On Indoor Kratky Style Hydroponic Vertical Farming Indoors

As I continue on my experiment of a year of doing the things I hate, I am now documenting at the half year mark of engaging in passive hydroponic growing using the Kratky method. At this juncture I have a working vertical farm, fitted to window sills. The process is being described below. 

Gardening has always been a thing I hated. It is exacting, requires care, and the regular production of foodstuff requires a certain discipline that was out of line with my ideal of not putting in too much effort into maintaining any system in particular. Setting up is one thing, but upkeep is a bear.

I did not know much about indoor gardening, so my first experiment was with regular soil. Growing plants in soil, particularly in pots, is an abomination in terms of effort. My first realization was that you could over and under water the plants, within the day! This meant daily waterings, at the precise correct amount for each plant. The wrong soil type would also be bad news. Worse yet, the soils were most definitely bug infested, and my grow wound up with an aphid infestation I am battling to this day, but more on that later. 

Clearly, soil was a highly problematic medium to work with if low involvement grows was the goal. I looked into alternatives, and explored hydroponic styles. I took stock of the situation, and drew out the parameters:

1. Window sill capable - I did not want the apartment floor space to be dominated by plants, but had sturdy window sills that were built into the walls of the apartment. The windows were also large and tall. Thus, I could support a multi-tier setup if it were narrow enough to sit on the window sills. 
2. Low maintenance/passive - I would prefer that the setup be as low maintenance as possible. Ideally this means if there is a complete power failure, the growth rate would slow but not be cut off entirely.
3. Low noise - I want a quiet apartment where possible, without the sound of circulating pumps.
4. Low effort - The method should not require my direct intervention more frequently than once a week, ideally less. Initial setup would require testing and calibration of course, but final form maintenance should not require micromanagement.
5. Low cost - This is relative. In Sweden, leafy greens are expensive, so “low cost” really was relative to the price of vegetables in this country. It simply takes less time to amortize the cost of the produce, once things are properly set up.

This required some homework. Firstly, discover which non-soil systems exist, evaluate their costs and lay out the options. There were multiple - ranging from the standard circulating methods to passive. These are the highlights of the different methods - 

Aeroponics - Sprays a fine mist of nutrient solution over roots of plants. Plants are suspended and their roots grow in air, essentially. 

• Pros: Good root growth with aeration, mostly self operating. Can use a central tank. Flowing liquid discourages insect growth.
• Cons: Requires maintenance of the equipment: If the spray head got clogged, the system would fail. Any power outage would rapidly result in roots drying out and death of plants. Nutrient evaporates rapidly because of micronization.
• Consideration: Real bad for a hands off system, quite ideal for larger grows. Pumps would likely be noisy in an apartment. Not a good choice. 

Nutrient film or ebb and flow - Technically these are different methods but the principles are similar. A pump introduces a steady thin stream of flowing nutrient for nutrient film, and an ebb and flow system floods an area with nutrient then drains it out. 

• Pros: Similarly good root aeration, mostly self operating. Can use a central tank. Flowing liquid discourages insect growth.
• Cons: Again, pump and filter maintenance. Any active system failure rapidly results in plant death. Nutrient evaporates rapidly because of circulation.
• Consideration: Similar to aeroponic drawbacks. Again, would be best for larger outdoor systems. 

Deep water culture - DWC is effectively a big tank of nutrient solution with a bubbler to aerate the water. Roots sit in a deep tank of solution.

• Pros: Pump maintains root aeration, mostly self operating. Can use a central tank. Agitated liquid discourages insect growth.
• Cons: Nutrient evaporates rapidly due to aeration. Plants degrade to an extent if pump fails, but will not die as quickly. Requires pumps. Best DWC setups required more space than I had available.
• Consideration: This was the closest active system to my requirements. The only real issue was the noise from pumps and the space requirement. Unfortunately, the space requirement was also a deal breaker in this case.

Aquaponics - Like DWC, but with fish added basically. The fish help to deal with insects, and their waste helps fertilize the plants. 

• Pros: One of the friendlier setups nutrient wise. Similar advantages to DWC otherwise.
• Cons: Similar drawbacks, but with even heavier dependency on active electrics because of the fish. Requires even more space.
• Consideration: Would love to try this in a larger setting, however impractical for my situation.

Passive hydroponics (Kratky) - The Kratky method is like DWC minus the pumps. Instead, root aeration is maintained by allowing the nutrient liquid to evaporate down, thus exposing roots to air. 

• Pros: It’s like DWC minus pumps. Adaptable to various sizes of containers.
• Cons: Stagnant water can breed insects. 
• Consideration: There are other related cons, but none relevant to my consideration. This seemed to be the lowest maintenance and lowest cost option.

From the readings, I realized that the Kratky method was most ideal because it was low maintenance, so I tested it with some jars. I procured hydroponic nutrient concentrates and prepared solutions of appropriate strength according to the instructions, and proceeded to let them operate by themselves. Initial results were promising. The seeds duly germinated and grew without requiring that I water them. In fact, they could sustain the initial growth without requiring new nutrient for about a month. 

After a few weeks, I procured some containers from Ikea and drilled holes in them for net cups, and transplanted the weeks old plants into these new tanks, and they thrived. Output was good. I proceeded to get some metal Hyllis shelves off Ikea, mounted them at the windows and used magnets to fasten thin LED bar lights on the shelves. This formed the basic template for my grow setup. I later cut up and tacked on Mylar space blanket cuttings to the shelves both to reflect some light back in at the plants, and to reduce the light pollution around my apartment.

The first crop worked well, before the aphid infestation spread from my soil grows and proceeded to become a problem. I have since discarded soil entirely, and acquired some ladybugs to combat the aphid problem. Initial results are promising. Due to the forested area in my vicinity, the plant lights have also proven to be attractive to bugs that may be passing through the mosquito screens I fitted at the windows. While sourcing finer screens, I have procured a fan driven insect trap, which has also produced promising initial results. May be hazardous to curious ladybugs however.

Notes

Insect/Water Trap Setup:

The biting gnats were small, and frequently smaller than the filter on the UV-baited fan trap. However, as insects are disoriented after exiting the trap, they fail to evade the water trap, thus guaranteeing their elimination.

Initial Kratky jars:

• Seeds can propagate just fine in rockwool without requiring an incubator. 
• Opaque coverings are recommended to avoid algae growth in case of strong side light, but otherwise not strictly necessary.
• Recommend exposing seedings to consumer grade 5000-6500k lights at the very least early on, to avoid legginess.
• If topping up nutrient, avoid reusing exhausted nutrient on new seedlings because the mix seems to lack nutrients promoting root growth. 

Grow lights:

• LED bulbs are cumbersome and rapidly become problematic in low clearance setups. They are also typically poor for scaling up. Not recommended.
• Consumer LED bars are inefficient (generate lots of heat) but are necessary in such a setup. Cost can also easily approach professional light prices (Spider Farmer and Mars Hydro are good professional brands at reasonable cost), however the light levels are not ideal for home use and should be deployed in grow tents to avoid disruptive and potentially injurious levels of light.

Hyllis shelving:

• All-metal shelving is excellent because it allows the use of magnets to rapidly fasten and reposition anything attached to it. This works exceedingly well with consumer-grade thin LED grow bars. 
• Low clearance is less than ideal for taller plants, which are prone to hitting the lamps and getting their leaves burned. 
• Hyllis shelves are cheap. Really cheap. 
• Recommend putting the larger bins on the lower shelves. This is not just for shelf stability but also for ease of moving them around.

Ikea grow bins:

• While Ikea bins are cheap and readily available, recommend using the food containers because the non-food containers are of an unspecified polypropylene type which may not be perfectly food safe.
• Drilling holes in the lids for net cups makes them ideal for grows.
• Smaller containers are prone to temperature fluctuations and require more frequent refilling. The small Sockerbit bins are used with 3L of solution, and require new nutrient every 2 weeks or so.

Plants:

• The ideal plants are indeterminate sorts. That is, you can remove their tops and they branch out sideways instead. Maintaining a permaculture is preferable to having to maintain a rotating cycle of new grows. 
• Suitable indeterminate plants:

1. Mints
2. Indeterminate tomatoes
3. Water spinach
4. Thyme
5. Basil

• As an additional bonus, indeterminate plants that have been topped may in turn be propagated in water for yet more plants. 

Insects/Pests:

• Aphids can become an ongoing problem once introduced.
• Lights on at night may attract insects, and can result in a biting insect pest problem. 
• Blood sucking insects (mosquitoes, biting midges) can be attracted to UV lights, fan traps and eliminated using water traps rigged in the vicinity.
• Ladybugs are silly and prone to wandering into strange areas and getting stuck there. They are also not very good at navigating back to the most infested plants in the grow area. However, when they are there they are excellent at culling the aphid herd. Warning: Ladybugs are prone to consuming ladybug eggs and should be kept away from the eggs where possible. Also, check that the ladybugs you get are indeed ladybugs and not asian lady beetles, because the latter are known to bite. 
• Ladybugs know when they are in a comfortable area, and will lay eggs quite quickly. If you manage to keep the eggs safe, there will be voracious larvae aggressively cleaning the plants on your behalf. Know what they look like to avoid removing the helpful bugs.

Current grow setup (1 module, 3 tiers):

1. Ikea Hyllis (taller four shelf model) for clearance of 40cm working height, alternatively, use shorter three shelf Hyllis and skip the middle shelf for taller plants with 60cm working height.
2. 3 x 15w Nelson Garden LED bars per shelf, for a total of 12 bars. Alternatively, 2x 20w Cosmorrow (Secret Jardin) bars per shelf.
3. Hydroponic nutrients, with supply of distilled water for dilution (optional, recommend using Zero Water for passive filtration of relatively low mineral tap water, or Reverse Osmosis water setup for higher volume). Demineralized water is not necessary, but may be helpful if tap water's quality fluctuates or you want accurate nutrient concentrations.
4. Rockwool - Grodan has some good affordable options
5. Net cups - Any size you like. I happened to have a ready supply of 55mm cups.
6. LECA or hydrotons - Good for stabilizing the rockwool in the net cups, and for covering the wool eventually to avoid insect ingress and algae growth.
7. Starting glass jars - Glass sauce jars or any jar with a mouth that's approximately the size of your net cups. Glass is preferred because it's real easy to clean.
8. Grow bins - Ideally food safe materials, otherwise if not a concern Ikea's small Sockerbit containers with lids (3L fluid capacity) or Gles with Samla lids (11/22L model). Also ideally block off light from the inside of the containers to avoid algae growth.

Future notes - The vertical farm is entering its calibration stage of construction, and once the insect issue is resolved it can be regarded as fully operational.