I thought you might be interested in seeing the results I got last year from growing potatoes in straw towers.
The potato towers I used were constructed and planted in the following way: (I used these materials because I happened to have them close at hand and at no charge - you can creatively make use of whatsoever you have available)
- Four corner posts of untreated 4x4" lumber, 6' long, are erected using concrete piers and spaced three feet apart, square
- Walls consist of 1" mesh, 20-gauge, galvanized hexagonal chicken wire, applied to three sides, one side left open for access
- Two three-stringer bales of straw cover the bottom of the tower, in turn layered with a 1-inch of compost, (a straw bale of this kind is 18"Wx36"Lx18"H in dimension - you can use bone meal and other amendments if you have them, but I didn't use any)
- Four seed potatoes are planted in each tower - the dimensions of the base can be divided into four equal quadrants of 18", square, with a seed potato in the center of each quadrant (a penpal told me they have had success planting them more closely, so try that if you like)
- Cover the seed potatoes with 6" of straw, let them sprout and grow to about 12" tall, then repeat a layer of straw and a few spades of compost each time they grow another six inches - this mimics the traditional method of "hilling" potatoes to improve yields
- The tubers can be harvested at the end of the growing season for the variety you are using - I harvested both varieties that I used in the last week of October after the first frost of the cold season
- (I planted from seed: horseradishes, marigolds and pole-beans sporadically on the exterior surface of the tower - success was marginal, as only the plants seeded early in the season had sufficient time to mature)
Last year, 2011, I planted three towers constructed in this way. Two towers were seeded with a late-season variety called Russet Burbank, the third was planted with early/mid-season Red Pontiac.
I weighed my harvest in at:
- Russet Burbank: 117 lbs (about 60 lbs per tower)
- Red Pontiac: 41 lbs (some were inedible because they were green, and had to be reused as seed potatoes - otherwise, the total would have been closer to 45 lbs)
- At the time of harvest, straw inside the towers was piled up to 4.5-5 feet high
- (Incidentally, I also harvested approximately 5lbs of horseradish at the time the potatoes were harvested and about 5-8 lbs of green beans over the course of the growing season)
In total, I used about 40 bales of straw, at $2.35 US per bale, (I attempted to find to find some available free, but was unable to locate any in late March when I started this project - mine were purchased at a local farmers supply store - the price includes delivery). I also used about a cubic meter of compost in the process, which I made on location.
Materials costs, in my case, were zero because I happened to have everything available. I would estimate the cost at about $40-$50 for each tower at local prices, if materials were bought new.
At harvest, I had approximately four cubic meters of mostly composted straw, which I used as mulch. An advantage to using fresh straw each year is that it reduces the risk of various diseased, which potatoes are prone to and can linger is infected soil for years, in some cases.
According to one source I read, there are around 400 calories in a pound of potatoes, (450 grams).
An average adult should consume 2500-3000 calories per day - assuming a quarter of daily caloric intake is from potatoes, about 1.5 lbs of potatoes would suffice per day. Assuming little or no waste applies, my harvest would have provided one adult with a quarter of their caloric needs for approximately 100 days. (I stored my potatoes in a galvanized steel garbage can amongst damp sawdust, and they lasted around four months until they began to dry out - a small quantity were lost to mildew caused by accidental skin puncture during harvest).
I estimate the water requirements of each tower to be about a gallon per day, with a higher requirement earlier in the season, and a lower requirement later in the season when the tower has more mass and is able to hold more water - towards the end of the growing season I gave each tower five gallons of water, once a week.
So, for anyone who is interested in earnestly provided themselves with all of their caloric needs on a piece of land, you can extrapolate what you might be able to produce using this method. I think the yield is pretty good for around 30 square feet of growing space, not counting room for maneuvering.
In terms of cost-saving, the price per pound is comparable to what it would have cost to buy potatoes in local grovery stores, but the flavor and wholesomeness of the produce was worthwhile.
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