Small Scale Hydroponic Lettuce – Method Testing

Now that I have a stable indoor growing environment I will test several hydroponic techniques.


Background:

Hydroponic growing methods have always interested me but I have never been able to pursue them in earnest due to lack of a stable indoor growing environment as well as the limited practicality of a small scale setup. Alas, soon I will be moving out of the house and away from my gardens (and land to plant on) but I would still like to be able to have immediate access to homegrown fresh vegetables. I will still be managing the gardens but now on a weekly basis instead of a daily basis and will forgo our community garden plot moving forward. This new scenario makes it a more practical to have an indoor hydroponic garden but I am still skeptical of the practicality of a small (2’x4′) hydroponic system. As a result, I am going to test several methods that require the least amount of maintenance and are easy to automate or manage before scaling up. I will test them in order of barrier to entry with regards to the cost of set up and time required to manage the method. These systems will be DIY to fit the form factor of the grow cabinet but I will try my best not to sacrifice the integrity of the tests by being so cheap that it cripples the technique tested. As a result of limited discretionary funds (read “broke student”) as well as test duration, it will probably take some time to get through all of the methods listed.

Update: July 18, 2017

We ended up putting in a 4×8 raised bed in at our new place so I haven’t had time to conduct these tests. I will do a post on the raised bed soon as well as push a bunch of updates on what I’ve been up to. Hopefully when the weather cools down I can pick and run one of these techniques in the grow cabinet.


Techniques:

  • Kratky ($)
  • Coco Coir SIP (EarthBox) ($$)
  • Coco Coir w/ GrowStone DTW ($$)
  • NFT ($$$)
  • Ebb and Flow ($$$)

Methodology:

I will grow at least three heads of lettuce in each test and document the grow. Each method will receive roughly the same nutrient solution concentration and will receive the same formulation. Recirculating systems will receive less nutrient solution because they tend to drift up as water evaporates or is consumed. The same type of lettuce, Burpee Buttercrunch, will be grown in all of the tests. They will all be germinated the same way and then transplanted bare root into the systems. At the end of the cycle they will be harvested and weighed. I will then report on the practicality, cost to operate, water usage, scalability, and overall performance.


Testing Parameters:

  • Rh: 35-55%
  • Temp: 65-78°F
  • Reservoir Temp: 65-78°F
  • EC: 1.8
  • pH: Tap †
  • Duration: 75 days (from seed)
  • Water: Tap ~0.6 EC / ~8.5 pH
  • Lighting: 150W HPS @ ~12-17″ ††
  • Day Length: 10 Hrs
  • Fertilizer: Jack’s Professional Hydro FeED (JR Peters)

† Note: I will initially use tap water that hasn’t been pH adjusted to test the claims that JR Peters makes about the buffering capabilities of their fertilizers. I will report back and adjust the water if necessary when I post my first test. I will not use RO water at any point as it is both wasteful and impractical. I realize this may prove to be quite challenging but practicality, efficiency, and cost are the main factors being tested.

†† Note: I realize that the light being at a fixed height will change the intensity of light that plants receive depending on the heights of the containers and as the plants grow in height. This unfortunately cannot be avoided so I will do my best to create systems with low and similar profiles. As a result of this key parameter flaw any and all results may vary.