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are, their character, and requirements. Examination of the roots of Early Ohio potatoes,1 made July 5, 1899, forty-three days after planting, about the time the crop received its third cultivation, showed that at this time there was little growth of fibrous roots-only the skeleton system supplied with numerous delicate root hairs. The seed tuber appeared to be sound and whole, but on closer examination it proved to be but a shell. Only a few eyes on the upper side of each tuber produced shoots; thus one hill produced three stalks from two eyes, and another had seven stalks springing from five eyes. The latter plant had more numerous but smaller roots than the former. Twenty-five small potatoes were set on the first plant, the largest of which were the size of a large pea. At this stage of development the main portion of the roots was in the surface eight inches, a few roots reached to the depth of eighteen inches, but the greatest root growth was in a horizontal direction. The roots from each hill had already met and interlaced, some having reached a length of two feet, the plants being three feet apart. At six inches from the hill some of the main lateral roots were but two and one-quarter inches from the surface of the ground, while midway between the rows their depth was barely three inches from the surface.

Further examination of Early Ohio potatoes seventytwo days after planting, when the tubers were nearly full size, showed that the main root growth was in the upper foot of soil; several of the large horizontal roots were within three inches of the surface, and one was but one inch deep. Some of the vertical roots reached

1 N. Dak. Bul. 45, p. 541.

[graphic]

FIG. 5-PLANT OF VERMONT GOLD COIN (VIEWED FROM ABOVE)

Grown under field conditions, 1904. There are ten good-sized tubers, weighing 31⁄2 pounds. The space occupied
by the tubers averaged about ten inches on all sides from the center. In this variety, during the past year, the
tubers were distributed all round the stem. In some varieties they tend to form on one side only.

FIG. 6-PLANT OF VERMONT GOLD COIN (SIDE VIEW)

Same plant as in Fig. 5, showing how completely the soil is filled with roots. The tubers were all well below
ground, the majority being between two and five inches. The roots extended outward two feet from the centre
of the plant, and downward to a depth of over three feet. Observe the potato bug about seven inches below the
surface. It was uncovered at this place.

[graphic]

a depth of two and a half feet. The deep-growing roots are very tender and brittle and easily broken, differing in this respect from corn roots. The horizontal roots send out vertical branches, which often descend to a depth of two feet or more.

Shallow tillage, such as hand-hoeing without hilling, retains all the roots. Moderately deep tillage

with a five-tooth single horse-cultivator and slight hilling destroys practically all the surface roots, and undoubtedly interferes seriously with the plant's development; while with deep tillage nearly all the long horizontal roots are destroyed, and with them all their numerous vertical branch-roots with their intricate system of fibres and root hairs, by which the potato receives its food. In very heavy soils it may be wise to plant potatoes shallow and then hill them, but in most soils it is better policy to plow deep, plant fairly deep, and give shallow flat cultivation. With deep tillage the roots nearest the surface were at a depth of seven inches, while in the case of those receiving shallow tillage the bulk of the horizontal roots were in the surface seven inches. The hilling covers the potatoes and prevents them from sunburning, and this seems to be all the benefit received. The loss of roots is very hurtful, and takes place at a time when the plant can least afford to suffer injury. Experiments conducted at Vermont Experiment Station' show that during the last weeks of growth the weekly increase in weight of tubers is at its maximum, and that checks when the tubers are approaching maturity depress the yield cor. respondingly.

1 Ver. Bul. 72, p. 5.

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A sample of Early Ohio potatoes taken ninety days. after planting, when the vines were beginning to die and the tubers were nearly ripe, showed that the roots penetrated to a depth of over two and a half feet.' The branches from the main lateral roots had reached about as deep as those immediately under the hill, and the soil was filled with roots to a depth of about two and a half feet. The system of rooting is similar to that of corn, but the plant is not so good a forager, and the roots do not fill the soil so completely; hence, plants can be placed closer together.

Late varieties have a similar root system, but root more freely, more deeply (a depth of three and a half feet being common if the soil conditions will permit), and occupy the ground more completely; hence, require more room than early varieties.

At Cornell University, during 1904, many potatoes had horizontal roots in the surface inch of soil. All of these would be destroyed by moderately deep tillage.

Influence of Depth of Planting on Roots.Generally speaking, the new potatoes and the roots start out above the seed, although if an under eye of the potato produces the shoot the roots and tubers may develop at the side of the seed. Depth of planting has some influence on the depth at which the tubers will form, and may have some on the roots. The question deserves investigation. Many plants prefer to send out their roots at a uniform depth below the surface: thus, at Cornell University, wheat, whether planted six inches deep or one inch deep, will send out its per

1 N. Dak. Bul. 43, P. 544.

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