What if you were told that you can grow nutritious leafy greens and fruits faster, with higher yields, using 5-10% of the water and a fraction of the space that is normally required?
Most would say that this is impossible, but hydroponics allows growers to do exactly this. This versatile growing method allows you to cultivate an endless variety of produce from microgreens and salad greens to strawberries and tomatoes.
Increasingly, there is a drive to improve agricultural efficiency and lower food production costs to feed our rapidly growing global population, while minimising environmental degradation. Find out more about why we think vertical, hydroponic farming in offices can help save the planet here.
What does hydroponic mean?
The word ‘hydroponics’ is derived from two words hydro (water) and ponos (Greek for labour). Simply put, hydroponics is the method of using water to labour for us in beneficial ways. Using pumps and gravity we can channel water through a system, delivering nutrients directly to the roots of plants in the absence of soil.
1. Hydroponics Saves Water
Growing with hydroponics can reduce water use significantly. Most systems use a recirculating system, where plants will absorb the water they need and any run-off is channeled back to a reservoir, the main water losses (in a system with no leaks) will be due to evaporation and transpiration. The vast majority of water absorbed by plants will be lost to transpiration through their leaves.
To create a closed system, some growers are now using water vapour condensers in their ventilation systems to capture and return the water back into their systems, this can bring the use down to 5-10% of what traditional outdoor growing uses.
2. Vertical, hydroponic systems are space efficient
In addition to using hydroponic methods, many growers are growing vertically to use space more efficiently. We do this ourselves at our Paddington rooftop farm: our vertical system allows us to grow up to 500% more leafy greens than a horizontal system. We have grown over 2,400 plants at one time in our 6m x 4m container.
Vertical systems have the added benefit of requiring less arduous labour, since there is no bending over when managing and harvesting plants. They are perfect for homes too, even the smallest flat or apartment has a wall which a hydroponic system can be mounted on or placed against.
Additionally, when a nutrient solution is delivered directly to roots in the absence of soil, the roots can grow far more compactly and close together. Root systems of plants constitute a significant amount of the plant’s biomass; when using hydroponics systems the dense root growth allows us to grow more plants in smaller spaces.
3. Farming in cities improves the resilience of our food supply
According to the UN, 55% of the world’s populations live in cities, with this projected to rise to 68% by 2050, it makes sense to grow produce close to these population centres so that we can build resistance to food insecurity. If we wanted to grow masses of produce using soil, most cities would not be able to allocate enough outdoor green space for this.
However there is lots of space where soilless hydroponic systems can be placed in cities. A recent study by the Institute for Sustainable Food found that Sheffield city centre has 32 hectares of flat roof space which can be used for soil-free farming. They found that using three-quarters of this space can feed sixty percent of Sheffield’s population with one of their five a day. This really shows the magnitude of how much we could meaningfully produce in vacant urban spaces. This produce can then be delivered locally with less food miles and a smaller carbon footprint.
4. You can grow without soil
Growing with soil is great when we have land with healthy soil - full of organic matter and soil biota. However this is becoming a scarce resource due to poor agricultural and land management practices. It takes time to modify your soil and it’s costly and labour intensive to import soil. There are also many locations across the globe with limited arable land (e.g. arid countries); many regions have very sandy soils which are not worth farming on because they leach out so much water and nutrients. Soilless farming is a great solution where soil resources are not available.
Beneficial relationships between plants and soil biota like bacteria and fungi need not be lost in soilless systems. There are many supplements on the market which contain beneficial bacteria and mycorrhizae. When added to our water these microorganisms create symbiotic relationships with the plant roots and increase resistance to pathogens and root-born diseases. The mycorrhizae increase the root surface area and increase plant nutrient uptake.
5. Plants grow faster and larger with hydroponics
We have an incredible amount of control with the conditions plants grow in controlled hydroponic systems. The nutrient solution can be adjusted to provide the optimum conditions for plants to grow, thus leading to faster growing, bigger plants. This can be hard to optimise when growing in soil as different plants have specific requirements and soil types vary greatly. The main two measurements we look to control are the amount of nutrients concentrated in the water (measured by Electrical Conductivity, EC) and the pH of the solution.
At our Paddington farm, we use an automated dosing system to feed our reservoir with just enough nutrients to stay in the optimum range. Nutrient levels drop continually as plants use them, they are then automatically dosed up to the right EC value. pH is an important control because it affects the availability of micronutrients such as iron and magnesium. Some plants have a very small pH range that they will grow well within; for example rosemary grows best between pH 5.5-6. When we maintain the right pH, plants can grow bountifully.
You can also change the amounts and types of nutrients for different stages in a plant's growth. For example, early in a strawberry plant’s life cycle you should grow them with nutrients to enhance vegetative growth (leaves and stems). This will be higher in nitrogen. Then nutrients are changed when plants begin their fruiting cycle to ensure you get a large fruit set. These are generally lower in nitrogen and high in phosphorus and potassium.
6. You can grow all year round with Controlled Environment Agriculture (CEA)
Advancements in technology have allowed commercial growers the ability to cultivate plants using hydroponics whilst maintaining all variables. Commercial growers practice CEA by controlling lights, temperature, humidity, air circulation and more, to provide the perfect conditions for the crops they are growing all year around, despite outside conditions.
Home growers can use the climate in their homes to grow leafy greens and herbs as temperatures and humidity are higher and fluctuate less indoors. Using simple hydroponic systems automated with timers to control lights and irrigation minimises the labour for busy urbanites to grow food.
7. Fewer Weeds, Pests and Diseases
It is time consuming to remove weeds and they can impact how well your plants grow. Soil can contain many dormant seeds of undesirable weeds, when using a hydroponic system this issue is eliminated because the plants are grown in a liquid medium. Soil-borne pests are also not a problem for this reason. This means that the requirement for pesticides and herbicides which can be harmful to humans is massively reduced.
Hydroponic systems can carry waterborne pathogens, but with appropriate maintenance and cleaning these risks can be eliminated. Commercial farms regularly test their irrigation water for pathogens.
Vertical, hydroponic farming has many benefits we can hold onto. Bringing food production into cities by using vacant land for commercial production and community gardens provides great potential to build resilience to food insecurity. Using CEA we can grow in all corners of the globe, especially where there are little soil resources or harsh climatic conditions.
The ability to produce high yields of nutritious food with less water will also become an increasingly important factor in the future as populations increase and many regions will suffer from water insecurity. This versatile growing method is also suited to both commercial and home growers, including city dwellers without gardens. For more information on how to grow from home using hydroponics, check out my Methods and Environment blog to get started.
Square Mile Farms bring vertical, urban farming to city dwellers in their homes and in the workplace. We aim to bring people closer to food production and help to create a culture of healthy, sustainable living. Find out more about our offering and get in touch here with any queries. Sign up to our newsletter for tips on a healthy lifestyle and a round-up of relevant news. You can also follow us on social media to stay up to date with our journey, find us on Instagram, Twitter and Facebook. Why not join our online Urban Growing Community for advice on growing at home and much more!
UN, '68% of the world population projected to live in urban areas by 2050', (2018).
Institute for Sustainable Food, ‘Urban land could grow fruit and veg for 15 percent of the population’, (2020).