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Whitney takes the position that if the soils of eastern and southern United States have any less plant food than when first cultivated, they at least have all the ingredients essential for crop production. This position is certainly supported by statistics that have been given on the amount of plant food contained by soils. An acre of very fertile soil contains about 70,000 pounds, or 2 per cent, of potash in the first foot of ground. A crop of wheat removes about 15 pounds of potash from each acre. It has been estimated that the first eight inches of soil contain on an average enough nitrogen to last 90 years, enough phosphoric acid to last 500 years, and enough potash to last 1,000 years.' T his supply is materially increased when we consider the great depth penetrated by the roots of wheat. It must also be borne in mind that the loss of plant food is often much greater than that removed by crops; for example, it has been given as three to five times as much in the case of nitrogen. Extensive farming, nevertheless, soon reduced the productivity of our first cultivated soils, and with the cpening of the large and level western wheat fields of fully as great fertility as was ever possessed by any soils of the United States, many of the older lands were abandoned. Now, however, most of the farm lands of the west have 'een occupied, the standard or farming is being raised, and conditions have so changed as to make it seem profitable again to resume the cultivation of these abandoned lands. But they must be farmed by intensive methods, of which fertilizing is a valuable part. Some lands have already been restored to fertility and are being cultivated with profit. Missouri soils are still rich in plant food, yet their productivity is much less than it was 50 years ago. Commercial fertilizers had been profitably used in wheat raising in Ohio over a decade ago. Growing a leguminous crop on light sandy soil deficient in humus increased the yield of the following crop of wheat over 50 per cent in Arkansas. When 400 pounds of a complete fertilizer were used in addition, the following 2 years the wheat crop averaged over 70 per cent more than on soil not thus treated. Manure treatment and the application of phosphorus is found very profitable in Illinois.

1 IRept. Mich. Loard Agr., 1905, p. 147.

As a rule, the land in the Red river valley is not fertilized, and produces less than 15 bushels per acre, but the application of fertilizers has given 26 bushels per acre. Rotation of crops is already widely practiced in the northwest, and as the soil becomes more exhausted and the prices of land and produce rise, fertilizers will be used there, just as they have in every other country where similar conditions arose. Even the largest bonanza farmers are looking forward to the time when they must fertilize. Stock will also be raised, and farming will become more diversified. This will give opportunity to utilize many of the products of wheat on the farms where they are produced, and the need for commercial fertilizers may ultimately be removed altogether. One-fourth of the nitrogen and nearly all of the phosphoric acid and potash which enter into a crop of wheat are contained in bran, screenings and middlings. Most of these can be returned to the soil by raising stock. These principles are not mere theories, for their practical working has been demonstrated in Michigan and Illinois, in portions of which the land has been continually growing more fertile under cultivation without the use of a pound of commercial fertilizer.

The average Kansas wheat grower has given little thought yet to fertilizing, but ‘‘his methods will change with the years and the necessities.” In Minnesota, “results already reached warrant the statement that the average yields per acre of wheat can be increased 25 to 50 per cent by so rotating the crops and manuring and cultivating the fields (as) best to prepare the soil for this grain.’’’ The necessity of fertilizing is little felt in Canada as yet.

Fertilizer Laws.-A majority of the United States, including nearly all the states east of the Mississippi, have statutes, most of them rather stringent, governing the sale of commercial fertilizers. That dealers were cheating farmers was first shown by the Massachusetts experiment station. This station was instrumental in the passage of the Massachusetts fertilizer law. which was more or less closely followed by other states. The department of agriculture has made efforts for a more uniform system of laws, and to regulate interstate trade. No general fraud is now practiced. Thousands of official analyses are

1 Minn. Bul. 12, p. 321.

made yearly, and these very largely eliminate fraud and extravagant claims. Fertilizer Statistics.-The annual sales of fertilizers in the United States exceed $50,000,000, and perhaps over 2,000,000 tons are consumed. During 1896 over 375,000 tons were imported, valued at about $19 a ton, and over 514,000 tons, valued at about $8.50 a ton, were exported. During the first six months of 1905 the importations were valued at nearly $2,000,000. The annual import of nitrate of soda is nearly 200,000 tons, having an average value of about $30 a ton. The first guano sold for about $95 a ton, but later fell to half that amount. A ton of cottonseed meal has a fertilizing value of over $20. A ton of fertilizer, costing $25, is applied to an acre of wheat land in New York. The phosphate mined in the United States in 1899 amounted to 541,045 tons. The average cost of phosphates at the quarry was $4.42 per ton in 1893. In Illinois rock phosphate could be procured at about $8 per ton in 1906, and bone phosphate at $25 per ton. California expended six times as much for fertilizers in 1900 as in 1890. About 1890 the farmers of Ohio were expending a million dollars annually for commercial fertilizers used in the production of wheat. It is claimed that a trust caused prices of fertilizers to advance from 15 to 25 per cent in 1900. Below is a schedule of prices given for the different fertilizing substances per pound:"

Nitrogen . . . . . . . . . . . . . . . . . . - - - - - - - - - - - - - - - - - - - - - - 1614 cents Potash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 cents Water-Soluble Phosphoric Acid . . . . . . . . . . . . . . . . . . 5% cents Citrate-Soluble Phosphoric Acid . . . . . . . . - - - - - - - - ... 5 cents Phosphoric Acid in fine bone . . . . . . - - - - - - - - - - - - - - - . 3 cents Phosphoric Acid in medium and coarse bone. . . . . . . . 21% cents

In Illinois the annual cost of fertilizing an acre of land is about $1.70. Tubercle organisms enable leguminous crops to add from $8 to $10 per acre in nitrogenous fertilizer. In the early nineties over 75 per cent of the fertilizers sold were equal to or above the guaranty under which they were sold. Most of the others were much less than 1 per cent below their guaranty. It has been estimated that with the use of all barn manures and proper cultivation, the soils of the Red river valley should yield good crops without commercial fertilizers for over a thousand years. “From 7 to 135 pounds of nitrogen, from 3 to 55 pounds of phosphoric acid, and from 3 to 36 pounds of potash are sold with every ton of produce leaving the farm.’’’ Eighty billion pounds of nitrogenous material entered into the creation of one harvest in the United States in the early nineties. The cereals annually took from the earth nearly 3 billion pounds of phosphoric acid, and the loss of potash was not less than 4 billion pounds.

* Miss. Bul. 77 (1902), p. 3.

* Yearbook U. S. Dept. A gr., 1897, p. 301.

CHAPTER IX
DISEASES OF WHEAT

Introductory.—Studies in plant pathology of any great practical bearing or importance are decidedly and characteristically modern and recent. In 1885 there were three institutions in the United States besides the department of agriculture which were making systematic efforts in experimental work with plant diseases, and in disseminating such knowledge as then existed in these lines. Ten years later over one hundred special investigators were devoting their time to this work, and 50 colleges and stations were endeavoring to solve its practical problems. The science of plant pathology has had its highest appreciation during the last decade, for some of the outlying problems have been solved, a working foundation has been laid from the facts that were acquired, and a body of institutions with specialists and resources has been developed for scientifi

:ally prosecuting the work.

The Classification here followed is practical and inclusive, rather than scientific and exclusive. There is nothing pathological in the sudden destruction of a field of wheat by floods or locusts, but excessive moisture or the presence of a parasite may each bring about diseased conditions, and every gradation of phenomena between these two types must be considered.

Sources of Injury and Weakness are of three kinds: (1) Unfavorable inanimate environment; (2) unfavorable animate environment; and (3) poor seed wheat. When these three sets of factors occur in combination, as they frequently do, their relations and inter-relations are so intimate and intricate as to be inseparable. Only in a general way can they be individually

studied.

WEATHER AND SOIL INFLUENCES

Unfavorable Inanimate Environment.—DROUGHT; HAIL, WIND AND RAIN Storyis; FLOops: FIRE. The operation of these destructive influences needs no further elucidation than a mere

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