Popular Science Monthly/Volume 84/January 1914/The Illinois System of Permanent Fertility
| THE ILLINOIS SYSTEM OF PERMANENT FERTILITY |
By Professor CYRIL G. HOPKINS
UNIVERSITY OF ILLINOIS
I HAVE been invited to write upon the Illinois system of permanent fertility; but I wish to state in the beginning that, in complying with this request, I am speaking in a representative capacity. Many have contributed to the development of this system, including both able investigators in other states and countries, my own colleagues in the investigation of Illinois soils, and the truly scientific farmers of this state, some of whom have kept their own farm practise so close up to the work of the experiment stations as to exert great influence upon the adoption of systems of permanent fertility.
It is more than fifty years since Liebig wrote the following words:
An important part of the work performed in Illinois has consisted in assembling the facts the world affords and cementing these into concrete forms which serve as a firm foundation upon which to build systems of permanent agriculture.
The main problem of permanent fertility is simple. It consists, in a word, in making sure that every essential element of plant food is continuously provided to meet the needs of maximum crops; and, of course, any elements which are not so provided by nature must be provided by man. The whole subject has been greatly and unnecessarily complicated, not only by erroneous theories commonly held by farmers and something advocated by unscientific "scientists" holding official positions, such as the theory that crop rotation will maintain the fertility of the soil, but also by the ruinous policy of most commercial fertilizer interests in urging and often persuading farmers to use small amounts of high-priced so-called "complete" fertilizers which add to the soil only a fraction of the plant food actually required by the crops removed, with the inevitable result that the land itself is steadily impoverished.
The more rational system makes use of abundant quantities of all essentials, but at a cost low enough to be within reasonable reach. Those materials which are naturally contained in the soil in inexhaustible amounts are liberated from the soil and thus made available for crop production; those contained in the air are likewise drawn upon as needed; while those materials which must be purchased are bought and applied in liberal quantities, but in low-pricecl forms, and then made available on the farm by economic natural methods.
Four Fundamental Facts
Nearly 150 years ago Sénébier, of Switzerland, found that the carbon of plants is derived from the carbon dioxid of the air, and it is more than a century since DeSaussure, of France, first gave to the world a correct and almost complete statement concerning the essential mineral food of plants. Later, Lawes and Gilbert, of England, established the fact that for most plants the soil must furnish the nitrogen as well as the mineral elements; and more than a quarter-century has passed since Hellriegel, of Germany, discovered that bacteria living in symbiotic relationship with legume plants have power to gather nitrogen from the inexhaustible atmospheric supply.
These are the four great fundamental facts upon which the science of plant growth and permanent fertility must be based, and they were all discovered before the Illinois Experiment Station was established.
Illinois Contributions
There remained, however, two very important general problems, and in the solution of these Illinois has made some contributions. One of these relates to the amount of nitrogen taken from the air by legumes under normal field conditions; and the other concerns the liberation of mineral plant food from insoluble materials.
It is not enough to know that clover has power to secure nitrogen from the air; we should know how much nitrogen is thus secured in order that we may plan intelligently to provide nitrogen for the production of corn, oats, wheat and other non-legumes, instead of using clover merely as a soil stimulant in systems of ultimate land ruin, as is still the most common practise.
It is also a matter of the greatest economic importance that definite information should be secured in regard to the practical means of utilizing mineral plant food from the abundant natural supplies nearest at hand, such as Tennessee phosphate rock, natural limestone, and the potassium minerals already present in our normal soils.
Plant-food Elements
In brief, there are ten elementary substances which bear the same relation to the making of crops as brick and mortar bear to a wall of masonry. If any one of these ten elements is entirely lacking, it is impossible to produce a grain of corn or wheat, a spear of grass, or a leaf of clover.
Two elements, carbon and oxygen, are taken into the plant from the air through the leaves; hydrogen is secured from water absorbed by the roots, and iron and sulphur are also supplied by nature in abundance. But the other five elements require careful consideration if lands are to be kept fertile. These are potassium, magnesium, calcium, phosphorus and nitrogen; and every landowner ought to be as well acquainted with these five elements as he is with his five nearest neighbors.
Instead of making this acquaintance and gaining a knowledge of important facts and principles, the average farmer in the older states, with failing fertility, has made the acquaintance of the fertilizer agent; and instead of purchasing what he needs for the permanent improvement of his soil, he buys what the agent wants to sell, with the common result that the seller is enriched while the soil is merely stimulated to greater poverty.
Potassium.—A careful study of the facts shows that potassium is one of the abundant elements in nature; that the average crust of the earth contains 212 per cent, of this element, and that normal soils bear some relation in composition to the average of the earth's crust.
If normal soil had the same percentage, then the plowed soil of an acre 623 inches deep (corresponding to 2 million pounds of soil) would contain 50,000 pounds of potassium. In Illinois, the normal soils actually do contain from 25,000 to 45,000 pounds per acre of this plantfood element in the first 623 inches, while less than 4 pounds of potassium would be added in an application of 200 pounds of the most common commercial fertilizer. The Illinois system of permanent fertility does not provide for the purchase of potassium for normal soils, but it does provide for the liberation of an abundance of that element from the practically inexhaustible supply in the soil. This liberation is accomplished by the action of decaying organic matter plowed under in the form of farm manure or crop residues, including clover or other legumes.
Only where the soil is positively deficient in potassium susceptible of liberation, as is the case with some sand soils and with most peaty swamp lands, need potassium be purchased in permanent systems of either grain farming or live-stock farming; but in market gardening or in raising timothy hay for the market commercial potassium may be required; and, on some worn soils especially deficient in decaying matter, temporary use of kainit is often advisable.
Magnesium and Calcium.—As a general average, normal soils contain more than four times as much potassium as magnesium, while the loss by leaching and cropping in rational systems of grain or live-stock farming may be actually greater for magnesium than for potassium, so that magnesium is more likely to become deficient in soils than is potassium.
The calcium supply in normal soils is also only one fourth that of potassium, while the average loss by cropping and leaching is four times as great, so that 16 to 1 expresses the relative importance of calcium and potassium in the problem of permanent fertility on normal soils.
All limestones contain calcium; and the common dolomitic limestone in the almost measureless deposits contains both calcium and magnesium in very suitable form both for plant food and for correcting or preventing soil acidity.
In the Illinois system of permanent fertility, ground natural limestone is applied, where needed, at the rate of about two tons per acre every four years. With the same price and purity, probably the dolomite is preferable to the high calcium stone, although both kinds have been used with very good results. Further data from investigations now in progress are expected to furnish definite information as to the relative value of these materials.
Phosphorus.—Attention was called to the fact that two million pounds of the average crust of the earth contains 50,000 pounds of potassium; but compared with this we find only 2,000 pounds of phosphorus. Likewise, the plowed soil of an acre of average Illinois land contains about 35,000 pounds of potassium, but less than 1,200 pounds of phosphorus. When grain is. sold from the farm, about equal amounts of phosphorus and potassium are carried away, while in independent systems of live-stock farming much more phosphorus than potassium leaves the farm.
At 3 cents a pound for phosphorus one can double the amount of that element contained in the plowed soil of our $200 land at a cost of $35 an acre,, while to double the potassium in the same stratum would cost more than $1,000 an acre.
Phosphorus can be purchased, delivered at the farmer's railroad station in Illinois, for about 3 cents a pound in the form of fine-ground natural rock phosphate, for 10 to 12 cents a pound in steamed bone meal, or for 12 to 15 cents in acid phosphate. It can be used with profit in any of these forms, but the data thus far secured in comparative experiments plainly indicate that, with equal amounts of money invested, the natural rock phosphate will give the greatest profit in rational permanent systems. At least 1,000 pounds per acre every four years should be applied, and for the first application even three or four tons per acre is not considered too much phosphate by those who best understand the need and value of phosphorus on normal land.
Nitrogen and Organic Matter.—There is a rather common opinion that the growing of clover enriches the soil in nitrogen, and many even believe that clover in crop rotation will maintain the fertility of the soil. These same people are likely to think that the application of limestone and phosphate involves much expense and work, and that the returns are much less certain than those from other labor and money investments.
Such opinions are largely erroneous. The mere growing of clover on normal land does not enrich it. Even the nitrogen is not increased unless the clover crop is returned to the soil either directly or in farm manure. Rotation with such crops as corn, oats and clover depletes the soil of all important elements of fertility, and on normal soils always results ultimately in land ruin, unless some system of restoration is practised. Clover takes large amounts of calcium and phosphorus from the soil, and does not increase the nitrogen content if only the roots and stubble are left, because they contain no more nitrogen than the clover itself will take from soils of normal productive power.
To increase or maintain the nitrogen and organic matter of the soil is the greatest practical problem in American agriculture. In an hour's time one can spread enough limestone or phosphate on an acre of land to provide for large crops of wheat, corn, oats and clover, for ten or twenty years, while to supply the nitrogen for the same length of time would require from 20 to 40 tons of clover, or from 80 to 160 tons of farm manure, to be added to the same acre of land, even though one of the four crops harvested secured its nitrogen from the air.
Certainly we are making no such additions to the soil in average corn-belt agriculture, and one may well ask, How then is it possible to grow the crops now produced in this country? In the simplest language the answer to this question is: By "skinning" the soil—by working the land for all that's in it—by following the example of our ancestors, who brought agricultural ruin to millions of acres of once fertile farm land in the original thirteen states.
To provide nitrogen in the Illinois system of permanent agriculture requires the use of common sense and positive knowledge, the same as in providing limestone and phosphorus.
For the live-stock farmer I would suggest a five-field system—a four-year rotation of-corn, corn, oats and clover, grown upon four fields for five years, while the fifth field is kept in alfalfa. At the end of the fifth year the alfalfa field is brought into the rotation and one of the four fields seeded to alfalfa for another five-year period, and so on.
If the crop yields are 50 bushels each of corn and oats, 2 tons of clover and 3 tons of alfalfa; if the straw and half the corn stalks are used for bedding and all other produce for feed, and if 60 per cent, of the nitrogen in the manure is used for the production of crops, then a system is provided which will permanently maintain the supply of nitrogen.
For the farmer who sells grain, a 25-bushel wheat crop may well be substituted for the first corn crop, clover being seeded on the wheat for plowing under next year before planting com. If the fall and spring growths of this clover aggregate 112 tons, and if only the grain and clover seed and the alfalfa hay are sold, all clover, stalks and straw being turned to the land, this also provides a system for the permanent maintenance of nitrogen.
If the crop yields are all increased by 50 per cent., or even by 100 per cent., these systems still provide for the nitrogen supply, unless with the larger yields on richer land a somewhat greater amount is likely to 
be lost by leaching than is added in the rain and by the azotobacter and other non-symbiotic bacteria.
While these systems are distinctly for live-stock farming or for grain and hay farming, they should be considered as only suggesting the basis for solving the nitrogen problem. In diversified farming a combination of these systems will often be preferred to either one alone. The important point is that the landowner should know the essential facts and base his practise upon them in order to provide for permanent fertility with respect to nitrogen, phosphorus and limestone.
Application of Principles Established
Louisiana Experiments.—The longest record of a rational permanent system of agriculture conducted in America is furnished by the Louisiana Experiment Station. As an average of nineteen years, the values per acre of three crops were $29.79 from unfertilized land, and $92.04 where organic manures and phosphorus were regularly applied[1] in a three-year rotation of (1) cotton, (2) corn and cowpeas, (3) oats and cowpeas. Here the crop values from the well-fertilized land average more than three times as great as those from the unfertilized land under the same rotation and with two legume cover crops grown every three years.
Ohio Experiments.—The Ohio Experiment Station has reported sixteen years' results from a three-year rotation of corn, wheat and clover, both from unfertilized land and from land treated with farm manure and phosphorus. As a general average, the values per acre of the three crops at conservative prices were $27.07 on untreated[2] land, $44.65 where farm manure was applied, $53.82 where manure and rock phosphate were used, and $53.61 where manure and acid phosphate were applied, practically the same yields having been secured whether the phosphorus was applied in raw rock phosphate or in acid phosphate, costing twice as much. The well-fertilized land has produced nearly twice as much as the land where no manure and phosphate were used, although clover was grown every third year in the rotation and all of the land was limed.
On the basis of these figures, 8 tons of manure were worth $17.58, or $2.20 per ton; and the rock phosphate, costing about $7.50 or $8 per ton, was worth $57.31; or, if we use the Ohio methods of computing the amount and value of the increase produced, each ton of raw phosphate was worth $65.63; and it may well be added that to obtain the same amount of phosphorus in the common high-priced mixed manufactured commercial fertilizer, such as farmers are advised by the 
fertilizer manufacturers and advertising agencies to use, would cost about $75.
Illinois Experiments.—As an average of 318 tests conducted in southern Illinois during a period of eight years, two tons of ground limestone, applied once in four years at a cost of about $2.50 per acre, has produced an increase of 5 bushels of corn, 612 bushels of oats, 4 bushels of wheat and 12 ton of hay; and where one ton per acre of fine ground rock phosphate was applied on the common corn-belt land in a rotation of wheat, corn, oats and clover, the value of the increase produce paid back more than 100 per cent, for the first crop rotation and nearly 200 per cent, for the second four-year period.
On one of our oldest soil experiment fields on typical Illinois prairie 
land, where soil enrichment has been practised for twelve years, during the last four years the value of the produce from the land receiving phosphorus has been twice as much as that from the untreated land. In other words, $2.50 invested in phosphorus has brought the same gross income as $250 invested in land; and even the interest on the land investment is five times the annual cost of the phosphorus. Furthermore, the addition of phosphorus tends toward enrichment and consequently toward the protection of the capital invested in the land.
It is sometimes suggested by people who have no intelligent basis for such an opinion, that the result secured by an experiment station upon relatively small tracts of land could not be secured in practical agriculture. In part to disprove such incorrect and unjust statements, 
I purchased a farm in southern Illinois ten years ago at a cost of less than $20 an acre. It comprised about 300 acres of poor gray prairie land (the commonest type of soil in about twenty counties in that part of the state) and a few acres of timber land. It was christened "Poorland Farm" by others who knew of its impoverished condition.
In 1913 a 40-acre field of this farm produced 1,320 bushels of wheat. This particular forty acres was bought at $15 an acre. It had been agriculturally abandoned for five years prior to 1904, and was covered with a scant growth of red sorrel, poverty grass and weeds.
During the ten years this field has been cropped with a rotation including one year each of corn, oats (or cowpeas) and wheat, and three 
years of meadow and pasture with clover and timothy. About 4 tons per acre of ground limestone and 2 tons per acre of fine-ground raw rock phosphate have been applied to 37 acres of this field. Two applications have been made of each material; the phosphate was plowed down for the corn crops of 1904 and 1910, and the limestone was applied in the fall and winter of 1904–5 and after the ground was plowed for wheat in the fall of 1912.
The entire 40-acre field was covered with one uniform application of six loads per acre of farm manure with a 50-bushel spreader.
A six-rod strip entirely across the field (80 rods) received the same application of manure and the same rotation of crops as the remaining 37 acres, but no phosphate was applied to this strip, and no limestone was applied to it until the fall of 1912, when the regular application (about 2 tons per acre) was applied to one half (three rods) of the six-rod strip.
Only 39 acres of this field were seeded to wheat in the fall of 1912, a lane having been fenced off on one side; and the 1,320 bushels were produced on the 39 acres.
The actual yields were as follows:
112 acres with farm manure alone produced 1112 bushels per acre.
112 acres with farm manure and the one application of ground limestone produced 15 bushels per acre.
36 acres with farm manure and two applications of ground limestone and two of fine-ground phosphate produced 3512 bushels per acre.
The cost of two tons of limestone delivered at my railroad station is $2.25, and raw rock phosphate has averaged about $6.75 per ton, making $9 per acre the cost for each six years.
To this must be added the expense of hauling these materials two miles from the station and spreading them on the land, which I estimate at 50 cents per ton. This makes the average annual cost $1.75 per acre for the limestone and phosphate spread on the field, and this average annual investment resulted in the increase of 24 bushels of wheat per acre in 1913.
Thus we may say that the previous applications of these two natural stones in this system of farming brought about the production in 1913 of 864 bushels of wheat, sufficient to furnish a year's supply of bread for more than a hundred people. And the soil is not being stimulated or depleted of any element in which it is naturally deficient. On the contrary, there is positive soil enrichment; "new" nitrogen is secured from the air, the phosphorus content has already been increased to that of the $200 corn-belt land, and sour land is changed to a "limestone soil." No high-priced or artificial commercial fertilizers are used on this farm; and the results secured from 40-acre fields on a 300-acre farm are practically the same as on the one fifth-acre plots of the state experiment fields under similar systems.
Poorland Farm is usually inspected each year by my class of university students in soil fertility, about one hundred of whom saw the fields of wheat and clover in June, 1913. It is for the benefit of such as these, who desire to know the truth regarding economic systems of permanent soil improvement, that this brief statement is published.