How Hydroponics Works, Types, And Pros and Cons

By Katherine Gallagher

May 28, 2021

Hydroponics is a form of farming that uses a nutrient solution root medium, rather than soil, to grow plants. Also referred to as tank farming, hydroponic plant roots may simply hang in water containing a mixture of dissolved nutrients or be supported by an inert substrate growing medium.

Often, the irrigation and fertilizing is performed mechanically in smaller spaces, and even vertically (known as vertical gardens), making it a more budget-friendly and labor-saving farming method. Vegetables like cucumbers and leafy greens like spinach are some of the most popular plants that are grown hydroponically, but gardeners can easily grow herbs or fruiting plants like strawberries, as well.  

How Does Hydroponics Work?

Hydroponics involves any plants that are grown without the use of soil, the plants simply get their essential nutrients from a different source. Depending on the type of hydroponic system used, the plant’s roots may grow directly into a liquid solution or into a medium such as clay pebbles, peat moss, or sand (in an aggregate system). This way, the grower has control over environmental conditions like temperature and pH balance as well as the plant’s exposure to nutrients.

Hydroponics can be as simple or as complicated as you want it to be. Some operations can range 25,000 square feet and produce 10,000 heads of lettuce per day, yet something as uncomplicated as sticking the base of a leafy vegetable into a glass of water to regrow is also a form of hydroponics. While soil is often the easiest method of growth among traditional gardens, plants don’t technically need it; the photosynthesis process, where they use sunlight to convert carbon dioxide and water into glucose for energy, only really requires water, sunlight, carbon dioxide, and nutrients. Nutrients for hydroponic gardening consist of both macronutrients and micronutrients, including carbon, phosphorus, hydrogen, nitrogen, oxygen, sulfur, potassium, magnesium, calcium, zinc, nickel, boron, copper, iron, manganese, molybdenum, boron, and chlorine.

Types of Hydroponics

There are several techniques when it comes to hydroponics, all with different levels of difficulty, maintenance requirements, and budget. Beginners are suggested to start with either the basic wick system or the deep water culture system before graduating to more expert-level systems like the nutrient film technique, the ebb and flow system, drip systems, and the aeroponic system. Non-soil growing mediums can include sand, rock wool, peat moss, perlite (a form of obsidian), and coconut coir (the fibrous, middle portion of the coconut between the shell and the outer coat). Because of the versatility of hydroponics, growers can also get creative with medium materials that might otherwise go to waste, such as sheep wool and rice husks.

Wick System

This system has no electrical component and doesn’t require any advanced machinery, which is why it is considered the most basic of the hydroponic systems. The plants are suspended in a growing medium above a tank filled with water and nutrient solution, which are transported to the plants’ roots by way of a wick (like a piece of rope or felt) connecting the solution with the growing medium.

While the wick system is cheap and easy, it’s not suitable for plants and vegetables that require a lot of water, plus it can be inefficient in delivering nutrients. Hydroponic aficionados refer to this system as the "training wheels" of hydroponics.

Deep Water Culture

Another easy system for new growers, the deep water culture system consists of plants that are suspended over a reservoir filled with water and nutrient solution. The roots are submerged into the liquid, so there is a constant supply of both water and nutrients, but need an air pump to continuously pump bubbles into the reservoir and provide the roots with oxygen. It's an inexpensive, recirculating process that creates less waste, but it doesn’t always work for plants that are larger or require longer growing periods.

Aeroponics

An aeroponic system is perhaps the most complex and expensive hydroponic method, but can also be the most effective. The plant’s roots are actually suspended in air and misted with a water/nutrient solution using an oxygenating air pump, either a small continuous mist or an interval cycle. That way, the roots are provided with continuous nutrients and exposed to constant oxygen without the risk of oversaturation. Aeroponic systems are relatively simple to monitor, but even a slight malfunction can cause the plant roots to dry out and die quickly.

Nutrient Film Technique

In the nutrient film technique, the water and nutrient solution are held in a larger reservoir with an air pump to keep it oxygenated. The plants themselves are grown in a nearby channel (called net pots) and the water pump is set on a timer that pushes the water through the channel at certain intervals. The roots aren’t completely submerged, but the pump helps deliver a thin film of nutrients and water to the plants.

At the end of the channel, the solution can be dropped back into the main reservoir to be reused. Apart from being a low-waste continuously flowing system, this method ensures that the roots don’t become suffocated with too much solution and requires little to no growing medium. However, it requires a lot of observation, since any malfunction in the pumps or clog in the channel can ruin the plants.

Hydroponics at Home?

Having your own hydroponic system at home is a great way to grow your own plants and vegetables faster than the traditional outdoor soil technique, or if you live in a city apartment without access to an outdoor gardening plot. For beginners, it's best to start with a simpler, less expensive system like deep water culture or wick. All systems, however, will require a reservoir or other large container, a nutrient source, and water, while many may also include a growing light, medium, and an air pump.

As urban gardening continues to rise in popularity, so does technology. There are plenty of indoor or outdoor hydroponics gardens in a wide range of budgets available to consumers who don’t have the time or space to create sophisticated hydroponic operations.

Pros and Cons

Not only do hydroponic plants yield more crops, they also require less space and can be used year-round. Plus, plants grown hydroponically typically use less water than traditional farming, can yield larger amounts, and rarely require pesticides or chemicals. For example, a 2018 study in the Journal of Soil and Water Conservation found that nutrient film technique hydroponic systems save 70% to 90% of water among leafy and other vegetables. By leaving out the soil component entirely, you’re also leaving out all of the potential issues (like plant pests and diseases) that can come with it. 

Used hydroponic water, however, contains nutrients like phosphorus and nitrogen that can be hazardous if it enters waterways, potentially causing excessive growth of algae that kills aquatic animals or contaminating drinking water. Most growers dispose of leftover hydroponic nutrients by filtering out the minerals and disposing of the remaining wastewater after it's been purified, and those who work on a smaller scale may reuse wasted nutrients in future hydroponic projects. Some researchers have even been successful in reusing the nutrients found in non-recycled hydroponic waste solution for growing other plants in greenhouses.

Lead photo: Chonticha Vatpongpee / Getty Images