Lettuce Harvest from Hydroponic System December 31st, 2010

Here is the latest video update showing lettuce harvest, a discussion on nutrient usage, lighting hardware, and my thoughts on the deep water culture and ebb and flow systems. 

I am truly astounded at the speed of growth and minimal nutrient usage!!

Grow Light Expenses????

   Ok, so how much does it cost to purchase and operate artificial lighting?

   Lighting expenses continue to be a concern for my indoor growing endeavor because I want to keep this cost neutral or preferably net positive if at all possible. After all, this is "Frugal Hydroponics" right?

   The lights I use are simple 2-bulb, 32W, T8, 48" shop lights with on/off pull chains. "T8" fluorescent bulbs are much more efficient than the standard T12 40W bulbs. "T5" systems are more expensive for the initial purchase, but are more efficient than the T8s. I may switch to T5 in the future, but for now I am happy with the results and efficiency of the T8 system.

   I bought 3 of these shop lights for less than $9 each and fashioned them together to operate as one 48", 6 bulb fixture of which all are plugged into the same light timer. In effect, I have 6 32W bulbs covering a 48" x 24" growing area. This easily accommodates several standard starter trays or least 3 of the hydro systems. I recommend watching your local big box stores for sales and manufacturers rebates. The lights I bought normally retailed at over $20 each, so wait for the sale.

   Since vegetative growth is achieved in the "blue" spectrum, I use 6500k bulbs. A 2-pack of Sylvania T8 6500k bulbs is around $3.50. Since I am growing lettuce, herbs, and my spring starters, the blue spectrum is all I need. If I were to grow plants requiring a flowering stage (peppers, cucumber, tomatoes, decorative flowers etc.), I would need red spectrum bulbs and additional shop light fixtures. At this point, I believe that is cost prohibitive for me as I will grow those type plants outdoors.

   Calculating Energy Consumption: 32W bulb x 6 bulbs = 192 watts. 14 hours of use per day x 30 days = 420 running hours. 420 running hours x 192 watts = 80640 monthly watts used. 80640 / 1000 = 80.64 Kilowatts used. My energy company charges $.0783 per kilowatt, so my total monthly expense to run these lights is $6.31.

   Expense re-cap: Total cost of shop lights: $27. Total cost of bulbs (replace yearly): $10.50 or $.875 per month. Total energy usage per month: $6-$7.

   I feel this is economically feasible for the production I am wanting to achieve. I recommend researching "High Intensity Discharge" systems for anyone wishing to produce flowering plants or increasing production by several magnitude. These systems do require many additional considerations, so research diligently.

Design and Build of the Deep Water Culture (DWC)

Here is a simple video explaining the design and build of the Deep Water Culture (DWC) system.   These two modules will replace the ebb and flow system as the primary growing vehicle for lettuce.  In a DWC system, the roots lay in a highly oxygenated nutrient solution while drawing dry air from the top area of the pot.  It is critical for the solution to maintain aeration or the roots will drown.

I chose a DWC and this particular design for a couple reasons.  1) A DWC is very simple and requires minimal parts (air stone, tubing, air pump). 2) This design will hold over 5 gallons of nutrient solution providing a stable nutrient base.  3) This design allows for easy replacement of nutrient solution by simply setting the lid / pots / plants aside and dumping and refilling the reservoir.

I expect the same rates of growth as I have experienced with the ebb and flow system.

Bigger and Better

We are still harvesting with no apparent end in sight.  The lettuce is greener and crisper than it has ever been.  This photo was taken today after being heavily harvested just a few short days ago!  Some sun dried tomato vinaigrette, olives, a few shreds of Romano and voila!

Steady Harvest!!

Since my last update, we have harvested lettuce for salads or sandwiches every other day.  That amounts to 2 large salads worth of growth in just 48 hours.

I have added about 2 gallons of plain water to keep the reservoir level stable, but have added NO additional nutrients since the 21st of November.  PH is staying in check as well.  This again shows how little maintenance this system requires.

The basil is beginning to shows some sign of mineral defficiency, but it is a more demanding plant than the lettuce.  The signs are minimal, but I am watching closely for the rates of change and hoping to squeeze another 7-10 days from the current nutrient batch.

Time to expand

We are steadily harvesting and eating the lettuce and using the lemon basil in some great Mediterranean dishes.  I have taken a few photos, but since we are steadily trimming the plants, there is really no need to post them. 

The PH has needed a couple very small adjustments and I have only added about a gallon of water in the past 6 days due to transpiration.  As I stated previously, it takes about 5 minutes of my time each day to monitor a couple things such as water level and PH.  Hydroponics continues to be virtually maintenance free.

I am very satisfied with the limited maintenance, high growth rates, and overall ease of use hydroponics.  It is time to expand our capacity to grow more greens and keep a crop in harvest rotation at all times.  We are getting pretty spoiled with fresh greens in salads and on sandwiches.  They are delicious!

I am still making some final decisions on the design of the Deep Water Culture system and will post when I begin the actual build.