Hydroponics, pt. 2

Short update again on chilies and hydroponics (apologies): my current work on this is focused on three areas. Firstly, I have been trying to figure out what growing method (or sub-method) to use. As I wrote earlier, there are reasons why ‘passive hydroponics’ looks like the best in my case. There are different ways of implementing this, though. Understanding in advance e.g. the risks associated in algae growth, over- (or under-) fertilisation, and pests in passive hydroponics appears to be important. As contrasted with growing in soil, the basic situation with nutrients is very different. In principle the hydroponic growing should be free of many risks coming with soil (less risk of pests and plant diseases, no need for pesticides, etc.) However, a hydroponic farmer needs to be bit of a scientist, in that you need to understand something about physics, chemistry and some (very basic) bioengineering. The choice of growing medium (substrate) is important as in passive hydroponics one should get enough moisture (water) to the plant roots without suffocating them – thus, the material needs to be neutral (no bio-actives or fertilisers by its own), porous and spongy enough to hold suitable amounts of water when irrigated, but also get dry enough so that air can get to the roots in-between drenching.

Secondly, I have been looking into the technical solutions for implementing the hydroponic growing environment. As I wrote, I have considered building my own ‘hempy bucket’ system. However, I kept thinking about root rot, fungus and other risks: in this kind of bucket system, there is always some fertilising liquid just standing in the water reservoir. The standing water provides ideal conditions for algae growth. Stagnate water system can cause lack of oxygen; build-up of salts and decomposing algae can produce toxins. I am not sure how significant those risks are (there are many hempy bucket gardeners who appear perfectly happy with their low-cost systems), but currently I am inclining more towards a commercial passive hydroponics system that also includes some kind of water valve: the idea here is, that the water valve will allow automatic, periodic watering of the growing media (and the root system), but also flush the water away as completely as possible, so that no similar stagnate water reservoir would be in the pots, as in the hempy bucket option. There are at least two models that are widely available and used: AutoPot and PLANT!T GoGro. I am not sure if there is much fundamental different between these two – GoGro appears to be more widely available to where I am living, but some gardeners appear to consider AutoPot (the original, older system) as more robust and a bit more sophisticated.

LED strip (Nelson Garden 23W).

Thirdly, I need to find a plant light solution that works. Currently, the tiny seedlings can nicely fit below the small LED plant light system that I have been long using. However, doing some hydroponic gardening indoors (before the greenhouse season starts) means that I need to be ready to provide enough, and right kinds of light for growing plants. We had an old fluorescent tube lamp, left from Laura’s old aquarium. That lamp was, however, too large and heavy for my needs, and I was also a bit suspicious how safe (in electronic terms) a 10+ year-old lamp setup would be today. Some chili gardeners appear to be using rather expensive, “hi-fi lamps” where different high-intensity discharge lamps (HIDs) have taken over from older incandescents and fluorescent tube lamp systems. Ceramic metal halide lighting and full-spectrum metal halide lighting are used to create powerful light with large amounts of blue and ultraviolet wavelengths that are good for plant growth. The price of good lamps of this kind can be rather high, however. I decided to go for a lightweight but plant-optimised LED system that was a comparably budget-friendly option. I am now setting up four 23W LED strips that were sold as Nelson Garden LED plant light (No.1 and No.2 systems use the same power transformer). Each LED strip is 85 cm long, is specified for 6400 K light temperature, and should provide 2200 lumen, or, more precisely, PPFD (100 mm) 570 µmol/s/m² of lighting power. Having four of those should be enough for four AutoPot style chili growing stations, at least in the early phases of gardening, I think. I am still thinking about how to suspend and adjust these LED strips to correct height above the plants. I am doing this pre-growing phase in my home office corner, in the basement, and e.g. the ceiling panels do not allow attaching anything into them.

Measuring the nutrients.
Measuring the nutrients.

Finally, the choice of growing medium has also an effect on the style of fertilisers to use, and most hydroponic gardeners invest to both EC and pH meters and adjustment solutions, in order to control the salts and acidity levels in the nutrient solution, and to adjust the values in different stages of growth, bloom and fruit production. Some do not take this so seriously, and just try to follow some fertiliser manufacturer’s guidelines and make no measurements at all, just trying to monitor how plants look like. Some study this very scientifically, measuring and adjusting various nutrients, starting from the “key three”: Nitrogen (N), Phosphorus (P) and Potassium (K), which are commonly referred to as the fertilizing products’ NPK value. All these three are needed: nitrogen boosts growth, phosphorous is needed by plant for photosynthesis, cell communication and reproduction; and potassium is crucial for plant’s water regulation. But there are also “micronutrients” (sometimes called “trace elements”) that are needed in smaller amounts, but which still are important for healthy growth – these include, e.g. magnesium. Popular fertilisers for hydroponic gardening often come in multiple components, where e.g. the mixtures for growth, bloom and then the micronutrients are sold and apportioned separately. It is possible to find quite capable all-in-one fertiliser products, however. I am currently planning of using coco coir (neutral side-product of coconut manufacturing) as the growing medium, so I picked “Canna Coco A+B” by Canna Nutrients as my starting hydroponic fertiliser solution. I also bought a simple pH tester for checking the acidity of fertilising solution, and I probably should also invest in a reliable EC meter, at some point. The starting solution for seedlings should be very mild in any case, to avoid over-fertilising.

Testing the pH of our tap water.
Testing the pH of our tap water.