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Wheat
Wheat

Wheat

by E.E. Elliott and T.L. Lyon

reprinted from the Cyclopedia of American Agriculture, edited by Liberty Hyde Bailey, copyright 1907

Wheat is a plant of vast economic importance, widely distributed over the civilized world and having a history coincident with that of the human race. The grain is used largely for human food, chiefly as food-stuffs made from its flour, and in the form of breakfast food. The by-products of its manufacture are used as stock-food. The grain, whole or ground, is also valuable for stock feeding.

By nature it is an annual, although cultivation and improvement have modified its habits to a large extent. The tribe Hordeae, in which wheat is included, is distinguished by its many-flowered spikelets which are arranged alternately on a stem or rachis, thus forming a spike. The close relationship of wheat with barley, rye, rice and other cereals having the familiar spike head is readily observable.

The genus Triticum embraces wheat proper, but includes in its species and varieties several plants differing slightly in structure or habits of growth. These species and varieties are further broken up into types. Extensive studies of these with the object of classifying them on a rational basis have been made by scientists in recent years, but as yet a generally accepted arrangement has not been fully worked out. The classifications adopted are further confused with the distinctions made in the various markets of the world and the uses to which the grain is put.

Botanical characters.

The wheat grain.—The wheat seed or berry is the part of the plant of greatest economic value. It is also the one means of reproducing the plant. The seed, or grain, as it is generally called, is a hard, dry, oblong fruit with a longitudinal furrow on one side. The seed varies greatly in size, shape, color, hardness and composition, but retains under all conditions, distinct and common characteristics. In size and weight it varies so that the number of grains in a pound ranges from 8,000 to 24,000, with a probable average of about 12,000. It is obvious that the number of seeds in a given quantity, either of weight or measure, will vary accordingly. Variations in the specific gravity range from 1.146 to 1.518.

In general, the shape is oblong with one end slightly pointed, but in some types the ends of the grain are much elongated, the berry itself being flattened, while in others it more nearly approaches a sphere. In color there is a wide range, from the paler shades of yellow through what is called amber, to deep red. Color is considered to have a close relationship to hardness of the grain and its composition.

The composition of wheat as reported by the United States Department of Agriculture is as follows:

Wheat

As will be noted, the grain contains 10 to 11 per cent of water. As a matter of fact, as grain is usually handled and shipped, the percentage of water would average much higher. It is well known that wheat transported from a dry climate to one more humid will absorb five to twenty-five per cent of additional weight in moisture. This is particularly true when shipments are made by water. As wheat is handled in milling it is customary to add to it a considerable amount of water before being processed, as in its normal condition it is too dry. It will be seen that the grain has large absorptive powers; and the same facts have been observed in the different manufactures produced from it.

Of the mineral elements in wheat, fully one-half is phosphoric acid, while the greater part of the remainder, consisting of one-third of the whole, is potash.

The wheat grain is characterized by a small embryo or germ, while the percentage of endosperm constitutes a very large proportion of the entire contents, the ratio being as one to thirteen. The embryo, while having a high nutritive value, is not a desired element in the manufacture of flour, although it is utilized to a considerable extent in the production of certain cereal foods and always constitutes a most valuable by-product.

The endosperm is composed largely of pure starch cells which form the chief constituent of wheat-flour as usually made. However, it contains proteids, which by their presence add largely to the value of flour as usually prepared in the form of baker’s bread. These proteids have been classified as follows: (1) globulin, (2) albumin, (3) proteose, (4) gliadin and (5) glutenin. For all practical purposes only the last two named are considered in the manufacture of flour. These two proteids combined compose what is known as gluten. It is the gluten contained in the starchy parts of the wheat grain which distinguishes it from flour made from certain other cereals, notably corn. Corn flour or meal is heavy and sodden when baked into bread as compared with flour made from wheat or rye. The difference is due to the presence of gluten. In the process of bread-making the flour is made into a dough by the use of water and the addition of leavening. When fermentation sets in, or, to use the common phrase, the bread begins to rise, carbonic acid gas is formed; this is imprisoned in the dough, which expands with the internal pressure and thus forms an open, porous loaf. The dough owes this elastic quality to the presence of the gluten. Gluten can be obtained from flour by washing the dough with water until all the starchy parts have been removed. The lump of gluten thus obtained will prove to be of a light, yellow color, tenacious and elastic. When dried, it will be semi-transparent, and closely resembles glue. The quantity of gluten in flour is important, but more depends on the quality. As it is not easy to determine the quality except by actual bread-making tests, millers usually select the wheats preferred on the basis of the percentage of total gluten contained.

In the manufacture of flour, the percentage of the grain recovered in the form of flour varies around 70 per cent. The lowest limit of the grades secured will depend on the markets open to the miller. The amount of merchantable flour recovered is also governed somewhat by the processes of milling. There remain always the by-products, known in commerce under the various names of bran, shorts, or middlings.

If a grain of wheat be cut into transverse sections, the various parts of which it is composed will be clearly seen. The embryo, which is rejected in milling, will be shown lying along the side opposite that on which is the furrow. Covering the starchy parts of the grain are several layers of fiber or husk, also rejected in the milling process. These layers are technically known as the aleurone, nucellus, testa and pericarp, although these blend more or less into each other according to the condition of maturity of the grain.

The wheat plant.—The wheat plant is strictly of artificial character and habits. This is well-illustrated by the nature of its growth. It is probable that if cultivation should cease for even a few years the plant would perish from the face of the earth. Under normal conditions wheat completes its round of growth within the limits of each recurring season. Seeded in the spring it will mature a crop in twelve to twenty weeks, according to season and variety. Its nature has been so adjusted, however, that what are called fall or winter varieties are cultivated, to a large extent, throughout much of the producing area of the world. These varieties are sufficiently hardy to withstand the winter season, and when planted in the fall will mature the following year, one to two months earlier than those seeded in the spring. There is relatively no variation in the different types and varieties so far as manner of life and growth are concerned.

In germinating, the seed or grain of wheat throws out a whorl of three temporary roots. With the development of the stalk, which immediately takes place, additional whorls are thrown out at each node. The permanent set of roots will be found near the surface branching outward and downward.

If the wheat has been planted deep the stalk may exhaust itself in reaching the surface, and, in the case of alternate freezing and thawing, the slender thread connecting the tiny plant at the surface with the parent seed may be separated too soon and the vitality of the plant be endangered. The roots of the growing plant may penetrate to a depth of four feet or more, a fact which is somewhat contrary to the common opinion.

While the stems of the wheat are hollow, it is not unusual for them to be more or less filled with pith.

In winter varieties the stalks of the plant do not rise above the crown of leaves, which are first produced, until the advent of spring. The mat of blades which covers the ground serves the useful purpose of protecting the plant throughout the dormant period of the winter season.

During the early growth the nodes are close together, but soon the wheat begins to joint or “shoot” and the stalks grow rapidly, while the space between the nodes increases until the full height of the plant is attained. The range of the height varies from two to six feet, and there does not appear to be any close relationship between this height of straw and the yield of grain. The less moisture in the soil the smaller the proportion of straw to grain. As the plant attains development the spike pushes up until it rises above the growth of foliage below, and a mature field of wheat shows a uniform surface of erect spikes. At this stage of growth the leaves at the surface of the ground, together with those attached to each node, wither and fall, the whole plant turning a golden yellow color.

The ability of the wheat plant to tiller or stool, throwing up additional stalks, is a marked characteristic. It often occurs that such stools may show twenty to even one hundred stalks starting from a single grain. This habit of tillering is governed by the variety and also may be modified by the climatic conditions of the season. It will readily appear that what is called the “stand” of wheat may depend in a large measure on the freedom with which the plant may send up these additional shoots.

The wheat head.— A discussion of the variations existing in the different types of wheat as shown by a study of the spike or head will be given under the classification of varieties. A somewhat technical description of the head is, however, necessary in order to make clear many references in this article.

“The flowering and fruiting cluster at the summit of the stem of a wheat plant is called the ‘head’ or ‘spike.’ The part of the stem running through the spike, on which the flowers or kernels are borne, is called the ‘rachis.’ The rachis is divided by a number of joints, or nodes, and at these nodes on alternate sides of the rachis are attached the spikelets — the several small secondary spikes which together with the rachis make up the spike proper. The short branch running through each spikelet is known as the ‘rachilla.’ Inserted on the rachilla are several concave scales which are called the ‘glumes.’ The two lowest and outermost of these contain no flowers or kernels and are designated as the ‘flowerless glumes.’ Above these, arranged alternately, are borne the flower, rarely less than two, or more than five. Each flower and, as it matures, each grain, is subtended by a single glume, known as the ‘flowering glume.’ Each flowering glume has a longitudinal nerve which at the summit extends into a prominent ‘awn’ or ‘beard.’ On the inner or creased side of the grain or berry, filling it very closely, and more or less hidden from view by the flowering glume, is borne the ‘palea’ or ‘palet,’ a thin scale with two nerves. The flowerless and flowering glumes and the palets are spoke of collectively as the ‘chaff’.”

In many varieties the outer glumes have their surfaces covered with short soft hairs which give the heads of wheat a velvety appearance. This velvet or fuzz, while present in many very productive types and varieties, is not considered by growers a desirable characteristic.

It would be easy to make a classification of wheat based on the striking differences of the spike, and to some extent these are considered, but such division can hardly be said to have a botanical basis.

Wheat

Production. (T. L. Lyon)

The report of the Twelfth census of the United States states that in the decade 1890 to 1900, the area planted to wheat in this country increased from 33,579,514 acres to 52,588,574 acres, or 56.6 per cent. In the preceding decade there had been a decrease of 5.2 per cent. The acreage reported in 1900 was 48.4 per cent greater than that of 1880.

The increase in production of wheat had been about proportional to that of acreage. The largest yield in this country for any one year was 748 million bushels, produced in 1901. The yield per acre for the last three decades has remained practically the same, but the value per bushel and consequently per acre has steadily declined. The cost of producing a bushel of wheat has likewise decreased in amount.

The United States leads all countries in the production of wheat. The other large wheat-producing countries are Russia, India, France and Austria- Hungary, while Canada and the Argentine Republic are rapidly increasing their output. Europe is still the largest wheat-producer of any continent, raising nearly twice as much as North and South America together.

During the last fifty years there has been a constant movement of the center of wheat production from east to west in the United States. This has proceeded much more rapidly than has the center of population. In 1850, New York was one of the great wheat-producing states, and the Genesee valley was the greatest wheat-growing region in the country. Since that time the wheat production of New York has decreased, according to the Twelfth census report, over 3,000,000 bushels, and its proportion of the total crop has declined from 13.1 per cent to 1.6 per cent, while the four states which now produce the most wheat were, with the exception of Ohio, still unsettled. The latter state was also at one time the leader in wheat production, and the rich Miami valley succeeded the Genesee valley as a wheat region. But while Ohio is still a large producer of wheat, its relative production has declined from 14.4 per cent to 7.6 per cent.

Southern Wisconsin and northern Illinois was once the great wheatgrowing region of the country, but this was again superseded by Minnesota and North Dakota. For the last few years Kansas has been producing more wheat than any other state. It seems probable that the great plains area of western Kansas and Nebraska, and of eastern Colorado and Wyoming and perhaps northern Texas, is to be the next great wheat-growing region.

Wheat

Types and varieties of wheat. (Figs. 894-901.)

Cerealists as well as practical producers of grains are gradually losing sight of those classifications of wheat which are based on purely botanical points. While not failing to recognize the scientific value in such analytical arrangements of the various differences discovered, they incline more and more to a study of those influences of soil, climate, moisture and cultivation which are now recognized as being the real causes of the existing differences, and to classify varieties on a geographical rather than botanical basis. Notwithstanding this, a statement of the botanical relationships has a proper place in this connection.

Botanical classification.— The classification conceded to be the most acceptable is that made by Hackel, and the outline here given is that arranged by Hunt.

It will be noted that there are eight types recognized as members of this great family. Some of these are very closely related, while others are so distinct as to refuse to reproduce by cross-fertilization.

(1) Einkorn (T. monococcum). Fig. 894.— This species of wheat has no English equivalent for the German name, nor has the plant been grown except in an experimental way in the United States. It most nearly approaches the assumed wild forms of wheat. The plant grows one and one-half to three feet in height; the leaves are narrow and heavy, stem slender and stiff, in color brownish green. The head is much flattened, compact, and heavily bearded, the grain being compressed until it shows an angular form. Einkorn has yet had no practical value for the American farmer.

(2) Spelt (T. sativum, var. Spelta) Fig. 895.— This is a very ancient form of wheat and has been cultivated for centuries in Europe and Africa. While still important in some European countries, it has been replaced largely by other types of wheat. It grows to the usual height of the wheat plant, according to variety and local conditions. In many varieties it would appear at first glance to be one of the wheats in common use. An examination of the spike will reveal the reasons for its distinct classification. The spikelets do not break off of the rachis and leave a zigzag-shaped terminal to the stalk, as in the case of common wheat, but they hold together, and in separating from the rachis a part is broken off and remains attached to each spikelet.

(3) Emmer (T. sativum, var. dicoccum). Fig. 896.— This is often confused with spelt and not easily distinguished. The stems are usually pithy and leaves covered with velvety hairs. The heads are flattened, two-rows and bearded. Of the three types mentioned, emmer probably is better adapted to dry regions where spring grain is usually grown. It is valuable as food for stock.

(4) Common wheat (T. sativum, var. vulgare). Figs. 897, 898.— This is the common type of wheat grown all over the world where wheat is produced. Closely akin to it is

(5) Club wheat (T. sativum, var. compactum). Fig. 899.— This sub-species has a short, compact head, and is the common wheat of the Pacific coast region, as well as of Chile and a few other countries. These Club wheats are chiefly of spring varieties and differ from the common sorts principally in color and softness of grain.

(6) Poulard (T. sativum, var. turgidum).— This is grown in the Mediterranean region, and is distinguished by its broad head, short bristling beards and stiff straw. The variety known as seven-headed or Egyptian wheat belongs to the sub-species. Poulard wheat is much like

(7) Durum wheat (T. sativum, var. durum). Fig 900.— This is often referred to as Macaroni wheat, since the flour from which is manufactured this and similar products is produced from this wheat. Durum wheat grows tall, and its broad, smooth leaves and heavily bearded heads attract attention. It is easily mistaken for barley, which it much resembles. The grains are large and pointed at each end and semi-transparent since the grain has less starch than common wheat.

“Durum wheat has been imported, tested and distributed by the United States Department of Agriculture and the agricultural experiment stations of a number of states within the last ten years. To some extent varieties of durum wheat had been grown previous to that time under the name of Goose wheat, but had never attained much importance, owing to a lack of knowledge in this country regarding its value in commerce and manufacture. Through the efforts of these national and state institutions, a ready market for durum wheat has been developed, and the product is now exported to Europe in large quantities, and also utilized in this country for the manufacture of macaroni, spaghetti, and the like, and for blending with softer wheats in the milling of flour. During the season of 1906, a crop of 50,000 bushels of durum wheat was produced.

“The qualities that give value to durum wheat are its ability to withstand drought and its resistance to rust. It is being grown now in regions of light rainfall, under which conditions it produces larger yields than any other spring variety of wheat. It has not so far proved more productive than winter wheat, and consequently has not taken a place among the crops of the winter wheat region.

“Some varieties of durum wheat have proved sufficiently hardy to live through the winter in southern Kansas, and by selection of hardy individuals its production will doubtless be extended northward. It has been grown as a winter wheat in an experimental way at the Nebraska Experiment Station for three years. If it can be developed into a successful winter wheat it will doubtless replace the common varieties in much of the great plains region.” (T. L. Lyon)

(8) Polish wheat (T. Polonicum). Fig. 901.— The Polish wheat is characterized by having the palea of the lowest flower half as long as the flowering glume, while the outer glumes equal or exceed in length the flowering glumes. This wheat may have some value for arid climates, but is not productive. The plant is sometimes called Giant or Jerusalem rye, because of the resemblance of the seeds of the two. It can be used for the making of macaroni. It is grown in southern Europe.

Geographical classification.— The United States Department of Agriculture, in 1895, made a collection of more than one thousand supposedly distinct varieties, but after testing these for several years it was found that very many were identical and that only one-fourth of the number were of any value to the American growers. It will be readily understood that a single variety grown under the wide range of climate and varying conditions which are to be found in this country would in the course of a few generations show widely differing characteristics. Few cultivated plants are so susceptible to such influences.

In his “Basis for the Improvement of American Wheats,” Carleton divided the entire country into districts according to the general character of the grains produced in each. A study of these districts reveals the fact that the varieties usually grown in any one given section will all possess so nearly the same values as to warrant their classification together and thus give the product of each district a distinctive character. According to the grouping we will have:

(1) The soft wheat district, including mainly the New England and middle states.

(2) Semi-hard winter wheat district, including the north central states.

(3) The southern district, including the northern part of the southern states.

(4) The hard spring wheat district, including the upper Mississippi river basin.

(5) The hard winter wheat district, including parts of the middle states of the plains.

(6) The durum wheat region, including parts of the southern states of the plains.

(7) The irrigated wheat district, scattered over the Rocky mountain region.

(8) The white wheat district, including the larger part of the Pacific coast states.

This classification recognizes certain qualifications, chief among which are color of grain and percentage of gluten, which form the basis of the arrangement. Since these qualifications are largely affected by the particular section of the country where the types are produced, it is a fair inference to speak of such a classification as a geographical one.

From such a study as the above it can readily be seen that there is no single variety or even type that can be suggested as the best for the whole country, and even if a single variety were universally adopted it would be but a few years until it would be found as varying in character as the many sections where grown. So marked is this that markets have been created, and with the opening up of new areas, producing grain of unusual character, the milling industry has at times undergone a complete change.

The production of varieties.

The greater number of the common varieties of wheat are the result of chance rather than of any scientific effort for improvement. Wheat is a self-pollinating plant, and because of this, rarely fails to reproduce true to its characteristics. As every grower knows, however, there will occasionally appear a new or even unusual form in a field of grain which may or may not resemble the variety among which it may be growing. Such forms are known as “sports,” and are the result of accidental crosses between plants of the same or different varieties. It is probable that these occur more frequently than they are discovered and that close observation would reveal many new and superior varieties that are never isolated and reproduced as distinct varieties. Without doubt the great majority of our commonly known wheats have thus originated, and it is only within a comparatively recent period that what are known as “pedigree” or scientifically produced varieties have been placed in the hands of growers. Every wheatgrowing region of the world has been explored for the best varieties it was able to produce, and it is safe to say that few promising varieties which can be found anywhere remain to be tested. Vast improvement to the wheat crop has thus resulted, particularly through the introduction many years ago of what are known as Mediterranean varieties. With the reaching of the limit of possible improvement by this means, attention is being more directed to the artificial production of new varieties and the future improvement of wheat, for particular purposes as well as increased yield, will be secured by these means.

As has already been proved, the varieties introduced from foreign lands have been found to be most valuable for producing new varieties by crossing. These wheats, coming as they do from those regions near the original habitat of the wheat plant, are found to have many of the very features it is desirable to reproduce.

A study of the needs of any region is always the first requirement when new creations are to be produced. If the region needs a hardier variety or one able to withstand some insect pest or disease; if it needs stiffer straw, or a head less likely to shatter, the proper combinations must be made to secure these.

The second natural step will be the study of those varieties which may show the desired characteristics. It is not always the case that a perfect combination will result even when the parents with which the crossing is effected present the desired characteristics. The resultant cross may show a weakening instead of a strengthening of some desired quality.

Rigid selection is the third step which must follow hybridization. It is not a difficult thing artificially to produce new wheats, but the real task is found in selecting those of value and growing them true to the type secured.

The good results secured by cross-fertilizing wheats in order to produce new varieties are numerous. Among these which almost always follow, are two: increased vigor and greater productiveness. On the other hand, so great is the disturbance caused by the crossing that difficulty often follows the effort to select fixed types.

Hybridizing wheats.— The first step in cross-fertilizing wheat is to remove the anthers from all the flowers on the spike to be fertilized. This must be done while the anthers are yet green and the pollen immature. If the head of wheat is compact it is well to remove each alternate spikelet and also the less perfect ones at the base and tip of the spike. The work is done by using ordinary botanist’s tweezers. Care must be taken not to break any of the anthers. It is best to protect the emasculated head by wrapping it with tissue paper. In a few days when the flowers on adjoining plants are seen to be ready to open, pollen may be brought from the chosen variety and deposited on the stigmas of the emasculated head, and this again protected as before. When ripe, the heads are threshed out by hand and the matured grains planted the following season. It often happens that the head is so injured in the process that the grain is shrunken or defective although still retaining vitality. Often it will be found that the work has not been properly timed and crossfertilization has not followed. By making several identical crosses a sufficient number of seeds can be secured for further plantings.

Various methods of growing such seed are suggested. Whatever the method followed, it should permit of the greatest possible development of the plants from each individual seed. It will be found that a great difference will appear in the plants succeeding from the first cross. A close study of these will reveal that only certain ones will possess the characters desired, and when these are planted and another generation secured, some will be found to reproduce as fixed types while others will show an unstable character. It is generally conceded by wheatbreeders that four to five years are necessary firmly to fix any desired type so that it will reproduce itself perfectly.

Selection.— It is possible from a single cross to secure a considerable number of new varieties. As soon as these are secured they must be carefully studied before being finally selected as desirable types. This study may reveal that further crossing with either of the parents or other types is needed to effect the improvement desired. In fact, many of the standard pedigreed wheats of the country are the product of successive crosses and inbreeding. This is well illustrated in the well-known variety, Genesee Giant, which is the result of no less than eight successive cross-fertilizations. This process increases the necessity for the important work of selection since the variations secured are so numerous.

Selection must begin with the individual plants. From these may be chosen the best and most perfect heads. In any number of plants which are the result of a single cross the most vigorous and productive can easily be noted. When a fixed type is secured and decided on as worthy of propagation, the next step will be to increase the amount of seed as quickly as possible. Selection should not cease even then, for further improvement in the quality produced is possible.

Practical methods of improving seed wheat.

It is contended that the larger grains found in any variety are capable of increasing the yield, and many experiments go to show that this is a fact. It is probable that size alone cannot be depended on, but rather weight of the grain. For this reason a machine has been devised to take the place of the screening machines usually employed. This machine has a cylinder which throws the grain by centrifugal force. The heavier grains naturally travel the farthest and the grain is graded by a series of receptacles into which it falls. Screening either by the use of a fanning mill or a perforated cylinder is also a good practice.

Other factors enter into the improvement of wheat. Among these will be its treatment for preventing smut and the use of fertilizers. It may also be benefited by being changed to a more congenial climate or soil.

Soil.

Wheat grows in a very great variety of soils, ranging from the stiff clays of the New England region to the volcanic ash of the Pacific coast. With such a great variation no set rule or method for preparation can be advised. In general, soils which are full of organic matter, loose in texture and dark in color are not so well suited for wheat-growing as the lighter clay and drift soils. As a rule, over much of the area devoted to wheat-growing, crop rotation or the use of some amendment to the soil is essential. In regions where this is not followed it is often customary to practice what is known as summer-fallowing.

Wheat
Fig. 902

Land intended for winter wheat should be plowed as early in the preceding season as possible. This permits of more thorough preparation of the soil and also of the absorption of moisture during the summer. Surface cultivation should be followed, particularly after each rain. The depth of the plowing should not be less than four inches nor more than eight inches. In regions where corn is a leading crop it is customary to seed such fields without replowing, specially designed tools for preparing the soil and seeding between the rows of corn being used. This allows of the economical use of the land, and the crops secured are generally equal to those secured by more expensive methods of preparations. Fig. 902 shows a field terraced to prevent soil washing.

When spring wheat is grown, the land should be plowed in the fall preceding or as soon as possible in the spring. Thorough preparation of the soil is important in all cases.

Fertilizers. (T. L. Lyon)

On the older soils of the eastern states, extending as far west as Ohio and Kentucky, barnyard manure or commercial fertilizer is commonly applied to the land for wheat or for some crop in the rotation of which wheat forms a course. The same is true of eastern Canada, including the province of Ontario. West of this, commercial fertilizers are used very little, although barnyard manure is used on grass-land and for cultivated crops in all the country lying east of the semi-arid region. On the light soils of the prairie region barnyard manure plowed under immediately before seeding to wheat is likely to make the soil too loose for the best yield of that crop.

Summer-fallowing is practiced extensively in the semi-arid regions, where the crop is not irrigated. A considerable proportion of the wheat of North America is now produced in regions having an annual rainfall of less than twenty inches. The soil of these regions is usually very deep, so that there is little loss of moisture by percolation; almost all of the rainfall that does not run off the surface or pass through the tissues of the plant is lost by evaporation from the soil. The effect of the summer-fallow is to conserve a large part of the rainfall during the year the land is kept fallowed, and thus greatly to increase the supply of soil moisture for the following crop. In very dry regions it is customary to fallow every other year, but where the rainfall is not so meager, two or three crops intervene. Summer-fallowing is very destructive to the humus, but it increases the supply of easily soluble plant-food materials, and these, with the greater moisture supply, produce much larger crops than can be secured when the land is cropped continuously. Barnyard manure cannot be used in this region for the wheat crop.

Wheat is raised under these conditions in central and western Kansas, Nebraska, most of the Dakotas, eastern Washington, Oregon and California, and in Manitoba, Alberta and Saskatchewan. Experiments indicate that the use of commercial fertilizers for wheat or other cereal crop is not of immediate profit in this region, and as barnyard manure dries out the soil the problem of maintaining fertility is a serious one. Doubtless it is to be accomplished by seeding to perennial grasses or legumes for a period of years. Throughout much of this region wheat is grown because it is useful in filling out a rotation or in providing a nurse crop for grass and clover rather than because it is profitable in itself.

If wheat follows corn the land should receive ten to thirty loads of barnyard manure before plowing for the latter crop. This is much better than applying manure directly to wheat. The only accurate method of ascertaining the manurial requirements for any particular soil is to conduct a test on the soil in question.

Place in the rotation. (T. L. Lyon)

Wheat should always be grown in a rotation with other crops. It is particularly benefited by such treatment and suffers in productiveness very rapidly when grown continuously on the same soil. Wheat yields begin to decrease on the prairie soils within a few years after they are broken, while corn will continue to yield without diminution for ten, twenty or even thirty years on some of the rich prairie soils.

The rotations in which wheat is grown vary in different parts of the country. In the New England and north Atlantic states, where corn is raised largely for silage, a system consisting of corn, wheat, clover is frequently followed. This is well suited to dairy-farming. Where oats are needed, they usually follow directly after corn and precede wheat, making the rotation corn, oats, wheat, clover. Potatoes are frequently substituted for corn.

In the corn-belt states, when wheat is raised the rotation is usually corn two years, oats, wheat, clover, except where spring wheat is grown, when it is often used to alternate with corn; thus — corn, spring wheat, using no other crop in the rotation. This is not an ideal system, but experience has shown that it is better than raising corn continuously. This method is also being followed at present with winter wheat by drilling the wheat between the corn rows with a one-horse drill. The cornstalks are pastured in winter, so that the wheat can be harvested the following summer.

In the semi-arid region the tendency is to rotate wheat with a summer-fallow, using the latter every two to four years. It is probable that this will be replaced in time by a rotation including a perennial grass or legume left on the land for several years, and alternating wheat with other small grains suited to the region as well as the summer-fallow.

On the irrigated lands, sugar-beets or potatoes are usually the cultivated crops. These follow alfalfa, which has been down for at least three or four years. Wheat follows the cultivated crop. A typical rotation is alfalfa (three or more years), sugar-beets, wheat. Where peas are raised for sheep, as is becoming common in Colorado, a good rotation is peas, potatoes, wheat.

Seed and seeding.

The great importance of securing good seed is evident. While efforts should not be neglected to improve the character of well-known varieties and to create new ones of superior merit, it must not be forgotten that the maximum of production from the varieties now in common use has by no means been reached. Much remains to be learned of the adaptability of existing wheats and the best methods of cultivating and handling the crop.

The wheat-grower cannot be too painstaking in the selection of his seed wheat. By employing the methods previously mentioned of cleaning and grading the seed, improvement is sure to follow. Shriveled wheat will germinate, but the best results cannot be expected from such seed. In many regions it is absolutely necessary to treat the seed with some chemical to destroy the germs of smut. [See below under Enemies.]

Seeding.— The time for sowing will depend on the climatic variations and on the dangers of attack from the Hessian fly. With fall wheat, time must be allowed for sufficient growth of the young plants to be able to withstand the rigors of winter. Wheat has the ability to germinate and grow at comparatively low temperatures, but due care should be exercised not to subject the early growth either to severe frost or to sudden changes of the season. No best time for seeding can be given for any locality. As a rule, the depth of seeding will vary with the porosity of the soil — the lighter the soil the greater the depth. The seed should be planted not less than one nor more than three inches deep, and by the use of such machinery as will place it uniformly and secure perfect covering by the soil.

Many factors enter into the question of the proper amount of seed to sow per acre. The yield will not depend on the quantity of seed sown, for the differences in varieties are very great; size of seed, quality, condition of seed-bed and time of seeding, character of the soil and climatic influences all have to be considered. Repeated experiments in many states lead to the conclusion that six to eight pecks would be the proper range for quantity.

As a rule, wheat is not cultivated after being planted. The practice of harrowing, once followed in England, has never been universally adopted in America. There are some wheat-growing sections where it is an advantage to harrow winter-sown land in the spring in order to break up the crust on the surface and thereby retain the moisture, as well as give the plants better conditions for growth.

Wheat
Fig. 903

Harvesting (Figs. 903, 904).

The period of growth needed to bring the wheat plant from seeding to maturity varies greatly. With fall-sown grain there is a long dormant period of almost if not quite half a year when there are few indications of activity or even life. With spring-sown grain where the growth is continuous and unbroken, the period will range from ninety to one hundred and twenty days. In the United States, harvesting begins in Texas as early as May, but may continue as late as September or even October in North Dakota and Washington. In the eastern states grain must be cut as soon as sufficiently ripe, and the entire crop must be put in the shock within a brief period. West of the Rocky mountains, where little or no rain falls during the summer months, harvesting is pursued more deliberately, and as the Club varieties are largely grown in these regions, the fields are often left standing for weeks or even months after the wheat is fully ripe.

Wheat
Fig. 904

Harvesting machinery.— The methods employed in harvesting wheat have undergone great changes during the past century. From the hand sickle, with which it was possible to reap but a small area each day, to the perfected harvester or the great combined machine, is but a brief step in point of time, but it represents a wonderful advance in human invention and application. At the present time machinery of some kind is universally used in America for harvesting wheat. So perfect is this that the grain is scarcely touched by the human hand during the entire harvesting process. Until within twenty years of the close of the past century the most perfect machine in use was the self-rake reaper, which mechanically cut and placed the wheat in bundles on the ground ready to be bound in bundles by hand. This machine was replaced by the self-binder, which at first used wire instead of twine. When a proper knotting device had been devised, the self-binder made possible a great expansion of the wheat industry. In many parts of the West the header is commonly used, but only in those regions where the wheat can be left standing after maturity until it can be harvested. With this machine only sufficient straw is cut to insure gathering the heads of the grain. The header cuts ten to twelve feet wide, and is pushed forward through the grain by six or eight horses. The headed grain may be taken immediately to the thresher or shocked.

The threshing of grain where the header or self-binder is used is generally done by threshers operated by steam- or horse-power. Various devices calculated to reduce manual labor to a minimum are employed in this connection: self-feeders, band cutters, straw carriers, elevators and sackers are all used, and even attachments to bale the straw for market directly from the thresher. By far the larger part of the wheat crop in the United States is cut by the binder and threshed directly from the field.

Enemies.

Insects.— The wheat plant has many enemies to contend with in the form of insect pests, fungous diseases and weeds of many sorts. The two most injurious insect enemies are the chinch-bug and the Hessian fly (Figs. 905-907). The annual losses caused by these two pests in the wheat-fields of the United States is beyond estimate, but will run into millions of dollars. Remedies to counteract their ravages are largely preventive; in the case of the chinch-bug, by clean tillage and rotation of crops, and of the Hessian fly by late seeding, burning stubble and otherwise hindering the propagation of the brood. Other insect pests may at times cause local damage to the wheat crop, but are of less importance.

Wheat

Diseases.— Two rusts commonly occur on wheat, the early orange leaf-rust (Puccinia rubigo-vera) and the late stem-rust (Puccinia graminis, occurring also on oats). These rusts may also destroy the crop within a few days. Rust is now being controlled by growing resistant varieties. Of wheat smuts there are two: The loose smut (Ustilago tritici) matures its spores at blossoming time, the succeeding crop becoming infected through the blossoms. No satisfactory treatment has as yet been worked out. The stinking smut or “bunt” (caused by Tilletia tritici or T. faetens) destroys only the kernel.

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