How Hydroponics Work
Traditionally, plants get all their nutrients from the soil, which is enriched with minerals, vitamins, and organic matter. With hydroponics, you don't use the soil to deliver these nutrients. Instead, the nutrients are dissolved into water to form a solution which comes into direct contact with the plant's roots. This allows for faster absorption, which leads to quicker growth and larger yields. The basis of this solution is 5 key macronutrients that all plants need: nitrogen, phosphorus, potassium, calcium, and magnesium. This solution also includes the micronutrients plants need, although in lesser quantity, which help promote healthy plant growth. These include substances like iron, copper, boron, nickel, and zinc. The ratio in which these macro and micronutrients are needed depends on the plant.
Hydroponics 101
Simply put, hydroponics is the technique of growing plants using a nutrient-rich water solution rather than soil. While there are various ways of employing this technique, plants are commonly grown using net pots or cups in which roots are suspended in nutrient solution or misted air. This allows for many benefits, including higher production, better resource management, and reduced environmental impacts. This section provides the basics of hydroponics, how it works, the various types, and how it can affect food production.
Benefits of Hydroponics
While hydroponics is a different approach from traditional farming, it boasts many benefits, the first of which is faster growth rates. While nutrients and climate are more precisely controlled, we can achieve a 25% increase in the growth rate using hydroponics. This means that while less time to grow food, we can also grow more in a year. The next benefit is that hydroponics produces heavier yields. While plants grow faster, they also grow larger, which means we get better overall yields from the same production period. Following this, hydroponic technologies have a higher efficiency than traditional open-field farming. Although seemingly counter-intuitive, hydroponics uses far less water as it reuses and recycles water within systems rather than seeing it lost through soil absorption and surface runoff.
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The combination of all these benefits means that hydroponics needs less land and less water to produce more food. On average, hydroponics can produce 6 times the yield over conventional farming. The image below visually demonstrates this by comparing the size of farmland needed to feed a typical family of four. Separated into three specific categories, it includes the land required for the average Canadian diet (includes meat production), a plant-based diet, and finally, just for grown produce like fruits and vegetables, and compares the reduction from the use of hydroponics (the dotted line shows land requirements without the use of hydroponics).
Types of Hydroponics
While there are many types of hydroponic systems, most fall into two categories: passive and active. A passive system tends to be simpler with less equipment. The plants are typically in direct contact with the nutrient water or have a delivery system which uses no moving parts (an example is a Deep Water Culture system). An active system uses a mechanical pump to transport water directly to the plants from a reservoir. This type of system has more variations and is typically more complex (an example is the Nutrient Film Technique or Aeroponics). The following are the 6 most common types of hydroponic systems. ​
Deep Water Culture (DWC): This type of system does not have a circulatory water system. Plants are directly in the water supply tank, typically on a floating top. While it usually has an air pump to promote aerobic bacteria (the kind that needs oxygen), it can have a variation, such as the Kratky Method, which does not introduce oxygen into the water, for an anaerobic condition.
Nutrient Film Technique (NFT): In this system, plants are typically in a separate container from the water reservoir. Cups filled with a soilless medium such as rock wool or clay pebbles hold the plants in place while nutrient water constantly flows past the root base and returns to the water reservoir.
Ebbs & Flow: Like the NFT system, plants are separate from the water reservoir. The plant containers are temporarily flooded with water, which is then drained on a cycle to introduce oxygen to the roots.
Aquaponics: Once again, this version of hydroponics is similar to the NFT system in that the plants are separate from the water reservoir. However, in Aquaponics, a symbiotic relationship is promoted between fish and plants. The fish excrement helps provide nutrients to the plants, while the plants act as a filter, which in turn cleans the water that is returned to the fish. This is one of the most challenging yet full-cycle approaches to hydroponics.
Aeroponics: In this version, the rot system is left exposed to the air and then misted or fogged using specialty nozzles. This is typically done in intervals, like the ebbs & flow systems. Water is then allowed to return to the reservoir.
Drip Irrigation: Often done as a hybrid system, a drip irrigation system can be used with or without soil. Plants are typically separated from the water reservoir, where a slow supply of nutrient water is supplied to each plant.
