Soil.—The soils best suited to the Potato are of the dryer and lighter descriptions; pasture lands, or new land, with the turf freshly turned, producing the most abundant as well as the most certain crops. On land of a stiff, clayey texture, or in wet soils, they are not only extremely liable to disease, but the quality is usually very inferior. "On soils which have been long cropped and heavily manured, they rarely succeed well; and hence garden ground, in most cases, does not produce tubers of so good quality as those obtained from the fields."
Fertilizers.—"In good garden soil, the less manure that is used, the better flavored will be the produce; and it will also be much less affected by the disease. Therefore, whilst the malady prevails, or symptoms of it still remain, it is not advisable to apply much manure.
"Amongst the fertilizers that are employed, may be enumerated, in addition to barnyard and stable manure, leaves, leaf-mould, peat-charcoal, and other carbonaceous substances, lime, gypsum, or plaster, and bone-dust.
"Wood-ashes are useful in supplying potash and other inorganic substances required by the plant; and they may be advantageously applied where the soil contains a large amount of decayed vegetable matter. The same remark will also apply to lime, which is useful in destroying slugs and other vermin, which attack the tubers. Plaster, bone-dust, and superphosphate of lime, are best for humid soils. They induce earliness; and where this is an object, as it must be so long as the disease continues, they may be applied with considerable advantage."—Thomp.
Propagation.—"This is almost universally from tubers; the seed being seldom sown, except for the production of new varieties. With many it is a doubtful question, whether the tubers cut, or planted whole, yield the greater return. From experiments made in the garden of the London Horticultural Society at Chiswick, it was found, on the mean of two plantations,—one made early in the season, and the other about one month later,—that the produce from cut sets exceeded that from whole tubers by nearly one ton per acre. In the latter planting, the produce from whole tubers was somewhat greater than that from single eyes: but, in the early plantation, the cut sets gave nearly two tons per acre more produce than the whole tubers; the weight of potatoes planted being deducted in every case.
"Another important consideration is, whether small tubers or large ones should be employed for making sets; for if, by using the former, an equally good crop could be obtained, a considerable saving in the expense of sets would be effected. Large tubers, however, are preferable, for the following reasons: In all plants, large buds tend to produce large shoots; and small or weak buds, the reverse. Now, the eyes of potatoes are true buds, and in small tubers they are comparatively weak: they consequently produce weak shoots, and the crop from such is inferior to that obtained from plants originating from larger tubers, furnished with stronger eyes; and this conclusion has been justified by the results of actual experiments.
"The part of the Potato employed for planting is not a matter of indifference. It was found, by an experiment made in the garden of the Horticultural Society, that sets taken from the points of the tubers, and planted early in the season, yielded at the rate of upwards of three tons per acre more produce than was obtained from employing the opposite end of the tubers. In a plantation made a month afterwards, the difference was much less, but still in favor of the point, or top end, of the Potato."—Thomp.
With regard to the quantity of seed per acre, great diversity of opinion exists among cultivators. Much, of course, depends on the variety, as some sorts not only have more numerous eyes, but more luxuriant and stronger plants, than others. Of such varieties, a much less quantity will be required than of those of an opposite character. From a series of experiments carefully made for the purpose of ascertaining the amount of seed most profitable for an acre, it was found that from six to eight bushels, if planted in hills, answered better than more: for, when too much seed was used, there were many small tubers; and where the tubers had been divided into very small parts, or single eyes, the plants were more feeble, and the yield less in number and weight, though usually of larger size.
Methods of Planting and Cultivation.—Potatoes are usually planted either in hills or ridges; the former method being the more common in this country. If planted in hills, they should be made from three feet to three and a half apart; the distance to be regulated by the habit of the variety under cultivation. If in ridges or drills, they may be made from two and a half to three feet apart; although some of the earlier and smaller kinds may be successfully grown at eighteen or twenty inches.
"Of sets formed by the division of an average-sized tuber into four parts, three may be allowed a hill; or, if planted in drills, the sets may be placed from seven to twelve inches asunder,—the distance to be regulated by the habit or size of the plant. On light, warm land, the sets should be covered about four inches in depth; but in wet, cold soil, three inches will be sufficient.