“. . . The majority of humankind has had to depend primarily on plant materials for energy and other nutrients. Even today most of the world's people live on about 2500 kcal per day and obtain most of their food energy protein from grains and legumes. . . .
“A study of 12 rural villages in southern India showed that individuals consumed, on average, between 210 and 330 g of rice and wheat, 140 ml of milk, and 40 g of pulses and beans per day. . . . This diet provided about 1500 kcal and 48 g of protein per day, with the major share of both calories and protein coming from plants.
“In Central America, laborers commonly consume about 500 g of corn per day. . . . Along with the corn they eat about 100 g of black beans per day, and together these staples provide about 2118 kcal and 68 g of protein daily. The corn and beans complement each other in providing the essential amino acids that humans need. Additional food energy is obtained from other plant and animal products.”
The above quantities are obviously intended to indicate dry weight, since 1 kg of dried corn supplies about 3,600 to 3,800 kcal, though estimates vary. (One kg of dry cornmeal is about 1.25 L, or 1 L is about 0.8 kg.)
"Corn" or "maize" here does not mean the vegetable that is normally eaten as "corn on the cob," but the types that are mainly used to produce cornmeal; these are sometimes referred to as "grain corn" or "field corn." Corn is very high-yielding and can be grown easily with hand tools, but it is only practical in areas with long periods of warmth and sunshine; even in most parts of North America it is not easy to grow north of about latitude 45. Corn also needs a good deal of light, so it is not planted where trees are going to cast a shadow.
In North America, both corn and beans need to be planted late in the spring, when all danger of frost is past, but that did not stop the native people from growing these crops quite far north; even the Huron of southern Canada had large corn fields.
Under primitive conditions, corn plants need plenty of room: the kernels should be planted about 2.5-5 cm deep and about 60 cm apart, in rows that are about 1 m apart, for a total sowing of only about 10 kg/ha. In an arid area, it might even be necessary to increase these distances. Many of the native tribes planted the kernels, not in rows, but in small clusters separated by perhaps 1 m in every direction; this method may have conserved water or ensured that a few plants would survive depredation by animals. At least after the corn had germinated or had grown a few cm, no water was used except whatever fell from the sky.
Most of the corn was left on the plants until it had dried, and the ears were then picked and hung up to dry more completely indoors. The dried kernels were stripped from the cobs and later made into a powder, either by being pounded in a huge wooden mortar and pestle, or by being crushed between two stones, the bottom one wide and flat, the top one smaller and rounder. The finished cornmeal was used to make several kinds of soups, pudding, or bread.
Corn is low in isoleucine and lysine, 2 of the essential amino acids that make up protein. To remedy this deficiency, corn should be eaten with beans, which have roughly the opposite amino-acid composition.
Corn is also low in vitamin B3 (also known as nicotinic acid or niacin), and this deficiency can lead to pellagra. The problem was usually remedied either by eating meat occasionally, or by soaking the corn in an alkaline (lye) solution, often made of wood ashes. In what is now the southwestern United States, the whole kernels were soaked for a few days in water with ashes. The ashes were make by burning juniper wood, corn cobs, saltbush (atriplex), or bean vines. The amount of ash used was between one-tenth and one-half as much as the amount of corn. (Ash water was sometimes prepared separately and strained through a grass or sage stirring brush to separate the ashes from the water before the maize was added. Ash water might also be prepared by boiling.) The soaking separated the hulls from the starch. The hulls and water were then discarded and the grains were thoroughly washed in pure water. This treatment reduced some amino acids but greatly increased the content of both niacin and the amino acid lysine, thus preventing pellagra.
Beans are another very important food, but especially for people living on a largely vegetarian diet. Beans are high in protein, they will grow almost anywhere, and once they have produced a few leaves they need little or no irrigation. Beans and other legumes also add nitrogen to the soil.
In modern times, beans are usually planted in rows, but the native people planted them like corn, in holes, with several to a hole, so that even if some did not sprout, or if they were eaten by animals, enough plants would grow. The natives generally planted the beans (and often squash) in the same fields in which the corn was planted, with the vines of the beans running up the stalks of the corn, and in that way more food could be grown on a piece of land.
When using primitive technology, about 120 kg/ha are sown. However, a harvest of about 20 kg of dried beans would be plenty for 1 person for 1 year, even on a vegetarian diet. To produce that amount, one would need about 140 m2 of room, about 12x12 m. That would mean sowing about 3 kg of beans.
One can also broadcast beans (scatter them randomly over the tilled ground), if it is desirable to save time and energy. The soil must be well dug, and there must be adequate moisture around planting time. Some of the seed beans may be wasted by broadcasting, but that method is quicker and easier than planting in rows. About 120 kg/ha are sown, as for row planting.
When the plants are brown, they are pulled up, and the pods are stripped off and put on a clean surface. The pods are left to dry further and turned occasionally, until the pods are so brittle that they crumble. The pods are then beaten thoroughly, or stamped on, to get the beans out.
The beans are winnowed to rid them of the bits of pods, leaves, and stems: on a windy day, the beans are tossed into the air, or poured from one container to another. Then the beans are left to dry for another week or so. They are stirred and turned until they are thoroughly dried. Beans often look dry when they are not, but if they retain moisture they will eventually rot.
How Much Land Is Needed?
Corn has a higher yield per hectare than any other temperate-climate grain (although, of course, no one would live entirely on corn). With non-mechanized agriculture, however, the yield of a hectare of corn is only about 2,000 kg, a third as much as with modern production. The resulting food energy from that non-mechanized hectare is about 7 million kcal. In less affluent societies, people get by with only about 2,500 kcal per day, or 900,000 kcal per year. On the other hand, a hard-working adult in the average modern country might burn about 5,000 kcal per day, or 2 million kcal per year. In other words, that non-mechanized hectare would support a maximum of somewhere between 3 and 8 people.
To supply the same number of kilocalories, beans would require about twice as much land as corn, but of course beans offset their low yield in calories by their high yield in protein: beans supply about 25 g of protein per kg, whereas corn supplies only about 3 g.
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