This section is from the book "The Potato: A Compilation of Information from Every Available Source", by Eugene H. Grubb, W. S. Guilford. Also available from Amazon: The Potato: A Compilation Of Information From Every Available Source.
The bulk of the potato crop of the world is grown in what may be called "short season" territory, and by that is meant that there is danger to the crop from frost at both ends of the growing period.
Because of this the main harvesting care is "weather." The potatoes must be out of the ground and cared for before the heavy freezes.
Potatoes that are not fully matured at the time in the fall of the year when frost threatens must be dug green.
Practically all large acreages of potatoes are now dug or "lifted" by machinery. There are several excellent horsepower potato diggers. These have a projecting "snout" or flat shovel which runs under the row, lifting the entire mass of dirt which contains the tubers to an apron made of iron rods. The dirt falls through these iron rods and the potatoes are passed along - to be finally dropped on the top of the ground.
The process of harvesting potatoes has passed through the same evolution as other farm operations. At first the tubers were dug by hand with a hoe or shovel, or "plowed out" with an ordinary moldboard walking plow. Then a pronged fork took the place of the hoe and shovel, and a flat nosed plow with wide double moldboard made of iron rods was used. With this sort of digger the dirt fell through and the potatoes were carried over.
To make a field trial of a machine in the particular character of soil it is to be used in is a safe way to select a digger.
Green, heavy tops clog a digger. Some pull the tops and haul them off the field in order to make digging easier. A simpler way to remedy this difficulty is to run a harrow over the field - in the same direction that the digger will run. This straightens out the tops and they make less trouble. A long spike tooth harrow, with teeth slanted back, should be used.
An essential in digging potatoes is to let the tubers lie on the top of the ground for two or six hours to dry out any dirt clinging to them and toughen the skin. In this way the potato is less liable to bruise in the after handling and much less dirt is carried from the field.
Some potato digging machinery manufacturers have been trying to perfect a device for sacking as well as digging potatoes. It would seem that the "drying out" in the sun, previously mentioned, is of such importance as to make this attachment impractical.
In the districts in the western part of the United States potatoes are picked by hand into pails or baskets and deposited in "half sacks." Regular potato sacks are half filled and pickers are paid a stated price for filling into each one bushel. Half sacks are used to make handling easier. (Filled and sewed, the sack holds about two bushels, or 120 pounds.) The usual price is three cents per bushel for picking.
These small sacks are hauled from the fields to the cellar and there the potatoes are spread out in thin layers. These layers gradually become thicker as the cellar is filled, but it is best not to fill any one part of the cellar too deep at one time.
Sometimes potatoes are run over a sorter in the field and the marketable ones either taken direct to the shipping point or stored separately in the cellar. Potatoes marketed from the field weigh 10 per cent, more than those taken to the cellar and rehandled. If weather conditions are urgent, and help scarce, this can often be done to better advantage in the cellar.
A machine digger will handle four to six acres a day.
Irrigated districts, where there is no rain during the growing and digging season, have a considerable advantage in the ability to turn out a product free from mud. This is emphasized by a study of the potato bulletins of the Eastern States and Europe, where the grower is admonished to "lift early," and in dry weather if possible.
Potatoes should always be dug when the vines die - frost conditions must indicate how long before that time. As long as the vine is green, the tubers are growing. One experiment shows that one third of the merchantable part of a crop was made (developed) in the last thirty of the 120-day period from planting to digging.
Careful handling pays at every stage of the harvesting process. A cut or badly bruised potato decays readily and every tuber lost reduces the profits.
While the toughening described is beneficial - especially as regards bruising in handling - the potato must not be left too long in the sun or it will turn green and be unfit for food.
In gardens, "grabbling" is sometimes practised, especially in Germany. This is to dig carefully into the sides of a hill of potatoes and remove the largest tubers for early use or market. If carefully done this will cause no injury to the smaller tubers.
An excellent description of handling potatoes in the field in the East is given by Alva Agee, in "Bulletin No. 105"of the Pennsylvania Department of Agriculture. It follows:
In great potato-growing sections years ago it was a common practice to pour bulk potatoes into wagon-beds, and to shovel them out into baskets when unloading. This primitive method was laborious, and did injury by bruising the tubers. Potato boxes have now come into common use in many districts. They are made of light material, preferably basswood or similar wood. The boards for sides and bottom should be three eighths inch in thickness, and the ends one half. The size of box should be such that it will contain 2,688 cubic inches, level full. The legal bushel measure for grain contains 2,150.4 cubic inches, and in measuring roots or potatoes the rule is to heap the half-bushel measure sufficiently to add one level peck to the two level half-bushels. Five level pecks, or 2,688 cubic inches, are the equivalent of two rounding half-bushels and of a level potato box rightly made. The following dimensions are the ones used by a leading manufacturer of these boxes: Twelve and one half inches deep, thirteen and one half inches wide, and sixteen inches long. This gives exactly 2,700 cubic inches. This size probably* is more convenient than any other that could be devised. The length of two boxes is near the width of the ordinary wagon-bed, leaving only room for the hands when putting them into position, and, when empty, one box can be placed inside of two others, economizing space. With high sideboards on the wagon-bed, it is convenient to tier up sixty bushels when drawing from the field to the cellar or to market, but the extensive grower may prefer a long platform that will hold twenty or more boxes in a single tier*