« AnteriorContinuar »
seeding may be done with safety, as the rich soil produces the growth needed in a shorter time. Wheat often suffers in the fall from lack of rainfall. It is seldom injured from an excess of rainfall. As the time and manner of preparing the seed bed materially affects the moisture of the soil, the preparation of the seed bed may have a decided influence upon the time of sowing. The earlier and better the seed bed is prepared the later the seeding is permissible. On the fortieth parallel at an altitude of 500 to 1,000 feet, winter wheat should be sown generally about September 20th, with variations of a week either way, depending upon various factors indicated above.
While obviously not as many factors enter into the time of seeding of spring wheat as winter wheat, climatic and seasonal variations necessitate as wide variations perhaps in the former as in the latter. It may be laid down as a general rule that spring wheat should be sown as early as the ground can be got in fit condition for seeding. In both North Dakota and Minnesota the earlier sown spring wheats gave best results, while in Utah a medium date gave the best yields. Delay of two or more weeks in sowing caused marked losses where conditions were those of Ontario and Quebec. In other provinces the loss from delay in sowing was less marked. Seeding should be finished by May 1 st in Ontario and Quebec, and in other provinces from May 15th to 25th.1
130. Depth of Sowing.—This will vary with the kind of soil, the moisture, and the levelness and the firmness of the seed bed. Wheat may be sown deeper in a sandy soil than in a clay soil. It is necessary to sow deeper in a dry than in a wet soil. Variations in rainfall often materially modify the depth of seeding. It is reasonably well established that, under ordinary conditions, the nearer the seed is covered with one inch of moist soil, the better. An uneven and cloddy soil would require that some be planted deeper than is desirable
1 Cent. Expt. Farm, Canada, Bui. 21.
in order that all may be covered. A summary of the work of eight stations, mostly in the Mississippi and Ohio Valleys, aggregating twenty years' results, shows that in some instances four inches was at least as good as shallower depth, but in most instances one to three inches gave the best results, and indicates that usually it is not safe to go beyond these extremes.
131. Drilling Compared with Broadcasting. — Stations of thirteen States have made experiments to compare drilling wheat with broadcasting it. The number of years' trial at a station varied from one to nine years and aggregate thirtythree years. Only two stations (Iowa and South Carolina) report, as the result of one year's trial, in favor of broadcasting. While in individual years broadcasting has produced the best results, at other stations the average of two or more years was in favor of drilling whether for fall or spring seeding. For fall seeding, the Ohio Station found as the result of nine years' trial two bushels in favor of drilling; Indiana in four years' trial reports eight bushels gain, and Kentucky in three years' trial reports four bushels gain. For spring seeding, Minnesota in three years' trial reports two bushels gain; North Dakota in two years' trial reports five bushels gain, and South Dakota in two years' trial reports two bushels gain. While these differences are not great, they generally amply pay for any extra cost of drilling, which is almost the universal practice for fall seeding.
A number of reasons may be given for this practice, not all of which, however, will apply in any given locality. The wheat is more uniformly distributed and covered and is sown at a more even depth. Quick germination is insured by having the seed in moist soil. It is believed also to be less easily winter killed either by freezing or heaving. The drill makes little furrows in which the snow lodges and is prevented from being blown away. It has been abundantly proved that the amount of snow held in the furrows is sufficient to modify the temperature of the soil considerably. The wheat is less likely to be heaved out from freezing and thawing. The soil at the bottom of the furrow offers greater resistance to the heaving than does that at the top of the ridge. The movement of the soil will take place at the point of least resistance, which will be at the top of the ridge, thus increasing the chances of the plant at the bottom of the furrow to remain undisturbed. At the same time the loosened soil, aided by the rains, tends to fall into the furrows and thus further protect the plant. Just how much effect this has one year with another is not known, but in some trials during one year by the writer, where the furrows were obliterated by rolling, the yield was not materially affected.
In the spring wheat districts, the winds tend to lay bare the seeds when broadcasted, while drilling rather tends to deepen the covering by partially filling up the furrows. Practice seems to show also that weeds are less troublesome in spring wheat when drilling is practiced, doubtless because it insures quicker germination of the wheat .
132. Quantity of Seed per Acre.—The quantity of seed to be sown per acre will vary with the character of the soil, climate, time of seeding, seed bed, size, quality and variety of seed, and method of seeding. If sown early, less would be required than when sown late, because each plant would become larger, tiller more, and thus cover more ground. If the seed bed is well prepared, and the vitality of the seed good, a larger percentage of the seed will grow than if the seed bed and seed are poor. Fertile soil requires a less number of plants per acre than a poor soil because each plant tillers more and grows larger and thus occupies more room. A bushel of one variety may contain three times as many grains as another. A variety which tillers profusely could be sown thinner than one that does not. If drilled, a less quantity could be sown than if sown broadcast.
The yield will not be at all in proportion to seed sown. The wheat plant adjusts itself to its surroundings. If sown thickly, it tillers but little and produces but few spikes per plant If sown thinly, it stools more and the spikes are larger, often sufficiently to counterbalance the thin seeding.
In climates where the winters are uniformly mild, much thinner seeding may be practiced than where the winters are severe. The fact seems to be that when the winters are mild the plant largely adjusts itself to its surroundings, so that it makes but little difference how much seed is sown within reasonable limits, but when the winter is severe and the wheat partly killed, if the wheat is sown thickly there may still be wheat enough left to raise a fair crop.
The Statistician of the United States Department of Agriculture estimates the average quantity of winter wheat sown at i 3-8 bushels per acre, and of spring wheat at 1 1-2 bushels per acre. Professor Brewer found by means of circular letters sent to representative farmers throughout the country that the amount sown in the Middle Atlantic States was seven to nine pecks, in the Mississippi and Ohio Valleys six to eight pecks, and in California three to eight pecks, the smaller amount being used in the drier regions.
Experiments have been carried on in the experiment stations of Ohio, Kentucky, Indiana, Illinois, Kansas and Oklahoma for periods ranging from three to eleven years, aggregating thirtythree years' trials. In no case was the largest average yield at any of these stations made with less than six pecks of seed per acre, or more than eight pecks. Two stations report in favor of six pecks, one in favor of seven pecks, and three in favor of eight pecks. The Ohio Station not only reports in favor of eight pecks, but also states that with the thicker seeding the weight per bushel is greater, and consequently the quality of seed better.1 In some cases, on moderately fertile soil, better results were obtained with nine to ten pecks. In experiments of all the stations the variation in yield between five and
1 Ohio Bui . 118.
eight pecks was not usually large. In ordinary practice the tendency seems to be to use too little rather than too much seed.
133. Influence of Size of Seed.—Ontario Agricultural College, by selecting seed of winter and spring wheat, oats, barley and peas during five to eight years, found the average yield of grain and straw and the weight of grain per measured bushel to be in favor of large, plump seed as compared with medium-sized or small seed.1 Indiana found an average gain during three years of 2.5 bushels in favor of large seed. Kansas Station found on an average of four years a slightly higher yield from wheat with high weight per bushel.2 Nebraska Station found that large heavy seed gave much better yields than unselected seed.8 North Dakota Station concludes as the result of four years' tests that perfect grains of large size and greatest weight produce better plants than perfect grains of smaller size and weight, even if the grains come from the same spike.4 A summary of nine years' results at the Ohio Station with selected seed, second grade and unscreened seed, shows that neither the quantity nor the quality of the crop was varied by the seed used.5 No marked difference was obtained at Penn
Spike of wheat grown in New South Wales, onehalf natural size, showing relative size of grains as extracted from spikelets on one side only of the spike (After Cobb.)