Recently I started the V anthroponics experiment at Hemmaodlat with the goal of testing if Iron is the limiting nutrient in an anthroponics system. I set up the usual three systems. Each received 165mL of aged urine and each received 37g of wood ash (as detailed in experiment IV). However, System 2 received an additional 1g of chelated iron and System 3 received 2g of chelated iron. System 1 received no iron and would serve as control.
The iron selected was the one available at Hemmaodlat: FeDPTA 10% (powder form). Considering that the anthroponic systems have around 30-35L of water volume, and a target iron concentration for healthy cucumber growth is of 3mg/L in the water, the calculations were simple:
1g of powder contains 0,1g Fe. To achieve the concentration of 3mg/L in 35L one would need to add 105mg of powder. Since the powder has a concentration of iron of 10%, then we need 1050mg or 1,05g of powder. System 3 would then receive double the amount to test for any extra benefits to a doubling of iron supplementation.
The experiment was set up on the 27/7/2016, but only one week afterwards (yesterday) I noticed the plants had been attacked by thrips. Below you can see some pictures of the set-up and plant damage.
You can see the actual thrips and their inflicted damage on this close-up picture.
So the experiment had to be stopped as the thrip infestation would affect the results. We are sterilizing the media and we will have to re-seed cucumber and wait for the seedlings to have a decent size before restarting the experiment.
In the meantime, I have also started a proof of concept of a different anthroponics system. The goal was to separate the growing component from the ageing & filtration components. The first component is a bucket inside a larger box with a lid. The bucket is filled with water and contains in it a water pump and air-stones. The bucket is also filled with plastic carriers/media (K1). The airstones are then connected to an air pump inside the box, and the water pump has a pipe/tubing to the growing component. The bucket system also contains crushed and dehusked watermelon seeds. As fresh urine is added, the urea will be converted to ammonia, and then the nitrifying bacteria will develop. Once nitrates are measured in the system, it is good to go.
Next to this box is a DWC (Deep Water Culture) hydroponic set-up, also with an airstone connected to an air pump. Given enough time after the urine insertion in the first box, part of the water is then ready to be pumped to the DWC component. I have added some basil seedlings we had available to see how they will react in this system.
Overall the point will be to test the proof-of-concept and to improve it rather than performing a more scientific trial. But if it works, one can imagine the applications of developing an anthroponic filter that connects to an existing (urine separation) toilet, and its discharge can be used directly as an organic hydroponic solution. This would finally solve the issue of urine handling, which is currently one of the least pleasant activities in anthroponic farming.