In our last post on hydroponics we provided an overview of the hydroponic plants we have found in Kathmandu. After this, we set out to install a test hydroponics installation.
The simplest hydroponics system we had in mind, is the rafting system. In a rafting system, the plants are set in small pots with a growing medium, which are inset into a raft, floating on a nutrient and water solution, filled with oxygen.
Since we are testing the feasibility, efficiency and cost-effectiveness of hydroponics, we decided on building a hydroponics installation and a simple in-soil boxed installation to compare it with. Here is a diagram of our experimental setup:
Parts and Costs
To build the hydroponic raft, we required the following items:
- Plastic Basin 250 NPR
- Growing Pots 2 NPR per piece
- Coco Peat 400 NPR for dry 5kg (25 kg after being soaked)
- AC Air-Pump 450 NPR
- Pipes 20 NPR per meter
- Airstone 30 NPR
- Styrofoam raft (free, recycled)
Then in order to run the system, we required:
- Macronutrients (N, P, K at 20:20:20), 250 NPR per kg (require 100 grams per week approximatively).
- Micronutrients 80 NPR for 100 ml, we used 25 ml (require 25 ml per week?)
- Electricity, the pump uses 3,5 Watts
To control the system, we required:
- PH testers 400
- EC tester (didn’t purchase for this small experiment)
- Acid (HCL) (didn’t purchase for this small experiment)
- Base (NaOH) (didn’t purchase for this small experiment)
To build the rafting hydroponics setup, we did the following:
- Soak a handful of coco peat in water, it will grow of 5 times it size after soaking.
- Cut the styrofoam raft to shape
- Add 3 to 4 gravels of 1 cm in size at the bottom of the perforated growing pots
- Add some coco peat in the pots
- Inset the growing pots
- Add water and nutrients into the lightproof basin
- Connect the pump to the air-stones with pipes and .set the airstones at the bottom of the basin
- Float the raft on the nutrient solution.
Additionally we installed a net around each installation to avoid pest contamination. We seeded in excess and we will thin out the weaklings as the seeds will germinate.
Important factors we should underline in this setup are:
- preventing light to reach the nutrient solution (light will stimulate the growth of algea which will compete with the plants for oxygen and nutrients)
- having the right PH (6.5) in the solution
- having the right amount of nutrients
- oxygenating the water (stagnating water would lack oxygen and the roots would rot)
We have found some limitations in the setup process of this experiment.
First of all it was difficult to find the right recipient. We though of using crates, but there are no non-perforated crates in Nepal. The few there are are imported at a prohibitive price. We reverted to locally produced, round, basins instead. Scaling up such a system would require thinking of a different recipient.
Second, the pump is an AC pump, I had hoped to find a DC pump to connect to a solar panel and battery. Scaling up the system again will require finding / making a DC pump, using AC on with solar panels would be too costly with the inverter.
Third, the nutrients are pre-mixed and we have no separate nutrients available here at the moment. Controlling them will require and EC tester and other kinds of tests, which are not cost-effective on a small scale experimental setup such as this one. The same goes for adjusting PH levels, the acids and bases are sold in 500 ml, which was too expensive for this experiment.
We are going to follow up this experiment, documenting and comparing the growth of the seeds in both installations as well as the cost and maintenance of the systems.
If this first experiment will be positive, we will engage in installing a larger system, not necessarily a rafting system, perhaps an aeroponics system. We will be looking for potential hosts and investors for larger experimental installations.