This tutorial aims to introduce hydroponics and how to build an individual system. This technology was documented during a stopover in Singapore of the "Nomade des Mers" expedition. We met Comcrop, a company that grows aromatic plants (basil, mint...) on an area that is usually unused and worthless: the roofs of buildings!
Hydroponics is the cultivation of plants and vegetation above ground and in water. The roots are immersed in a neutral and inert substrate (such as clay balls, sand...) which serves as a support. They directly capture the nutrients necessary for their growth in water enriched with a nutrient solution. Unlike conventional hydroponics, bioponics (hydroponics+organic) allows fruits and vegetables to be grown organically without the use of synthetic chemical fertilizers. These are replaced by organic fertilizers such as manure, earthworm, urine or compost juice.
In biopony, the nutrient solution is not sterile and bacteria, micro-organisms and fungi can develop. These active micro-organisms will make it possible to transform certain substances such as ammonia into nitrate, one of the nutrients essential for plant growth. In our case we use an organic solution by mixing water with human urine (1% urine in relation to the volume of water).
"'Hydroponics has many advantages in certain contexts:"'
"'But hydroponics can also have disadvantages:"'
1. Crop gutters
2. Irrigation system
3. Filter and bio-filter
The system used measures 2m long by 50cm wide. The skeleton is made up of 4 cleats / bamboos fixed in parallel at a distance of 15 cm thanks to wooden cleats. It is covered with an agricultural cover (width 1m) so as to form 3 gutters about 10cm deep. These gutters are filled with clay balls. An aquarium pump immersed in the biofilter tank propels the nutrient solution from the top side of these gutters (inclination of about 10 degrees) so that it flows through the clay balls until it returns to the storage tank (biofilter). The table is about 1.2m high (ergonomic for taking care of plants). A shade screen is attached like a skirt on the sides to protect the biofilters, nutrient solution storage tank and mushroom farm from the sun.
2. Water recovery
The water system operates in a closed circuit. The water is pumped into the biofilter that serves as a reservoir, exits at one end of the gutter and is recollected at the other end before passing through a filter and returning to the initial reservoir.
In order to recover the water, the tarpaulin is pierced very finely (to prevent the clay balls from escaping) at the opposite end of the water inlet. Below this end, another tarpaulin is stapled to form a pocket to collect and channel the water before it flows into the filter.
Once passed through the plants, the water flows into two separate tanks: the filter and the biofilter.
- The purpose of the filter is to block all coarse particles that could block the pumps (root and leaf residues, erosion of clay balls, etc.). The filter has three stages of filtration, from the finest to the coarsest.
- The biofilter constitutes the water reservoir, to which is added about a quarter of the volume in clay beads. These serve as a culture medium for bacteria that will allow the transformation of natural inputs (urine, compost juice, etc.) into nutrients that can be assimilated by plants. In particular, the transformation of ammonia into nitrite and then nitrate, essential for foliar development (leaf development). Bacteria develop naturally after 6 weeks or can be purchased in culture at hydroponics sites.
For their proper development, bacteria need:
For our part, we only use human urine as an input (1mL/1L of water)
After being filtered, oxygenated and recharged with nutrients, the water is ready to be re-injected into the system. For this purpose, a small submersible pump is used. The power of the pump depends on the size of your system.
In order to gain in autonomy, it is possible to install a timer system thanks to a programmable electrical socket or an arduino allowing to program the starting of the pump and the bubbler.
For this purpose, we recommend that the pump be switched on for 30 minutes every 2 hours during the day. No watering at night.
We recommend lighting the bubbler for 1 minute every 5 minutes, 24 hours a day.
Arduino control system:
Not all crops are suitable for hydroponics. It is easier, especially without chemical fertilizers, to prefer leafy vegetables (lettuce, cabbage, spinach, sweet potatoes...) and herbs (mint, basil, coriander).
"Plant" them in the clay balls, making sure that the roots are well immersed.
"It is always necessary to integrate the plants after sowing or cutting them so that they have developed a long and strong root system. "
This section gathers the most frequently asked questions about this tutorial and the progress of the Low-tech Lab's thinking on these topics.
1L of urine contains on average 6g of nitrogen, 1g of phosphorus (directly assimilable) and 2g of potassium. Nitrogen is in the form of urea, which will be transformed into ammonia on contact with the air. It is this step that produces the odor associated with urine, but it is eliminated by the action of micro-organisms or by storage without contact with air.
Plants are able to assimilate nitrogen in two forms: ammonium NH4+ and nitrate NO3-, with a preference given to nitrate in most cases. The biofilter enables this transformation.
Il est important de diluer l'azote pour éviter une concentration trop forte en sels.