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come when the corn is tasseling. They cause the pollen to dry up, and the silk is not fertilized. Even with a sufficient rainfall, a few days of these withering blasts from the southwest, in tasseling time, may reduce the yield of corn fifty per cent. Kafir corn is not affected in the same way. Fertilization takes place more readily and the whole plant is better adapted to stand dry weather. The leaves are thicker and coarser than corn leaves, and do not dry out so readily; they are closer together and partly protect each other, and the plant is not so tall and, therefore, not so much exposed. When corn has once been stunted by drought or hot winds, it never recovers. Not so with Kafir corn. It may remain stationary and curled for days and even weeks, but when the hot winds cease and rain comes it will revive and, if not too late in the season, will still produce a crop of grain."1 i
It is necessary to distinguish between possible climatic range and the economic climatic range of sorghum. While sorghum can be grown in almost any climate in which maize can be grown, its economic climatic range does not extend north of the fortieth parallel.
545. Soil. The soil requirements of sorghum are similar to those of maize, although the Kafir varieties are believed to succeed on land too poor to raise the latter. The plant also seems to be rather more resistant to alkali. For its best development, broom corn requires rich soil. Ordinarily it would not be wise to attempt to raise it on any but the best maize lands, although river bottoms are usually not desirable on account of the weeds. Dwarf broom corn succeeds best on dry, sandy soils, the brush having a tendency to grow coarse on the richer soils. The same principles apply in the use of fertilizers as in maize. (285-294)
546. Rotation.—Ordinarily sorghum takes the same place in the rotation as maize. It is a general experience that a crop following sorghum, particularly the Kafir varieties, is not so good as one following maize. The reason for this appears to be that the sorghum being more resistant to drouth continues to grow and thus exhaust the soil of its moisture, and possibly its plant food, when the maize would be prevented from doing so. The land thus breaks up hard and lumpy after the sorghum. As a
I U. S. Dept. of Agr., Farmers' Bul. 37. p. 5
remedy for this, the Kansas Station recommends more thorough surface tillage of the sorghum. Inasmuch as broom corn is harvested soon after the flowers have set, the crop is not an exhaustive one. Broom corn is frequently raised continuously for many years on the same land without material diminution of the crop or injury to the land. Rotation of crops, however, is desirable on account of injury from insects and fungous diseases, particularly the latter.
III. CULTURAL METHODS.
547. Preparation of Seed Bed.—The preparation of the seed bed is similar to that for maize except that greater care is imperative on account of the smaller seed and the slow early growth of the sorghum plant. For the first month after planting the growth of sorghum is much less rapid than that of maize, and the difficulty of keeping the land free of weeds is therefore greatly increased because of the difficulty of killing weeds without covering the plants.
548. Time of Planting.–In the sections in which it is grown the time required to mature a crop is rather less than that required for maize. During germination and early growth sorghum is very sensitive to cold, wet weather. It should not, therefore, be planted until the land has become thoroughly warm, usually from one to three weeks after the time for planting maize.
549. Rate of Planting.–Generally speaking, about twice the number of plants per acre should be raised of sorghum as of maize. That is to say, if at the rate of one grain every twelve inches in rows forty-two inches apart is the best rate in a given locality for maize for the production of grain, then one grain every six inches would be the best for the Kafir varieties of sorghum for the production of the seeds or grains. If one grain every six inches is the best for the production of maize fodder. or silage, then one grain every three inches would be the best for the production of sorghum fodder or silage. Since the Kafir varieties of sorghum do not grow as tall as maize, the rows may be closer together; three feet being often recommended where the rows of maize are usually planted three feet eight inches apart. Experiments, however, do not show that any greater yields of grain or roughage can be obtained by having the rows closer together, provided the same number of plants are raised per acre. Standard varieties of broom corn are planted at the rate of one plant every three inches in rows three feet six inches or three feet eight inches apart; and dwarf varieties are planted with plants two inches apart in rows three feet apart. The quality of the broom may be affected by the rate of planting; the thicker the planting, the finer the brush. Sorghum may be drilled or planted in hills; the former being the more common method. When the latter method is followed the hills are about eighteen inches apart in the rows. There are no experiments to show that the yield is greater in one case than in the other.
550. Quantity of Seed.—The quantity of seed per acre used in practice is quite variable because of the variety of purposes for which it is raised, different methods of handling, difference in size of seed and liability of low germination. Three to four pounds of good seed are sufficient to plant an acre of broom corn. Where Kafir varieties are grown for grain alone five to six pounds of seed are used and twice this amount where fodder is also wanted. Where sweet sorghum is grown for forage fifteen to thirty pounds planted in rows and cultivated produce a palatable product, and is usually the most satisfactory method of handling the crop. When sown broadcast or drilled, as in the case of wheat, to be mown and treated as hay, as high as 100 pounds of seed per acre are used. There is no evidence to show that this method produces greater yields, but it is preferred by some on account of the method of handling the crop, and because of its better keeping quality. Where the canes of sweet
sorghum are large they are apt to retain their juices, which when frozen ferment, and rapid deterioration of the fodder results. Where sweet sorghum is grown for seed for subsequent planting or for sirup two to three pounds per acre are sufficient.
551. Method of Planting.–Any form of maize planter may be used for planting sorghum by substituting special plates. In case special plates are not available the rotary disk plate of the maize planter may be filled with melted lead and bored out the proper size. The wheat drill can also be used as suggested for maize. (305)
"Perhaps the best and most practical is the ordinary grain-drill. As the rows should be thirty to thirty-six inches apart, the holes may be stopped by tacking a piece of pasteboard over all except those which will plant the rows the proper distance. On an eleven-hole drill, by stopping all but the outside holes and the middle one, the rows will be thirty inches apart; or by arranging a thirteen-hole drill the same way the rows will be thirty-six inches apart, providing the distance between the shoes is six inches. A marker may be put on the drill by bolting a twoby-four timber to the middle post of the frame and letting it project behind to fasten the marker to, and pull the other end by a rope or chain from the marker to the doubletree. Or a slat may be fastened to the frame of the drill and project out to the sides in front of the wheels, and a light chain or wire be fastened to the slat to drag in the wheel mark made the previous round, and so adjusted as to indicate the proper distance from the last row planted.” 1
Listing is frequently practiced, but more difficulty is experienced on account of the weeds and the slow growth of sorghum than in the case of maize. More injury also is experienced from flooding for the same reasons.
552. Cultivation.—The principles underlying the cultivation of sorghum and the tools used are the same as those for maize, the only difference being that greater vigilance must be exercised to prevent weeds from getting a start. (312) The land should be kept harrowed sufficiently before the sorghum comes up to prevent weeds getting a start, and after it is up may be harrowed with a weeder or light harrow as suggested for maize.
1 Rpt. Kan. St. Bd. Agr., March, 1900, p. 56.
(299) While the plant is between three and eight inches in height it will stand harrowing better than maize.
553. ENEMIES ɔr SORGHUM.—Weeds are especially troublesome to sorghum on account of its slow early growth; but there are none that are not common to maize. The sorghum plant is attacked by maize rust (Puccinia sorghi Schw.) and also by smut (Sphacelotheca sorghi (L. K.) Clint.), which frequently does much damage to broom corn by producing its black smut spores in the seeds. It may be controlled by soaking the seed for fifteen minutes in hot water at 135° F.1 or by the formalin treatment. The principal insect enemies are the chinch bug (151) and the plant'louse. (333)
554. Time of Harvesting.–The stage of maturity depends upon the purpose for which it has been raised. When raised for grain the seeds are allowed to become thoroughly mature, which usually happens while the stem and leaves are still green. Plants may stand in the field in this condition for several weeks without material injury, although there will be some loss from the shattering of the seed. It is desirable, however, especially when use is made of the fodder, to cut and shock it as soon as the seeds have become thoroughly mature. With broom corn, brush of a light color is desired and is obtained by cutting as soon as may be after the pollen has fallen. The early cut brush is also said to be heavier and more durable. The milk stage is as late as it may be safely allowed to stand, although in California seed is allowed to ripen, greatly to the detriment of the brush, as much as a ton of seed per acre being obtained.?
555. Method of Harvesting.–No thoroughly satisfactory method of handling the crop has yet been devised, especially in humid regions where there is some difficulty in keeping both the stover and the grain. It may be cut and shocked after the manner of maize by any of the methods recommended for that crop. (342) In some cases the header has been used, which gathers only the heads and leaves, the stalks standing in the field. In other cases the heads are removed by hand with a
1 III. Bul. 47 ; 57. 2 U. S. Dept. of Agr., Farmers' Bul. 174, p. 17.