Analyst.Carbon.Hydrogen.Oxygen.Nitrogen.1—Sphagnum, undecomposedWebsky49.886.5442.421.162—Peach wood, undecomposedChevandier49.906.1043.100.903—Poplar wood, undecomposedChevandier50.306.3042.401.004—Oak wood, undecomposedChevandier50.606.0042.101.305—Peat, porous, light-brown, sphagnousWebsky50.865.8042.570.776—Peat, porous, red-brownJæckel53.515.9040.597—Peat, heavy, brownJæckel56.435.3238.258—Peat, dark red-brown, well decomposedWebsky59.476.5231.512.519—Peat, black, very dense and hardWebsky59.705.7033.041.5610—Peat, black, heavy, best quality for fuelWebsky59.715.2732.072.5911—Peat, brown, heavy, best quality for fuelWebsky62.546.8129.241.41
From this table it is seen that sphagnum, and the wood of our forest trees are very similar in composition, though not identical. Further, it is seen from analyses 1 and 5, that in the first stages of the conversion of sphagnum into peat—which are marked by a change of color, but in which the form of the sphagnum is to a considerable extent preserved—but little alteration occurs in ultimate composition; about oneper cent.of carbon being gained, and one of hydrogen lost. We notice in running down the columns that as the peat becomes heavier and darker in color, it also becomes richer in carbon and poorer in oxygen. Hydrogen varies but slightly.
As a general statement we may say that the ripest and heaviest peat contains 10 or 12per cent.more carbon and 10 or 12per cent.less oxygen than the vegetable matter from which it is produced; while between the unaltered vegetation and the last stage of humification, the peat runs through an indefinite number of intermediate stages.
Nitrogen is variable, but, in general, the older peats contain the most. To this topic we shall shortly recur, and now pass on to notice—
The ultimate composition of the compounds of which peat consists.
Below are tabulated analyses of the organic acids of peat:—
Carbon.Hydrogen.Oxygen.Ulmic acid, artificial from sugar67.104.2028.70Humic acid, from Frisian peat61.104.3034.60Crenic acid56.472.7440.78Apocrenic acid45.704.8049.50
It is seen that the amount of carbon diminishes from ulmic acid to apocrenic, that of oxygen increases in the same direction and to the same extent, viz.: about 21per cent., while the hydrogen remains nearly the same in all.
b.The mineral part of peat, which remains as asheswhen the organic matters are burned away, is variable in quantity and composition. Usually a portion of sand or soil is found in it, and this not unfrequently constitutes its larger portion. Some peats leave on burning much carbonate of lime; others chiefly sulphate of lime; the ash of others again is mostly oxyd of iron; silicic, and phosphoric acids, magnesia, potash, soda, alumina and chlorine, also occur in small quantities in the ash of all peats.
With one exception (alumina) all these bodies are important ingredients of agricultural plants.
In some rare instances, peats are found, which are so impregnated with soluble sulphates of iron and alumina, as to yield these salts to water in large quantity; and sulphate of iron (green vitriol,) has actually been manufactured from such peats, which in consequence have been characterized asvitriol peats.
Those bases (lime, oxide of iron, etc.,) which are found as carbonates or simple oxides in the ashes, exist in the peat itself in combination with the humic and other organic acids. When these compounds are destroyed by burning, the bases remain united to carbonic acid.
5.—Chemical Changes that occur in the formation of Peat.When a plant perishes, its conversion into humus usually begins at once. When exposed to the atmosphere, the oxygen of the air attacks it, uniting with its carbon producing carbonic acid gas, and with its hydrogen generating water. This action goes on, though slowly, even at some depth under water, because the latter dissolves oxygen from the air in small quantity,[2]and constantly resupplies itself as rapidly as the gas is consumed.
Whether exposed to the air or not, the organic matter suffers internal decomposition, and portions of its elements assume the gaseous or liquid form. We have seen that ripe peat is 10 to 12per cent.richer in carbon and equally poorer in oxygen, than the vegetable matters from which it originates. Organic matters, in passing into peat, lose carbon and nitrogen; but they lose oxygen more rapidly than the other two elements, and hence the latter become relatively more abundant. The loss of hydrogen is such that its proportion to the other elements is but little altered.
The bodies that separate from the decomposing vegetable matter are carbonic acid gas, carburetted hydrogen (marsh gas), nitrogen gas, and water.
Carbonic acid is the most abundant gaseous product of the peaty decomposition. Since it contains nearly 73per cent.of oxygen and but 27per cent.of carbon, it isobvious that by its escape the proportion of carbon in the residual mass is increased. In the formation of water from the decaying matters, 1 part of hydrogen carries off 8 parts of oxygen, and this change increases the proportion of carbon and of hydrogen. Marsh gas consists of one part of hydrogen to three of carbon, but it is evolved in comparatively small quantity, and hence has no effect in diminishing theper cent.of carbon.
The gas that bubbles up through the water of a peat-bog, especially if the decomposing matters at the bottom be stirred, consists largely of marsh gas and nitrogen, often with but a small proportion of carbonic acid. Thus Websky found in gas from a peat-bed
Carbonic acid2.97Marsh gas43.36Nitrogen53.67100.00
Carbonic acid, however, dissolves to a considerable extent in water, and is furthermore absorbed by the living vegetation, which is not true of marsh gas and nitrogen; hence the latter escape while the former does not. Nitrogen escapes in the uncombined state, as it always (or usually) does in the decay of vegetable and animal matters that contain it. Its loss is, in general, slower than that of the other elements, and it sometimes accumulates in the peat in considerable quantity. A small portion of nitrogen unites with hydrogen, forming ammonia, which remains combined with the humic and other acids.
After the foregoing account of the composition of peat, we may proceed to notice:
1.—The characters that adapt it for agricultural uses.
These characters are conveniently discussed under two heads, viz.:
Those which render it useful in improving the texture and physical characters of the soil, and indirectly contribute to the nourishment of crops,—characters which constitute it anamendmentto the soil (A); and
Those which make it a directfertilizer(B).
A.—Considered as an amendment, the value of peat depends upon
Its remarkable power of absorbing and retaining water, both as a liquid and as a vapor(I):
Its power of absorbing ammonia(II):
Its effect in promoting the disintegration and solution of mineral ingredients, that is the stony matters of the soil(III):and
Its influence on the temperature of the soil(IV).
The agricultural importance of these properties of peat is best illustrated by considering the faults of a certain class of soils.
Throughout the State of Connecticut, for instance, are found abundant examples of light, leachy, hungry soils, which consist of coarse sand or fine gravel; are surface-dry in a few hours after the heaviest rains, and in the summer drouths, are as dry as an ash-heap to a depth of several or many feet.
These soils are easy to work, are ready for the plow early in the spring, and if well manured give fair crops in wet seasons. In a dry summer, however, they yield poorly, or fail of crops entirely; and, at the best, they require constant and very heavy manuring to keep them in heart.
Crops fail on these soils from two causes, viz.;want of moistureandwant of food. Cultivated plants demand as an indispensable condition of their growth and perfection, to be supplied with water in certain quantities, which differ with different crops. Buckwheat will flourish best on dry soils, while cranberries and rice grow in swamps.
Our ordinary cereal, root, forage and garden crops require a medium degree of moisture, and with us it is in all cases desirable that the soil be equally protected from excess of water and from drouth. Soils must be thus situated either naturally, or as the result of improvement, before any steadily good results can be obtained in their cultivation. The remedy for excess of water in too heavy soils, is thorough drainage. It is expensive, but effectual. It makes the earth more porous, opens and maintainschannels, through which the surplus water speedily runs off, and permits the roots of crops to go down to a considerable depth.
What, let us consider, is the means of obviating the defects of soils that are naturally too porous, from which the water runs off too readily, and whose crops "burn up" in dry seasons?
In wet summers, these light soils, as we have remarked, are quite productive if well manured. It is then plain that if we could add anything to them which would retain the moisture of dews and rains in spite of the summer-heats, our crops would be uniformly fair, provided the supply of manure were kept up.
But why is it that light soils, need more manure than loamy or heavy lands? We answer—because, in the first place the rains which quickly descend through the open soil, wash down out of the reach of vegetation the soluble fertilizing matters, especially the nitrates, for which the soil has no retentive power; and in the second place, from the porosity of the soil, the air has too great access, so that the vegetable and animal matters of manures decay too rapidly, their volatile portions, ammonia and carbonic acid, escape into the atmosphere, and are in measure lost to the crops. From these combined causes we find that a heavy dressing of well-rotted stable manure, almost if not entirely, disappears from such soils in one season, so that another year the field requires a renewed application; while on loamy soils the same amount of manure would have lasted several years, and produced each year a better effect.
We want then toamendlight soils by incorporating with them something that prevents the rains from leaching through them too rapidly, and also that renders them less open to the air, or absorbs and retains for the use of crops the volatile products of the decay of manures.
For these purposes, vegetable matter of some sort is the best and almost the only amendment that can be economically employed. In many cases a good peat or muck is the best form of this material, that lies at the farmer's command.
I.—Its absorbent power for liquid wateris well known to every farmer who has thrown it up in a pile to season for use. It holds the water like a sponge, and, according to its greater or less porosity, will retain from 50 to 100 or moreper cent.of its weight of liquid, without dripping. Nor can this water escape from it rapidly. It dries almost as slowly as clay, and a heap of it that has been exposed to sun and wind for a whole summer, though it has of course lost much water, is still distinctly wet to the eye and the feel a little below the surface.
Its absorbent power for vapor of wateris so great that more than once it has happened in Germany, that barns or close sheds filled with partially dried peat, such as is used for fuel, have been burst by the swelling of the peat in damp weather, occasioned by the absorption of moisture from the air. This power is further shown by the fact that when peat has been kept all summer long in a warm room, thinly spread out to the air, and has become like dry snuff to the feel, it still contains from 8 to 30per cent.(average 15per cent.) of water. To dry a peat thoroughly, it requires to be exposed for some time to the temperature of boiling water. It is thus plain, as experience has repeatedly demonstrated, that no ordinary summer heats can dry up a soil which has had a good dressing of this material, for on the one hand, it soaks up and holds the rains that fall upon it, and on the other, it absorbs the vapor of water out of the atmosphere whenever it is moist, as at night and in cloudy weather.
When peat has once becomeair-dry, it no longer manifests this avidity for water. In drying it shrinks, losesits porosity and requires long soaking to saturate it again. In the soil, however, it rarely becomes air-dry, unless indeed, this may happen during long drouth with a peaty soil, such as results from the draining of a bog.
II.—Absorbent power for ammonia.
All soils that deserve to be called fertile, have the property of absorbing and retaining ammonia and the volatile matters which escape from fermenting manures, but light and coarse soils may be deficient in this power. Here again in respect to its absorptive power for ammonia, peat comes to our aid.
It is easy to show by direct experiment that peat absorbs and combines with ammonia.
In 1858 I took a weighed quantity of air-dry peat from the New Haven Beaver Pond, (a specimen furnished me by Chauncey Goodyear, Esq.,) and poured upon it a known quantity of dilute solution of ammonia, and agitated the two together occasionally during 48 hours. I then distilled off at a boiling heat the unabsorbed ammonia and determined its quantity. This amount subtracted from that of the ammonia originally employed, gave the quantity of ammonia absorbed and retained by the peat at the temperature of boiling water.
The peat retained ammonia to the amount of 0.95 ofone per cent.
I made another trial at the same time with carbonate of ammonia, adding excess of solution of this salt to a quantity of peat, and exposing it to the heat of boiling water, until no smell of ammonia was perceptible. The entire nitrogen in the peat was then determined, and it was found that the dry peat which originally contained nitrogen equivalent to 2.4per cent.of ammonia, now yielded an amount corresponding to 3.7per cent.Thequantity of ammonia absorbed and retained at a temperature of 212°, was thus 1.3per cent.
This last experiment most nearly represents the true power of absorption; because, in fermenting manures, ammonia mostly occurs in the form of carbonate, and this is more largely retained than free ammonia, on account of its power of decomposing the humate of lime, forming with it carbonate of lime and humate of ammonia.
The absorbent power of peat is well shown by the analyses of three specimens, sent me in 1858, by Edwin Hoyt, Esq., of New Canaan, Conn. The first of these was the swamp muck he employed. It contained in the air-dry state nitrogen equivalent to 0.58per cent.of ammonia. The second sample was the same muck that had lain under the flooring of the horse stables, and had been, in this way, partially saturated with urine. It contained nitrogen equivalent to 1.15per cent.of ammonia. The third sample was, finally, the same muck composted with white-fish. It contained nitrogen corresponding to 1.31per cent.of ammonia.[3]
The quantities of ammonia thus absorbed, both in the laboratory and field experiments are small—from 0.7 to 1.3per cent.The absorption is without doubt chiefly due to the organic matter of the peats, and in all the specimens on which these trials were made, the proportion of inorganic matter is large. The results therefore become a better expression of the power ofpeat, in general, to absorb ammonia, if we reckon them on the organic matter alone. Calculated in this way, the organic matter of the Beaver Pond peat (which constitutes but 68per cent.of the dry peat) absorbs 1.4per cent.of free ammonia, and 1.9per cent.of ammonia out of the carbonate of ammonia.
Similar experiments, by Anderson, on a Scotch peat, showed it to possess, when wet, an absorptive power of 2per cent., and, after drying in the air, it still retained 1.5per cent.—[Trans. Highland and Ag'l Soc'y.]
When we consider how small an ingredient of most manures nitrogen is, viz.: from one-half to three-quarters of oneper cent.in case of stable manure, and how little of it, in the shape of guano for instance, is usually applied to crops—not more than 40 to 60 lbs. to the acre, (the usual dressings with guano are from 250 to 400 lbs. per acre, and nitrogen averages but 15per cent.of the guano), we at once perceive that an absorptive power of one or even one-halfper cent.is greatly more than adequate for every agricultural purpose.
III.—Peat promotes the disintegration of the soil.
The soil is a storehouse of food for crops; the stores it contains are, however, only partly available for immediate use. In fact, by far the larger share is locked up, as it were, in insoluble combinations, and only by a slow and gradual change can it become accessible to the plant. This change is largely brought about by the united action ofwaterandcarbonic acid gas. Nearly all the rocks and minerals out of which fertile soils are formed,—which therefore contain those inorganic matters that are essential to vegetable growth,—though very slowly acted on by pure water, are decomposed and dissolved to a much greater extent by water, charged with carbonic acid gas.
It is by these solvents that the formation of soil from broken rocks is to a great extent due. Clay is invariably a result of their direct action upon rocks. The efficiency of the soil depends greatly upon their chemical influence.
The only abundant source of carbonic acid in the soil, is decaying vegetable matter.
Hungry, leachy soils, from their deficiency of vegetable matter and of moisture, do not adequately yield their own native resources to the support of crops, because the conditions for converting their fixed into floating capital are wanting. Such soils dressed with peat or green manured, at once acquire the power of retaining water, and keep that water ever charged with carbonic acid: thus not only the extraneous manures which the farmer applies are fully economized; but the soil becomes more productive from its own stores of fertility which now begin to be unlocked and available.
Dr. Peters, of Saxony, has made some instructive experiments that are here in point. He filled several large glass jars, (2-½ feet high and 5-½ inches wide) with a rather poor loamy sand, containing considerable humus, and planted in each one, June 14, 1857, an equal number of seeds of oats and peas. Jar No. 2 had daily passed into it through a tube, adapted to the bottom, about 3-¼ pints of common air. No. 3 received daily the same bulk of a mixture of air and carbonic acid gas, of which the latter amounted to one-fourth. No. 1 remained without any treatment of this kind,i. e.: in just the condition of the soil in an open field, having no air in its pores, save that penetrating it from the atmosphere. On October 3, the plants were removed from the soil, and after drying at the boiling point of water, were weighed. The crops from the pots into which air and carbonic acid were daily forced, were abouttwice as heavyas No. 1, which remained in the ordinary condition.
Examination of the soil further demonstrated, that in the last two soils, a considerably greater quantity of mineral and organic matters had become soluble in water,than in the soil that was not artificially aërated. The actual results are given in the table below in grammes, and refer to 6000 grammes of soil in each case:—
ACTION OF CARBONIC ACID ON THE SOIL.
Substances soluble in water, etc.No. 1,WithoutNo. 2,No. 3,ArtificialCommonAir andSupply ofAirCarbonicAir.Added.acid added.Mineral matters2.043.714.99Potash0.070.170.14Soda0.170.230.28Organic matters2.764.322.43Weight of Crops5.8910.4912.35
It will be seen from the above that air alone exercised nearly as much solvent effect as the mixture of air with one-fourth its weight of carbonic acid; this is doubtless, in part due to the fact that the air, upon entering the soil rich in humus, caused the abundant formation of carbonic acid, as will be presently shown must have been the case. It is, however, probable that organic acids (crenic and apocrenic,) and nitric acid were also produced (by oxidation,) and shared with carbonic the work of solution.
It is almost certain, that the acids of peat exert a powerful decomposing, and ultimately solvent effect on the minerals of the soil; but on this point we have no precise information, and must therefore be content merely to present the probability. This is sustained by the fact that the crenic, apocrenic and humic acids, though often partly uncombined, are never wholly so, but usually occur united in part to various bases, viz.: lime, magnesia, ammonia, potash, alumina and oxide of iron.
The crenic and apocrenic acids (that are formed by the oxidation of ulmic and humic acids,) have such decided acid characters,—crenic acid especially, which has a strongly sour taste—that we cannot well doubt their dissolving action.
IV.—The influence of peat on the temperatureof light soils dressed with it may often be of considerable practical importance. A light dry soil is subject to great variations of temperature, and rapidly follows the changes of the atmosphere from cold to hot, and from hot to cold. In the summer noon a sandy soil becomes so warm as to be hardly endurable to the feel, and again it is on such soils that the earliest frosts take effect. If a soil thus subject to extremes of temperature have a dressing of peat, it will on the one hand not become so warm in the hot day, and on the other hand it will not cool so rapidly, nor so much in the night; its temperature will be rendered more uniform, and on the whole, more conducive to the welfare of vegetation. This regulative effect on temperature is partly due to the stores of water held by peat. In a hot day this water is constantly evaporating, and this, as all know, is a cooling process. At night the peat absorbs vapor of water from the air, and condenses it within its pores, this condensation is again accompanied with the evolution of heat.
It appears to be a general, though not invariable fact, that dark colored soils, other things being equal, are constantly the warmest, or at any rate maintain the temperature most favorable to vegetation. It has been repeatedly observed that on light-colored soils plants mature more rapidly, if the earth be thinly covered with a coating of some black substance. Thus Lampadius, Professor in the School of Mines at Freiberg, a town situated in a mountainous part of Saxony, found that he could ripen melons, even in the coolest summers, by strewing a coating of coal-dust an inch deep over the surface of the soil. In some of the vineyards of the Rhine, the powder of a black slate is employed to hasten the ripening of the grape.
Girardin, an eminent French agriculturist, in a series of experiments on the cultivation of potatoes, found that thetime of their ripening varied eight to fourteen days, according to the character of the soil. He found, on the 25th of August, in a very dark soil, made so by the presence of much humus or decaying vegetable matter, twenty-six varieties ripe; in sandy soil but twenty, in clay nineteen, and in a white lime soil only sixteen.
It cannot be doubted then, that the effect of dressing a light sandy or gravelly soil with peat, or otherwise enriching it in vegetable matter, is to render it warmer, in the sense in which that word is usually applied to soils. The upward range of the thermometer is not, indeed, increased, but the uniform warmth so salutary to our most valued crops is thereby secured.
In the light soils stable-manure wastes too rapidly because, for one reason, at the extremes of high temperature, oxidation and decay proceed with great rapidity, and the volatile portions of the fertilizer are used up faster than the plant can appropriate them, so that not only are they wasted during the early periods of growth, but they are wanting at a later period when their absence may prove the failure of a crop.
B. The ingredients and qualities which make peata direct fertilizernext come under discussion. We shall notice:
The organic matters including nitrogen (ammonia and nitric acid)(I):
The inorganic or mineral ingredients(II):
Peculiarities in the decay of Peat(III),and
Institute a comparison between peat and stable manure(IV).
I.—Under this division we have to consider:
1.The organic matters as direct food to plants.
Thirty years ago, when Chemistry and VegetablePhysiology began to be applied to Agriculture, the opinion was firmly held among scientific men, that the organic parts of humus—by which we understand decayed vegetable matter, such as is found to a greater or less extent in all good soils, andaboundsin many fertile ones, such as constitutes the leaf-mold of forests, such as is produced in the fermenting of stable manure, and that forms the principal part of swamp-muck and peat,—are the true nourishment of vegetation, at any rate of the higher orders of plants, those which supply food to man and to domestic animals.
In 1840, Liebig, in his celebrated treatise on the "Applications of Chemistry to Agriculture and Physiology," gave as his opinion that these organic bodies do not nourish vegetation except by the products of their decay. He asserted that they cannot enter the plant directly, but that the water, carbonic acid and ammonia resulting from their decay, are the substances actually imbibed by plants, and from these alone is built up the organic or combustible part of vegetation.
To this day there is a division of opinion among scientific men on this subject, some adopting the views of Liebig, others maintaining that certain soluble organic matters, viz., crenic and apocrenic acids are proper food of plants.
On the one hand it has been abundantly demonstrated that these organic matters are not at all essential to the growth of agricultural plants, and can constitute but a small part of the actual food of vegetation taken in the aggregate.
On the other hand, we are acquainted with no satisfactory evidence that the soluble organic matters of the soiland of peat, especially the crenates and apocrenates, are not actually appropriated by, and, so far as they go, are not directly serviceable as food to plants.
Be this as it may, practice has abundantly demonstrated the value of humus as an ingredient of the soil, and if not directly, yet indirectly, it furnishes the material out of which plants build up their parts.
2.The organic matters of peat as indirect food to plants.Very nearly one-half, by weight, of our common crops, when perfectly dry, consists ofcarbon. The substance which supplies this element to plants is the gas, carbonic acid. Plants derive this gas mostly from the atmosphere, absorbing it by means of their leaves. But the free atmosphere, at only a little space above the soil, contains on the average but 1/2500 of its bulk of this gas, whereas plants flourish in air containing a larger quantity, and, in fact, their other wants being supplied, they grow better as the quantity is increased to 1/12 the bulk of the air. These considerations make sufficiently obvious how important it is that the soil have in itself a constant and abundant source of carbonic acid gas. As before said,organic matter, in a state of decay, is the single material which the farmer can incorporate with his soil in order to make the latter a supply of this most indispensable form of plant-food.
When organic matters decay in the soil, their carbon ultimately assumes the form of Carbonic acid. This gas, constantly exhaling from the soil, is taken up by the foliage of the crops, and to some extent is absorbed likewise by their roots.
Boussingault & Lewy have examined the air inclosed in the interstices of various soils, and invariably found itmuch richer (10 to 400 times) than that of the atmosphere above. Here follow some of their results:
CARBONIC ACID IN SOILS.
Key:A -Volumes of Carbonic acid in 100 of air in pores of Soil.B -Cubic feet of air in acre to depth of 14 inches.C -Cubic feet of Carbonic acid in acre to depth of 14 inches.D -Volumes of Carbonic acid to 100 of air above the soil.E -Cubic feet of air over one acre to height of 14 inches.F -Cubic feet of Carbonic acid over one acre to a height of 14 inches.Designation and Condition of Soil.ABCSandy subsoil of forest0.244,32614Loamy subsoil of forest0.823,45828Surface soil of forest0.865,76856Clayey soil of artichoke field0.6610,09471Soil of asparagus bed, unmanured for one year0.7910,94886Soil of asparagus bed, newly manured1.5410,948172Sandy soil, six days after manuring, and three days of rain2.2111,536257Sandy soil, ten days after manuring, and three days of rain9.7411,5361144Compost of vegetable mold3.6420,608772Carbonic Acid in AtmosphereDEF0.02550,82014
From the above it is seen that in soils containing little decomposing organic matters—as the forest sub-soils—the quantity of carbonic acid is no greater than that contained in an equal bulk of the atmosphere. It is greater in loamy and clayey soils; but is still small. In the artichoke field (probably light soil not lately manured), and even in an asparagus bed unmanured for one year, the amount of carbonic acid is not greatly larger. In newly manured fields, and especially in a vegetable compost, the quantity is vastly greater.
The organic matters which come from manures, or from the roots and other residues of crops, are the source of the carbonic acid of the soil. These matters continually waste in yielding this gas, and must be supplied anew. Boussingault found that the rich soil of his kitchen garden (near Strasburg) which had been heavily manuredfrom the barn-yard for many years, lost one-third of its carbon by exposure to the air for three months (July, August and September,) being daily watered. It originally contained 2.43per cent.At the conclusion of the experiment it contained but 1.60per cent., having lost 0.83per cent.
Peat and swamp-muck, when properly prepared, furnish carbonic acid in large quantities during their slow oxidation in the soil.
3.The Nitrogen of Peat, including Ammonia and Nitric Acid.
The sources of the nitrogen of plants, and the real cause of the value of nitrogenous fertilizers, are topics that have excited more discussion than any other points in Agricultural Chemistry. This is the result of two circumstances. One is the obscurity in which some parts of the subject have rested; the other is the immense practical and commercial importance of this element, as a characteristic and essential ingredient of the most precious fertilizers. It is a rule that the most valuable manures,commercially considered, are those containing the most nitrogen. Peruvian guano, sulphate of ammonia, soda-saltpeter, fish and flesh manures, bones and urine, cost the farmer more money per ton than any other manures he buys or makes, superphosphate of lime excepted, and this does not find sale, for general purposes, unless it contains severalper cent.of nitrogen. These are, in the highest sense, nitrogenous fertilizers, and, if deprived of their nitrogen, they would lose the greater share of their fertilizing power.
The importance of the nitrogen of manures depends upon the fact that those forms (compounds) of nitrogen which are capable of supplying it to vegetation are comparatively scarce.
It has long been known that peat contains a considerable quantity of nitrogen. The average amount in thirty specimens, analyzed under the author's direction, including peats and swamp mucks of all grades of quality, is equivalent to 1-½per cent.of the air-dried substance, or more than thrice as much as exists in ordinary stable or yard manure. In several peats the amount is as high as 2.4per cent., and in one case 2.9per cent.were found.
Of these thirty samples, one-half were largely mixed with soil, and contained from 15 to 60per cent.of mineral matters.
Reducing them to an average of 15per cent.of water and 5per cent.of ash, they contain 2.1per cent.of nitrogen, while the organic part, considered free from water and mineral substances, contains on the average 2.6per cent.See table, page 90.
The five peats, analyzed by Websky and Chevandier, as cited on page 24, considered free from water and ash, contain an average of 1.8per cent.of nitrogen.
We should not neglect to notice that peat is often comparatively poor in nitrogen. Of the specimens, examined in the Yale Analytical Laboratory, several contained but half aper cent.or less. So in the analyses of Websky, one sample contained but 0.77per cent.of the element in question.
As concerns the state of combination in which nitrogen exists in peat, there is a difference of opinion. Mulder regards it as chiefly occurring in the form ofammonia(a compound of nitrogen and hydrogen), united to the organic acids from which it is very difficult to separate it. Recent investigations indicate that in general, peat contains but a small proportion of ready-formed ammonia.
The great part of the nitrogen of peat exists in an insoluble and inert form: but, by the action of theatmosphere upon it, especially when mixed with and divided by the soil, it gradually becomes available to vegetation to as great an extent as the nitrogen of ordinary fertilizers.
It appears from late examinations that weathered peat may containnitric acid(compound of nitrogen with oxygen) in a proportion which, though small, is yet of great importance, agriculturally speaking. What analytical data we possess are subjoined.
PROPORTIONS OF NITROGEN, ETC., IN PEAT.
Analyst.TotalNitrogen.Ammonia,per cent.Nitric Acid.1—Brown PeatAir dry (?)Boussingault2.200.0180.0002—Black PeatAir dry (?)BoussingaultUndetermined0.025Undetermined3—PeatDried at 212°Reichardt[4]Undetermined0.1520.4834—PeatDried at 212°ReichardtUndetermined0.1650.5255—PeatDried at 212°ReichardtUndetermined0.3050.2416—PeatDried at 212°ReichardtUndetermined0.3350.421