Hydroponics – Everything You Need to Know

What Is Hydroponics

Hydroponics is a cultivation method that grows plants in water instead of soil. It is part of the broader “soil-less” cultivation methods, which include aquaponics and aeroponics.

Most of the time, the cultivation is done with the plant’s roots in water, but it can also occasionally be done in other substrates, like gels or an inert medium like perlite, gravel, etc.

As there is no soil, the plant nutrition in mineral elements is done by having it dissolved in the water. In many cases, hydroponics cultivation is equivalent to indoor cultivation, with the light provided by artificial lightning. However, hydroponics is also possible outside, as it provides “free” sunlight at the cost of increased risk of contamination (see below).

The hydroponic market size grew to nearly $5B billion in 2023, and is expected to grow by 12.4% CAGR until 2030.

The Science of Hydroponics

While most plants can be grown with hydroponic systems, some will require a substrate to anchor their roots. This is why inert substrates like coconut coir, vermiculite (a silicate rock), and perlite (an amorphous volcanic glass) are used.

Source: Climate Control

Nutrients like phosphate, potassium, and nitrogen (“NPK”), as well as micronutrients, are dissolved into the water, allowing for an almost 100% efficiency in the use of the fertilizers.

Hydroponics can be separated into 2 different types of designs: open and closed systems.

Open systems: require the nutrient-loaded water to flow from the reservoir to the growth chamber.
Closed systems: have the roots directly submerged in the nutrient solution and, therefore, do not need pumps.

Passive systems, in opposition to active systems, are hydroponic systems that do not require electrical components like pumps, ventilation, artificial lights, and timers.

What Can Be Grown With Hydroponics

Hydroponics is used to grow many different high-value, sensitive crops.  The most common of which are as follows, in order: Tomatoes, Herbs, Lettuce, Cucumber.

Source: Grand View Research

Another less documented but significant use of hydroponics has been small or medium-scale cannabis cultivation.  While this practice remains illegal in most countries, there is a growing list of nations that allow such crop growth with the proper licensure in a commercial setting – Canada is one of the prime examples of this.

Many commercial farms of cannabis operating in the U.S. states where cannabis cultivation is legal favor cultivation in greenhouses.  Here, hydroponic methods are used to produce a more consistent result than what is possible with soil.

The Pros Of Hydroponics

Control

Hydroponics’ main advantage is the level of control offered by the technique. This is especially true when combined with indoor cultivation, compared to cultivation in soil or even greenhouses.  This translates into multiple advantages for commercial cultivation.

It can produce more consistent results.  For example, the exact chemical composition of a cannabis plant that is meant to be later used for the production of pharmaceuticals. This allows for research and development efforts to find the perfect conditions, resulting in the highest quality product.

It can also result in more control over the timing of growth to obtain a very consistent and stable production. This is very valuable for products with relatively constant demand but seasonal production spikes in fields, like tomatoes or berries.

Combining each of the capabilities, the level of control made possible can be used to optimize the growth speed, taste, smell, or aspect of the final plant product, which is likely to command a price premium.

Lastly, it can also be used to monitor the crops and detect any problems early on.

Space

Thanks to optimal conditions, more crops can be grown per square meter than in other conditions. This makes it a good option for urban farming, as discussed in our article “Scaling Urban Agriculture to Bring Many Benefits“. This can allow food to be locally grown instead of imported for hundreds or thousands of miles, even if land and space are more expensive locally.

It will be an extremely valuable farming method for adverse environments like future Moon or Martian bases, where prohibitively expensive transportation costs will make locally grown food supplies extremely valuable.

Nutrient Demand And Wastes

As mentioned, because the nutrients are in the water and that water stays in the growth chambers and/or a reservoir, there is no loss of nutrients in the system except by what is effectively absorbed in the plant during its growth.

Source: Unsplash

This makes fertilizer usage to grow the crops as close as possible to optimal. In more traditional approaches to agriculture, overuse of fertilizers in open fields leads to multiple issues.  These extend to include soil ecosystems getting damaged to toxic algal bloom and even freshwater bodies’ eutrophication. So, reducing the amount of fertilizer leaching into the environment is an important and often overlooked ecological concern.

Source: Britannica

Water Usage

Contrary to appearance, hydroponics use much less water than traditional cultivation methods.  This is true whether taking place in open fields or greenhouses.

This is because the evaporation of water is kept to a minimum due to minimal surface contact with the air, and does not leak out into soil. Essentially, the water stays inside the closed system.

As a result, hydroponics can use as little as 1/10th of the water than traditional field crop watering methods. So this can make it an excellent option for areas with water scarcity and/or crops especially hungry for water, like leafy greens.

Labor Intensity

Because the plants are growing in a controlled and custom-designed environment, they can also be designed to optimize labor costs. Automation can replace most of the more dangerous traditional farm work, and plants already growing in pots without soil can save time for harvesting, cleaning, and packaging.

The Cons of Hydroponics

Costs

The main limitation of hydroponics is its costs. Because it requires dedicated facilities, and often pumps, ventilation, etc., it is much more expensive to set up than traditional farming methods. This is exacerbated further in cold climates that require additional hardware like climate control and artificial lights – each of which only adds to the energy costs of the cultivation operations.

Due to this limit, most commercial farms relying on hydroponics are focused on high-value crops like fruits, berries, leafy greens, cannabis, etc., in an effort to maximize their return on investment.

To date, this issue has hindered the broader adoption of vertical farming in general, including not just hydroponics but aquaponics and aeroponics, as well.

Resilience

Hydroponic systems are, by design, more artificial than crops in an open field. This means they are dependent on each of the following things running smoothly:

• Supply chain in parts and components.
• Electric power supply.
• Electronic connected system for highly automated and advanced operations.
• Skilled labor able to efficiently perform the required monitoring and maintenance.

While there are ways to mitigate these risks, for example with systems redundancy or larger inventory (which add to setup costs), or localized supply of energy through renewable power generation, hydroponics will never be as resilient as a rain-watered crop in an open field.

Water-born Diseases & Algae Contamination

Pathogens

Removing soil obviously removes all risks related to soil-born diseases, but it also means removing a whole ecosystem of beneficial microbes that protect against plant diseases. Meanwhile, the constantly circulating water can be a vector for spreading other pathogens, meaning adverse events can be devastating and occur even quicker in hydroponic systems.

The two most common organisms that cause hydroponics diseases are Pythium and Phytophthora, both fungal diseases. Pythium can attack all plants, while phytophthora tends to mostly affect flower crops.

To address these issues, farmers typically employ regularly scheduled cleaning and sanitation practices and the use of filters, which can significantly reduce the risk of water-borne plant pathogens.  Building on this, regular testing and monitoring are equally beneficial in detecting early signs of contamination.

Multiple parallel and unconnected hydroponics systems for large installations are also recommended to avoid widespread contamination. Controlling the pH of the water can help reduce fungal growth.

Algae

Another contaminant that can affect hydroponic systems is algae. While the water contains the perfect mix of nutrients to boost plants’ growth, the same mix is, at the same time, the perfect environment for the unicellular algae. If present, algae will create a slimy and difficult-to-clean layer on surfaces and can even block water filters or small tubes.

While hydroponic systems do not need to be concerned with weeds like in a field, algae are essentially equivalent. Like weeds, algae will deprive the crops of their nutrients, reducing growth and plant health.

In addition, algae will reduce the oxygen concentration in the water. The first effect is that it can damage the plant roots and its growth. The second problem is that it helps the growth of fungal diseases such as Pythium.

Multiple ways exist to control algal growth, from using filters to clean the water going in, to exposing the water to UV light to kill the algae (UV lamps are routinely used to kill microorganisms to make drinking water in public utilities).

Innovation in Hydroponics

LED Lighting

LED lights are a crucial technology in hydroponics, making the entire practice feasible on a commercial scale. This is because such lights consume far less energy than traditional light sources, lasting longer and emitting significantly less heat.

In addition, not all the visible light spectrum is helpful for plants in photosynthesis, so dedicated LEDs without green light can be used to reduce further the electricity consumed by artificial lightning.

Source: Agritecture

IoT & Sensor-Based Automation

The declining costs of sensors and electronics have made continuous monitoring of temperature, humidity, light, pH levels, and nutrient volume possible.

Although more advanced, this sensor-based farming helps to track and adjust growing conditions in real-time to ensure optimal crop yields, bolstering the grower’s bottom line.

AI-Based Technologies

As mentioned, hydroponics requires an intense level of monitoring of the water system, diseases, nutrient levels, etc. To that end, AI is increasingly being used to help optimize existing environmental conditions, including light levels, humidity, and nutrient levels.

AI also helps optimize investment and reduce costs by creating personalized growth plans for each plant type.

It can also use machine vision or biochemical tests to warn about the presence of pathogens before a human ever could.

Lastly, with the rise of autonomous farming robots, we can envision a hydroponic system where planting, pruning, harvesting, and replacing plants can be done in a fully automatic manner.

New Farming Innovations

Hydroponic cultivation allows for direct control over plants in a way impossible in traditional farming. This opens the door to experimentation for new ways to boost crop productivity beyond increasing access to light or nutrients.

For example, we explore one such option in our article “Electricity Set to Supercharge Growth in Hydroponic Crops”. Researchers used a custom artificial substrate, or “conductive soil / eSoil” made of cellulose (the main component of paper) mixed with a conductive polymer called PEDOT (poly(3,4-ethylenedioxythiophene)).

This way, they could expose seedlings to continuous low voltage, resulting in a 50% increase in growth rate.

Source: PNAS

This is one example of how hydroponic systems could offer significant productivity gains thanks to their increased level of control.

Building A Hydroponics Installation

When planning to build a hydroponic installation, the first question should be – Why choose hydroponic over other cultivation methods? There can be many reasons:

• Saving water or reducing pollution.
• Being able to experiment with new cultivation methods.
• Small-scale home consumption or pedagogical tools.
• Growing at scale high-quality, high-value crops.

Depending on the answer, different hydroponic systems can be chosen.

A commercial operation will have to balance out the available resources with the startup costs while looking to minimize operating costs. Considering local markets and margins will be extremely important in crop choice. The level of automation and the maturity of the technology used should also be considered.

A homemade small-scale system must be tailored to its builders’ and users’ technical skills, as an “optimized” but too complex design will likely not work well. Off-the-shelf components will probably be a better option in that case.

A system dedicated to solving a specific problem, like water scarcity, will need to focus on this metric, especially if it makes other elements less optimized.

Hydroponics as part of a larger system, like combined with aquaculture (aquaponics), will need to be designed with the other steps and components in mind.

Conclusion

Hydroponics is a powerful approach to cultivation systems, offering exceptional levels of control over growth conditions. These are typically very efficient systems, boasting optimized usage of fertilizers and water. This makes it an ideal commercial-scale cultivation method for difficult-to-grow crops or high-value products where perfect timing, taste, composition, aspect, or other qualitative metrics can justify a much higher price.

Thanks to its density and high productivity, it is also a good system for home-scale food production or urban farming, where space is often a constraint.

It is, however, a much more complex system than traditional farming or gardening. This makes it more expensive, more technical to install and maintain, and more prone to unique issues like algal contamination and water-born diseases that must be managed through dedicated solutions. In certain instances, it will be equally challenging for people or companies lacking the technical abilities to handle these associated in-house challenges.

Overall, while unlikely to be as cost-efficient as crops grown in bulk at low prices in open fields, Hydroponics can be a good solution to specific problems or a good method for growing high-quality, local products.