Hydroponics

Over the past 12 months, Abingdon School’s Hydroponics Club has been attempting to cultivate plants using nutrient-rich water, rather than soil. The students have been growing tomatoes, lettuces, peppers, spring onions, and strawberries. Each week, they have checked the equipment and taken tests to establish the pH level and electrical conductivity of the water ensuring optimised conditions for plant growth. In our latest blog, Fourth Year student Elon, shares his observations and findings in the cultivation of lettuce.

Hydroponics is centred around the idea of growing plants in water, however, different plants require different levels of nutrition and prefer different levels of electrical conductivity and light intensity. This varies significantly across flora, with some, including lettuce, flourishing whereas others including corn being unsuitable for hydroponic systems.

Instead of cultivating plants in soil, which is often nutrient deprived, hydroponics uses nutrient-rich water to maximise the nutrient and water supply, thereby allowing a plant to take what it needs whenever it may need it. This results in more growth, as often the limiting factor to plant growth is principally the amount of resources it has access to. In this case, plants have an ample supply of nutrients, and the environment can also be strictly controlled to benefit the plant, including the nutrient content, pH, temperature, and light intensities. This ensures that the environment is tailored to a specific species which thereby maximises its growing potential instead of a ‘one size fits all’ approach with the content in soil.

This is a more sustainable approach to growing plants, because it doesn’t deplete the soil of nutrients as often occurs on farmland. Additionally, hydroponics also ensures the cleanliness of plants and the elimination of any potential soil-borne pathogens which can contribute to better consumer health as well as improved plant health. Additionally, less water is lost using hydroponics. This may sound ironic given that the main intention of hydroponics is to grow plants in water, however, traditional farming practices consume 70% of the world’s freshwater, with a further 40% being wasted on inadequate irrigation systems. This is a result of evaporation and potentially runoffs which reduce infiltration thereby wasting water. Hydroponics, on the other hand, contains the water content with minor amounts lost through evapotranspiration. The setup can also contribute to higher yields because its design ensures it can be stacked, reducing land consumption.

Lettuces

Lettuce is particularly well adapted for hydroponic environments, and it’s a staple across many cuisines for its delicate flavour and nutrient-rich composition. One of its defining traits is its rich antioxidant content, which can prevent eye diseases amongst other chronic conditions. It is well known for its easy to grow nature, particularly in containers, and its ability to grow all year round. This – coupled with the fact it needs plenty of water – makes it the perfect plant for a hydroponic environment. Growing plants through hydroponics has many benefits including faster growth, more sustainable food production, and higher yields.

Conditions for Optimum Lettuce Growth

Lettuce prefers 6-8 hours of sunlight per day, which can be monitored through the control of light intensity. Additionally, plants usually photosynthesise only during the day when the sun is out, as stomata close at night to conserve water. A hydroponic environment solves both problems by providing constant access to nutrient-rich water and light; which can be controlled to conform to these growing conditions, maximising plant growth. Furthermore, the nutrient-rich water also adds to lettuce’s preferential nature for nutrient-rich soil, which can offer constant access to the nutrients it needs for growth. Lettuce prefers a pH condition from 6 to 6.8 to assist with plant nutrient absorption, which can also be monitored through the use of a pH meter, and changed using buffer solutions. It also prefers moist soil which perfectly conforms to the conditions provided by a hydroponics setup. Additionally, the isolation of disease through sanitation and the lack of biological pests – including slugs – provides the optimal environment for lettuce growth, allowing it to grow to its full potential, while ensuring protection from disease.

Nutrient Film Technique (NFT)

The NFT method is often used to cultivate lettuce because of its effective and efficient delivery of oxygen and nutrients. It works by passing a shallow, nutrient-rich solution through the roots of a plant. This ensures a constant supply of water and nutrients. The water can be recirculated and recycled through the entire setup, and often moves under the influence of gravity, thereby mitigating the need for most machinery, which can carry water to the top for it to circulate back down again. An advantage of this is that no pots are needed as the plants are directly grown in channels reducing the need for nutrient-rich growing media. Additionally, the ability to stack plants vertically (known as vertical farming) can further increase the growing potential in space-restricted environments while also maximising growing potential. Moreover, less water is lost because direct evaporation of the water is prevented by a plastic casing, and water is predominantly lost through transpiration, which is negligible and results in a high water efficiency. The NFT Method is easy to maintain and set up, making it suitable for cultivating quick-growing plants including lettuce. However, it may require monitoring to ensure the balancing of conditions to maximise plant growth and reduce plant stress.

In conclusion, our group has discovered that, compared to soil-grown plants in the greenhouse, the constant source of water and nutrients and the carefully monitored (and adapted) growing conditions of hydroponics, has significantly boosted plant – and particularly lettuce – growth.