The Potato - With Information on Varieties, Seed Selection, Cultivation and Diseases of the Potato

THE POTATO

THE potato (Solanum tuberosum) was introduced from South America in the sixteenth century, but in those early days it was regarded rather as a curiosity than as an article of commerce, and it was not until about two centuries later that it was cultivated to any extent on a field scale.

As a producer of human food the potato is the most valuable crop grown in this country; it is cheap, and its dietetic value is considerably higher than was for a long time supposed. As a food for stock, especially pigs, it is of great importance, but because only a certain proportion of the crop is marketable and there is a considerable residue of diseased, damaged, and small tubers, which can be used only as stock food, it is not customary to cultivate the crop for this purpose. Boiled potatoes will develop acidity and ensile quite satisfactorily if they are packed tightly in a pit, tank, or other suitable container. The silage can be used for pigs and poultry when fresh potatoes are not available.

The potato crop has, however, a number of disadvantages. Its bulky nature makes it not only costly but difficult to market, and for this reason, even where the soil is suitable, very few potatoes are grown at any great distance from market centres. Again, even where a ready market is at hand, the large number of workers required for timely planting and harvesting restricts cultivation (on a large scale) to districts where casual labour is available. The crop was formerly very speculative, the yield being variable and the demand very inelastic, so that in years of high yield the market was glutted and prices fell to an unprofitable level. Prices are now fixed in advance and a market is assured, though the grower cannot always sell at the time he would prefer.

Quality of Potatoes.—The farmer, of course, requires a variety that will produce the greatest possible yield per acre, but he must also consider the buyer’s point of view or his crop will not meet with a ready sale. Apart from yield, the most important points are keeping quality and resistance to disease. Potatoes have to be stored for considerable periods, and it is disastrous if a large proportion decays or deteriorates in the clamp, as a good crop may in this way be reduced to an inferior one, and the expense of picking over diseased tubers is extremely heavy. Not only should the variety be capable of resisting disease and decay in the pit, but it should withstand the effects of the many and serious pests that beset it in the field, the most devastating of which are blight, wart disease, and the virus or degeneration diseases. No varieties yet in general cultivation are immune from blight, though many are resistant in greater or less degree. Moreover there is real promise that completely immune forms may be produced by hybridization between cultivated varieties and various wild species of Solanum. As regards Wart disease, it is fortunate that many completely immune varieties have been produced, so that it is possible to grow healthy crops on land that is heavily infested with the disease. For general economy it is also advisable to obtain varieties that develop their tubers at a suitable depth below the surface; if they protrude above the soil they become greened by the light and are then difficult to sell, while if too deep they are difficult to get out with an ordinary potato digger and, apart from the numbers that are sliced and damaged, many may be left in the ground to become a source of trouble in the following crops. The potato is the principal cleaning crop in the rotation of many farms, and a variety that develops a large amount of surface growth and leafage is most efficient as a smotherer of weeds, and most likely to leave the soil in a clean condition. There are varieties that cannot be cut for seed as they do not grow well from cut sets, while at the other extreme there are potatoes that give excellent yields when cut to a single eye.

From the point of view of the consumer the cooking quality of the variety is most important. In England, white-fleshed sorts that become mealy on boiling are generally the most popular for the ordinary domestic trade. On the Continent yellow-fleshed potatoes possessing a waxy texture are preferred. Varieties that produce either very large or very small tubers are not in demand, and varieties that are irregular in shape or deep in the eye, and are consequently difficult to peel without occasioning considerable loss, are never popular. The colour of the skin varies through a wide range—purple, red, pink, red-eyed, russet, and white all being common, but colour does not matter much when the other qualities of the variety are satisfactory. The shape may be round, oval, or kidney, but this is of little importance in the domestic trade provided the tubers are regular. For the chipping trade, which absorbs an enormous tonnage, the potato should make a firm chip that turns golden brown on frying and stays firm. As a rule the best boiling varieties are also the best for frying and absorb least fat. The potatoes should also be without sunken eyes and of regular shape—preferably round—so that they can be dealt with efficiently by peeling machines. Blemished tubers that require hand trimming are greatly disliked.

Apart