Section Iv.—on the Absolute Quantity of Food Yielded by Different Crops.

The quantity of food capable of yielding nourishment to man, which can be grown from an acre of land of average quality, depends very much upon the kind of crop we raise.

In seeds, when fully ripe, little sugar or gum is generally present, and it is chiefly by the amount of starch and gluten they contain, that their nutritive power is to be estimated. In bulbs, such as the turnip and potato, sugar and gum are almost always present in considerable quantity in the state in which these roots are consumed, and this is especially the case with the turnip. These substances, therefore, must be included among the nutritive ingredients of such kinds of food.

If we suppose an acre of land to yield the following quantities of the usually cultivated crops, namely—

Of wheat, 25 bushels, or 1500 lbs. Of barley, 38 ” or 2000 ” Of oats, 50 ” or 2250 ” Of peas, 15 ” or 1000 ” Of beans, 25 ” or 1600 ” Of Indian corn, 60 ” or 3120 ” Of potatoes, 10 tons, or 22400 ” Of turnips, 25 ” or 56000 ”

The weight of dry starch, gluten, sugar, and gum, reaped in each crop, will be represented very nearly by the following numbers:—

Starch. Gluten and Sugar and Woody Albumen. Gum. Fibre. Wheat, 825 lbs. 315 lbs. 60 — Barley, 1200 ” 120 ” 160 — Oats, 1215 ” 100 ” 250 — Peas, 420 ” 260 ” 20 — Beans, 670 ” 370 ” — — Indian corn, 2100 ” 280 ” 90 — Potatoes, 2688 ” 224 ” — 1253 Turnips, 3090 ” 1400 ” 5000 —

If it be granted that the crops above stated are fair average returns from the same quality of land—that the acre, for example, which produces 25 bushels of wheat, will also produce 10 tons of potatoes, and so on—then it appears that the land which, by cropping with wheat, would yield a given weight of starch, would, when cropped with barley or oats, yield one-half more, with Indian corn or potatoes about three times as much, and with turnips five times the same quantity. In other words, the piece of ground which, when sown with wheat, will maintain one man, would support one and a half if sown with barley or oats, three with Indian corn or potatoes, and five with turnips—in so far as the nutritive power of these crops depends upon the starch and sugar they contain.

Again, if we compare the relative quantities of gluten, we see that wheat, beans, and Indian corn yield, from the same breadth of land, nearly an equal quantity of this kind of nourishment—potatoes one-third less, and barley and oats only one-third of the quantity—while turnips yield four times as much as either wheat, beans, or Indian corn.

On whichever of these two substances, therefore, the starch or the gluten, we consider the nutritive property of the above kind of food to depend, it appears that the turnip is by far the most nutritive crop we can raise. It is by no means the most nutritive weight for weight, but the largeness of the crop (25 tons) affords us from the same field a much greater weight of food than can be reaped in the form of any of the other crops here mentioned.

In this the practical farmer will see the peculiar adaptation of the turnip husbandry to the rearing and fattening of stock. Could the turnip be made an agreeable article of general human consumption, the produce of the land might be made to sustain a much larger population than under any other of the above kinds of cropping.

The relative nourishing power or value as food of different vegetable substances, is supposed by some to depend entirely upon the relative proportions of gluten they contain. According to this view, the pea and the bean are much more nourishing, weight for weight, even than wheat, and this latter grain, than any of the other substances mentioned in the above table. Thus, 56 lbs. of beans would afford as much sustenance to an animal as 67 of pease, 100 of wheat-flour, or 177 of rice.

In order to understand the value of this opinion, it will be proper to consider the several purposes which the food is destined to serve in the animal economy—what the animal must derive from its food to maintain its existing condition, or to admit of a healthy increase of bulk.