Welcome to our ongoing series highlighting our Aquaponics Curriculum!
Over the coming weeks, we will be posting a series of articles covering the basics of each Curriculum Topic. Today, we are covering Topic 1, Lesson 2, Hydroponics, Aquaponics, Aeroponics. Each of these blog posts is aimed to give an overview of the subject and provide one or more critical thinking questions. You can find our first post in this series here. Enjoy!
Hydroponics is not a new technology. Both the Hanging Gardens of Babylon and the Floating Gardens of China employed hydroponic concepts. Hydroponics is the growth of plants without soil. Hydroponic plants are most commonly grown in nutrient solution, rock, sand, Rockwool, or a combination of these. Because the plants are grown in a liquid medium or a nutrient deficient substance, nutrients are supplied to the water or substrate as a supplement for plant intake. Hydroponic systems can easily be scaled up or down as the maintenance is relatively low. The components in the system are often automated from nutrient injection to drainage pumps. Generally the pH of the system does not change easily because the system does not decompose organic matter. However, many hydroponic systems do have algae growth which could attract insects and consequently viruses and diseases can be vectored to the plants. Additionally, hydroponic systems tend to accumulate salt deposits in the pipes that need to be flushed regularly.
Aquaponics combines aquaculture and hydroponics. Aquaculture is the cultivation of freshwater and saltwater aquatic organisms. Aquaponics uses fish waste and sometimes crustacean waste to generate the nutrient solution for hydroponic plants. Because aquaponics has both aquatic life and plants, the system is more complicated and therefore requires more maintenance. The nutrients that fertilize the plants come from the fish waste. Because fish also produce ammonia, certain bacteria convert the ammonia to nitrites, and another set of bacteria convert nitrites to nitrates. All three of these forms of nitrogen are toxic to fish at high levels. However, because plants absorb nitrates, the system balances out. In aquaponics the water is recirculated and does not need to be flushed out as often as a hydroponic system. The pH should be monitored closely as there is a narrow window that both the plants and fish can survive in. In addition, dead fish must be removed promptly because large amounts of ammonia from the fish can throw the system out of balance.
A newer technology that was developed in the 1920s by plant scientists, aeroponics, suspends plant roots in the air. The plant roots in an aeroponics system are misted with a nutrient solution. Aeroponics also requires constant monitoring; if the spraying automation is interrupted, the roots can dry out quickly and the whole plant will collapse. However, many people use aeroponics because roots are have higher oxygen exposure. This increase in oxygen exposure increases root growth and therefore increases nutrient uptake efficiency. On the contrary, these systems provide little support for a large plant compared to hydroponic and aquaponic systems.
Plants using these techniques are generally grown in controlled environments such as greenhouses, growing chambers or warehouses. The plants in all of these systems do need to be pruned or trimmed to provide plant structures that are compatible with each system. For example, a commonly used technique for tomato plants in hydroponic systems is the “lean and lower.” This technique allows for the plant to grow in a vertical vine-like fashion by coiling the “vine” portion of the plant.
Critical Thinking Question
Is soil necessary for plant growth? What are some advantages of soilless technique?