT and Aeroponics)

Nutrient Film Technique (NFT):
A thin film of nutrient solution flows along shallow channels. Plants sit in small rockwool cubes placed at intervals. Their roots form a dense mat, absorbing water and nutrients while still receiving oxygen. The surplus solution drains back to the tank and is pumped around again.

Aeroponics:
Here, roots hang in the air and receive periodic sprays of nutrient solution. Because the roots receive so much oxygen, growth can be extremely vigorous.

However, both systems rely heavily on pumps. If the pump fails, roots dry out quickly and plants can die within hours.

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Why Choose Hydroponics?

Hydroponics offers many advantages over traditional soil cultivation. For example:

• Plants grow faster because nutrients are always available.
• Yields are often higher and more consistent.
• Space is used more efficiently, which is ideal for urban growing.
• Growers can cultivate crops where soil is poor or inaccessible.

As a result, hydroponics is now used worldwide in commercial greenhouses, educational projects, and home grow rooms.