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- The Farm That Won't Wear Out - 5/9 -
and then the crop residues or farm manure is returned to the soil to provide sufficient nitrogen for the grain crops. In all cases phosphorus was used for these yields.
Even more encouraging than these six-year average results from Illinois are the results of sixty years from Agdell Field at Rothamsted.
Where mineral plant food was regularly applied, and where all the manure produced by feeding the turnips was returned to the soil, in a four-year rotation of turnips, barley, clover (or beans) and wheat, with no other provision made for supplying nitrogen, the yields per acre were as follows:
Turnips, 24,724 lbs. in 1848, and 26,410 in 1908.
Barley, 42.8 bushels in 1849 and 22.1 in 1909
Clover, 5586 pounds in 1850 and 7190 in 1910.
Wheat, 32 bushels in 1851 and 37.8 in 1911.
Here we have data which span a period of sixty years and which show that where mineral plant food has been provided the clover in rotation and the manure produced by the feeding of only one of the four crops have maintained the yield of all crops except the barley-the third crop after clover-and without the application of nitrogen in any other form. If the clover and straw had been returned to the land either directly or in farm manure the additional nitrogen thus provided would have been sufficient both to maintain the yield of barley and to prevent the moderate decrease which has occurred in the nitrogen content of the soil.
PHOSPHORUS: THE MASTER KEY
TO PERMANENT AGRICULTURE
THE greatest economic loss that America has ever sustained has been the loss of energy and profit in farming with an inadequate supply of phosphorus. Phosphorus is a Greek word which signifies "light-bringer"; but it is a light which few Americans have yet seen, else we should not permit the annual exportation of more than a million tons of our best phosphate rock, for which we receive at the mines the paltry sum of five million dollars, carrying away from the United States an amount of the one element of plant food we shall always need to buy, which if retained in this country and applied to our own soils would be worth not five million but a thousand million dollars for the production of food for the oncoming generations of Americans.
For five million dollars we export to Europe each year enough phosphorus for 1,400,000,000 bushels of wheat, or twice the average crop of the entire United States. Meanwhile our ten-year-average yield of wheat is 14 bushels an acre, while Germany's yield has gone up to 29, Great Britain's to 33, England's to 37-1/2 and Denmark's to more than 40 as the average for a decade.
Potato Yield Twice Doubled
There is only one place in the world where we can go for the results of soil improvement for more than a quarter of a century in connection with the growing of potatoes. Of course this place is Rothamsted, England, where as an average for twenty-six years the yield of potatoes was 51 bushels an acre on unfertilized land and exactly 102 bushels where only a phosphate fertilizer was applied. Where the same amount of phosphorus--29 pounds of the element per acre per annum--was used in connection with other minerals--300 pounds of potassium sulfate and 100 pounds each of the sulfates of magnesium and sodium--the average yield of potatoes was 109 bushels. Where 86 pounds of nitrogen was applied in sodium nitrate the average yield was 79 bushels; but where the nitrogen, phosphorus and other minerals were all applied the average yield for the twenty-six years was 203 bushels.
At 50 cents a bushel for potatoes, the investment in phosphorus alone paid 600 per cent net profit; and even the complete fertilizer, including 392 pounds of acid phosphate, 550 pounds of sodium nitrate and 500 pounds of alkali salts, aggregating 1442 pounds, and costing at moderate prices $24.28 an acre per annum, paid back $76 a year as a twenty-six year average, thus making 300 per cent even on an investment of nearly $25 an acre a year.
Phosphorus Helps Good Farming
There is also but one place in the world where we can learn the results secured from the application of phosphorus for a period of thirty-six years in a good system of farming; and again this place is Rothamsted.
In 1848 Sir John Lawes and Sir Henry Gilbert began investigations on Agdell Field. The Norfolk rotation, already known at that time as one of the best rotation systems, was turnips, barley, clover, and wheat; and in these practical field experiments the turnips were fed on the land and the animal fertilizer thus produced was returned to the soil, which was well supplied with limestone.
During the next thirty-six years $29.52 worth of phosphorus per acre was applied to one part of the field; and in comparison with another part of the same field cropped and managed similarly, except that no phosphorus was applied, the $29.52 worth of phosphorus produced $98.02 increase in the value of the turnips, $37.45 in barley, $48.93 in clover (and beans) and $45.99 in wheat.
The total value of the crops grown on the land not receiving phosphorus during the thirty-six years was $432.43 an acre, while on the phosphated land the crop values amounted to $662.82, an increase of $230.39 from an investment of $29.52, the turnips being figured at $1.40 a ton, barley at 50 cents a bushel, clover hay at $6 a ton, beans at $1.25 a bushel, wheat at 70 cents a bushel, and phosphorus at 12 cents a pound. As a general average at these conservative prices, the investment of $3.28 an acre every four years paid back $25.60 in the four crops.
In most states the legal rate of interest is 6 per cent but here is an investment that paid the principal and 680 per cent interest every four years. And these investigations show that the phosphorus was used with profit for the production of markedly different crops, including potatoes and turnips, barley and wheat, clover and beans.
But the soil at Rothamsted is no poorer in phosphorus than is the average soil of the United States; and these results are given here not only because they are the oldest and most trustworthy the world affords, but because they are strictly applicable to the production of common crops on vast areas of agricultural land in our own country.
The Form of Phosphorus to Use
The unfertilized soil at the Rothamsted station contains, in 2,000,000 pounds--corresponding to about 6-2/3 inches to the acre--1000 pounds of phosphorus and 35,000 of potassium, while an acre of plowed soil of the same weight at State College, Pennsylvania, contains 1100 pounds of phosphorus and 50,700 of potassium.
In a word, normal soils are deficient in phosphorus, and the application of phosphorus in good systems of farming produces marked and profitable increases in crop yields. But what form of phosphorus shall we apply? This is a very important question in agricultural economics, for we have many different kinds of fertilizing materials that contain phosphorus, and one may cost ten times as much as another as a source of phosphorus. Thus 250 pounds of phosphorus in a ton of finely ground natural rock phosphate can be purchased at the mines in Tennessee and delivered at the farmer's railway station in the heart of the Corn Belt for $8. Or the ton of raw phosphate may be mixed with a ton of sulfuric acid in the fertilizer factory, and the two tons of acid phosphate may be sold to the same farmer for $32. Or the fertilizer manufacturer may mix the two tons of acid phosphate with two tons of "filler," containing a little nitrogen and potassium, and then sell the same farmer the four tons of so-called "complete" fertilizer for $80; and the farmer gets no more phosphorus in the four tons of "complete" fertilizer for $80 than in the one ton of natural phosphate for $8.
The Pennsylvania State College conducted an experiment for twelve years--1884 to 1895--in which $1.05 an acre was invested in ground raw rock phosphate with a rotation of corn, oats, wheat and hay (clover and timothy), and the value of the increase produced by the phosphorus amounted to $5.85 as an average for the twelve years, and to $8.41 as an average for the last four years. Thus the profit was from about 560 to 800 per cent on the investment, counting corn at 35 cents a bushel, oats at 30 cents, wheat at 70 cents, and hay at $6 a ton. These figures represent the increase produced by phosphorus over and above the value of the crops grown without phosphorus fertilizer. In this case no farm manure was used on either part of the field; but commercial nitrogen and potassium were applied alike on both parts, and clover was grown in the rotation.
Acid phosphate was also used in direct comparison; and, in answer to the question whether the general farmer should apply liberal amounts of finely ground natural rock phosphate, or whether he should pay four times as much for phosphorus after the fertilizer manufacturer has mixed one part of the raw rock with one of sulfuric acid and thus produced two parts of acid phosphate, these Pennsylvania experiments tell us that the yearly average for the twelve years gave a gain per year of $2.45 from the raw phosphate and 48 cents from the acid phosphate, at the prices used by the Pennsylvania Experiment Station. But we must not draw general conclusions from this one experiment, even though it covers twelve years.
In 1895 the Maryland Experiment Station began field experiments with different forms of phosphorus; and, as an average of six tests every year for twelve years, $1.965 invested in ground raw rock phosphate produced increases in corn, wheat and hay that were worth $22.11, at 35 cents a bushel for corn, 70 cents for wheat, $6 a ton for hay, and 3 cents a pound for phosphorus in the ground natural phosphate. How would you like 1000 per cent profit as the result of mixing brain with brawn, in connection with the improvement of your own business, thus keeping the investment under your own control?
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