"BUT I have rambled far from the subject assigned me," Percy continued.
"That's only because I interrupt and ask so many side questions," replied Mr. Thornton, "but I hope yet to learn more about those 'suitable conditions' for nitrogen-fixation and nitrification. It begins to look as though the nitrogen cycle deviates a good deal from a true circle, and nature seems to need some help from us to make that element circulate as fast as we need it. I confess, too, that this method appeals to me much more than the twenty-cent-a-pound proposition of the fertilizer agent."
"Yes, indeed," added Miss Russell; "and if we had to spend three dollars an acre on this farm our 'Slough of Despond' would be worse than the slough, or swamp, Mr. Johnston has told us about."
"I fear the practical and profitable improvement of an acre of this land is more likely to cost thirty dollars than three," said Percy.
"Oh, for the land's sake!" came the ejaculation.
"Yes, 'for the land's sake,'" repeated Percy; "and for the sake of those who must depend upon the land for their support for all time hereafter."
"How ridiculous! Thirty dollars an acre for the improvement of land that will not bring ten dollars to begin with!"
"It is better to look at the other end of the undertaking," said Percy. "Suppose you invest thirty dollars an acre and in a few years make your ten-dollar land produce as much as our two-hundred dollar land!"
"But, Mr. Johnston; do you realize how much money it would require to expend thirty dollars an acre on nine hundred acres?" continued Miss Russell, with stronger accentuation.
"Twenty-seven thousand dollars," was the simple reply.
"Well, Sir," she said, "you are welcome to this whole farm for ten thousand dollars."
"I am not wishing for it," he answered. "In fact I would not take this farm as a gift, if I were obliged to keep it and pay the taxes and had no other property or source of income."
"That's just the kind of talk I've been putting up to these girls," said Mr. Thornton. "By the time we live and pay about two hundred dollars a year taxes on all this land, I tell you, there is nothing left; and we'd been worse off than we are, except for the sale we made to the railroad company."
"Well, the Russells lived here very well for more than a hundred years," she retorted, "and my grandfather supported one nigger for every ten acres of the farm, but I would like to know any farmers about here who can put thirty dollars an acre, or even ten dollars an acre, back into their soil for improvement."
"The problem is indeed a serious one," said Percy. "Unquestionably much of the land in these older states is far past the point of possible self-redemption under the present ownership. Land from which the fertility has been removed by two hundred years of cropping, until it has ceased to return a living to those who till it, cannot have its fertility restored sufficiently to again make its cultivation profitable, except by making some considerable investment in order to replace those essential elements the supply of which has become so limited as to limit the crop yields to a point where their value is below the cost of production. Even on the remaining productive lands in the North Central States, if we are ever to adopt systems of permanent agriculture, it must be done while the landowners are still prosperous. If the people of the corn belt repeat the history of the Eastern States until their lands cease to return a profit above the total cost of production, then they, too, will have nothing left to invest in the improvement of their lands."
"But their fertility could still be restored by outside capital?" suggested Mr. Thornton. "I know very well that is the only solution of our problem."
"Well, Tom, I would like to know where the outside capital is coming from," said Miss Russell.
"Marry rich," he replied. "Don't make such a blunder as your sister did."
"I fear that Mr. Johnston will suggest that we sell some more land," remarked Mrs. Thornton.
"All right," replied her sister; "and we will sell it to him. If he won't take the whole farm as a gift, we'll cut it to any length he wishes. Do you consider 'Ten Acres Enough,' Mr. Johnston; or would you prefer 'Three Acres and Liberty?' We'll do our best to enable you to enjoy 'The Fat of the Land.' Just tell us how large a farm you want, I know already that you do not want nine hundred acres."
"My dear Miss Russell," said Percy. "This is so sudden"; whereupon Mr. Thornton nearly fell from his chair and Mrs. Thornton laughed heartily at the sister's expense who blushed as she might have done twenty years before.
"However," Percy resumed, "if you should decide to dispose of about half of that seven hundred acres which you use only as a safety bank for most of your two hundred dollars in taxes, please consider me a prospective taker."
"Take her," said Mr. Thornton, and again confusion reigned.
"Tom is so anxious to get rid of his sister-in-law that he reminds me of the man whose mother-in-law died," said Miss Russell. "He was too far from home to return to the usual funeral, and they telegraphed him the sad news and asked if they should embalm, cremate, or bury the remains. He wired back: 'Embalm, cremate, and bury'"
"That matter of outside capital is by no means so substantial as it might seem," said Percy. "It is worth while to consider how little real wealth there would be in America if the remaining rich lands should become impoverished. The railroads would at once cease to pay dividends, and those who are now millionaires in railroad stock would find themselves on the rapid road to poverty. The manufacturer of finished products from the raw materials raised on the farm, the manufacturer of agricultural implements, and the great urban population whose income is from the trade in raw materials and manufactured goods would soon see their wealth shrivel. The great sky scrapers of the cities would be left for the owls and bats to harbor in, if our agricultural lands ceased to yield their great harvests. Meanwhile the farming people would continue to live upon the meager products still produced from the impoverished soil, even though they had no surplus food to ship into the cities. Human labor would replace that of domestic animals on the farm, just as it has done in China and India, in part because man's labor is worth more than that of the beast, when measured only by the amount of food consumed, and in part because a thousand bushels of grain will support five times as many people can be supported for the same time upon the animal products that could be produced by feeding the grain."
"Oh, that is such a gloomy view to take of it," said Miss Russell.
"And all the world loves an optimist," replied Percy laughingly. "Soils do not wear out; there is no poor land; the farms are better and the crops larger than ever before; and we are the people of the world's greatest nation, with an assured future glory which surposses all conception."
"As soon as we get the canal dug," suggested Mr. Thornton.
"Yes, we will surely be able to dig that Panama ditch," said Percy; "and probably our resources will last to cut a gash or two in our own interior, if we don't build too many battle ships. You know Egypt built three great pyramids before her resources became reduced to such an extent that the people required all their energies to secure a living."
"NOW let us give Mr. Johnston a chance to tell us about the nitrogen problem," said Mr. Thornton. "I'm pretty well satisfied with the natural circulation of carbon, oxygen, and hydrogen; but I want to understand all I can of the practical methods of securing and utilizing nitrogen; and we have heard almost nothing about the other six essential elements which the soil must furnish. Let me see.—I think you said that iron, calcium, magnesium and potassium are usually abundant in the soil, while phosphorus and sulfur are very limited."
"Yes, that is the rule under general or average conditions, but it should be stated that the amount of sulfur required by plants is very small as compared with phosphorus, a difference which places a great distinction between them. Besides considerable quantities of sulfur are returned to the air in the combustion of coal and organic matter, and this returns to the soil in rain. The information thus far secured shows that sulfur rarely if ever limits the crop yields under field conditions; and the same may be said of iron, which is required by plants in very small amount and is contained in practically all soils in enormous quantities.
"While normal soils contain abundance of potassium, with about half as much calcium and one-fourth as much magnesium; yet, when measured by crop requirements for plant food, the supplies of these three elements are not markedly different. On the other hand, about 300 pounds of calcium are lost per acre per annum by leaching from good soils in humid climates, compared with about 10 pounds of potasssium and intermediate amounts of magnesium; so that, of these three elements, calcium requires by far the most consideration and potassium the least, even aside from the use of limestone to correct or prevent soil acidity.
"Among the conditions essential for nitrification may be mentioned the presence of free oxygen and limestone; and of course all bacteria require certain food materials, resembling other plants in this respect."
"Are they plants?" asked Mrs. Thornton. "I thought they were tiny little animals."
"No, they are classified as plants," replied Percy; "but the scientists have difficulty with some of the lower organism to decide whether they are plants or animals. The college boys used to say that some animals were plants in the botanical department and animals again when they studied zoology. Orton says it is easy to tell a cow from a cabbage, but impossible to assign any absolute, distinctive character which will divide animal life from plant life.
"The oxygen is essential for nitrification, because that is an oxidation process. That is, it is a kind of combustion, so to speak. The organic matter is oxidized or converted into substances containing more oxygen than in the original form. In ammonification the carbon is separated or divorced from the nitrogen and united with oxygen. Some of the hydrogen of the organic matter remains temporarily with the carbon, and some is held temporarily with the nitrogen in the form of ammonia.
"The nitrite bacteria replace two of the hydrogen atoms in ammonia with one of oxygen, and insert another oxygen atom between the nitrogen and the remaining hydrogen, thus forming nitrous acid; H-O-N=O, or HNO2.
"The nitrate bacteria then cause the direct addition of another oxygen atom, which is held by the two extra bonds of the nitrogen atom, which you will remember is a five-handed atom.
"Thus you will see the absolute need of free oxygen in the nitrification process; and we can control the rate of nitrification to a considerable extent by our methods of tillage. In soils deficient in organic matter, excessive cultivation may still liberate sufficient nitrogen for a fairly satisfactory crop; and the benefits of such excessive cultivation for potatoes and other vegetables is more often due to increased nitrification than to the conservation of moisture, to which it is frequently ascribed by agricultural writers.
"Thus the more we cultivate, the more we hasten the nitrification, oxidation, or destruction of the organic matter or humus of the soil. Where the soil is well supplied with decaying organic matter, we rarely need to cultivate in a humid section like this, except for the purpose of killing weeds.
"The presence of carbonates in the soil is essential for nitrification, because the bacteria will not continue the process in the presence of their own product. Nitrification ceases if the nitrous or nitric acid remains as such; but, in the presence of carbonates such as calcium carbonate (ordinary limestone) or the double carbonate of magnesium and calcium (magnesian limestone, or dolomite), the nitrous acid or nitric acid is converted into a neutral salt of calcium or magnesium, one of these atoms taking the place of two hydrogen atoms and forming, say, calcium nitrate: Ca(NO3)2. At the same time the hydrogen atoms take the place of the calcium in limestone ( CaC03), and form carbonic acid (H2CO3), which at once decomposes into water (H2O) and carbon dioxid (CO2), which thus escapes as a gas into the air or remains in the pores of the soil.
"The fact that nitrification will not proceed in the presence of acid reminds us that only a certain degree of acidity can be developed in sour milk. Here the lactic acid bacteria produce the acid from milk sugar, but the process stops when about seven-tenths of one per cent. of lactic acid has developed. If some basic substance, such as lime, is then added, the acid is neutralized and the fermentation again proceeds.
"In the general process of decay and oxidation of the organic matter of the soil, the nitrogen thus passes through the forms of ammonia, nitrous acid, and nitric acid, and at the same time the carbon passes into various acid compounds, including the complex humic and ulmic acids, and smaller amounts of acetic acid (found in vinegar), lactic acid, oxalic acid (found in oxalic), and tartaric acid (found in grapes). The final oxidation products of the carbon and hydrogen are carbon dioxid and water, which result from the decomposition of the carbonic acid.
"Now the various acids of carbon and nitrogen constitute one of the most important factors in soil fertility. They are the means by which the farmer can dissolve and make available for the growing crops the otherwise insoluble mineral elements, such as iron, calcium, magnesium, and potassium, all of which are contained in most soils in great abundance. These elements exist in the soil chiefly in the form of insoluble silicates. Silicon itself is a four-handed element which bears somewhat the same relation to the mineral matter of the soil as carbon bears to the organic matter. Quartz sand is silicon dioxid (SiO2). Oxygen, which is present in nearly all substances, including air, water, and most solids, constitutes about one-half of all known matter. Silicon is next in abundance, amounting to more than one-fourth of the solid crust of the earth. Aluminum is third in abundance (about seven per cent), aluminum silicate being common clay. Iron, calcium, potassium, sodium, and magnesium, in this order, complete the eight abundant elements, which aggregate about ninety-eight per cent. of the solid crust of the earth.
"It is worth while to know that about two and one-half per cent. of the earth's crust is potassium, while about one-tenth of one per cent. is phosphorus; also that when a hundred bushels of corn are sold from the farm, seventeen pounds of phosphorus, nineteen of potassium, and seven of magnesium are carried away.
"The acids formed from the decaying organic matter not only liberate for the use of crops the mineral elements contained in the soil in abundance, but they also help to make available the phosphorus of raw phosphate, when naturally contained in the soil, as it is to some extent in all soils, or when applied to the soil in the fine-ground natural phosphate from the mines.
"Now the increase or decrease of organic matter in the soil is measured with a very good degree of satisfaction by the element nitrogen, which is a regular constituent of the organic matter of the soil; and you are already familiar, Mr. Thornton, with the amounts of nitrogen contained in average farm manure and in some of our most common crops."
"Yes, Sir, I have some of the figures in my note book and I mean to have them in my head very soon. But, say, that organic matter seems to be a thing of tremendous importance, and I'm sure we've got mighty little of it. I think about the only thing we'll need to do to make this old farm productive again is to grow the vegetation and plow it under. As it decays, it will furnish the nitrogen, and liberate the phosphorus, potassium, calcium, and magnesium; and we may have plenty of all of them just waiting to be liberated."
"That is altogether possible," said Percy; "but it must be remembered that your soil is acid and consequently will not grow clover or alfalfa successfully, or even cowpeas very satisfactorily. A liberal use of ground limestone and large use of clover may be sufficient to greatly improve your soil; but if I am permitted to separate Miss Russell and the Thorntons "—Mr. Thornton's hilarious "Ha, ha" cut Percy short. He crimsoned and the ladies smiled at each other with expressions that revealed nothing whatever.
"Now let me finish," Percy continued, when Mr. Thornton had somewhat subsided. "I say, if I am permitted to separate Miss Russell and the Thorntons from about three hundred acres of their land, I shall certainly wish to know its total content of phosphorus, potassium, magnesium, and calcium, before I make any purchase; and, if you will remember the pot cultures and the peaty swamp land, I think you'd agree with me.
"Well, I shall be mighty glad to know that myself," said Mr. Thornton, "and we shall much appreciate it if you can tell us how to secure that information."
"We can collect some soil to-morrow," Percy replied, "and send it to a chemist for analysis."
"Good," said Mr. Thornton; "now just one more question, and I think I shall sleep better if I have it answered to-night. Just what is meant by potash and phosphoric acid?"
"Potash," said Percy, "is a compound of potassium and oxygen. The proportions are one atom of oxygen and two atoms of potassium, which you may remember are single-handed and weigh thirty-nine, so that seventy-eight of potassium unite with sixteen of oxygen. A better name for the compound is potassium oxid: K20. The Latin name for potassium is kalium, and K is the symbol used for an atom of that element. If you were to purchase potassium in the form of potassium chlorid, which in the East is often called by the old incorrect name 'muriate of potash,' the salt might be guaranteed to contain a certain percentage of potash, which, however, consists of eighty-three per cent. of potassium and seventeen of oxygen."
"Just what is this potassium chlorid, or 'muriate of potash'?"
"Pure potassium chlorid contains only the two elements, potassium and chlorin."
"But didn't you say that it was guaranteed to contain potash and that potash is part oxygen? Now you say it contains only potassium and chlorin."
"Yes, I am sorry to say, that this is one of those blunders of our semi-scientific ancestors for which we still suffer. The chemist understands that the meaning of the guarantee of potash is the amount of potash that the potassium present in the potassium chlorid could be converted into. The best you can do is to reduce the potash guarantee to potassium by taking eighty-three per cent. of it; or, to be more exact, divide by ninety-four and multiply by seventy-eight, in order to eliminate the sixteen parts of oxygen.
"It may be well to keep in mind that when the druggist says potash he means potassium hydroxid, KOH, a compound of potassium, hydrogen, and oxygen, as the name indicates."
"You mentioned the word chlorin," said Mr. Thornton. "That is another element?"
"Yes, that is a very common element. Ordinary table salt is sodium chlorid: NaCl. Sodium is called natrium in Latin, and Na is the symbol used in English to be in harmony with all other languages, for practically all use the same chemical symbols. Sodium and potassium are very similar elements in some respects, and in the free state they are very peculiar, apparently taking fire when thrown into water. Chlorin in the free state is a poisonous gas. Thus the change in properties is well illustrated when these two dangerous elements, sodium and chlorin, unite to form the harmless compound which we call common salt.
"It is a shame," continued Percy, "that agricultural science has so long been burdened with such a term as 'phosphoric acid,' which serves to complicate and confuse what should be made the simplest subject to every American farmer and landowner. As agriculture is the fundamental support of America and of all her other great industries, so the fertility of the soil is the absolute support of every form of agriculture. Now, if there is any one factor that can be the most important, where so many are positively essential, then the most important factor in the problem of adopting and maintaining permanent systems of profitable agriculture on American soils is the element phosphorus.
"Phosphorus in very appreciable amount is positively necessary for the growth of every organism. It is an absolutely essential constituent of the nucleus of every living cell, whether plant or animal. Nuclein, itself, which is the substance nearest to the beginning of a new cell, contains as high as ten per cent. of the element phosphorus.
"On the other hand, phosphorus is the most limited of all the plant food elements, measured by supply and demand and circulation.
"What is phosphoric acid? Well, the professor of chemistry says it is a compound containing three atoms of hydrogen, one of phosphorus, and four of oxygen. It is a syrupy liquid and one of the strongest mineral acids. In concentrated form it is as caustic as oil of vitriol. Why, here you have a Century dictionary. That should tell what phosphoric acid is. This is what the Century says:
"'It is a colorless, odorless syrup, with an intensely sour taste. It is tribasic, forming three distinct classes of metallic salts. The three atoms of hydrogen may in like manner be replaced by alcohol radicles, forming acid and neutral ethers. Phosphoric acid is used in medicine as a tonic.'
"That," continued Percy, "is the complete definition as given by the Century dictionary as to what phosphoric acid is, and I note that this is the latest edition of the Century, copyrighted in 1902."
"We bought it less than a month ago," said Mrs. Thornton. "We can have so few books that we thought the Century would be a pretty good library in itself; Mr. Thornton has had too little time to use it much as yet."
"Well, even if I had used it," said Mr. Thornton, "you see there are five volumes before I'd get to the P's. But, joking aside, I don't get much out of that definition except that phosphoric acid is a sour liquid and is used in medicine."
"The definition is entirely correct," said Percy "Any text on chemistry will give you a very similar definition, and your physician and druggist will give you the same information."
"Well, I know the fertilizer agents claim to sell phosphoric acid in two-hundred-pound bags which wouldn't hold any kind of liquid."
"True," replied Percy, "and I consider it a shame that the farm boy who goes to the high school or college and is there taught exactly what phosphoric acid is, must. when he returns to the farm, try to read bulletins from his agricultural experiment station in which the term 'phosphoric acid' is used for what it is not. At the state agricultural college, the professor of chemistry correctly teaches the farm boy that phosphoric acid is a liquid compound containing three atoms of hydrogen, one of phosphorus, and four of oxygen in the molecule; and then the same professor, as an experiment station investigator, goes to the farmers' institutes and incorrectly teaches the same boy's father that phosphoric acid is a solid compound pound containing two atoms of phosphorus and five atoms of oxygen in the molecule."
"But why do they continue to teach such confusion?"
"Well, Sir, if they know, they never tell. In some manner this misuse of the name was begun, and every year doubles the difficulty of stopping it."
"Like the man that was too lazy to stop work when he had once begun," remarked Mr. Thornton.
"Yes," said Percy, "but it is true that some of the States have adopted the practice of reporting analyses of soils and fertilizers on the basis of nitrogen instead of ammonia; and in the Corn Belt States, phosphorus and potassium are the terms used to a large extent instead of 'phosphoric acid,' and potash. The agricultural press is greatly assisting in bringing about the adoption of the simpler system, and the laws of some States now require that the percentages of the actual plant food elements, as nitrogen, phosphorus, and potassium, shall be guaranteed in fertilizers offered for sale. It is one of those questions that are never settled until they are settled right; and it is only a question of time until the simple element basis will be used throughout the United States, or at least in the Central and Western States."
"The so-called 'phosphoric acid' of the fertilizer agent is a compound whose molecule contains two atoms of phosphorus and five atoms of oxygen; and, since the atomic weight of phosphorus is thirty-one and that of oxygen sixteen, this compound contains sixty-two parts of phosphorus and eighty parts of oxygen. In other words, this phosphoric acid, falsely so-called, contains a trifle less than forty-four per cent. of the actual element phosphorus."
"Is the bone phosphate of lime that the agents talk about the same as the 'phosphoric acid'?" asked Mr. Thornton.
"No, by 'bone phosphate of lime,' which is often abbreviated B. P. L., is meant tricalcium phosphate, a compound which contains exactly twenty per cent. of phosphorus. Thus, you can always divide the guaranteed percentage of 'bone phosphate of lime' by five, and the result will be the per cent. of phosphorus.
"As stated in your Century dictionary, true phosphoric acid forms three distinct classes of salts, because either one, two, or all of the three hydrogen atoms may be replaced by a metallic element. Thus, we have phosphoric acid itself containing the three hydrogen atoms, one phosphorus atom, and four oxygen atoms. This might be called trihydrogen phosphate (H3PO4). Now if one of the hydrogen atoms is replaced by one potassium atom, we have potassium dihydrogen phosphate (KH2PO4); with two potassium atoms and one hydrogen, we have dipotassium hydrogen phosphate (K2HPO4); and if all hydrogen is replaced by potassium the compound is tripotassium phosphate (K3PO4). To make similar salts with two-handed metallic elements, like calcium or magnesium, we need to start with two molecules of phosphoric acid H6(PO4)2; because each atom of calcium will replace two hydrogen atoms. Thus we have mono calcium phosphate, CaH4(PO4)2, dicalcium phosphate, Ca2H2(PO4)2, and tricalcium phosphate, Ca3(PO4)2. It goes without saying that monocalcium phosphate contains four atoms of hydrogen and that dicalcium phosphate contains two hydrogen atoms. By knowing the atomic weights (40 for calcium, 31 for phosphorus, and 16 for oxygen), it is easy to compute that the molecule of tricalcium phosphate weighs 310 of which 62 is phosphorus. This is exactly one-fifth, or twenty per cent. This compound you will remember is sometimes called 'bone phosphate of lime'. It is also called simply 'bone phosphate'; because it is the phosphorus compound contained in bones. It is sometimes called lime phosphate, although it contains no lime in the true sense, for it has no power to neutralize acid soils, except when the phosphorus is taken up by plants more rapidly than the calcium, which in such case might remain in the soil to act as a base to neutralize soil acids; but even then the effect of the small amount of calcium thus liberated from the phosphate would be very insignificant compared with a liberal application of ground limestone."
"Well," said Mr. Thornton, stretching himself, "orange phosphate is my favorite drink but I fear some of these phosphate you have just been giving me are too concentrated. I ought to have the dose diluted; but I like the taste of it, and if you'll write a book along this line, in this plain way just about as you have been giving it to me straight for almost twelve hours, I tell you I'll read it over till I learn to understand it a heap better than I do now."
THE following day Percy collected soil samples to represent the common type of soil on the farm. In the main the land was nearly level and very uniform, although here and there were small areas which varied from the main type, and in places the variation was marked. Percy and his host devoted the entire day to an examination of the soils of the farm and the collection of the samples.
"The prevailing soil type is what would be called a loam," said Percy, "and a single set of composite samples will fairly represent at least three-fourths of the land on this farm.
"It seems to me that it is enough for the present to sample this prevailing type, and later, if you desire, you could collect samples of the minor types, of which there are at least three that are quite distinct."
"A loam soil is one that includes a fair proportion of the several groups of soil materials, including silt, clay, and sand."
"What is silt?" asked Mr. Thornton.
"Silt consists of the soil particles which are finer than sand,—too small in fact to be felt as soil grains by rubbing between the fingers, and yet it is distinctly granular, while clay is a mere plastic or sticky mass like dough. What are commonly called clay soils consist largely of silt, but contain enough true clay to bind the silt into a stiff mass. In the main such soils are silt loams, but when deficient in organic matter they are yellow in color as a rule, and all such material is usually called clay by the farmers."
"Well, I had no idea that it would take us a whole day to get enough dirt for an analysis," remarked Mr. Thornton, as they were collecting the samples late in the afternoon. "Five minutes would have been plenty of time for me, before I saw the holes you've bored to-day."
"The fact is," replied Percy, "that the most difficult work of the soil investigator is to collect the samples. Of course any one could fill these little bags with soil in five minutes, but the question is, what would the soil represent? It may represent little more than the hole it came out of, as would be the case where the soil had been disturbed by burrowing animals, or modified by surface accumulations, as where a stack may sometime have been burned. In the one case the subsoil may have been brought up and mixed with the surface, and in the other the mineral constituents taken from forty acres in a crop of clover may have been returned to one-tenth of an acre."
"Certainly such things have occurred on many farms," agreed Mr. Thornton, "and they may have occurred on this farm for all any one knows."
"Fifty tons of clover hay," continued Percy, after making a few computations, "would contain 400 pounds of phosphorus, 2400 pounds of potassium, 620 pounds of magnesium, and 2340 pounds of calcium."
"I don't see how you keep all those figures in your head," said Mr.Johnston.
"How many pounds are there in a ton of hay?" asked Percy.
"Two thousand."
"How many pounds in a bushel of oats?"
"Thirty in Virginia, but thirty-two in Carolina."
"How many in a bushel of wheat?"
"Sixty"
"Corn?"
"Fifty-six pounds of shelled corn, or seventy pounds of ears."
"Potatoes?"
"Eighty-six pounds,—both kinds the same, but most States require sixty pounds for the Irish potatoes."
Percy laughed. "You see," he said, "you have more figures in your head than I have in mine. You have mentioned twice as many right here, without a moment's hesitation, as I try to remember for the plant food contained in clover. I like to keep in mind the requirements of large crops, such as it is possible to raise under our climatic conditions if we will provide the stuff the crops are made of, so far as we need to, and do the farm work as it should be done. I never try to remember how much plant food is required for twenty-two bushels of corn per acre, which is the average yield of Virginia for the last ten years, while an authentic record reports a yield of 239 bushels from an acre of land in South Carolina. On our little farm in Illinois we have one field of sixteen acres, which was used for a pasture and feed lot for many years by my grandfather and has been thoroughly tile-drained since I was born, that has produced as high as 2,015 bushels of corn in one season, thus making an average of 126 bushels per acre.
"What I try to remember is the plant food requirements for such crops as we ought to try to raise, if we do what ought to be done. I try to remember the plant food required for a hundred-bushel crop of corn, a hundred-bushel crop of oats, a fifty-bushel crop of wheat, and four tons of clover hay. It is an easy matter to divide these amounts by two, as I have really been doing here in the East where it is hard for people to think in terms of such crops as these lands ought to be made to produce.
"The requirements of the clover crop I certainly want to have in mind as a part of my little stock of ever-ready knowledge. It is not very hard to remember that a four-ton crop of clover hay, which we ought to harvest from one acre in two cuttings, contains:
160 pounds of nitrogen, 31 pounds of magnesium, 20 pounds of phosphorus, 120 pounds of potassium, 117 pounds of calcium.
"It is just as easy to think in these terms as in per cent. or pounds of butter fat, which I understand is the basis on which you sell your cream."
"Yes, I believe you are right in this matter, Mr. Johnston, but I have never been able to see how we could apply the figures reported from chemical analysis."
"Neither do I see how any one but a chemist could make much use of the reports which the analyst usually publishes. Such reports will usually show the percentages of moisture and so-called 'phosphoric acid,' for example, in a sample of clover hay, and perhaps the percentages of these constituents in a sample of soil; but to connect the requirements of the clover crop with the invoice of the soil demand more of a mental effort than I was prepared for before I went to the agricultural college.
"On the other hand we were taught in college that the plowed soil of an acre of our most common Illinois corn belt land contains only 1200 pounds of phosphorus, and that a hundred-bushel crop of corn takes twenty-three pounds of phosphorus out of the soil. Furthermore that about one pound of phosphorus per acre is lost annually in drainage water in humid regions. By dividing 1200 by 24 it is easy to see that fifty corn crops such as we ought to try to raise would require as much phosphorus as the present supply in our soil to a depth of about seven inches. Of course there is some phosphorus below seven inches, but it is the plowed soil we must depend upon to a very large extent. The oldest agricultural experiment station in the world is at Rothamsted, England. On two plots of ground in the same field where wheat has been grown every year for sixty years, the soil below the plow line has practically the same composition, but on one plot the average yield for the last fifty years has been thirteen bushels per acre, while on the other the yield of wheat has averaged thirty-seven bushels for the same fifty years."
"The same kind of wheat?" inquired Mr. Thornton.
"Yes, and great care has always been taken to have these two plots treated alike in all respects, save one."
"And what was that?"
"Plant food was regularly incorporated with the plowed soil of the high-yielding plot."
"You mean that farm manure was used?"
"No, not a pound of farm manure has been used on that plot for more than sixty years; and, furthermore, the two plots were very much alike at the beginning; but, to the high-yielding plot, nitrogen, phosphorus, potassium, magnesium, calcium, and sulfur have all been applied in suitable compounds every year."
"That is to say," observed Mr. Thornton, "that the land itself has produced thirteen bushels of wheat per acre and the plant food applied has produced twenty four bushels, making the total yield thirty-seven bushels on the fertilized land."
"That is certainly a fair way to state it," replied Percy.
" Well, that sounds as though something might be done with run-down lands. About what part of the twenty-four bushels increase would it take to pay for the fertilizers?"
"About 150 per cent. of it," Percy replied.
"One hundred and fifty per cent! Why, you can't have more than a hundred per cent. of anything."
"Oh, yes, you can. The twenty-four bushels are one hundred per cent. of what the fertilizers produced, and the land itself increased this by fifty per cent., so that the fertilized land produced one hundred and fifty per cent. of the increase from the plant food applied.
"Well, that's too much college mathematics for me; but do you mean to say that it would take the whole thirty-seven bushels to pay for the plant food that produced the increase of twenty-four bushels?"
"That is exactly what I mean. I see that you do not like percentage any better than I do. Really the acre is the best agricultural unit. We buy and sell the land itself by the acre; we report crop yields at so many bushels or tons per acre; we apply manure at so many loads or tons per acre; we apply so many hundred pounds of fertilizer per acre; sow our wheat and oats at so many pecks or bushels per acre; and we ought to know the invoice of plant food in the plowed soil of an acre and the amounts carried off in the crops removed from an acre.
"Now, referring again to these figures from the forty acres of clover at two tons per acre. If the eighty tons were burned and the ashes mixed with the surface soil on a tenth of an acre the increase per acre would be as follows:
4,000 pounds of phosphorus 24,000 pounds of potassium 6,200 pounds of magnesium 23,400 pounds of calcium.
"These, remember, are the amounts per acre that would be added to the soil by burning the eighty tons of clover on one-tenth of an acre.
"Now compare these figures with the total amounts of the same elements contained in the common corn belt prairie soil of Illinois, which are as follows:
1,200 pounds of phosphorus 35,000 pounds of potassium 8,600 pounds of magnesium 5,400 pounds of calcium.
"From these figures you will see that the analysis of a single sample of soil collected from a spot of ground that had sometimes received such an addition as this would be positively worse than worthless, because it would give false information, and that is much worse than no information.
"The methods of chemical analysis have been developed to a high degree of accuracy, and it is not a difficult matter to find a chemist who can make a correct analysis of the sample placed in his hands; but the chief difficulties lie, first, in securing samples of soil that will truly represent the type or types of soil on the farm; and, second, in the interpretation of the results of analysis with reference to the adoption of methods of soil improvement."
"Is the report of the analysis as confusing with respect to other elements as with potassium and phosphorus, which, I understand, are likely to be reported in terms of potash and a 'phosphoric acid' that is not true phosphoric acid?"
"Still worse," Percy replied. "The calcium is commonly reported in terms of lime, or, as you would say, quick lime; and vet the soil may be an acid soil, like yours, and contain no lime whatever, neither as quick lime nor limestone. I have seen an analysis reporting half a per cent. of calcium oxid, which would make five tons of quick lime in the plowed soil of an acre; whereas the soil not only contained no lime whatever, but was so acid that it needed five tons of ground limestone per acre to correct the acidity.
"The trouble is that when the chemist found calcium in the soil existing in the form of acid silicate, or calcium hydrogen silicate, he reported calcium oxid, or lime, in his analytical statement, assuming apparently that the farmer would understand that the analytical statement did not mean what it said."
"But some soils do contain lime, do they not?"
"Some soils contain limestone," replied Percy, "and the analysis of such a soil should report the amount of limestone, or calcium carbonate, based upon the actual determination of carbonate carbon or carbon dioxid, which is a true measure of the basic property of the soil, even though the limestone may be somewhat magnesian in character."
For a set of soil samples. Percy collected soil from three different strata. The first sample represented the surface stratum from the top to six and two-third inches; the second sample represented the subsurface stratum from six and two-thirds to twenty inches; and the third sample represented the subsoil from twenty to forty inches, each sample being a composite of about twenty borings.
In collecting these the hole was bored to six and two-third inches and somewhat enlarged by scraping up and down with the auger, all of the soil being put into a numbered bag. Then, the hole was extended and the subsurface boring removed without touching the surface soil. This boring to a depth of twenty inches was put into a second bag. The hole was then enlarged to the twenty-inch depth but the additional soil removed was discarded as a mixture of the surface and subsurface strata. Finally the hole was extended to the forty-inch depth and the subsoil from one groove of the auger was put into a third bag. In this manner about an equal quantity of soil was bagged from each stratum; and twenty such borings taken with an auger about one inch in diameter make a sufficient quantity to furnish to the chemist.
"Of course the surface soil is by far the most important," Percy explained. "It represents just about the depth of earth that is turned by the plow in good farming on normal soils; and it weighs about two million pounds per acre. The subsurface stratum extending from six and two-thirds to twenty inches in depth represents the practical limit of subsoiling; and this stratum weighs about four million pounds; while the subsoil stratum weighs about six million pounds, where the soil is normal, such as loam, silt loam, clay loam, or sandy loam. Pure sand soil weighs about one-fourth more, while pure peat soil weighs only half as much as normal soil."
"I wish you would tell me," said Mr. Thornton, "what the fertilizers cost that have been used on that Rothamsted wheat field."
"The annual application of nitrogen has been one hundred twenty-nine pounds per acre," said Percy. "What will it cost?"
"Well, at twenty cents a pound, it would cost $25.80," was Mr. Thornton's reply after he had figured a moment. "But why didn't they grow clover and get the nitrogen from the air?"
"For two reasons," replied Percy. "First, when those classic experiments were begun by Sir John Lawes and Sir Henry Gilbert in 1844, it was not known that clover could secure the free nitrogen from the air; and, second, the experiment was designed to discover for certain whether wheat must be supplied with combined nitrogen, by ascertaining the actual effect upon the yield of wheat of the nitrogen applied."
"And what was the actual effect of the nitrogen?" questioned Mr. Thornton. "How much did the wheat yield when they left out the nitrogen and applied all the other elements?"
"Only fifteen bushels," was the reply.
"Only fifteen bushels! Only two bushels increase for all the other elements, phosphorus, potassium, magnesium, and calcium,—and I remember you said that sulfur also was applied. Why didn't they leave off all these other elements, and just use the nitrogen alone?"
"They did on another plot in the same field."
"Oh, they did do that? What was the yield on that plot?"
"Only twenty bushels."
"Only twenty bushels! Well, that s mighty queer. How do you account for that?"
"Does Mrs. Thornton sometimes make dough out of flour and milk?" asked Percy.
"Another Yankee question, eh?" said Mr. Thornton. "I told my wife once that I wished she could make the bread my mother used to make, and she said she wished I could make the dough her father used to make. Yes, my wife makes dough, a good deal more than I do, and she makes it of flour and milk, when we aren't reduced to corn meal and water."
"Can she make dough of flour alone?" continued Percy.
"No," replied Mr. Thornton.
"Nor of milk alone?"
"No."
"Well, wheat cannot be made of nitrogen alone, nor can it be made without nitrogen. On Broadbalk field at Rothamsted, where the wheat is grown, the soil is most deficient in the element nitrogen. In other words, nitrogen is the limiting element for wheat on that soil; and practically no increase can be made in the yield of wheat unless nitrogen is added. However, some other elements are not furnished by this soil in sufficient amount for the largest yield of wheat, and these place their limitation upon the crop at twenty bushels. To remove this second limitation requires that another element, such as phosphorus, shall be supplied in larger amount than is anually liberated in the soil under the system of farming practiced."
"Yes, I see that," said Mr. Thornton, "it's like eating pancakes and honey; the more cakes you have the more honey you want. I think I can almost see my way through in this matter; we are to correct the acid with limestone, to work the legumes for nitrogen, and turn under everything we can to increase the organic matter, and if we find that the soil won't furnish enough phosphorus, potassium, magnesium, or calcium, even with the help of the decaying organic matter to liberate them, why then it is up to us to increase the supply of those elements."
"You must remember that the calcium will be supplied in the limestone;" cautioned Percy. "And, if you use magnesian limestone, you will thus supply both calcium and magnesium. Keep in mind that _magnesian _only means that the limestone contains somemagnesium.and that it is not a pure calcium carbonate. The purest magnesian limestone consists of a double carbonate of calcium and magnesium, called dolomite."
"But I have heard that magnesian lime is bad for soils," said Mr.Thornton.
"That is true," Percy replied, "and so is ordinary lime bad for soils. The Germans say: 'Lime makes the fathers rich but the children poor.' The English saying is:
'Lime and lime without manureWill make both farm and farmer poor.'
"Both of these national proverbs are correct for common, every-day lime; but you know, do you not, that limestone soils are usually very good and very durable soils?"
"That's what I've always heard," replied Mr. Thornton.
"Well, there is no danger whatever from using too much limestone; and all the information thus far secured shows that magnesian limestone is even better than the pure calcium limestone. I know two Illinois farmers who are using large quantities of ground magnesian limestone, and one of them has applied as much as twenty tons per acre. On that land his corn crop was good for eighty bushels per acre this year. Of course that heavy application was more than was needed, but initial applications of four or five tons are very satisfactory, and these should be followed by about two tons per acre every four to six years."
Mr. Thornton took his guest to Blairville that evening as they had planned and he assured Percy that should he decide to purchase land in that section they would let him have three hundred acres of their land at ten dollars an acre.
"I will let you know after I get the samples analyzed for you," said Percy. "The price is low enough and the location ideal, but still I want to have the invoice before I buy the goods. I will write you about sending the samples to the chemist after I hear from some I sent him from Montplain."