The 100USD Prize Essay on the Cultivation of the Potato Part 2

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 quant.i.ty 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.

It is found that plaster in contact with soil undergoes decomposition, part of the lime separating from the sulphuric acid, and magnesia and potash taking its place, quite contrary to the ordinary affinities.

These facts show that the action of plaster is very complex, and that it promotes the distribution of both magnesia and potash in the ground, exercising a chemical action upon the soil which extends to any depth of it; and that, in consequence of the chemical and mechanical modifications of the earth, particles of certain nutritive elements become accessible and available to plants that were not so before.

It is said plaster is of most benefit in wet seasons; such is not always the case. It is certainly beneficial to clover, wet or dry; so of potatoes.

A few years since, when the drought was so intense in this section as to render the general potato crop almost a total failure, the writer produced a plentiful crop by the use of plaster alone. On examination at the dryest time, the bottoms of the hills were found to be literally dust, yet in this dust the tubers were swelling finely: the leaves and vines were of a deep rich green, and remained so until frost, while other fields in sight, planted with the same variety, but not treated with plaster, were brown, dead, and not worth digging. That gypsum attracts moisture may be proved by plastering a hill of corn and leaving a hill by it unplastered; the dew will be found deposited in greater abundance on the plastered hill. But, according to Liebig, certain products of the chemical action of plaster enter into and are incorporated with the structure of the plant, closing its breathing pores to such an extent that the plant is enabled to withstand a drought which would prove fatal to it una.s.sisted.

Certain it is that plaster renders plants less palatable to insects, and, so far as the writer's experiments extend, it is fatal to many of the fungi family. To obtain the best results, the vines of potatoes should be dusted with plaster as soon as they are fairly through the soil, again immediately after the last plowing and hoeing, and, for reasons hereafter given, at intervals throughout the whole growing season. The first application may be light, the second heavier, and thereafter it should be bountifully applied, say two hundred pounds per acre at one sowing.

THE POTATO-ROT--ITS CAUSE

The year 1845 will ever be memorable by its giving birth to a disease which threatened the entire destruction of the potato crop, and which caused suffering and pecuniary ruin to an incredible extent throughout Europe.

The potato, at the time of the appearance of the potato disease, was almost the sole dependence of the common people of Ireland for food.

That over-populated country experienced more actual suffering in consequence of the potato disease than has any other from the same cause. Although this disease has never, in this country, prevailed to the same ruinous extent that it has in some others, yet we are yearly reminded of its existence, and in some seasons and localities its destructive effects are seriously apparent.

The final or culminating cause of the disease known as the "potato-rot"

is _Botrytis (peronospora) infestans_. This may be induced by many and various predisposing causes, such as feebleness of const.i.tution of the variety planted, rendering them an easy prey to the disease; by planting on low, moist land, or on land highly enriched by nitrogenous manures, causing a morbid growth which invites the disease; also by insects or their larvae puncturing or eating off the leaves or vines. But by far the most wide-spread and most common cause of the disease is sudden changes of atmospheric temperature, particularly when accompanied by rain.

Drought, though quite protracted and severe, unless accompanied by strong drying winds, and followed by sudden and great reduction of temperature, seldom affects the potato seriously. It is not uncommon in the Northern States, during the months of August and September, for strong westerly winds to prevail for many days in succession. These winds, coming from the great American desert, are almost wholly devoid of moisture, and their aridity is often such that vegetation withers before them as at the touch of fire. Evaporation is increased in a prodigiously rapid ratio with the velocity of wind. The effects of the excessive exhalation from the leaves of plants exposed to the sweep of such drying winds are at once seriously apparent.

When these winds finally cease, the atmosphere has a low relative humidity, not enough moisture remains in the air to prevent radiation; the heat absorbed by the earth through the day is, during the bright, cloudless night, rapidly radiated and lost in s.p.a.ce, and a reduction in temperature of twenty to thirty degrees is the consequence.

In the first place, the potato-vines suffer by excessive exhalation; in the second, by sudden reduction of temperature, and, though not frozen, their functions are much deranged, and their vitality greatly enfeebled.

To use a common expression, the plant "has caught a violent cold that has settled on the lungs."

The leaves (which are the lungs of plants) now fail to perform their functions properly. The points of many of the leaves turn brown, curl up, and die.

The ascending sap, not being fully elaborated by the diseased leaves, oozes out through the skin of the stalk in a thick, viscous state, and the plant to all appearance is in a state of consumption.

At this stage the ever-present minute spores of the _Botrytis infestans_ eagerly pounce on the sickly plant, fastening themselves on its most diseased parts. The _Botrytis infestans_ is a cryptogamous plant, and is included in the Mucidineous family, (moulds.) It is a vegetable parasite preying upon the living potato plant, like lice or other animal parasites upon the animal species.

At first this mould forms webby, creeping filaments, known in botanical language as mycelium. These root-like fibres then branch out, sending out straight or dec.u.mbent articulated stems. These bead-like joints fill up successively with seeds or spores, which are discharged at the proper time to multiply the species.

Under favorable conditions of warmth and moisture, the mycelium spreads very rapidly. Spores are soon formed and matured, to be carried to plants not yet infected. Rains also wash the seminal dust down the plant, causing it to fasten and grow on the vine near the ground. The roots of the parasite penetrate and split up the stalk even to the medullary ca.n.a.l.

These roots exude a poisonous substance, which is carried by the elaborated descending sap down to the tubers, and as the largest tubers require the largest amount of elaborated sap for their development, they will, consequently, receive the greatest quant.i.ty of the vitiating principle, and will, on digging, be found a ma.s.s of rottenness, when the smaller ones are often but slightly affected. The _Botrytis infestans_ can not gain a lodgment on vines that are truly healthy and vigorous, high authority to the contrary notwithstanding.

Healthy varieties, growing in a sheltered situation on dry, new soil, to which no nitrogenous manures have been applied, can not be infected, though brushed with other vines covered with the fungus. Different varieties, and sometimes different members of the same variety, are not always alike affected by the disease, though growing in the same hill.

As will be noticed, the potato disease is rather an effect than a cause, and appears to have been designed to prevent members enfeebled by accident or otherwise from propagating their species by putting such members out of existence. Ozone, supposed to be a peculiar form of oxygen, is exhaled from every part of the green surface of plants in health, and effectually repels the attacks of mildew; but it is found that when the atmosphere is very dry, or, on the other hand, very humid, plants cease to evolve ozone, and are therefore unprotected. Winds from the ocean are strongly ozonic, and it is ascertained that plants growing on soil to which salt has been applied evolve more ozone than others.

Hence the benefit derived from the use of salt on potato lands.

The "Black knot," another species of fungus that attacks the branches of the plum and Morello cherry, operates very similarly to the potato mildew. The roots of the parasite penetrate and split up the cellular tissue of the branch on which it fastens, and if the limb be not promptly amputated, the descending sap carries the deleterious principle through the whole system, and the following year the disease appears in a greatly aggravated form in every part of the whole tree. The remedy in this case is prompt amputation of the part diseased on its first appearance, and a judicious application of salt to the soil.

Common salt, to a certain extent, is as beneficial to some plants as to animals; and every intelligent farmer knows that if salt be withheld from the bovine _genus_ for any considerable length of time, the general health droops and parasites are sure to abound. The object of nature in bringing into existence the large family of mildews, each member of which is a perfect plant in its way, and as capable of performing its functions as the oak of the forest, was undoubtedly to prevent propagation from sickly stock, and by the decomposition of feeble plants to make room and enrich the soil for the better development of healthier plants. But it by no means follows that, because a plant is attacked by mildew, it must necessarily be left to die, any more than it follows that, because an animal is infested with vermin, it should be let alone to be eaten up by them.

REMEDY FOR THE POTATO-ROT.

In treating for the potato-rot, "an ounce of prevention is worth a pound of cure;" for when leaves or vines are once dead, they ever remain so.

All that can be done for potatoes infested is to stop the mildew from spreading, by destroying it where it is, and by strengthening "those things which remain." The writer was led to the adoption of the remedy proposed by experiments made upon fruits.

Every one who has an apple or pear-orchard must have observed that mildew of fruit supervenes after some sudden change of temperature, especially when accompanied by rain. Spots of mildew invariably form on the young fruit immediately after a cold night, when the thermometer has indicated a change of twenty to twenty-five degrees. This growth of mildew takes place when the apples are of various sizes, from the earliest formation to the size of large marbles. These fungous growths appear as dark-colored spots, which arrest the growth of the apple immediately beneath, causing it to become distorted, while the expansion and contraction bring on diseased action, which results in the cracking and general scabbiness of the fruit.

Knowing that dry-rot (_Merulius Lachrymans_, Schum,) another species of fungus, was remedied by an application of sulphuric acid, I thought it might possibly destroy the fruit mildew. An application of plaster, (gypsum,) which is composed of lime and sulphuric acid, was made with the happiest results. It was found that an apple dusted with ground plaster at its first formation remained free from mildew and came to maturity, while apples growing by it, but not so treated, became scabby and worthless. It was also ascertained that a thorough application of plaster destroyed the mildew after it had formed, and that such fruit came to maturity. On the potato mildew, so far as the writer's experience extends, plaster, if applied early, is a perfect prevention, and if not delayed too long after the disease appears, is a certain remedy.

The vines should be watched closely, and on the first appearance of the disease plaster should be applied; not merely sowing it broadcast, but dashing it over and under the vines, bringing it in contact with the stalks, using a handful to three or four hills. Plaster for this purpose should be very dry and powdery, and should be applied when the air is still. One application is seldom sufficient; it should be renewed as often as circ.u.mstances require. Examine the vines about three days after a cold night, or about the same length of time after a heavy rain. If the leaves begin to curl and wither, apply plaster at once; and, in short, whenever the vines show any signs of drooping, be the cause bites of insects, excessive aridity, or excessive humidity of the atmosphere, or sudden change of temperature, drooping from any cause whatever indicates the approach of mildew, which should be promptly met with an application of plaster. As before stated, plaster the vines as soon as they are up, again after the last plowing and hoeing; after that, one, two, or three times, as circ.u.mstances indicate.

By this method the vines are kept of a bright lively green, and the tubers are kept swelling until growth is stopped by frost. Another point gained is, potatoes so grown are so sound and free from disease as to be easily kept for spring market without loss by rot.

Whether the surprising effects of plaster on the potato mildew is attributable to the sulphuric acid, to the lime, or to its simply being a dust, has not been determined. It is well known that the fruits of a vineyard or orchard in close proximity to a dusty and much frequented highway are remarkably free from mildew, which can only be due to dust settling on the trees and fruit. But in the case of plaster, the writer is inclined to believe its efficacy is mainly due to the sulphuric acid, probably a.s.sisted by the lime in a state of dust. Be this as it may, it matters not. The result is all that can be desired; the remedy is easily applied, costs but a trifle, and a single season's trial is all that is needed to convince the most skeptical grower of its merits.

DIGGING AND STORING

Is full half the labor of growing and securing a crop of potatoes.

Digging is a long, laborious task. Many small fortunes are sunk yearly by inventors in experimenting with and constructing "potato-diggers;"

but, so far, no machine has done the work properly except under the most favorable circ.u.mstances. Stones, vines, and weeds are obstacles not yet fully overcome. Many tubers are left covered with earth, and so lost; and besides, some machines so bruise the potatoes in digging as to injure their appearance and keeping qualities. Undoubtedly, the day will come when the great bulk of potatoes will be dug well and rapidly by horse-power; but until that day does come, the potato-hook must be used.

Much of the back-ache and general unpleasantness incident to digging is avoided, or greatly mitigated, by having the potatoes large and sound, turning out a peck to the hill, especially if the digger is the owner of the crop.

Digging should be done only when the ground is dry, that the potatoes may come out clean and bright. A small plow, to turn a light furrow from each side of the rows, is some help. Pull up the vines, and lay them down so that they will be covered by the dirt dug from the hill.

Commence on one side of the hill; press the hook or hoe down, so that it will reach a trifle below the potatoes, and draw the implement firmly toward you. Repeat the operation, each time placing the tool a few inches further in or across the hill, until the whole hill is dug. By this method the potatoes will not be bruised; whereas, if the digging be commenced in the centre of the hill, many potatoes will be sacrificed and much injured. Potatoes should be picked up as soon and as fast as dug; and immediately covered with straw or other material, to protect them from the light. A few hours' strong sunshine will ruin the best potato ever grown. Light changes the natural color to green, and renders the potato so bitter and unpalatable as to be wholly unfit to eat.

Owing to the inconsiderate way in which potatoes are often dug, and the light to which they are exposed while being transported to and while in market, the denizens of our cities seldom, if ever, taste this vegetable in its greatest excellence. If to be stored in the cellar, the potatoes should be left in the field, in heaps covered with straw, until the sweating is over, and then be removed to the cellar and lightly covered with dry sand, or earth, just sufficient to exclude the light.

If to be buried in the field, choose a dry, sideling place; sc.r.a.pe out a slight hollow, by merely removing the surface soil with a hoe; into this, pile ten to twelve bushels; place the potatoes properly, and cover them carefully with clean straw, six inches deep; cover over the straw with four or five inches of earth, except a small opening at the top; over this opening place a board or flat stone, elevated a little on one side, to lead off the rain.

Let them remain so until the sweating is completely over, or so long as prudence will permit; and when cold weather fairly sets in, add more earth to keep from freezing, leaving only a wisp of straw protruding through to carry off any foul air that may be generated.

Where the winters are intensely cold, it is best to cover but lightly with earth, say five or six inches deep; and when freezing is becoming severe, spread over the heap buckwheat straw, or coa.r.s.e manure, to the depth of six inches. There is danger in covering very deep at first, especially if the autumn should prove warm. If kept too warm, rot is sure to ensue. Experience shows that any vegetable keeps better buried in pits that contain not more than ten or twelve bushels each.

Where large quant.i.ties are to be buried, it is advisable to open a long, shallow, broad trench, leading up and down a hill, if possible, to secure good drainage. Commence, at either end, by placing a desirable quant.i.ty of potatoes as soon as dug; next to these put a little straw; against the straw place about six inches of earth; then more straw and more potatoes; and so keep on until the trench is full. A few furrows plowed on each side a.s.sist in covering; and make a drain to lead off the rains, which is a matter of the first importance. By this method each lot of potatoes is kept separate; and any section can be opened at any time to be taken to market, without endangering the others.

Potatoes buried properly are usually of better flavor in the spring than it is possible for potatoes to be which are kept in a common cellar.

And here let me add that, if leaves from the woods be used instead of straw, to cover potatoes to be buried, such potatoes will be of better flavor; and further, if nothing but dry earth comes in contact with them, they will be better still. Straw is used for the twofold purpose of securing an air-chamber to keep out frost, and to prevent the earth from mingling with the tubers on opening the pits.