Prepare the ground by thorough plowing, making it decidedly mellow. Mark it out four feet apart each way, if to be planted in hills, by plowing broad, flat-bottomed furrows about three inches deep. At the crossings drop three pieces of potato, cut, as directed, in sections of two or three eyes each. Place the pieces so as to represent the points of a triangle, each piece being about a foot distant from each of the other two. If the cut side is put down, it is better; cover about two inches deep. Where land is free from stone and sod, the covering may be well and rapidly done with a light plow. Immediately after planting, sprinkle over and around each hill a large handful of unleached wood-ashes and salt, (a half-bushel of fine salt mixed with a barrel of ashes is about the right proportion.) If ashes can not be obtained, as is sometimes the case, apply instead about the same quantity of lime slacked in brine as strong as salt will make it. The potato from its peculiar organization has a hungering and thirsting after potash. Wood-ashes exactly meet its wants in this direction. Lime indirectly supplies potash by liberating what was before inert in the soil. Salt in small quantities induces vigorous, healthy growth. To obtain the best results, the ashes or lime should be covered with about half an inch of soil. This plan of manuring in the hill is recommended only in cases where the fertilizers named are in limited supply, and it is desirable to make the most of them. Maximum crops have been obtained by using the fertilizers named in the manner described; but where they can be obtained at low prices, it is certainly advisable, and requires less labor, to apply all three, ashes, lime, and salt, broadcast in bountiful quantities, and harrow it in before the ground is marked out for planting.
CULTIVATION.
If weeds are expected, pass a light harrow over the rows just before the vines are ready to burst through; this will disturb them and render them less troublesome. As soon as the tops are two inches high, run a corn-plow five inches deep close to the hills, turning the furrows from the rows.
Plow both ways twice between the rows, finishing on the rows running east and west, which will give the sun's rays a better chance to warm the ground properly. Standing on the squares of earth, warmed on all sides by the air and sunlight, the potatoes will grow amazingly. Just as soon as the tops have attained a height of six or seven inches, hitch a strong horse to a two-horse plow, and turn furrows fully seven inches deep midway between the rows to the hills. Plow twice between the rows both ways; and if the ground be a side-hill, turn the first furrow between the rows up-hill, which will leave the rows in better shape. Hoeing is often wholly unnecessary; but where, from weeds or poor plowing, it is needed, draw mellow earth to the plants with the hoe, keeping the top of the hills somewhat hollow to catch the rains. Then, so far as stirring the soil is concerned, let it alone.
After potatoes are fairly up, their cultivation should be crowded through with all possible speed, or at least as rapidly as the growth of the tops will permit.
If the last plowing be deferred until the vines are large, a large proportion of small potatoes is sure to be the consequence. After a certain stage of growth, new tubers are formed each time the soil is disturbed; these never fully develop, they rob those first formed, and make the crop much inferior to what it should be. By the mode of culture described, the ground is made warm and mellow close up to the seed-potatoes, the roots soon fill the whole hill, and tubers are formed that have nothing to do but to grow. The writer is aware flat culture has strong advocates; but, after many experiments, he is convinced that hills are much the best.
PLASTER.
However much lime or other fertilizers may be applied to the soil, still great benefit is derived from the use of plaster, (sulphate of lime.)
After all, plaster is the main dependence of the potato-grower, a help on which he may rely with the utmost confidence. Astonishing results are obtained from its use, when applied in a proper manner. The writer has seen a field, all of the same soil, all prepared alike, and all planted with the same variety at the same time, on one half of which, that had no plaster, the yield was but sixty bushels per acre, and many rotten; the other part, to which plaster was applied in the manner hereafter explained, yielded three hundred and sixty bushels per acre, and not an unsound one among them.
The action of plaster is often puzzling. From the fact that where land has been strongly limed, a small quantity of plaster applied shows such decided benefit, there would seem plausibility in Liebig's theory that its effects must be traceable not to the lime, but to the sulphuric acid. The ammonia in rain-water in the form of carbonate (a volatile salt) is decomposed by plaster, the sulphuric acid having greater affinity for it, thus forming two new compounds, sulphate of ammonia and carbonate of lime. But as arable soil has the same property of absorbing ammonia from the air and rain-water, and fixing it in the same or even a higher degree than lime, there is only the sulphuric acid left to look to for an explanation of the favorable action of plaster on the growth of plants.