10 mins August 7, 2016 Walter Haugen
Yesterday I harvested these Red La Soda potatoes from half of a 4’x8′ raised bed (the other half is in strawberries). The yield was 17 pounds, so in the 16 square feet I got a yield of 1.06 lb/sq ft or about 1 pound per square foot. This is not an uncommon yield using raised beds for growing potatoes. I like raised beds because yields are higher and it is easier to control weeds by hand. The link below lists six other methods.
Per USDA statistics, the average US yield for Big Ag potato producers was 421 cwt (hundred weight) per acre. This is .97 lb/sq ft (421×100/43560 = .966), or just slightly under the yield I got from this raised bed. Now, what was the energy input for these potatoes? On the short-term energy consumption side, I put in about 15 minutes planting and preparing the soil and 15 minutes weeding and harvesting – about half an hour or 65 kilocalories of human input. There were no fossil fuel inputs. The output is 5,950 kilocalories since potatoes have 350 kilocalories of food energy per pound (17*350 = 5950). So the EROI (energy return on investment) for these potatoes was 92:1. This is quite high and better than wheat. Since industrial agriculture uses 10 kilocalories of fossil fuel to produce 1 kilocalorie of food, my raised bed potatoes were 920 times more efficient.
Now, you may ask, “What about the embedded energy in the potato seed AND the raised bed itself?” Okay, fair question. However, the embedded energy of a few boards of wood and a few nails is far, far lower than the embedded energy of a tractor, harvester, transport by trucks, etc. It is well below a 5% margin of error. As for the potato seed, the embedded energy of the potato seed is microscopic if I use my own seed from previous years. The embedded energy of my own seed can be discounted because it is far lower than even a 1% margin of error compared to buying commercial seed (i.e. 1/920 or 1/10th of 1 percent, since the seed potatoes have 920 times more energy in their production than mine).
However, let’s calculate the embedded energy of the seed potatoes I bought. I used about a pound and these seed potatoes were bought at the local farmer’s co-op in Ferndale. They were grown locally BUT we can still assume a 10:1 ratio of fossil fuel kilocalories to the finished product. One pound of seed potatoes then will have an embedded energy of 3500 kilocalories (350 kcal/lb x 10 kcal/pound for the energy cost to produce). Wow!
Do you see the trap? If you use commercial seed every year, you need to keep your production high EVEN IF YOU USE NO FOSSIL FUELS. The EROI of my raised bed using commercial seed drops to 1.7:1. [5950/3500 = 1.7 EROI.] This is still high if you compare it to using commercial seed AND using machinery that consume a tremendous amount of fossil fuel BUT it puts a different spin on your backyard garden.
As I sort out this 17 pounds of Red La Soda potatoes, I will keep some for next year’s seed. Then my EROI will jump up to the higher level that I first calculated.
Are you convinced yet that you MUST grow your own seed? Not only for food security in times of collapse, but to salve your conscience in this most wasteful of countries, the USA.
http://www.rodalesorganiclife.com/…/7-ways-grow-pot…/slide/1
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