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The individual plant is the complex resultant of two forces, heredity and environment. Those characteristics of wheat which are acquired from environmental influences and which are transmissible from generation to generation of plants may be considered as belonging to heredity, a subject fully treated in the preceding chapter. The natural environment, consisting of soil and climate, is a pronounced factor in the growth of wheat, independent of the artificial modifications known as cultivation. The latter subject is treated in a later chapter.
ENVIRONMENTAL INFLUENCES. „
Soil.—There are mechanical and chemical differences in soil that exert a varying influence upon the quantity and quality of wheat. The effect upon yield is more pronounced than that upon quality. In North Dakota 39 different samples of Blue Stem and Scotch Fife wheats of known history were obtained from farms representing the varied soils of the state. Sown upon the same soil, all gave approximately the same results in yield and quality of grain and straw. They also matured at the same date, and had like periods of development. Another experiment was made in which seed raised from one soil was hand picked to uniformity, and then grown upon various types of North Dakota soil in different portions of the state. The resulting grain and straw showed great variation.1 Similar experiments were made in Indiana2 and Maryland* with practically the same results.
The soil has been a great factor in determining the distribution of wheat. Much of the wheat of the United States is grown upon glacial drift soil. There are two general types of this soil: The uplands, which are usually of a light-colored, tenacious clay; and the lowlands and prairies, which have a dark, loamy, organic, friable soil. Common bread wheats are usually grown on black soils. These soils are not well adapted to fall wheat, however, for it is apt to winterkill. Durum wheats thrive best in alkaline soils rich in nitrogenous matter. Sandy bottom land is best adapted to the production of soft wheat. Richardson attributed the low protein content of some American wheat to a deficiency in soil nitrogen. The ash of wheat stands next to the gluten in variability, and the factor most concerned in its variation is the soil.
1 N. D. Bui. 17, pp. 89-95. 'Ind. Bui. 41. • Md. Bui. 14.
DURUM WHEAT DISTRICTS OF THE UNITED STATES (By Carleton)
The lined districts show where durum wheat will succeed best and the dotted districts where it may be grown with grain of less quality.
Climate.—Seasonal differences are included under this subject, because their effects are the same in kind as those of climatic differences. Certain climates produce certain corresponding characteristics in wheat, regardless of what the soil conditions are. The protein content of wheat, and correspondingly its moist and dry gluten, is extremely sensitive to environment of a meteorological nature. The starch content is also sensitive, but in an inverse ratio. Climate varies from year to year in any locality, and it is well known that this causes corresponding variations in wheat, even under similar soil conditions. In the gluten content is seen the first reflection of a change in environment. The claim has even been made that a number of varieties of wheat grown under uniform soil and meteorological conditions would yield relatively the same percentages of gluten, however much these might vary from the normal.1
Northern grown seed of spring wheats will mature plants earlier than southern-grown seed of the same variety, but the reverse is true of fall-sown grain, which ripens earlier from southern-grown seed.2 Wheat raised on the sea coast develops special characteristics due, at least in part, to climate. In southern Russia Arnautka wheat attains its highest perfection only when grown within a limited area bordering the Azov sea. All wheat raised directly on the Pacific coast in western United States is soft, damp, dark and has a very thick skin. It shades off gradually to that grown inside of the coast range and protected from the fogs. This inland grain is bright, very hard and dry, and has a thin skin.
Regions having cold winters produce most of the world's wheat. Marked exceptions to this are California, Egypt and India. Small, hard, red grains having a high nitrogen content are usually found in a climate characterized by extremes of temperature and moisture. Climate and season both affect the length of the period of growth. This has an important influence on the chemical composition of wheat, for a short season of growth raises the percentage of protein and lowers that of starch. In Canada, a shorter period of time is required for maturity in northern latitudes. The growing season of Winnipeg is about one week longer than that prevailing 500 miles farther north.
It has been said that "other things being equal, varieties which have become acclimated are to be preferred." While this is true, it still leaves us the case where other things are not equal. Nearly every climate has its disadvantages for wheat growth, and, as we have seen, wheat always adapts itself to overcome these disadvantages. The greater they are, the
1 O. Bui 129, p. 5.
2 Yearbook U. S. Dept Agr., 1901, p. 235; S. C. Bui. 56, p. 12.
more highly developed must be the resisting qualities of wheat to overcome them. By the law of the survival of the fittest, a very detrimental condition in climate or soil develops in wheat a correspondingly great power of resistance. This is the scientific foundation of the importation of seed wheat. It has been recognized and taken advantage of to a certain extent, but not as fully as might have been, and consequently this point will merit subsequent mention. Advantageous importations are well illustrated by the introduction of hardy and drought and rust resistant varieties from the cold and the hot and dry parts of Russia into sections of the United States having a similar climate. A low altitude and an abundance of moisture seem to produce softer wheats.
Soil and Climate.—Many characteristics of wheat are due to the combined influences of soil and climate. Environments that differ widely are characterized by peculiar varieties of wheat varying in composition and physical appearance. Soft wheat repeatedly sown on heavy, black, upland soil tends to become hard, while hard wheat becomes soft after years of successive planting on bottom lands. Experiments have shown that the environment of Colorado affects the composition of wheat by increasing its gluten content at the expense of the starch content, while the environments of Oregon, California and North Carolina have the opposite effect. A study of the map1 showing wheat districts will show the general effects of climate and soil in the United States. Broadly speaking, the hard, red wheats are found in the central, elevated plains, and the grain becomes softer and of lighter color as either ocean is approached. American, Russian and Algerian wheats have about 12 per cent of moisture, while those of Europe have about 14 per cent.2 As early as 1884 it was determined by chemical analyses that the wheats of the Pacific coast in the United States have a smaller percentage of albuminoids than those of the rest of the country. In recent years there has also been a gradual deterioration in the gluten content of North Dakota wheats. The attention of the Department of Agriculture was called to these deteriorations, which are due to the combined effects of soil and climate, and extensive experiments were carried on to determine the exact causes and afford relief. 1 See p. 9.
3 Girard & Lindet, Lie Froment et sa Mouture, pp. 86-93.
Wheats are easily changed as to the season in which they are sown, the winter to spring and the spring to winter varieties. The change is most readily effected in warm, arid climates, where irrigation is practically the sole source of moisture. It can also be accomplished by sowing the winter wheats later and the spring wheats earlier each season. Winter wheat may be sown in spring and spring wheat in the fall. Only a very few plants will ripen seed, but when this is continuously sown, in three years the spring variety will be changed to the winter, and vice versa. In 1857 Klippart wrote that red bearded wheat could be changed to white, smooth wheat, and vice versa. Kubanka, a yellowish-white spring wheat, found in its perfection east of the Volga on the Siberian border, developed into a red winter wheat in the Caucasus.1 Red wheat is usually more hardy than white wheat, while bald wheat is usually not so well adapted to a hot, dry climate or alkali soil as bearded wheat. When seed from irrigated soft wheat has been planted without irrigation, it has been known to harden remarkably in a single year.
Seed Wheat—In each kernel of wheat are embodied the latent possibilities of its future development. Consequently, it is very important to select the seed which will bring the best results possible in the environment under which it must be grown. A knowledge of the importance of good seed wheat, and of the principles of its development, does not eliminate all of the practical difficulties involved in securing good seed. Frequently the grower is so situated that he must purchase his seed, and he should not follow the common practice of waiting to do this until the sowing season has arrived. It is then too late to ascertain the origin and history of the grain, or even to test its vitality. The speculative markets do not trade in seed wheat, and they are not a factor in determining its price. The great bulk of seed wheat does not move far, but is grown in the locality where it is to be used. Good seed of any of the different classes of wheat may generally be procured from the section in which that class is most commonly grown. For example, Turkey Red wheat should be bought in Kansas, Ne1 Carleton, Macaroni Wheats, p. 11.