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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

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manent roots about one and a half inches below the surface.

Blossoming, Tuber Formation, and Hilling.Potatoes are hilled about the time they come into bloom, and this is the time that tuber formation is beginning. The ancestral type of potato developed seed about this time and died; the tendency acquired by cultivation is to throw all the reserve material into tuber production. These reproductive processes cause a severe drain upon the plant's energies, and the fortnight immediately following the blossoming period is therefore a peculiarly critical time for the plant, during which time its life hangs in the balance. At this time it is subject to extreme heat, and may be injured; also insects, fungi, etc., may attack it, and, to add to its troubles, cutting off a lot of its roots, either just before or about this time, is no doubt the common cause of a decline from which the plant never recovers. Even tuber formation, without the influence of other agencies, may cause a plant to die. The importance of studying the condition of the plant at this time will be appreciated when it is remembered that the entire crop of salable tubers is formed after this critical period is past, and full success with the crop depends upon retaining the plant healthy for from one to three months after the blossoming period. During August, in one case,' the crop of potatoes increased at the rate of over 50 bushels, or over 3,000 pounds, weekly per acre. The importance of avoiding checking growth preparatory to or during such a time is evident.

1 Ver. Bul. 72, p. 5.

CHAPTER III.

SOILS

THE soil considered best is a deep, mellow, freeworking loam, grading either to a sandy loam or clay loam, although the crop may be raised on lighter or heavier soils, provided the latter are drained. Tile drainage should be resorted to, if necessary, to reduce the water table to from 3 feet 6 inches to 4 feet below the surface.

Some reasons for selecting a light, sandy, or gravelly loam for the crop are : 1. Such soils can be worked early in spring, and gotten

ready for early planting, if desired ; 2. The lighter soil becomes warm more readily in the

spring than a heavier soil, and germination of the tuber and growth of the plant proceeds more

rapidly ; 3. They can be easily worked, and placed and main

tained in good tilth without a heavy labor bill ; 4: The effects of the manures and fertilizers applied

are generally perceptible for a longer period of

time than on lighter soils; 5. The potatoes grown on such a soil usually come out

bright and clean, smooth and of more uniform size — important factors when they go on the market;

6. Light soils usually produce potatoes of better qual

ity, because they tend to shorten the growing period by cutting off the moisture supply, and thus

forcing the potatoes to mature earlier; 7. Those grown on well-drained sandy loam soils 11:su

ally keep better than those grown on stiff clay

soils. Aroostock County, Maine, is famous for its potatoes. Its soil presents a gently rolling surface, and is composed essentially of drift deposited during the melting of the ice after the ice age, and resting on a stratum of limestone, which in many places comes to the surface. The soil partakes of the general nature of drift containing a considerable portion of sand and the usual amount of organic matter. It is peculiarly suited to potatoes, because it does not pack after hard rains nor during periods of drouth. Its open and porous nature permits the free development of tubers and the ramification of the roots. The soil was originally covered with a growth of hard and soft woods, consisting chiefly of maple, cedar, birch, white poplar, spruce, hemlock, and pine. The forest growth was dense, and in clearing large quantities of ashes were produced, which fitted the virgin fields particularly for the production of large crops of potatoes. After a few years of cultivation, the crop-producing power of the soil showed a diminution, and to-day applications of farm manures and commercial fertilizers containing a large percentage of potash are resorted to. Analyses of Maine soils show that they are silicious, contain considerable organic matter, and are reasonably rich in lime and magnesia, which seem to be essential constituents of a soil suited to the growth of potatoes. The potash is also in fair quantity, but not sufficient to produce maximum crops. The famous potato-growing counties of Wisconsin, Portage, Waushara, and Waupaca had over 60,000 acres in potatoes in 1899, and these are as important to the Central States as Aroostock County, Maine, is to the Eastern States. The soil is glacial drift, some of it being made up of level deposits of sand and gravel covered with a light loam. The sand is usually underdrained by a bed of coarse gravel. Sandy loams prevail. Clayey loams occupy some areas, but are not prevalent. The average yield is 100 bushels per acre.

a V. S. D. A., Div. of Chemistry, Bul. 58, p. 5-8.

On Long Island, N. Y., the chief potato soils on the south side of the island are light silt loams underlain either by gravel or sand, while gravelly till is the main type on the northern side. The yields vary from 80 to 250 bushels per acre.

The Influence of Soil on Different Varieties.Professor Buffum,' of Wyoming Experiment Station, reported on eight varieties grown on each of two kinds of soil represented on the experiment farm. The soil and crops were treated alike. Plat 1 is bench-land above the river, and is a deep red colluvial soil containing little humus. Plat 2 is bottom-land next the river, and is a black soil containing a large amount of humus.

1 Wyo. Bul. 32, p. 6.

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