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It will be seen that in seasons unfavorable for the yield the weight per bushel was light but the nitrogen content as well as the ash content was high, and on the other hand that in seasons of favorable growth the weight per bushel was high and the nitrogen and ash content were low. In these cases, covering a series of years and several conditions of fertilization, high weight per bushel was associated with large percentage of starch. Lawes and Gilbert conclude that "High percentage of nitrogen is by no means a characteristic of the wheats held in highest estimation either by the miller or the baker; and that so far as both the baker and consumer are concerned the condition of nitrogenous matters is of more importance than their total amounts. Comparing one description of wheat with another, the one with a relatively high percentage of nitrogen may be better, provided the grain be at the same time fully ripened and not too horny. But when the percentage exceeds a certain limit, the grain is generally either too hard, or there is deficient storing up of starch and an unfavorable condition of the nitrogenous substances.”
74. Influence of Environment on Composition of Grain.-Environment is a combination of influences of which the following three are the most important :
3. Culture, including preparation of seed bed, time and method of seeding and quantity of seed, etc.
It has been shown that the composition of the wheat grain varies in different localities when grown from seed of a common origin. For example, Richardson found that the per cent of protein in a number of varieties of wheat was considerably higher when grown in Colorado than when grown in Oregon. He also found that the grains of wheat were much larger when grown in Oregon than when grown in Colorado. Deherain makes a similar observation with regard to the influence of different seasons. High temperature during July (in France) increased the per cent of protein but diminished the yield so that the amount of the protein was no greater than under normal conditions. The high per cent of protein in the hard spring wheats of the northwest is likewise attributed to the arrested development of the endosperm or starchy portion of the grain.
Richardson attributes the variation in the per cent of protein to the differences in soil and attributes low per cent of protein found in some American wheat to a deficient supply of nitrogen. Lawes and Gilbert state that the low percentage of nitrogen is more probably due to the enhanced formation of starch under the influence of high ripening temperatures, and that, comparing the grain grown from the same description of seed but on different soils, or in different seasons, high percentage of total nitrogenous matter is almost invariably coincident with inferior ripening. Wiley attributes the variation in per cent of protein to climatic conditions, but attributes variation in the ash occurring in the same varieties of wheat to the soil and fertilizers. 1
1 Influence of Environment on the Composition of Plants. By H. W. Wiley. Yearbook, Dept. of Agr., 1901, p. 306.
Carleton believes that localities with black soils (high in organic matter) and extreme climatic variations are most favorable for the production of high protein content. William E. Edgar says:
“Gradually as the northwestern States have become cultivated the original hard wheat has grown scarcer. Wheat raised on virgin lands has a peculiar strength lacking in that produced in older fields. It is capable of improving the character of other wheat blended with it when the mixture is made into four.” 1
Lawes and Gilbert, in an elaborate series of analyses of wheats grown on unmanured and variously manured plats during twenty seasons, have shown the variation in composition of wheat to be much more influenced by season than by manuring. There was very little variation in the mineral composition of the wheat grain accorded to manuring except in cases of abnormal exhaustion. Commenting upon the significance of the facts presented, the authors say:
“The character of development of a crop left to ripen, depends very much more upon season than upon manuring. Indeed, if one crop (of wheat for example) grows side by side with another of exactly the same description, but yielding under the influence of manure twice the amount of produce, and both under such conditions of season that each fully and normally ripens, the composition of the final product, the seed, will be very nearly identical in the two cases. In other words, there is scarcely any difference in the composition of the truly and normally ripened seed. But, as variations of season affect the character of development, and the conditions of maturation, there may obviously be, with these, very wide differences in the composition of the product. The wide range in the composition of the ash of the grain, which the table shows according to season, represents in fact a corresponding deviation from the normal development.”2
The climatic condition which seems most uniformly to affect the composition of the grain is the length of season of growth. The shorter the season of growth, the higher the percentage of protein and the lower the percentage of starch. Doubtless the shorter the season of growth, the smaller the grain.
It does not follow that strains may not be selected which will contain high per cents of protein and at the same time produce more protein per acre, although the facts stated above suggest that difficulty may be found in doing so.
1 The Story of a Grain of Wheat, p. 126. New York, D. Appleton & Co., 1903.
2 Lawes and Gilbert on the composition of the ash of wheat-grain and wheatstraw, p. 8.
75. Germination.—Wheat absorbs upon germination from five to six times its weight of water. Various experimenters have reported that dilute solutions of fertilizers and other salts accelerate germination. The salts dissolved in soil water probably exert a favorable influence. Whether this is a physical or physiological influence has not been proven, but it has been shown that absorption of water goes on as rapidly in dead seeds as in live ones.1
More concentrated solutions used to prevent smut have in some instances been reported injurious. Much less injury is done by soaking the seeds in the solution before sprouting than by bringing the solution in contact with the young plantlet. It has been shown that nitrate of soda and muriate of potash when used in too large quantities or not properly distributed in the soil may destroy germination, while fertilizers composed of lime and phosphoric acid are much less injurious. In no case should the seeds be brought in direct contact with nitrate of soda and muriate of potash.
Sachs gives the minimum and maximum temperatures at which wheat will germinate as 41° F. and 108° F., and the most favorable temperature as 84° F. Haberlandt reports that wheat germinated at 41° F. at the end of six days, that the maximum temperaturt of germination was between 88° and 100° F., and that the most favorable temperature was somewhere between 61° to 88° F.3
Saunders determined the viability of three varieties of wheat during six years with the following average results: 80; 82; 77 ; 37 ; 15; 6 per cent.* The germination ability showed a marked decrease at the end of four years, and at the end of six years was entirely lost in two of the three varieties.
1 Wyo. Bul. 39, p. 44. 2 U. S. Dept. of Agr., Div. of Bot. Bul. 24. 3 Landw. Vers.-Stat. XVII, 104. 4 Can. Expt. Farms Rpt. 1903, p. 44.
1. BOTANICAL RELATIONS.
176, The Wheat Genus (Triticum L.).—The plants of this genus are all annuals. The commonly cultivated species have apparently been so changed from the wild type as to be dependent upon man's agency for their existence. Sir John Lawes was wont to say that if man should disappear from the earth wheat would follow him in three years. This is true, also, of the common field bean, maize, tobacco, and a few other less commonly grown species.
Hackel divides the genus into two sections, viz., Ægilops L. and Sitopyros. In the former the glumes are flat or rounded on the back, while in the latter they are distinctly keeled. To the latter section belong the cultivated species.
77. The Species of Wheat.—There are eight cultivated types of wheat which are usually considered of greater value than the variety type. Hackel recognizes but three true species and the other types are treated as subspecies.
The structural relationship is much closer between Tr. sativum and Tr. polonicum than between Ty. monococcum and either of the former. The palea of Tr. monococcum falls into two parts at maturity, while in the other two species the palea remains entire. Tr. sativum spelta and Tr.sat. dicoccum are to be distinguished from the other four subspecies of sativum by the grains remaining enclosed in the glumes upon threshing and by the rachis breaking up at maturity. The common and
1 In the following division into species and subspecies Hackel has been followed. See The True Grasses. By Edward Hackel. Translated from Die Naturlichen Pflanzenfamilien by F. Lamson-Scribner and Effie A. Southworth, pp. 179-187.