Friday, October 22, 2021

Corn or Potatoes?

 Reader Jonathan H asked:

"Is corn ahead of potatoes for total calories?

I've heard the claim that potatoes are the only crop that can feed a family of 4 from an acre of ground. Is this accurate?"

First, lets look at modern yields of potatoes and corn and then guestimate what might be likely under post-Apocalypse conditions.

Starting with virus-free seed potatoes, irrigating and fertilizing with 200 pounds of Nitrogen per acre, good weed and insect control, yields of 40,000 pounds of potatoes are very possible. Many of those will be too big or two small or too knobby to be salable but that is not a concern if you are just trying to fill your belly.

If you choose "high specific gravity" varieties then 15% of that weight (6000 pounds). If an adult needs 2500 Calories a day, then 40,000 lbs of potatoes will feed 4 adults for 1,200 days. If you can find fuel to cook them.

Modern yields of hybrid corn in the Corn Belt can easily produce 200 bushels/acre without irrigation. They require the same 200 pounds of Nitrogen, weed control and so on. In my experience, corn is more forgiving regarding insects and weeds than potatoes.

A bushel of corn weighs 56 pounds and 50 pounds are a guess at the digestible portion. 50 pounds/bushel * 200 bushels =10,000 pounds or 2000 days feeding a family of four adults.

Pre-fertilizer/pre-hybrid corn farmers were happy to get 40 bu/acre but even a little bit of fertilizer and stress-tolerant hybrids could hit 80 or 100 bu/acre.

Potato yields are likely to sag more as they are sensitive to the soil drying out, virus, insects and weeds. Let's guess 10,000 pounds/acre as an achievable target.

Of the two choices, potatoes come closer meeting a human's nutritional needs. It seems likely that families would supplement with greens, beans, dairy and whatever meat they can harvest.

Coming back to your question: "Is it true?", it depends on how restrictively you want to interpret the question. I think both have a place in the p-A garden. The corn is more resilient to less-than-optimal conditions and stores better while the potatoes can help avoid diet fatigue and have vitamin C.

The smart money would probably plant a quarter acre patch of each (35 paces square).

Regarding the specific claim regarding potatoes being the only... That claim is usually made to explain the population over-shoot problem in Ireland and the resulting famine in 1847-49. Ireland has reliable rainfall making it potato (and Late-blight) friendly and is cool making it unfriendly to corn. In the context of the crops widely available in Ireland in 1847, the statement is 100% true. In the wider context it is not.


  1. So as some people like to say "embrace the power of AND"

  2. Good analysis, Joe. An advantage that potatoes has is that you can harvest them over a longer time frame, even over the winter into the next spring, they are less susceptible to animal damage and you can hide them where they grew to reduce the chances of theft by others or government looters. Also they don't provide cover for intruders like standing corn does. And they don't have to be ripe and are eatable at any stage of maturity. ---ken.

  3. Several other things could be factored in.

    Potato bugs and other pests of potato's require vigilance and labour to keep under control. Corn seems to have fewer pests.

    Corn is more easily stored long term and less susceptible to freezing and rot.

    Finally, corn can be fed to many different animals to fatten them for meat. Potatoes can really only be fed to pigs.

    I grow both. Corn is way less work and more useful than spuds for me.

    1. I worked for an old dairy farmer in the seventies an he was telling me about feeding potatoes to the cows during WW2 when grain was sccarce. Sharpen a square point shovel and chop them up so the cows don't choke! I cook potatoes for my chi lens daily, mash them up and add a little cheap rice for thickening plus all the kitchen scraps and plate scrapings. I got that from reading about drifting in the Scotish Hiradies in the fifties.

  4. The corn will need grinding for humans. That will be labor intensive. As a child on a non electric farm, I remember eating lots of potatoes, little corn. We ate the corn in the form of eggs, chicken, pork, and a little beef. The fallback meal was always "taters and eggs".

  5. These hypotheticals are, IMHO, a waste of time. You can figure it out fairly easily by doing just what you've done. Research and actual skull sweat. This stuff isn't rocket surgery, as they say...

  6. As the old saying goes, Why Choose? I'll take both.

    If the question came in the form of an ultimatum, man the taters sure sounds a lot better to me. Leavin some in the ground, some ready to be processed like in the cellar, and some more ready to go along with the eggs; wow, that sounds a heck of a lot better than a nitro-packed bucket of shell corn. Mucho grinding. Ugh.

    Mill Tone

  7. One problem with potatoes that I've had is that yield from planting leftover potatoes from my garden don't come anywhere near the yields from good quality seed potatoes that I buy. So if certified seed potatoes become unavailable, they're not really a dependable crop.

    Open pollinated corn doesn't have that problem, it will perform about the same year after year. But then, you have to fight the raccoons for the corn.

  8. I'm stuck with potatoes because we can't grow corn on Alaska. A few thoughts, the Irish pre famine made potatoes work in tandem with dairy and pigs. Long grazing season,surplus milk and skim going to chickens and hogs,potatoes providing calories. 2500 calories wouldn't do it to do hand work in subsistence farming. On the farm I used to loose weight on 4000 during summer work,haying and such. Gained it back in the winter. Look into what colonial settlers did to survive in your area!


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