At its most basic, hydroponics is the act of growing plants in water as opposed to soil. Here, you will simply be growing your plants using water to carry nutrients as your medium instead of soil. This means that the nutrients are now dissolved into the water allowing the roots to drink them up. Of course the plants themselves are suspended above the water (so you can see them).
That’s the basics but things get a lot more complicated as you get more involved with the process. And what’s more, there is of course a lot more going on beneath the surface that ensures it all works…
This introduction then will go a little deeper and look in more depth at where specifically hydroponics comes from and at the science behind it all.
To look at, rows of plants suspended in water can look quite high tech and even ‘futuristic’. In fact though, nothing could be further from the truth. Hydroponics has actually been around for centuries and one of the wonders of the ancient world featured it heavily even. That wonder? The Hanging Gardens of Babylon of course – which worked using hydroponic principles as early as 600BC! Specifically, the gardens were watered using a chain pull system which would carry water up from the river so that it would then trickle down throughout the hanging gardens.
In the 10th and 11th centuries meanwhile, the Aztecs had a system of floating gardens that used similar principles. Because the marshes at Lake Tenochtitlan were not suitable for growing crops, they instead resorted to building rafts made from reeds with roots hanging out the bottom into the water.
The subject of hydroponics made it into the mainstream though in the 17th century when Sir Francis Bacon began researching the idea of soil-less gardening. This triggered a lot of interest in the subject when it was published and led to the likes of John Woodward promoting its use in agriculture (which he called ‘aquaculture’). Commercial use began in 1938 following research at Berkeley and in WW2, the method was used to grow crops for the troops located on the Pacific Islands.
These days, hydroponics is used far more widely and the process has become much more systematic. Today we know how to set up a hydroponic farm to grow plants as efficiently as possible and this can have many benefits.
How Plants Survive and Why You Don’t Need Soil
Basically, hydroponics simply does away with the soil. Contrary to popular belief, soil is not actually a crucial component when it comes to growing plants. The job of the soil is to anchor the plants and to serve as a medium – allowing water and nutrients to travel so that they can be consumed by the plants.
Plants need water and they also need nutrients. These nutrients are what the plant can use to build tissue and grow/repair damaged leaves etc. The final piece of the puzzle is the sun, which the plants need for photosynthesis – in order to create glucose for energy.
As you can see then, the soil itself is not actually providing anything that the plant needs to survive – it’s just that without the soil, the plant would blow away and wouldn’t be able to reach the all-important water and nutrients. In theory, a plant could grow in cat hair – as long as you watered it occasionally and provided it with sun and water.
The Set Up
Most of the minerals and vitamins that plants need to survive are water soluble. This means they’ll dissolve in water just as sugar dissolves in your tea. Roots don’t have teeth and so this is how plants are able to get the nutrients out of the soil – the water absorbs them and the plant then absorbs the water.
With hydroponics you intentionally infuse the water with the necessary nutrients and then feed that water directly to the roots. Thus there is actually no need for soil as long as you find another way to hold the plant in place and above the water. Depending on the type of hydroponics system used then, the plants will usually be suspended in some way, or will use an alternative medium such as perlite, rockwool, clay pellets or something else.
This actually means that the plants have even better access to the nutrients. Normally the roots of plants will spread out under the ground not only to provide a more stable anchor but also to help them find more water and more nutrients. The larger the surface area covered by the roots, the greater chance there is that some part of that root system will happen on water and nutrients. With hydroponics, the roots are directly growing into the water, meaning there’s no need for them to spread out. This in turn means they are much smaller and that more plants can be stacked in a row. This makes hydroponics much more space efficient as compared with ‘normal’ agriculture and somewhat ironically, it also means that hydroponic plants require less water overall. This makes hydroponics very eco-friendly and efficient, which is one of the reasons it now has so many fans.
But there is one other important use of soil that needs to be considered – and that’s the fact that it also provides the soil with air. If you have ever kept houseplants, then you will likely be aware that it’s possible to over water them resulting in them becoming drowned and dying. Normally, soil is able to trap ‘pockets’ of air which the plants can then use to breathe.
So if you can overwater plants, how is it that submerging the roots entirely in water doesn’t do the exact same thing? Well it would, which is why hydroponics needs to use various different systems in order to ensure the plants still are getting oxygen. For instance, some hydroponics systems will use an air pump in order to oxygenate the nutrient solution.