“Only by adopting a mentality that focuses on maximizing conservation and ethical food production techniques, can we establish a future of production that works. We need to intensify production. But it needs to be intensifying in the right way, not just relying on finite resources, because in the long run it won’t work. It’s a false economy, we’ll run out.” – Antonio Paladino
Hydroponics is the science, or art, of growing plants without soil while providing adequate water, oxygen and nutrients with very little waste. In my opinion it is the single most important tool we have as a species for securing enough food to feed our bursting population, without destroying any more of the planet. Hydroponics, if set up correctly, can use up to 95% less water that traditional farming techniques and can allow plants to grow two to three times faster than they otherwise would. Not only this but since the system is soil-less, one eliminates soil borne pests, diseases and weeds which in turn lessens the need for the use for pesticides and herbicides, this means that hydroponics has a lesser negative impact on the environment.
One of the biggest issues facing society at large is where all the food we need will be grown, we just don’t have the space so we destroy natural areas and turn them into food production areas. 7 million hectares of forests are cleared for agriculture every year which equates to roughly 3.5 to 7 billion trees cut down. With this in mind, hydroponics becomes even more of a tempting option for food production since the system uses at least 4 times less space than traditional farming. I also feel this figure is an understatement since with hydroponics vertical farming and urban agriculture become viable options and these further reduce the space we need to grow our food.
In my BTech year of my horticultural sciences studies we were tasked to create a hydroponics system that could grow 40 plants perfectly within 3 and a half months. Although we were provided with certain materials I decided that I would rather scavenge and reuse old materials so that when complete I could use my project to grow food ethically at home. This meant making some new friends in the agriculture industry and spending a bit out of my own pocket, but it was absolutely worth it as I now own a fully functional mini hydroponics farm.
Step one was to come up with a basic plan for our projects. We decided that we would build both an “ebb and flow” system as well as a “nutrient flow technique” system so that we could learn multiple techniques through a single project. An ebb and flow system is basically a system where every few hours (I used every 3) the gullies that the plants are seated in, fill up briefly and then drain back into the storage reservoir. This system allows oxygen to be added to the water through the action of filling and emptying of the reservoir which means that no air pump is necessary. The nutrient flow technique however is whereby a very shallow stream of water flows continuously at the bottom of a water-tight gully where the tips of the roots reach and this water is continuously recirculated. With such a slow flow of water this system does generally require an air pump in order to oxygenate the water.
Step two was to decide what materials we could most easily and cheaply source, so old farming underground irrigation pipes seemed be an ideal solution for the gullies. They would be water-tight and wouldn’t let any algae causing light in, they were also relatively easy to source for free. We sourced old pots and drilled extra drainage holes in them as well as two old black plastic boxes that we used as reservoirs. We combed our parents and friends garages and sheds for old garden irrigation pipes and connectors. Then admittedly, we did have to buy pumps, a timer and medium but I am sure if we had put in some more effort we could have found these for free too. Being a bit of a procrastinator, I didn’t have time to grow my kale from seed for the project, so I bought these too.
Pictured above is our majestic rescue doggette, Honey. Her favourite pass times are sleeping under my duvet in my bed and getting in the way.
Step three was to drill holes in our pipes and to start putting everything together. Drilling 8 and 10 cm holes in these awfully thick pipes proved to be more of a problem than anticipated. First time round we used an adjustable attachment which on the round pipes slipped an cracked the pipes, we counteracted this with super glue and pretty pink duct tape, which was surprisingly effective , and promptly went to the hardware store to get the right equipment. My fathers voice ringing in my head the whole time saying “always have the right tool for the job” and of course he was right. Back to work with the correct tools and things went more smoothly, holes were drilled for the pots and pipes and things were starting to come together. The inlet holes were drilled at the top of the end cap of the pipe in order to get some oxygen into the water when it splashed in. However the outlet holes were drilled on the lower end of the end cap in order to let the gullies fully empty of water when needed.
As you can see above I used pink duct tape to neaten up the pot holes and we had to do some creative brick work to hold the nutrient flow system in a spiral (but we probably should have made a wooden frame).
Step four was putting the black irrigation pipes in place, complete with flow regulators and tank connectors and this, funnily enough, proved to be the most frustrating step. The most valuable lesson that we learned is that when connecting pipes, boiling water is your best friend. Not only this, but nothing is ever water tight and marine silicone is vital. Once we learned these most important lessons, we managed to connect the pipes to the gullies and reservoirs via tank connectors, to each other via pipe connectors and flow regulators in between the reservoirs and gullies. Once everything was together the medium (made up of inert leca clay pebbles and vermiculite) needed to be measured out and mixed up, I also but small pieces of shade cloth at the bottom of each pot so that the roots could grow through but the vermiculite would not be lost.
Pictured above one can see the tank connectors connecting the pipes to the end caps as well as the fact that there is an emergency drainage system on the outlet end of the gullies that lacks flow regulators as to not waste water in case of a timer failure.
Step five was to work out the timing for the ebb and flow system and get the plants planted in both systems. Through a series of trial and error of filling and draining the timer was set to 3 hours off to 2 minutes on and we also tinkered with the flow regulators for both systems at this stage in order to make everything run as smoothly as possible. We then rinsed the soil off our plants and placed them in their pots in the leca clay, vermiculite mixture.
Here you can see the size of the plants at the time of planting, they aren’t very sizable yet. We left them like this in their systems for a week with just water flowing through, no added nutrients. This was in order to flush the roots and give the plants a chance to settle in so that they don’t go into shock. We did however make sure that the pH was correct for the plants, for Swiss chard and kale this was between 5.5 and 6.6. Since our tap water here in Cape Town, South Africa is at a pH of about 8.0 we used phosphoric acid to lower the pH and when we accidentally made it too low once or twice, we used potassium hydroxide to raise it. I have however read that citric acid can be used to lower pH and baking soda will bring the pH up, I haven’t given this a try yet so let me know if it has worked for you. We were lucky enough to be able to use the digital meters at our university but paper and liquid test kits are easily available an cheap.
When we did add nutrients after a week, we kept the electro-conductivity (EC) between 1.8 and 2.3 mS (1260 to 1610 ppm). Besides watching the EC one must make sure that the nutrient mix used contains; Nitrogen (N), Potassium (K), Phosphorous (P), Calcium (Ca), Magnesium (Mg), Sulphur (S), Iron (Fe), Manganese (Mn), Copper (Cu), Zinc (Zn), Molydenum (Mo), Boron (B) and Chlorine (Cl). These macro and micro-nutrients are especially important in hydroponics because unlike in traditional farming, the medium is inert and has no nutrient bank or buffer capacity. Although we used a mix and changed the water every two weeks (although every week is recommended), I do believe that if one can get these nutrients separately and keep a good eye on how the plant is responding, one can virtually eliminate needing the replace and waste water. Aquaponics is another option for the environmentally conscious, whereby fish create the nutrients the plants need via their waste products, however I won’t go into detail here about this, perhaps another time.
Above, on the left, one can see the root development after just a week and a half in the system and on the right, after 2 months. The root growth in the nutrient flow system was actually so vigorous that it blocked the pipes and caused the pump to burn out. This however was a learning curve and now we know to trim the roots regularly!
Below you can see the growth that occurred in just 3 months. This is also taking into account that pH was not checked every day, due to the fact that we had protests on campus intermittently for months, and often there were no nutrients to add to the system. Not only this but the entire green house was plagued with an aphid infestation and although I treated my plants, they kept being reinfected by neighboring projects. In a perfect world I’m sure they would have grown even larger and more vigorously in the time they had.
All in all this project was an absolute blast, we learned so much and gained a skill I will most definitely use later in life. Hydroponics truly is the future, growing food in very little space, quickly and efficiently. It could solve the world hunger crisis twice over so I think its time to change to a more environmentally friendly, economically viable system of food production.
Love and light, Jen