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starch) is usually inversely proportional to that of the protein and fat . If maize were bred for the manufacture of starch or glucose, only low protein content would be desired, since the fat or maize oil, which is a by-product of the manufacture of starch, is worth more per pound than the starch.
262. Advantage of Breeding for Composition.—Throughout the North Central and Eastern States, and especially in those States which raise a great surplus of maize, stock foods generally contain too small a proportion of digestible protein. The protein is, therefore, the most expensive ingredient of stock foods, being several times more expensive per pound than maize itself. The raising of maize with a higher percentage of protein would reduce the need of purchasing more expensive nitrogenous foods, and would thus cheapen the food supply, provided the yield of maize is not reduced as the per cent of protein is increased. In the Southern States, the food supply for live stock is highly nitrogenous, due to large surplus of cotton seed, cottonseed meal and cowpeas. In this section, a high starch content may be desirable. Large quantities of maize are annually used for the manufacture of starch and glucose. The Glucose Sugar Refining Company1 says:
"A bushel of ordinary corn, weighing 56 pounds, contains about 4 1-2 pounds of germ, 36 pounds of dry starch, 7 pounds of gluten and 5 pounds of bran or hull, the balance in weight being made up of water, soluble matter, etc. The value of the germ lies in the fact that it contains over 40 per cent of corn oil, worth, say, 5 cents per pound, while the starch is worth 1 1-2 cents, the gluten 1 cent and the hull about 1-2 cent per pound.
"It can readily be seen that a variety of corn containing, say, one pound more oil per bushel would be in large demand."
263. Disadvantage of Breeding for Composition.—One disadvantage of breeding for composition and yield at the same time is that breeding for two characteristics at one time is several times more difficult than breeding for one. An objection to breeding for high protein is that the amount of nitrogen re
1 11i. Bui. 82 (1902), p. 526.
moved from the soil will be increased, unless the yield of maize is decreased. No results have been reported of the influence upon yield of breeding for high protein or other modifications in composition. Whether it is better to raise the surplus nitrogen needed in leguminous crops like clover, alfalfa, soy beans, cowpeas, field peas, etc., and to raise maize primarily as a source of easily digestible carbohydrates, will need to be settled by each grower in accordance with local conditions, assuming that composition has no influence upon yield.
264. Methods of Breeding.—Breeding for composition has served to call attention to the method of testing hereditary power, whether the character to be tested was high protein, fat or yield.
After several ears of maize have been selected for high protein, it becomes necessary to determine whether they will reproduce ears with high protein, and also to place the plants produced from such selected ears where they will be fertilized by pollen from plants having high protein content. If this is an advantage in the case of ears selected for high protein, it is also an advantage for ears selected for high yield. Large ears may be the result of environment or may be due to hereditary power. Of two ears of equal merit (as, for example, size), one grown on very rich soil and the other on ordinary soil, the latter should be preferred for seed.
265. The Breeding Plat.—Assuming total yield of grain to be the character bred for, the following is an outline of plan to be followed in the breeding plat, the details to be modified according to circumstances:
(1) First carefully consider the variety of maize best suited to conditions. Do not waste time improving a poor variety or strain. Having selected the variety, it will generally be wise to grow no other.
(2) Select 100 ears of perfect vitality of this variety. Weigh each ear separately and arrange in order of weight .
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(3) From these 100 ears select forty nearest the ideal sought, giving due importance to weight of ear, but not neglecting other qualities.
(4) Next shell each ear separately, weigh cobs and determine total weight and per cent of shelled grain to ear. The total weight of grain is more important than the per cent . There is no necessary relation between per cent of grain to ear and yield. Large cobs may, however, be objectionable for other reasons, as, for example, their influence upon maturity and preservation of the ear. With the information obtained, select twenty-five out of the forty ears and number ears 1 to 25, making the best ear No. 13, the next best ears 12 and 14 and the poorest ears 1 and 25.
(5) Lay off a piece of uniform land fifty hills square and plant rows 1 and 26 to ear 1; rows 2 and 27 to ear 2, until ear 25 is planted on rows 25 and 50. Place five grains in each hill, and when plants are three to four inches high, thin so that each row has 150 plants. If this plat of maize is planted by itself, four rows should be planted clear around the plat from what is left of the twenty-five selected ears. In many cases the most practical way will be to plant the plat in the body of a field containing the ordinary crop, which will be the same variety. The breeding plat should not be within twenty rods of neighboring maize fields, especially if the variety is different.
Diagram showing the influence of heredity and environment upon yield of maize. Curves show yield per row in pounds of field cured grain of fifty rows grown from twenty-five different ears of the same variety. Rows No. I and No. 26 grown from seed of ear No. I; rows No. 2 and No. 27 from ear No. 2, etc. The rows were each fifty hills long, and each hill, with very few exceptions, had exactly three stalks per hill. Grown in Fayette county, Ohio, by L. H. Goddard.
(6) When properly matured, husk and weigh the ears from each row separately under exactly uniform conditions. If the progeny of a certain ear yields more maize than does either row from another ear, it may be assumed that the former has the superior hereditary force and that the greater yield was not the result of environment, as, for example, better soil.
(7) For next year's breeding plat, select twenty-five ears from the progeny of a few of the best ears, say the best five ears. It would probably not be safe to select all the ears from the progeny of the best ear, as that would lead to very close breeding. It will also be desirable to arrange for as much crossing as possible between ears of unlike parentage. Select the best of what is left from the breeding plat for the field crop. The breeding plat is to be continued indefinitely.
266. Field Selection.—The usual method of obtaining seed is to select ears from the regular field crop. There are three methods:
(1) Selection of ears from the crib.
(2) Selection of ears at the time of husking.
(3) Selection of ears by passing through the field before husking and while plants are still standing in the field.
The reason for employing the second method over the first is that the seed may be dried before low temperature has an opportunity to injure or destroy the vitality. The advantage of the third method over the first is that it gives opportunity to observe the character of stalk and leaves when selection is made. The advantage of the second method is that it gives a wider range of selection and makes more certain the finding of the best ears, since every ear is handled.
267. Field Seed and Breeding Plat Seed Compared.—The advantage of the breeding plat method of securing seed is that it permits the selection of seed that has shown its ability to produce the highest yield or the highest per cent of protein, as the case may be, under substantially similar environment. Under field selection it is not so certain that size of ear was not the result of environment, and the ability of a strain to produce occasional large ears is not necessary proof of large average yield. Undoubtedly, however, field selection has great merit, since it enables the selection of the finest ears of the character desired. The disadvantage of the breeding plat is that it limits the range of selection to perhaps an acre of maize, while in field selection twenty, forty or even 100 or more acres may be available from which to make selections. The importance of this wider selection will depend upon the extent to which the finest ears under ordinary field culture are due to the environment and to what extent they are hereditary variations. This has not yet been satisfactorily proven. Another possible disadvantage of the breeding plat is that it leads to close breeding. (254)
268. Vitality of Seed.—Owing to the time of maturity, the vitality of seed is often injured by freezing before the grain is thoroughly dry. It is the water that freezes and thereby destroys the tissue. The vitality may be preserved in two ways: first, by thorough drying; second, by not subjecting to a low temperature. If the grain is dried thoroughly, low temperature will not injure it. The first method is usually the most feasible. In southern latitudes this may be accomplished by storing in narrow cribs, but in more northern latitudes hanging in an airy place sufficiently protected from cold to cause thorough drying before severe weather begins, or drying by means of artificial heat, is desirable. The latter method is now being practiced by some who make a specialty of raising seed maize.
269. Importance of Testing Vitality of Seed.—It is very important, not only that seed should grow, but that it should grow