"I AM interested to know where you learned these things about acid soils and lime and limestone," said Mr. Thornton.
"Mostly in the agricultural college," replied Percy, "but much of the information really comes from the investigations that are conducted by the experiment stations. For example, the best information the world affords concerning the comparative value of burned lime and ground limestone is furnished by the Pennsylvania Agricultural Experiment Station. Those experiments have been carried on continuously since 1882, and the results of twenty years' careful investigations have recently been published. A four-year rotation of crops was practiced, including corn, oats, wheat, and hay, the hay being clover and timothy mixed. With every crop the limestone has given better results than the burned lime. In fact the burned lime seems to have produced injurious results of late years, and the analysis of the soil shows that there has been large loss of humus and nitrogen where the burned lime has been used, the actual loss being equivalent to the destruction of more than two tons of farm manure per acre per annum."
"Well, we surely need this information," said Mr. Thornton. "I have always supposed that the teachers in the agricultural college knew little or nothing of practical farming."
"I did not go to college to learn practical farming, if we mean by that the common practice of agriculture," replied Percy. "I already knew what we call practical farming; that is, how to do the ordinary farm work, including such operations as plowing, planting, cultivating, and harvesting; but it seems to me, Mr. Thornton, that this sort of practical farming has resulted in practical ruin for most of these Eastern lands. The fact is there is a side to agriculture that I knew almost nothing about as a so-called practical farmer, and I am coming to believe that what we commonly call practical farming is often the most impractical farming,—certainly this is true if it ultimately results in depleted and abandoned lands. The truly practical farmer is the man who knows not only how to do, but also what to do and why he does it. The Simplon railroad tunnel connecting Switzerland with Italy is twelve miles long,—the longest in the world. It was dug from the two ends, but under the mountain, six miles from either end, the two holes came together exactly, within a limit of error of less than six inches, and made one continuous tunnel twelve miles long. Now, this was not all accomplished by the practical men who knew how to handle a spade in digging a ditch. The work was controlled by science, and it was known in advance what the results would be. I do not mean that it was known how hard the digging would be, nor how much trouble would be caused by caving or by water; but it was known that if the practical work was done, the final outcome would be successful.
"I think it is even more important that we understand enough of the sciences which underlie the practice of agriculture so we may know in advance that when the practical farm work is done the soil will be richer and better rather than poorer and less productive because of our impractical farming.
"As I said, I did not go to the agricultural college to learn the practice or art of farming; I went to learn the science of agriculture; but, as a matter of fact, I found the college professor knew about as much of practical agriculture as I did and a great deal of science that I did not know. I found that the Dean of the college, who is also Director of the Experiment Station, had been born and raised on the farm, had done all kinds of farm work, the same as other farm boys, had gone through an agricultural college, and after his graduation had returned to the farm and remained there for ten years doing his own work with his own hands. He has had as much actual farm experience as you have had, Mr. Thornton, and ten years more than I have had. He was finally called from the farm to become an assistant in the college from which he was graduated, and in a few years he was advanced to head professor in agriculture. About ten years ago he was made dean and director of the agricultural college and experiment station in my own state; and I have been told that he will not recommend any one for a responsible position in an agricultural college unless he has had both farm experience and scientific training. He and most of his associates are owners of farms and would return to them again if they did not feel that they are of more service to agriculture as teachers and investigators."
"I am very glad to know about this," said Mr. Thornton. "Certainly your opinion, based upon such knowledge as you have of your own college, is worth more than all the common talk I have ever heard from those who never saw an agricultural college. I wish you would tell me something more in regard to what crops are made of and about the methods of making land better even while we are taking crops from it every year."
"THE subject is somewhat complicated," Percy replied, "yet it involves no more difficult problems than have been solved in many other lines. The chief trouble is that we have done too little thinking about our own real problems. Even in the country schools we have learned something of banking and various other lines of business, something of the history and politics of this and other countries, something of the great achievements in war, in discovery and exploration, in art, literature, and invention; but we have not learned what our soils contain nor what our crops require. Not one farmer in a hundred knows what chemical elements are absolutely required for the production of our agricultural plants, and one may work hard on the farm from four o'clock in the morning till nine o'clock at night for forty years and still not learn what corn is made of.
"All agricultural plants are composed of ten chemical elements, and the growth of any crop is absolutely dependent upon the supply of these plant food elements. If the supply of any one of these plant food elements is limited, the crop yield will also be limited. The grain and grass crops, such as corn, oats, wheat, and timothy, also the root crops and potatoes, secure two elements from the air, one from water, and seven from the soil.
"The supply of some elements is constantly renewed by natural processes, and iron, one of the ten, is contained in all normal soils in absolutely inexhaustible amount; while other elements become deficient and the supply must be renewed by man, or crop yields decrease and farming becomes unprofitable.
"Matter is absolutely indestructible. It may change its form, but not a pound of material substance can be destroyed. Matter moves in cycles, and the key to the problem of successful permanent agriculture is the circulation of plant food. While some elements have a natural cycle which is amply sufficient to meet all requirements for these elements as plant food, other elements have no such cycle, and it is the chief business of the farmer to make these elements circulate.
"Take carbon, for example. This element is well represented by hard coal. Soft coal and charcoal are chiefly carbon. The diamond is pure crystallized carbon, and charcoal made from pure sugar is pure, uncrystallized carbon. This can easily be made by heating a lump of sugar on a red hot stove until only a black coal remains. Now these different solid materials represent carbon in the elemental form or free state. But carbon may unite with other elements to form chemical compounds, and these may be solids, liquids, gases.
"Thus carbon and sulfur are both solid elements, one black and the other yellow, as generally found. If these two elements are mixed together under ordinary conditions no change occurs. The result is simply a mixture of carbon and sulfur. But, if this mixture is heated in a retort which excludes the air, the carbon and sulfur unite into a chemical compound called carbon disulfid. This compound is neither black, yellow, nor solid; but it is a colorless, limpid liquid; and yet it contains absolutely nothing except carbon and sulfur."
"That seems strange," remarked Mr. Thornton. "Yes, but similar changes are going on about us all the time," replied Percy. "We put ten pounds of solid black coal in the stove and an hour later we find nothing there, except a few ounces of ashes which represent the impurities in the coal."
"Well, the coal is burned up and destroyed, is it not?"
"The carbon is burned and changed, but not destroyed. In this case, the heat has caused the carbon to unite with the element oxygen which exists in the air in the form of a gas, and a chemical compound is formed which we call carbon dioxid. This compound is a colorless gas. This element oxygen enters the vent of the stove and the compound carbon dioxid passes off through the chimney. If there is any smoke, it is due to small particles of unburned carbon or other colored substances.
"As a rule more or less sulfur is contained in coal, wood, and other organic matter, and this also is burned to sulfur dioxid and carried into the air, from which it is brought back to the soil in rain in ample amounts to supply all of the sulfur required by plants.
"Everywhere over the earth the atmosphere contains some carbon dioxid and this compound furnishes all agricultural plants their necessary supply of both carbon and oxygen. In other words, these are the two elements that plants secure from the air. The gas, carbon dioxid, passes into the plant through the breathing pores on the under side of the leaves. These are microscopic openings but very numerous. A square inch of a corn leaf may have a hundred thousand breathing pores."
"Now, as we go on, I am especially anxious to get at this question of supply and demand," said Mr. Thornton. "I think I understand about iron and sulfur, and also that these two elements, carbon and oxygen, are both contained in the air in the compound called carbon dioxid, and that this must supply our crops with those two elements of plant food. I'd like to know about the supply. How much is there in the air and how much do the crops require?"
"As you know," said Percy, "the atmospheric pressure is about fifteen pounds to the square inch."
"Yes, I've heard that, I know."
"Well, that means, of course, that there are fifteen pounds of air resting on every square inch of the earth's surface; in other words, that a column of air one inch square and as high as the air goes, perhaps fifty miles or more, weighs fifteen pounds."
"Yes, that is very clear."
"There is only one pound of carbon in ten thousand pounds of ordinary country air. Now, there are one hundred and sixty square rods in an acre, and since there are twelve inches in a foot and sixteen and one-half feet in a rod, it is easy to compute that there are nearly a hundred million pounds of air on an acre, and that the carbon in this amounts to only five tons. A three-ton crop of corn or hay contains one and one-fourth tons of the element carbon; so that the total amount of the carbon in the air over an acre of land is sufficient for only four such crops; while a single crop of corn yielding a hundred bushels to the acre, such as we often raise in Illinois on old feed-lots or other pieces of well treated land would require half of the total supply of carbon contained in the air over an acre. However, the largest crop of corn ever grown, of which there is an established authentic record, was not raised in Illinois, but in the state of South Carolina, in the county of Marlborough, in the year 1898, by Z. J. Drake; and, according to the authentic report of the official committee that measured the land and saw the crop harvested and weighed, and awarded Drake a prize of five hundred dollars given by the Orange Judd Publishing Company,—according to this very creditable evidence, that acre of land yielded 239 bushels of thoroughly aid-dried corn; and such a crop, Mr. Thornton, would require as much carbon as the total amount contained in the air over an acre of land."
"Well, that is astonishing! Then there must be some other source of supply besides the air."
"There is no other direct source from which plants secure carbon; but of course the air is in constant motion. Only one-fourth of the earth's surface is land, and perhaps only one-fourth of this land is cropped, and the average crop is about one-fourth of three tons; so that the total present supply of carbon in the air would be sufficient for about two hundred and fifty years. But as a matter of fact the supply is permanently maintained by the carbon cycle. Thus the carbon of coal that is burned in the stove returns to the air in carbon dioxid; and all combustion of coal and wood, grass and weeds, and all other vegetable matter returns carbon to the atmosphere. All decay of organic matter, as in the fermentation of manure in the pile and the rotting of vegetable matter in the soil, is a form of slow combustion and carbon dioxid is the chief produce of such decay. Sometimes an appreciable amount of heat is developed, as in the steaming pile of stable refuse lying in the barnyard, while the heat evolved in the soil is too quickly disseminated to be apparent.
"In addition to all this, every animal exhales carbon dioxid. The body heat and the animal force or energy are supplied by the combustion of organic food within the body, and here, too, carbon dioxid is the chief product of combustion.
"Thus, as a general average, the amount of carbon removed from the atmosphere by growing plants is no greater than the amount returned to the air by these various forms of combustion or decay. In like manner the supply of combined oxygen is maintained, both carbon and oxygen being furnished to the plant m the carbon dioxid.
"As a matter of fact, the air consists very largely of oxygen and nitrogen, both in the free state, but in this form these elements cannot be utilized in the growth of agricultural plants. The only apparent exception to this is in case of legume crops, such as clover, alfalfa, peas, beans, and vetch, which have power to utilize the free nitrogen by means of their symbiotic relationship with certain nitrogen-fixing bacteria which live, or may live, in tubercles on their roots.
"Carbon and oxygen constitute about ninety per cent. of the dry matter of ordinary farm crops, and with the addition of hydrogen very important plant constituents are produced; such as starch, sugar, fiber, or cellulose, which constitute the carbohydrate group. As the name indicates, this group contains carbon, hydrogen, and oxygen, the last two being present in the same proportion as in water.
"Water is composed of the two elements, hydrogen and oxygen, both of which are gases in the free state. Water is taken into the plant through the roots and decomposed in the leaves in contact with the carbon dioxid under the influence of sunlight and the life principle. The oxygen from the water and part of that from the carbon dioxid is given off into the air through the breathing pores, while the carbon, hydrogen, and part of the oxygen, unite to form the carbohydrates. These three elements constitute about ninety-five per cent. of our farm crops, and yet every one of the other seven plant food elements is just as essential to the growth and full development of the plant as are these three."
"Then so long as we have air above and moisture below, our crops will not lack for carbon, oxygen, and hydrogen. Is that the summing up of the matter?"
"Yes, Sir," Percy replied.
"And those three elements make up ninety-five per cent. of our farm crops. Is that correct?"
"Yes, Sir, as an average."
"Well, now it seems to me, if nature thus provides ninety-five per cent. of all we need, we ought to find some way of furnishing the other five per cent. It makes me think of the young wife who told her husband she could live on bread and water, with his love, and he told her that if she would furnish the bread he'd skirmish around and get the water. But, say, did that South Carolina man use any fertilizer for that immense crop of corn?"
"Some fertilizer, yes. He applied manure and fertilizer from February till June. In all he applied 1000 bushels (about 30 tons) of farm manure, 600 bushels of whole cotton seed, 900 pounds of cotton seed meal, 900 pounds of kainit, 1100 pounds of guano, 200 pounds of bone meal, 200 pounds of acid phosphate, and 400 pounds of sodium nitrate."
"I would also like to know the facts about this nitrogen business," said Mr. Thornton. "I've understood that one could get some of it from the air, and I would much rather get it that way than to buy it from the fertilizer agent at twenty cents a pound. Cowpeas don't seem to help much, and we don't have the cotton seed, and we never have sufficient manure to cover much land."
"It is a remarkable fact," said Percy, "that of the ten essential elements of plant food, nitrogen is the most abundant, measured by crop requirements, and at the same time the most expensive. The air above an acre of land contains enough carbon for a hundred bushels of corn per acre for two years, and enough nitrogen for five hundred thousand years; and yet the nitrogen in commercial fertilizers costs from fifteen to twenty cents a pound. At commercial prices for nitrogen, every man who owns an acre of land is a millionaire.
"You mean he has millions in the air," amended Mr. Thornton.
"Yes, that is the better way to put it," Percy admitted, "but the fact is he can not only get this nitrogen for nothing by means of legume crops, but he is paid for getting it, because those crops are profitable to raise for their own value. Clover, alfalfa, cowpeas, and soy beans are all profitable crops, and they all have power to use the free nitrogen of the air.
"There are a few important facts to be kept in mind regarding nitrogen:
"A fifty-bushel crop of corn takes 75 pounds of nitrogen from the soil. Of this amount about 50 pounds are in the grain, 24 pounds are in the stalks, and 1 pound in the cobs. A fifty-bushel crop of oats takes 48 pounds of nitrogen from the soil, 33 pounds in the grain, and 15 in the straw. A twenty-five bushel crop of wheat also takes 48 pounds of nitrogen from the soil, 36 pounds in the grain and 12 in the straw.
"These amounts will vary to some extent with the quality of the crops, just as the weight of a bushel of wheat varies from perhaps 56 to 64 pounds, although as an average wheat weighs 60 pounds to the bushel."
"You surely remember figures well," remarked Mr. Thornton as he made some notations.
"It is easy to remember what we think about much and often," said Percy; "as easy to remember that a ton of cowpea hay contains 43 pounds of nitrogen as that Blairville is 53 miles from Richmond."
"I have added those figures together," continued Mr. Thornton, "and I find that the three crops, corn, oats, and wheat, would require 171 pounds of nitrogen. Now suppose we raise a crop of cowpeas the fourth year, how much nitrogen would be added to the soil in the roots and stubble?"
"Not any."
"Do you mean to say that the roots and stubble of the cowpeas would add no nitrogen to the soil? Surely that does not agree with the common talk."
"It is even worse than that," said Percy. "The cowpea roots and stubble would contain less nitrogen than the cowpea crop takes from a soil capable of yielding thirty bushels of corn or oats. Only about one-tenth of the nitrogen contained in the cowpea plant is left in the roots and stubble when the crop is harvested. Suppose the yield is two tons per acre of cowpea hay! Such a crop would contain about 86 pounds of nitrogen, and about 10 pounds of nitrogen per acre would be left in the roots and stubble."
"Well, that wouldn't go far toward replacing the 171 pounds removed from the soil by the corn, oats, and wheat, that's sure," was Mr. Thornton's comment.
"It is worse than that," Percy repeated. "Land that will furnish 48 pounds of nitrogen for a crop of oats or wheat will furnish more than 10 pounds for a crop of cowpeas. At the end of such a four-year rotation such a soil would be about 200 pounds poorer in nitrogen per acre than at the beginning, if all crops were removed and nothing returned."
"How much would it cost to put that nitrogen back in commercial fertilizer?" asked Mr. Thornton.
"That depends, of course, upon what kind of fertilizer is used."
"Well, most people around here who use fertilizer buy what the agent calls two-eight-two, and its costs about one dollar and fifty cents a hundred pounds; but it can be bought by the ton for about twenty-five dollars."
"'Two-eight-two' means that the fertilizer is guaranteed to contain two per cent. of ammonia, eight per cent. of available 'phosphoric acid,' and two per cent. of potash."
"Ammonia is the same as nitrogen, is it not?"
"No, it is not the same," replied Percy. "Ammonia is a compound of nitrogen and hydrogen. In order to have a clear understanding of the relation between ammonia and nitrogen we only need to know the combining weights of the elements. The smallest particle of an element is called an atom. Hydrogen is the lightest of all the elements and the weight of the hydrogen atom is used as the standard or unit for the measure of all other atomic weights; thus the atom of hydrogen weighs one."
"One what?" interrupted Mr. Thornton.
"No one knows," replied Percy. "The atom is extremely small, much too small to be seen with the most powerful microscope; but you know all things are relative and we always measure one thing in terms of another. We say a foot is twelve inches and an inch is one-twelfth of a foot, and there we stop with a definition of each expressed in terms of the other, and both depending upon an arbitrary standard that somebody once adopted; and yet, while the foot is known in most countries, it is rare that two countries have exactly the same standard for this measure of length.
"We do not know the exact weight of the hydrogen atom, but we do know its relative weight. If the hydrogen atom weighs one then other atomic weights are as follows:
12 for carbon 14 for nitrogen 16 for oxygen 24 for magnesium 31 for phosphorus 32 for sulfur 39 for potassium 40 for calcium 56 for iron
"This means that the iron atom is fifty-six times as heavy as the hydrogen atom. These atomic weights are absolutely necessary to a clear understanding of the compounds formed by the union or combination of two or more elements.
"One other thing is also necessary. That is to keep in mind the number of bonds, or hands, possessed by each atom. The atom of hydrogen has only one hand, and the same is true of potassium. Each atom of oxygen has two hands; so that one oxygen atom can hold two hydrogen atoms in the chemical compound called water (H-O-H or H20). Other elements having two-handed atoms are magnesium and calcium. Strange to say, the sulfur atom has six hands but sometimes uses only two, the others seemingly being clasped together in pairs. I will write it out for you, thus:
Hydrogen sulfid: H-S-H or H2S
Sulfur dioxid: O=S=0 or S02
"The carbon atom has four hands, and atoms of nitrogen and phosphorus have five hands, but sometimes use only three. Thus, in the compound called ammonia, one atom of nitrogen always holds three atoms of hydrogen; so, if you buy seventeen pounds of ammonia you would get only fourteen pounds of nitrogen and three pounds of hydrogen. This means that, if the two-eight-two fertilizer contains two per cent. of ammonia, it contains only one and two-thirds per cent. of the actual element nitrogen, and a ton of such fertilizer would contain thirty-three pounds of nitrogen. In other words it would take six tons of such fertilizer to replace the nitrogen removed from one acre of land in four years if the crop yields were fifty bushels of corn and oats, twenty-five bushels of wheat, and two tons of cowpea hay."
"Six tons! Why, that would cost a hundred and fifty dollars! Well, well, I thought I knew we couldn't afford to keep up our land with commercial fertilizer; but I didn't think it was that bad. Almost forty dollars an acre a year!"
"It need not be quite that bad," said Percy. "You see this two-eight-two fertilizer contains eight per cent. of so-called 'phosphoric acid' and two per cent. of potash, and those constituents may be worth much more than the nitrogen; but, so far as nitrogen is concerned, the two hundred pounds would cost from thirty to forty dollars in the best nitrogen fertilizers in the market, such as dried blood or sodium nitrate."
"Well, even that would be eight or ten dollars a year per acre, and that is as much as the land is worth, and this wouldn't include any other plant food elements, such as 'phosphoric acid' and potash."
"No, that much would be required for the nitrogen alone if bought in commercial form. I understand that the farmers who use this common commercial fertilizer, apply about three hundred pounds of it to the acre perhaps twice in four years. That would cost about eight dollars for the four years, and the total nitrogen applied in the two applications would amount to 10 pounds per acre."
"It is not quite correct to call 'phosphoric acid' and potash plant food elements. They are not elements but compounds."
"Like ammonia, which is part nitrogen and part hydrogen?"
"The problem is somewhat similar, but not just the same," Percy replied. "These compounds contain oxygen and not hydrogen."
"Well, I understand that both oxygen and hydrogen are furnished by natural processes, the oxygen from carbon dioxid in the carbon cycle, and the hydrogen from the water which falls in rain."
"That is all true, but you really do not buy the hydrogen or oxygen. While they are included in the two-eight-two guarantee, the price is adjusted for that. Thus the cost of nitrogen would be just the same whether you purchase the fertilizer on the basis of seventeen cents a pound for the actual element nitrogen, or fourteen cents a pound for the ammonia."
"Yes, I see how that might be, but I don't see why the guarantee should be two per cent. of ammonia instead of one and two-thirds per cent. of nitrogen, when the nitrogen is all that gives it value."
"There is no good reason for it," said Percy. "It is one of those customs that are conceived in ignorance and continued in selfishness. It is very much simpler to consider the whole subject on the basis of actual plant food elements, and I am glad to say that many of the state laws already require the nitrogen to be guaranteed in terms of the actual element, a few states now require the phosphorus and potassium also to be reported on the element basis."
"That is hopeful, at least," said Mr. Thornton. "Now, if I am not asking too many questions or keeping you here too long, I shall be glad to have you explain two more points that come to my mind: First, how much of that two hundred pounds of nitrogen can I put back in the manure produced on the farm; and, second, just what is meant by potash and phosphoric acid?"
Percy made a few computations and then replied: "If you sell the wheat; feed all the corn, oats, and cowpea hay and half of the straw and corn fodder, and use the other half for bedding; and, if you save absolutely all of the manure produced, including both the solid and liquid excrement; then it would be possible to recover and return to the land about 173 pounds of nitrogen during the four years, compared with the 200 pounds taken from the soil."
"I can't understand that," said Mr. Thornton. "How can that be when one of the crops is cowpeas?"
"In average live-stock and dairy farming," Percy continued, "about one-fourth of the nitrogen contained in the food consumed is retained in the milk and animal growth, and you can make the computations for yourself. It should be kept in mind, moreover, that much of the manure produced on the average farm is wasted. More than half of the nitrogen is in the liquid excrement, and it is extremely difficult to prevent loss of the liquid manure. There is also large loss of nitrogen from the fermentation of manure in piles; and when you smell ammonia in the stable, see the manure pile steaming, or colored liquid soaking into the ground beneath, or flowing away in rainy weather, you may know that nitrogen is being lost. How many tons of manure can you apply to your land under such a system of farming as we have been discussing?"
"Well, I've figured a good deal on manure," was the reply, "and I think with four fields producing such crops as you counted on, that I could possibly put ten or twelve tons to the acre on one field every year."
"That would return from 100 to 120 pounds of nitrogen;" said Percy, "instead of the 173 pounds possible to be returned if there is no loss. There are three methods that may be used to reduce the loss of manure: One of these is to do the feeding on the fields. Another is to haul the manure from the stable every day or two and spread it on the land. The third is to allow the manure to accumulate in deep stalls for several weeks, using plenty of bedding to absorb the liquid and keep the animals clean, and then haul and spread it when convenient."
"I'm afraid that last method would not do at all for the dairy farmer," said Mr. Thornton. "You see we have to keep things very clean and in sanitary condition."
"Most often the cleanest and most sanitary method the average farmer has of handling the manure in dairying," said Percy, "is to keep it buried as much as possible under plenty of clean bedding; and one of the worst methods is to overhaul it every day by 'cleaning' the stable, unless you could have concrete floors throughout, and flush them well once or twice a day, thus losing a considerable part of the valuable excrement. If you allow the manure to accumulate for several weeks at a time, it is best to have sufficient room in the stable or shed so that the cows need not be tied. If allowed to run loose they will find clean places to lie down even during the night.
"In case of horses, the manure can be kept buried for several weeks if some means are used to prevent the escape of ammonia. Cattle produce what is called a 'cold' manure, while it is called 'hot' from horses because it decomposes so readily. One of the best substances to use for the prevention of loss of ammonia in horse stables is acid phosphate, which has power to unite with ammonia and hold it in a fixed compound. About one pound of acid phosphate per day for each horse should be sprinkled over the manure. Of course the phosphorus contained in the acid phosphate has considerable value for its own sake, and care should be taken that you do not lose more phosphorus from the acid phosphate applied than the value of all the ammonia saved by this means. Porous earth floors may absorb very considerable amounts of liquid from wet manure lying underneath the dry bedding, and the acid phosphate sometimes injures the horses' feet; so that, as a rule, it is better to clean the horse stables every day and supply phosphorus in raw phosphate at one-fourth of its cost in acid phosphate."
"Before we leave the nitrogen question," said Mr. Thornton, "I want to ask if you can suggest how we can get enough of the several million dollars' worth we have in the air to supply the needs of our crops and build up our land?"
"Grow more legumes, and plow more under, either directly or in manure."
"That sounds easy, but can you suggest some practical system?"
"I think so. I know too little of your conditions to think I could suggest the best system for you to adopt; but I can surely suggest one that will supply nitrogen for such crop yields as we have considered: Suppose we change the order of the crops and grow wheat, corn, oats, and cowpeas, and grow clover with the wheat and oats, plowing the clover under in the spring as green manure for corn and cowpeas. If necessary to prevent the clover or weeds from producing seed, the field may be clipped with the mower in the late summer when the clover has made some growth after the wheat and oats have been removed. Leave this season's growth lying on the land. As an average it should amount to more than half a ton of hay per acre. The next spring the clover is allowed to grow for several weeks. It should be plowed under for corn on one field early in May and two or three weeks later the other field is plowed for cowpeas. The spring growth should average nearly a ton of clover hay per acre. In this way clover equivalent to about three tons of hay could be plowed under. Clover hay contains 40 pounds of nitrogen per ton; so this would supply about 120 pounds of nitrogen in addition to the 173 pounds possible to be supplied in the manure. This would make possible a total return of 293 pounds, while we figured some 200 pounds removed. Of course if you save only 100 pounds in the manure the amount returned would be reduced to 220 pounds."
"There are two questionable points in this plan," said Mr. Thornton, " one is the impossibility, or at least the difficulty, of growing clover on this land. The other point is, How much of that 120 pounds of nitrogen returned in the clover is taken from the soil itself? I remember you figured 86 pounds of nitrogen in two tons of cowpea hay, but you also assumed that about 29 pounds of it would be taken from the soil."
"Yes, that is true," Percy replied, "at least 29 pounds and probably more. You see the cowpeas grow during the same months as corn and on land prepared in about the same manner. If the soil will furnish 75 pounds of nitrogen to the corn crop, and 48 pounds to the oats and wheat, it would surely furnish 29 pounds to the cowpeas. Of course this particular amount has no special significance, but the other definite amounts removed in corn, oats, and wheat aggregate 171 and the 29 pounds were added to make the round 200 pounds. Perhaps 210 pounds would be nearer the truth, in which case the soil would furnish about half as much nitrogen to the cowpea crop as to the corn crop. This is reasonable considering that corn is the first crop grown after the manure is applied. You will remember that only one-tenth of the total nitrogen of the cowpea plant remains in the roots and stubble?"
"Yes, that's what we figured on."
"The cowpea is an annual plant. It is planted, produces its seed, and dies the same season. It has no need to store up material in the roots for future use. Consequently the substance of the root is largely taken into the tops as the plan approaches maturity. It is different with the clover plant. This is a biennial with some tendency toward the perennial plant. It lives long and develops an extensive root system, and its stores up material in the roots during part of its life for use at a later period. About one-third of the total nitrogen content of the clover plant is contained in the roots and stubble. This means that the roots and stubble of a two-ton crop of clover would contain about forty pounds of nitrogen, or more than we assumed was taken from the soil by the cowpeas. But there is still another point in favor of the clover. The cowpeas make their growth during the summer months when nitrification is most active, whereas the clover growth we have counted on occurs chiefly during the fall and spring when nitrification is much less active, consequently the clover probably takes even a larger proportion of its nitrogen from the air than we have counted on."
"That is rather confusing," said Mr. Thornton, "you say the cowpea grows when nitrification is most active, and yet you say that it takes less nitrogen from the air than clover. Isn't that somewhat contradictory?"
"I think not," said Percy." Let me see.—Just what do you understand by nitrification?"
"Getting nitrogen from the air, is it not?"
"No, no. That explains it. Getting nitrogen from the air is called nitrogen fixation. This action is carried on by the nitrogen-fixing bacteria, such as the clover bacteria, the soy bean bacteria, the alfalfa bacteria, which, by the way, are evidently the same as the bacteria of sweet clover, or mellilotus. Then we also have the cowpea bacteria, and these seem to be the same as the bacteria of the wild partridge pea, a kind of sensitive plant with yellow flowers, and a tiny goblet standing upright at the base of each compound leaf,—the plant called Cassia Chamaecrista by the botanist."
"Nitrification is an altogether—"
"Well, I declare! Excuse me, Sir, but that's Charlie calling the cows. Scotts, I don't see where the time has gone! You'll excuse me, Sir, but I must look after separating the cream. You will greatly oblige me, Mr. Johnston, if you will have dinner with us and share our home to-night. In addition to the pleasure of your company, I confess that I am mightily interested in this subject; and I would like especially to get a clear understanding of that nitrification process, and we've not had time to discuss the potash and 'phosphoric acid,' which I know cost some of our farmers a good part of all they get for their crops, and still their lands are as poor as ever."
"I appreciate very much your kind invitation, Mr. Thornton. I came to you for correct information regarding the agricultural conditions here, and you were very kind and indulgent to answer my blunt questions, even concerning your own farm practice and experience. I feel, Sir, that I am already greatly indebted to you, but it will certainly be a great pleasure to me to remain with you to-night."
For more than two hours they had been standing, leaning, or sitting in a field beside a shock of cowpea hay, Percy toying with his soil auger, and Mr. Thornton making records now and then in his pocket note book.
PERCY took a lesson in turning the cream separator and after dinner Mrs. Thornton assured him that she and her sister were greatly disappointed that they had not been permitted to hear the discussion concerning the use of science on the farm.
"We have never forsaken our belief that these old farms can again be made to yield bountiful crops," she said, "as ours did for so many years under the management of our ancestors. 'Hope springs eternal in the human breast.' I stop with that for I do not like the rest of the couplet. We can see that some marked progress has been made under my husband's management, although he feels that it is very slow work building up a run-down farm. But he has raised some fine crops on the fields under cultivation,—as much as ten barrels of corn to the acre, have you not, Dear?" she asked.
"Yes, fully that much, but even ten barrels per acre on one small field is nothing compared to the great fields of corn Mr. Johnston raises in the West. and it makes a mighty small show here on a nine-hundred-acre farm, most of which hasn't been cropped for more than twenty years; and even then it was given up because the negro tenants couldn't raise corn enough to live on.
"I've talked some with the fertilizer agents, but they don't know much about fertilizers, except what they read in the testimonials published in the advertising booklets. I have had some good help from the agricultural papers, but most that is written for the papers doesn't apply to our farm, and it's so indefinite and incomplete, that I've just spent this whole evening asking Mr. Johnston questions; and I haven't given him a chance to answer them all yet."
"I am sure you have not asked more questions this afternoon than I did this forenoon," Percy remarked; "and all your answers were based on authentic history or actual experience, while my answers were only what I have learned from others."
"Well, if we were more ready to learn from others, it would be better for all of us," said Mr. Thornton. "Experience is a mighty dear teacher and, even if we finally learn the lesson, it may be too everlasting late for us to apply it. Now we all want to learn about that process called nitrification."
"It is an extremely interesting and important process," said Percy. "It includes the stages or steps by which the insoluble organic nitrogen of the soil is converted into soluble nitrate nitrogen, in which form it become available as food for all of our agricultural plants."
"Excepting the legumes?" asked Mr. Thornton.
"Excepting none," Percy replied. "The legume plants, like clover, take nitrogen from the soil so far as they can secure it in available form, and in this respect clover is not different from corn. The respect in which it is different is the power of clover to secure additional supplies of nitrogen from the air when the soil's available supply becomes inadequate to meet the needs of the growing clover. If the conditions are suitable for nitrogen-fixation, then the growth of the legume plants need not be limited by lack of nitrogen; whereas, nitrogen is probably the element that first limits the growth and yield of all other crops on your common soils."
"Now, what do you think of that, Girls? With millions of dollars' worth of nitrogen in the air over every acre, our crops are poor just because we don't use it. I wish you would tell me something about the suitable conditions for nitrogen-fixation, Mr. Johnston. You understand, Girls, that nitrogen-fixation is simply getting nitrogen from the inexhaustible supply in the air by means of little microscopic organisms called bacteria, which live in little balls called tubercles attached to the roots of certain plants called legumes, like cowpeas and clover. Corn and wheat and such crops can't get this nitrogen. Now, Mr. Johnston is telling about nitrification, a process which is entirely different from nitrogen-fixation. Excuse me, Mr. Johnston, but I wanted to make this plain to Mrs. Thornton and Miss Russell."
"I am glad you did so," Percy replied. "As I was saying, nitrification has no connection whatever with the free nitrogen of the air.
"All plants take their food in solution; that is, the plant food taken from the soil must be dissolved in the soil water or moisture. Of the essential elements of plant food, seven are taken from the soil through the roots into the plant. These seven do not include those of which water itself is composed. Now, these seven plant food elements exist in the soil almost exclusively in an insoluble form. In that condition they are not available to the plant for plant food; and it is the business of the farmer to make this plant food available as fast as is needed by his growing crops.
"The nitrogen of the soil exists in the organic matter; that is, in such materials as plant roots, weeds, and stubble, that may have been plowed under, or any kind of vegetable maker incorporated with the soil, including all sorts of crop residues, green manures, and the common farm fertilizers from the stables. When these organic materials are decomposed and disintegrated to such an extent that their structure is completely destroyed, the resulting mass of partially decayed black organic matter is called humus. The nitrogen of the soil is one of the constituents of this humus or other organic matter. It is not contained in the mineral particles of the soil. On the other hand the other six elements of plant food are contained largely in the mineral part of the soil, as the clay, silt, and sand. thus the iron, calcium, magnesium, and potassium, all of which are called abundant elements, are contained in the mineral matter, and usually in considerable amounts, while they are found in the organic matter in very small proportion. The phosphorus and sulfur are found in very limited quantities in most soils, but they are present in both organic and mineral form.
"Practically the entire stock or store of all of the elements in the soil is insoluble and consequently unavailable for the use of growing plants; and, as I said, some of the chief plans and efforts of the farmer should be directed to the business of making plant food available.
"The nitrogen contained in the insoluble organic matter of the soil is made soluble and available by the process called nitrification. Three different kinds of bacteria are required to bring about the complete change."
"Are these bacteria different from the nitrogen fixing bacteria?" asked Mr. Thornton.
"Entirely different," Percy replied, "and there are three distinct kinds, one for each of the three steps in the process.
"The first may be called ammonia bacteria. They have power to convert organic nitrogen into ammonia nitrogen; that is, into the compound of nitrogen and hydrogen; and this step in the process is called ammonification.
"The other two kinds are the true nitrifying bacteria. One of them converts the ammonia into nitrites, and the other changes the nitrites into nitrates. These two kinds are known as the nitrite bacteria and the nitrate bacteria.
"Technically the last two steps in the process are nitrification proper; but, speaking generally, the term nitrification is used to include the three steps, or both ammonification and nitrification proper.
"Now, the nitrifying bacteria require certain conditions, otherwise they will not perform their functions. Among these essential conditions are the presence of moisture and free oxygen, a supply of carbonates, certain food materials for the bacteria themselves, and a temperature within certain limits.
"You may remember, Mr. Thornton, that more soil nitrogen is made available for cowpeas during the summer weather than for clover during the cooler fall and spring?"
"Yes, I remember that distinction."
"I declare," said Miss Russell, "Tom talks as though he had been there and seen the things going on. I haven't seen you using any microscope."
"Well, I tell you, I've mighty near seen 'em," was the reply. "Mr. Johnston makes everything so plain that I can mighty near see what he saw when he looked through the microscope."
"I greatly enjoyed my microscopic work," said Percy, "and still more the work in the chemical laboratory where we finally learned to analyze soils, to take them apart and see what they contain,—how much nitrogen how much phosphorus, how much limestone, or how much soil acidity, which means that limestone is needed. Then I also enjoyed the work in the pot-culture laboratory, where we learned not to analyze but to synthesize; that is, to put different materials together to make a soil. Thus, we would make one soil and put in all of the essential plant food elements except nitrogen, and another with only phosphorus lacking, and still another with both nitrogen and phosphorus present, and all of the other essential elements provided, except potassium, or magnesium, or iron. These prepared soils were put in glass jars having a hole in the bottom for drainage, and then the same kind of seeds were planted in each jar or pot. Some students planted corn, others oats or wheat or any kind of farm seeds. I grew rape plants in one series of pots, and I have a photograph with me which shows very well that all of the plant food elements are essential.
"You see one pot contained no plant food and one was prepared with all of the ten essential elements provided. Then the other pots contained all but one of the necessary soil elements, as indicated in the photograph."
"Why, I never saw anything like that," said Mrs. Thornton.
"But I have many a time," said her husband, "right here on this old farm; I don't know what's lacking, of course, but some years I've thought most everything was lacking. But, according to this pot-culture test, you can't raise any crops if just one of these ten elements is lacking, no matter how much you have of the other nine; and it seems to make no difference which one is lacking, you don't get any crop. Is that the fact, Mr. Johnston?"
One pot with no plant food, and one with all the essential elements provided, and still others with but one element lacking. All planted the same day and cared for alike.
"Yes, Sir," Percy replied. "Where all of the elements are provided, a fine crop is produced, but in each case where a single element is omitted that is the only difference, and in some cases the result is worse than where no plant food is supplied. It seems to hurt the plant worse to throw its food supply completely out of balance than to leave it with nothing except what it draws from the meager store in the seed planted. Of course all the pots were planted with the same kind of seed at the same time, and they were all watered uniformly every day."
"Those results are very striking, indeed," said Miss Russell," but I suppose one would never see such marked differences under farm conditions?"
"Only under unusual or abnormal conditions," Percy replied, "but the fact is that as a very general rule our crop yields are limited chiefly because the supply of available plant food is limited. Sometimes the clover crop is a complete failure on untreated land, while it lives and produces a good crop if the soil is properly treated; and in such cases the difference developed in the field is just as marked as in the pot-cultures. In general we may set it down as an absolute fact that the productive power of normal land depends primarily upon the ability of the soil to feed the crop.
"I have here a photograph of a corn field on very abnormal soil. They had the negative at the Experiment Station and I secured a print from it, in part because I became interested in a story connected with this experiment field, which our professor of soil fertility reported to us.
"This shows a field of corn growing on peaty swamp land, of which there are several hundred thousand acres in the swamp regions of Illinois, Indiana, and Wisconsin. This peaty soil is extremely rich in humus and nitrogen, well supplied with phosphorus and other elements, except potassium; but in this element it is extremely deficient. This land was drained out at large expense, and produced two or three large crops because the fresh grass roots contained some readily available potassium; but after three or four years the corn crop became a complete failure, as you see from the untreated check plot on the right; while the land on the left, where potassium was applied, produced forty-five bushels per acre the year this photograph was taken, and with heavier treatment from sixty to seventy-five bushels are produced."
"Seventy-five bushels would be fifteen barrels of corn per acre.How's that, Little Wife?" asked Tom.
"It's even more wonderful than the pot culture," replied Mrs.Thornton; "but how much did the potassium cost, Mr. Johnston."
"About three dollars an acre," replied Percy; "but of course the land has almost no value if not treated; and as a matter of fact the three dollars is less than half the interest on the difference in value between this land and our ordinary corn belt land. These peaty swamp lands are to a large extent in scattered areas, and commonly, if a farmer owns some of this kind of land, he also owns some other good land, perhaps adjoining the swamp; but this is not always the case, and was not with the man in the story I mentioned. This man lived a few miles away and his farm was practically all of this peaty swamp land type. He heard of this experiment field and came with his family to see it.
"As he stood looking, first at the corn on the treated and untreated land, and then at his wife and large family of children, he broke down and cried like a child. Later he explained to the superintendent who was showing him the experiments, that he had put the best of his life into that kind of land. 'The land looked rich,' said he,—'as rich as any land I ever saw. I bought it and drained it and built my home on a sandy knoll. The first crops were fairly good, and we hoped for better crops; but instead they grew worse and worse. We raised what we could on a small patch of sandy land, and kept trying to find out what we could grow on this black bogus land. Sometimes I helped the neighbors and got a little money, but my wife and I and my older children have wasted twenty years on this land. Poverty, poverty, always! How was I to know that this single substance which you call potassium was all we needed to make this land productive and valuable? Oh, if I had only known this twenty years ago, before my wife had worked like a slave,—before my children had grown almost to manhood and womanhood, in poverty and ignorance!'"
"Why wasn't the matter investigated sooner?" asked Miss Russell. "Why didn't the government find out what the land needed long before?"
"I am a Yankee," said Percy. "Why have American statesmen ridden back and forth to the national capitol through a wilderness of depleted and abandoned farms in the eastern states for half a century or more before the first appropriation was made for the purpose of agricultural investigation? and why, even now, does not this rich federal government appropriate to the agricultural experiment station in every state a fund at least equal to the aggregate salaries of the congressmen from the same state, this fund to be used exclusively for the purpose of discovering and demonstrating profitable systems of permanent agriculture on every type of soil? Why do we as a nation expend five hundred million dollars annually for the development of the army and navy, and only fifteen millions for agriculture, the one industry whose ultimate prosperity must measure the destiny of the nation?
"Moralists sometimes tell us that the fall of the Babylonian Empire, the fall of the Egyptian Empire, of the Grecian Empire, and the Roman Empire, were all due to the development of pride and immorality among those peoples; whereas, we believe that civilization tends rather toward peace, security, and higher citizenship. Is not the chief explanation for the ultimate and successive fall of those great empires to be found in the exhausted or wasted agricultural resources of the country?
"The land that once flowed with milk and honey might then support a mighty empire, with independent resources sufficient for times of great emergencies, but now that land seems almost barren and supports a few wandering bands of marauding Arabs and villages of beggars.
"The power and world influence of a nation must pass away with the passing of material resources; for poverty is helpless, and ignorance is the inevitable result of continued poverty. Only the prosperous can afford education or trained intelligence.
"Old land is poorer than new land. There are exceptions, but this is the rule. The fact is known and recognized by all America.
"What does it mean? It means that the practice of the past and present art of agriculture leads toward land ruin,—not only in China, where famine and starvation are common, notwithstanding that thousands and thousands of Chinese are employed constantly in saving every particle of fertilizing material, even gathering the human excrements from every house and by-place in village and country, as carefully as our farmers gather honey from their hives; not only in India where starvation's ghost is always present, where, as a rule, there are more hungry people than the total population of the United States; not only in Russia where famine is frequent; but, likewise in the United States of America, the present practice of the art of agriculture tends toward land ruin.
"Nations rise and fall; so does the productive power of vast areas of land. Better drainage, better seed, better implements, and more thorough tillage, all tend toward larger crops, but they also tend toward ultimate land ruin, for the removal of larger crops only hastens soil depletion.
"To bring about the adoption of systems of farming that will restore our depleted Eastern and Southern soils, and that will maintain or increase the productive power of our remaining fertile lands of the Great Central West, where we are now producing half of the total corn crop of the entire world, is not only the most important material problem of the United States; but to bring this about is worthy of, and will require, the best thought of the most influential men of America. Without a prosperous agriculture here there can be no permanent prosperity for our American institutions. While some small countries can support themselves by conducting trade, commerce, and manufacture, for other countries, American agriculture must not only be self-supporting, but, in large degree, agriculture must support our other great industries.
"Without agriculture, the coal and iron would remain in the earth, the forest would be left uncut, the railroads would be abandoned, the cities depopulated, and the wooded lands and water-ways would again be used only for hunting and fishing. Shall we not remember, for example, that the coal mine yields a single harvest—one crop—and is then forever abandoned; while the soil must yield a hundred—yes, a thousand crops, and even then it must be richer and more productive than at the beginning, if those who come after us are to continue to multiply and replenish the earth.
"Even the best possible system of soil improvement, we must admit, is not the absolute and final solution of this, the most stupendous problem of the United States. If war gives way to peace and pestilence to science, then the time will come when the soils of America shall reach the limit of the highest productive power possible to be permanently maintained, even by the general adoption of the most practical scientific methods; and before that limit is reached, if power, progress, and plenty are to continue in our beloved country, there must be developed and enforced the law of the survival of the fittest; otherwise there is no ultimate future for America different from that of China, India, and Russia, the only great agricultural countries comparable to the United States. An enlightened humanity must grant to all the right to live, but the reproduction and perpetuation of the unfit can never be an absolute and inalienable right.
"Under the present laws and customs, a man may spend half his life in the insane asylum or in the penitentiary, and still be the father of a dozen children with degenerate tendencies. There should be no reproduction from convicted criminals, insane persons, and other degenerates. Thieves, grafters, bribers and bribe-takers all belong in the same class, and it should not be left possible for them to reproduce their kind. They are a burden upon the public which the public must bear, but the public is under no obligation to permit their multiplication. The children of such should never become the parents of others. It is a crime against both the child and the public.
"No doubt you will consider this extremely visionary, and so it is; but unless America can see a vision somewhat like this, a population that is doubling three or four times each century, and an area of depleted soils that is also increasing at a rapid rate will combine to bring our Ship of State into a current against which we may battle in vain; for there is not another New World to bring new wealth, new prosperity, and new life and light after another period of 'Dark Ages.'
"Whether we shall ever apply any such intelligence to the possible improvement of our own race as we have in the great improvement of our cattle and corn is, of course, an open question; but to some extent you will agree that the grafter and the insane, like the poet, are born and not made. Of course there are, and always will be, marked variations, mutants, or 'sports,' but, nevertheless, natural inheritance is the master key to the improvement of every form of life; and it is an encouraging fact that some of the states, as Indiana, for example, have already adopted laws looking toward the reduction of the reproduction of convicted degenerates."