Most efficient use of land for growing food?

Factual Questions
1

I’m arguing with someone about using land to grow animals, or grow plants. Eventually he decided to pull out some hard figures:

Idk man, so if I had a 5x5 foot chicken coup I could house about a 10 chickens comfortably, that’s about 300x10 or 3000 eggs a year, in a 5x5 plot of land. That’s approximately 3000x70 or 210000 (!!!) calories. With lots of protein and other vitamins and minerals. (and you could fit even MORE chickens in if you were an inhumane asshole)

Now if you planted about 1 corn stalk per square foot, you’d get 5x5x1 about 25 corn stalks, and lets say you get lucky and get two harvests in, and even luckier and get 2 corn on the cob per stalk. So that’s 100 corn on the cob, or 100x100 or 10,000 calories.

Now, that’s a huge margin but of course you need to factor in the calories needed to feed the chicken, which is about 50 calories a day, (they can get away with less if you have land for them to peck at shit) or 500 calories per day for all 10 chickens, or 182500 calories per year. But then you have to factor in eating the chickens, which is about 5000 calories/chicken. Or 25,000 calories total.

25,000 + 210,000 - 182500 = 52500 calories/year for chicken

or

10,000 calories a year for corn.

Now, I’ve tried carrots, potatoes, and other foods, but somehow I can’t get the same amount of calories from the given land as the chickens. I know I’m doing something wrong, because he’s still losing potential energy, all that stuff going into bones, feathers, eyes, in the chickens moving around and making noise. Every time you go up the food chain, there’s always losses. Which also doesn’t make sense, because he’s getting more calories out than he’s putting in, even with all the energy expended to make chicken.

So anyone mind helping me out? I don’t mean drafting a response for me of course, but maybe point out what I’m missing, or what crop might be a better point-maker than corn?

2

You have to FEED THE CHICKENS!!

Especially if you want eggs out of them.

Subtract from the total calories all of the calories necessary to keep 10 chickens fed for a year, then look at your totals.

(And no, I’m not looking that part up. I’m lazy.)

3

I think your numbers for feeding 50 cals a day are off.

Also, if they’re “pecking at the land” that’s still caloric energy coming off the land that isn’t being taken into account.

Also, you’re not counting the energy needed to produce the calories in the form that the chickens need. It has to come out of the total somehow. If you’re growing corn on that 5x5 plot to feed the chickens, there’s less land there to keep the chickens ON, you see?

4

All calories come from the sun. Plants converts solar energy to calories; animals can take these calories and convert them to calories in a different form. Conservation of energy - which cannot be ignored, ever - demands that the calories produced by animals thus be no greater than the calories produced by plants. Otherwise, what you’ve got is essentially a perpetual-motion farm.

5

You can’t get a 70 calorie egg a day out of a chicken which consumes 50 calories per day. Where did the 50 calorie per day per chicken come from? Because that’s where the mistake is.

6

Yep, did some looking, and that’s what was up. Hard to find how much they need given all the human diet sites, but they need at least 3 - 4 times as much.

Even then, what is the most efficient crop in terms of calorie output per land unit?

7

Could it possibly be some type of nut? Like almonds, perhaps?

8

It has to be a staple of some sort, like wheat or rice or corn. I mean, that’s why they’re staples - because you can use them to feed the largest amount of people per acre.

9

I remember the introduction of the Potato in Europe caused an agriculture revolution. It nearly tripped the amount of calories produced per acre.
Yep Potatos

http://www.waldeneffect.org/blog/Calories_per_acre_for_various_foods/

10

Linkie: Nutrition for backyard Chicken Flocks says laying hens need 260-340 kcal per day. That makes chooks severely negative calorie producers, which is more what I’d expect.

A bit of Googling suggests that rice is the most productive cereal crop. Potatoes can yield 40 tonnes per hectare, and rice 9.5. Rice has less than 4 times the calories of potato, giving potatoes the edge. But it would probably depend on the land and climate where they were grown.

Nuts seem to yield around 4 tonnes per acre unshelled, and have only twice the calories of potatoes, so they are not even close.

11

Also, I don’t think you can keep 10 chickens on a 5x5 plot. Not without them getting stressed or sick.

12

It’s not only the question of efficiency of the plot of land, it’s the question of quality of output. In terms of efficiency, depending on your latitude, planting photo-voltaic solar panels in a 5x5 foot area will produce the most usable calories (on the order of 300,000 kCal per year if I did my math correctly). Unfortunately, we can’t eat electricity.

There cannot be a perpetual motion farm, but it is not inconceivable that if you take into consideration all the associated energy costs until the output is metabolized by your body, then there are scenarios that raising animals is more efficient than plants.

13

Is that per year or per harvest? Because while you only get one crop of potatoes out of a field in a year, it’s my understanding that you can get three (four?) harvests of rice in the right climate.

I wonder about sugar cane. This siteclaims that sugar cane produces a kilogram of sugar per square meter, so that’s 10 tonnes of sugar per hectare (usually per year-it’s usually a 12 month crop). However, sugar has seven times the calories of potatoes. On the other hand, sugar takes more additional energy to process (though possibly only if you talk about the energy to process before sold to consumers. After purchase, consumers will use energy to cook potatoes, but probably not to cook sugar. Or at least less.)

So, I dunno. Lots of variables.

14

All of these scenarios, though, have to ignore the land required to grow the food the animals eat.

15

That depends on the land. There are large areas of the world that won’t grow anything that humans can eat directly, or at least not in any quantities worth mentioning. But they will grow grass, and you can let livestock loose to graze on that grass, and then eat the meat. It’s not very efficient, but any other use to which you can put that land would be even less efficient.

16

If you’re only getting 2 ears of corn off of each stalk, you have some seriously lousy seed there! Modern hybrid corn should produce 3-4 ears per plant, even more in some years.

17

The basic mistake has already been pointed out, so I just want to add that there is no single answer to your question: different crops grow in different climates and need different soil.

If you talk about efficiency, it’s also a difference what farming method you use - some crops can be better cultivated and harvested with machines than others.

In addition, modern crops have been bred to produce high yields in terms of calories/ volume only, and pushing them with mineral fertilizier increases that, but the other contents often diminish (the same amount of vitamins in a bigger volume), so a lot of the volume is water. So just saying that the harvest is x kg of potatoes or corn is not enough if you don’t know how much water is in those big-ass potatoes.

18

Which brings up another complicating factor to efficiency: how much work has to be done on the land. If growing something like corn on marginal-quality land requires you to bring in all the water, fertilizer, pesticides and machines, that’s a hell of a lot more expensive in terms of total resources than letting grass grow there unaided.

19

That is the beauty of chickens. They’re too stupid to understand the laws of physics. One day scientists will develop a chicken so stupid it forgets it needs to be fed and all of our food troubles will be solved.

20

There was an essay in one of the Malcolm Gladwell books about efficient management of rice paddies in southern China. These guys got to keep much of the profits of their labor unlike his counter-example of French medieval peasants, but they had to apply themselves and micromanage the paddy. In some cases they could expect 3 crops a year, very high yields. Outliers, CH.8, “Rice Paddies and Math Tests”.