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shown that while no relation could be traced between temperature and yield of maize, a very direct relationship could be traced between rainfall and yield. The yield did not depend merely upon the total rainfall for the five growing months of May to September, but much depended upon the distribution. The June, July and August rainfall had the greatest influence, and of these July was the most important. The September rainfall had no noticeable effect, while much rainfall and cloudy weather in April and May decreased the yield. A July rainfall of from 4.75 to 5.25, and a June, July and August rainfall of 11.75 to I2-2S inches, was found most desirable. The most favorable condition for the growth of maize is comparatively heavy rains at considerable intervals, with clear sunshiny weather in the meantime.
II. THE SOIL AND ITS AMENDMENTS.
282. Soil.—The yield of maize is greatly influenced by the character of the soil, perhaps even more so than any other cereal. Alluvial river bottom soil and tile drained swamps furnish the best conditions. A large proportion of the maize crop is grown on drift soil, but not all portions of the glaciated land are equally well adapted to this crop. (115) In the Southern States the red or chocolate-colored upland soils with red clay subsoils are better for maize than the gray soils with yellow clay subsoils.1 For its best growth, maize requires a friable
1 Ga. Bui. 46, p. 73.
A comparison of the average rainfall for July and the
Average precipitation in July in inches.
soil that is easily drained and does not bake during drouth. While the water should drain freely from the surface, a watertable within three feet of the surface is not objectionable and probably desirable. The free movement of water through the soil in all directions, especially during the period of fastest growth, is essential to the largest yields.
283. Rotations.—The maize crop, while not considered an exhaustive crop, requires a fertile soil, that is, one with a high crop producing capacity. The rotation and fertilization are such as to bring this crop on the soil at the time of its greatest producing power. Throughout the main "corn-belt," a good rotation is, maize, two years; wheat or oats, one year; timothy and clover, three years. In the Northern States outside the distinctive "corn-belt," maize is grown only one year, generally followed by oats; then wheat seeded with timothy and clover. The length of time the seeding is left to stand is quite variable. Economic conditions have a controlling influence, but for the good of the land probably one to three years will give the best results. (119) The Louisiana Station1 has decided that a threeyear rotation, consisting of maize, oats, followed by cowpeas and cotton, is the best attainable for that section. To get the maximum yield, it is necessary to sow the oats in October. The cotton cannot be removed in time for the oat crop, but maize can.
The Indiana Station2 found that a rotation that included timothy and clover, beans and roots, gave during seven years a yield of twenty per cent more grain of maize than did a rotation containing only maize, oats and wheat. The last year the gain was forty-eight per cent, indicating a continuous widening in productive capacity.
284. The Continuous Cropping of Maize.—On deep black friable prairie soils, as well as upon the fertile river bottom soils
1 La. Bui . 35, p. 1,211. * bid. Bui. 5 5, p. 28.
of the North Central States, maize has been raised continuously for many years with success when more or less frequent applications of stable manure have been made. The Illinois Station raised maize continuously for twenty years upon a black friable prairie soil. The average annual yield from the plat receiving no fertilizers was, during the last eight years of this period (18881895), 35.7 bushels; from the plat receiving commercial fertilizer, 35.6 bushels, and from the plat receiving stable manure, 47.3 bushels. A six-course rotation, maize, two years; oats, one year;
In referring to the different sections of the United States the nomenclature of the United States Census Bureau is followed, as shown above. Northern States include North Atlantic and North Central States, and Southern States include South Atlantic and South Central States.
and clover, three years, was carried out during twenty years as uniformly as the exigencies of the clover catch would permit. During the last eight years five comparisons as to increase of yield, both first year and second year after clover, could be made with the plat continuously in maize and receiving no fertilizer. The average increase the first year was twenty bushels and the second year 15.2 bushels per acre. In a similar comparison, where maize alternated with oats, the average increased yield as compared with the plat continuously in maize without fertilizer was 2.6 bushels per acre.1
285. Maintaining the Crop Producing Power of the Soil.— The use of stable manure and the rotation of crops in connection with stock raising are the chief means of keeping the land in good condition to grow maize. Maize is not an exhaustive crop because (1) it removes from the soil comparatively small quantities of soil elements for food produced; (2) it produces large quantities of organic matter which when fed to live-stock makes large quantities of organic manure to return to the soil; (3) the intercultural tillage is doubtless beneficial, although this has not been as fully demonstrated as the expression of Jethro Tull,—"Tillage is manure,"—might indicate.
The Indiana Station2 manured for two years a series of alternate plats which had grown maize continuously for five years with fresh horse manure amounting for two years to about fifty tons per acre. No manure was used before or since. During twelve years the average yield was nearly ten bushels per acre more on the manured than on the unmanured plats and on the last year of the period was nearly five bushels greater.
286. Influence of Organic Matter.—Stable manure is more frequently applied to land intended for maize than to any other. Grass and clover are usually followed by maize. One reason why stable manure is found generally beneficial for maize is that it supplies organic matter, which when in proper condition may modify the water content of the soil. Instances are known where no influence whatever was obtained from the use of large quantities of commercial fertilizers, but where the use of stable manure increased the crop. The Wisconsin Station found that while the total amount of water in the upper six feet of soil was essentially equal in both manured and unmanured
1 11i. Bui. 42, p. 177. * Ind. Bui. 55, p. 29. ground,1 yet there was a marked difference in the distribution of it, the upper three feet of the manured ground being decidedly more moist than the unmanured. This may have been due to one or more of four reasons:
(1) The increased vegetable matter in the soil may cause more of the rainfall to be absorbed and allow less to run off the surface.
(2) Less water may be evaporated from such a soil, as indicated by laboratory experiments.
(3) The water may drain off into subterranean channels less rapidly.
(4) More water may be brought up from below by capillary attraction.
It is not unlikely that all four of these causes operated to produce the observed results.
287. Application of Stable Manure.—The amount of stable manure per acre may vary from ten to twenty tons. Where feasible, an ideal method is to apply the stable manure to the meadow in August and plow land late in the fall for the next spring's planting. For practical reasons, however, the manure is usually hauled in winter and spring and the manured land is then spring plowed. When hauling manure in the winter, care should be taken not to haul when the land will be seriously injured from puddling, and not to spread manure on top of a considerable thickness of snow lest it should run off suddenly and carry the manure with it. Well rotted manure will bring the most immediate results and the largest yield per acre, but hauling manure before much decay has taken place causes it to go farther, since there is considerable loss through decay. In regions or seasons of deficient rainfall the application of unrotted manure may cause a reduction in yield. The moisture in the soil being insufficient to cause decay, the undecayed organic
1 After making a correction for water used in producing the increased yield of maize upon the manured portion.