Microfarm is a test stand for learning principles of plant growth and effects of fertilizers. It can also be used for gardening when you don’t have a garden.

Instead of soil, it uses perlite as a substrate – a completely inert, stone-like medium. All nutrients for plants are supplied from a solution mixed of water and basic chemicals. By varying the mix, you learn what elements are important for particular plants at different stages of growth, and find the optimal profile. Results with the system should translate well to traditional gardening too.

The frame is built from a single 30x40x1820 mm piece of wood, glued and coated with polyurethane. Plants are suspended from the frame using a steel wire coated in plastic.

Plastic bucket under the plants contains ~4L of solution, and a small aquarium pump circulates it to plants. Hose splitters and diffusors are 3D printed from PLA. The cover is made from aluminum foil and tape, and it is needed to reduce growth of algae in the bucket.

For more details about the process, read about “hydroponics”.

Finding chemicals to make the solution was the hardest part of the project.

Selection of fertilizers at local gardening shops is extremely confusing. They sell only mixes with actual chemical composition obfuscated as much as possible. You get “for flowers” or “for strawberry”, and NPK percentages (Nitrogen, Phosphorus and Potassium) without any details. With single-digit percentages of actual chemicals, and the rest being bulked with dirt, these mixes are terrible value for money and I have no idea how to use them even for soil, let alone for hydroponics.

Luckily, there are specialized stores online that sell chemicals for agriculture. These are clearly labeled, contain a single substance, and pure enough to completely dissolve in water. You know exactly what you’re getting, and the desirable composition of fertilizers can be achieved from ~7 different chemicals.

Chemicals should be mixed into 3 bottles of concentrates: one bottle for nitrites, another for sulfates and phosphates. The last one is for elements like Fe, Mg, Mo, and I’ve purchased a single bottle that contains all of them. The final solution is diluted with tap water, and measured by pH and EC meter.

After ~1 month of use, I find this system to be “good enough” for the task. The main problem now is tuning the solution for different purposes (root development, vegetation, etc.)

Some automation is required for summer time. I plan to add a timer circuit for the pump to make it circulate water ever hour.

Strawberry seems to overheat in direct sun, so perhaps a “roof” structure is necessary.