« AnteriorContinuar »
from one spike in four years to sow about 500 acres.1 In ten years, one grain of North Dakota wheat, now known as Minnesota 163, without any attempt to increase it rapidly the first few years, actually produced about 300,000 bushels of wheat. One thousand acres of land south of Walla Walla in eastern Washington yielded 51,000 bushels in 1881. "This yield was made the subject of a careful measurement and reported to the Agricultural Department, where it stands today as the largest yield for a thousand-acre field ever reported.''2 The greatest wheat crop ever recorded in the world's history as being produced from unfertilized land was that of western Canada in 1901, where 63,425,000 bushels were harvested from a little over 2,500,000 acres; an average yield of over 25 bushels per acre.
Physical Properties.—The number of grains in a pound of wheat varies from 7,500 to 24,000; from 377 determinations the average was 12,000 grains. The number in a bushel has been given as varying from 446,580 to 971,940. The Winchester bushel (2150.42 cubic inches) used in the United States, has a standard and legal weight of 60 pounds. The measured bushel generally varies in weight from 54 to 65 pounds, and greater extremes occur. The Imperial bushel (2218.192 cubic inches) used in England, has a corresponding weight of 61.89 pounds. This is the reason why English wheat appears heavier than American grain.
The specific gravity of American wheat has been found to vary from 1.146 to 1.518. Lyon found high specific gravity associated with low nitrogen content. As a rule, the harder the grain, the higher is the gluten and nitrogen content, and the deeper red the color.
Viability of Wheat.—Experiments have shown the optimum period for germination to be the second year after harvest. Seed one year old often gives better results than fresh seed, but after the first year the viability generally diminishes rapidly from year to year. Ordinarily it is not advisable to sow wheat over two, or at the most three, years of age, at least not without testing its germinating powers, which have been found to vary from 15 to 75 per cent after five years. The longest
1 Neb. Bui. 32, p. 84.
'Kept. Bureau of Statistics, Washington, 1903, p. 69.
period for which conclusive modern scientific experiments have shown wheat to be viable is ten years. During six successive years Saunders found the average viability of three varieties to be respectively: 80, 82, 77, 37, 15 and 6 per cent.1 Varro, speaking of the granaries of the first century B. C, remarks that the vitality of wheat can be preserved in them for 50 years. Daubeny questioned this in 1857, and stated that wheat does not retain its vitality over 40 years. Humboldt states that for causes not well known, Mexican grain is preserved with difficulty for more than two or three years. The reported germination of wheat taken from Egyptian mummies thousands of years old is a modern myth originating in the impositions of fraud and cunning upon credulity.
The highest temperature at which dry wheat seed can retain its vitality is also an unsettled question. Chambers's Cyclopedia makes the statement that some dry seeds survive 212 ° F., and —248° F., but does not state what kind. Klippart gives —58° F. as the point at which wheat loses its vitality, and says that the germinating power is completely destroyed if the grain is steeped 15 minutes in water having a temperature of 122° F. According to the same writer, it could perhaps stand 170° F. in a dry atmosphere without serious injury. He gives this as a probable reason why wheat does not grow in the tropics, where the soil often has a temperature of 190° F. Recent experience has shown that steeping wheat ten minutes in water of 132 to 133° F. to kill smut germs does not injure its viability. In northern Canada, —52° F. has no injurious effect upon the vitality of dry and implanted wheat. Beyond these temperatures, no scientific experiments have been found recorded by the author.
Time Required for Ripening.—The mean temperature required for the successful cultivation and ripening of wheat has been given as 65° F. for 45 to 60 days, and 55° F. for three or four months of the growing season. Of the wheat in the United States, according to the census of 1880, 67.5 per cent was grown where the mean annual temperature was between 45 and 55° F., and 62.7 per cent of it where the annual rainfall was between 35 and 50 inches. It has been claimed that the total amount of sunshine and heat units required to mature a crop 1 Rept. Can. Exp. Farms, 1903, p. 41.
of wheat is the same for all latitudes, and that if these vary, the period of growth will vary in inverse proportion. In support of this position Cooke* collected the statistics given below.
Cooke found the number of heat units required to be approximately the same for different countries, i. e., about 8,500. Experiments conducted at Fargo, N. D., to verify this failed of their purpose, and gave approximately 6,500 heat units. The period of growth was about 100 days. Recent observations have shown that the number of heat units decreases when the growing period shortens. In general, the growing period is shortest in the coldest climate.
The Weight of Different Materials entering into an acre of the wheat crop is shown in the table given below. All weights are in pounds. The grain and straw are given as air dry material, which contains about 15 per cent of water.
WEIGHT OF MATERIALS IN AN ACRE OF WHEAT.
1 Yearbook U. S. Dept. Agr., 1894, p. 174.
2 Rept. Mont. Exp. Sta., 1902, p. 61. 3 Evidence of Saunders, 1900, p. 23.
* Neb. Bui. 19. p. 15.
* N. D. Bui. 47, p. 704.
Chemistry.—The five outer layers of the wheat grain are composed chiefly of cellulose, a woody, fibrous substance. The endosperm, the food part of the grain, contains large quantities of starch, a nitrogenous substance known as gluten, a little sugar, and the cellulose of its cell walls. The gluten content is greatest at the hard exterior of the endosperm. The softer center makes better flour, however, for it remains freer from the bran in the grinding. The germ is composed of cellulose, nitrogenous substances, and about 10 per cent of fat.
The following table gives in per cents of the entire weight the comparison of different kinds and commercial grades of wheat, and of wheat straw and chaff.
The substances of which wheat flour is composed may be divided into three classes: (1) Nitrogenous, which include mainly gluten, fibrin, albumen, casein, cerealin, and modifications of some of these; (2) non-nitrogenous, embracing sugar and dextrin, but chiefly starch, fat and cellulose; and (3) the minerals, for the largest part alkaline phosphates and silicates, especially phosphate and silicate of potash.
Water.—Wheat ordinarily contains from 10 to 15 per cent of moisture. Changes in the moisture content of the air cause corresponding variations in wheat, and consequently in its weight. Usually such fluctuations in weight do not exceed 6 per cent, but they may be as much as 25 per cent, and an increase of 9 per cent in 24 hours has been observed. When wheat is shipped, especially if it is transported long distances, this may be a matter of great commercial importance. Wheat transported from the dry atmosphere of the inland of California to ordinary temperate regions will invariably gain from 5 to 15 per cent in weight. In a voyage from San Francisco to Liverpool, the increase in weight due to the moisture absorbed en route may be sufficient to pay all expense of transportation. Every portion of the wheat grain is so susceptible to influence from hydroscopic conditions that all of the products of wheat exhibit similar oscillations in weight. Two days equalized the moisture content in samples of flour varying from less than 8 to over 13 per cent.1
Ash.—Lawes and Gilbert observed the composition of the ash of wheat grown on unmanured ground during 20 years. The average results are given in the table below.2
Ferric oxide 0.645 0.69
Lime 3.175 5.075
Magnesia 10.48 1.525
Potash 33.345 15.355
Soda 0.18 0.265
Phosphoric anhydride (P20B) 50.065 3.10
Sulphuric anhydride (SO3) 1.42 3.84
Chlorine ....'0.05 2.13
Silica 0.655 68.505
Total 100.015 100.485
1 Hunt. Cereals in Amer. (1904), p. 38; Mich. Bui. 191, p. 159-164. - Hunt, Cereals in Amer. (1904) p. 39.