Home / Yard Challenge #1 - Sour makes plants happy

In order to absorb minerals edible plants (e.g. herbs, salads) need a water-nutrient solution with a rather constant pH value between 5.5 and 6.

Since YardCube is a smart controlled system we can measure (pH electrode sensor) pH value constantly. Further, we can control the addition of acids, CO2 or other substances into the water reservoir.

Keep in mind that we want the system to be as natural as possible and are avoiding conventional methods used in agricultural industry (e.g. nitric acid).


In our aeroponics system the water-nutrient solution is in constant motion. The plants' roots are sprayed via a micro pump and nozzle and the water that is not absorbed flows back into the reservoir (sketch of the system here). Due to that a water-nutrient solution that is orginally set to a pH value of around 5.5 (e.g. lemon juice, CO2) and a carbonate hardness of 5 will increase to a ph value of above 7 within 24 hours. We use a 2 liter water reservoir and coconut fiber as a grow medium.


pH value, buffer, hard water, bicarbonate, distilled water, reverse osmosis, CO2, acid


Find an applicable and cost-effective way to keep the pH value constant at 5.5 to 6 within the YardCube aeroponics system.


If you (alone or as a team) are interested press "Apply now" below. You will be asked to provide a short description on why you believe you are able to solve this challenge. All teams that are selected will be provided with a YardCube to experiment.


March 15th 2018


To be announced

To be announced

Stefan Gaertner, Co-Founder Yard

Bounty price

1,000 euros for the winning team / person



Apply now