« AnteriorContinuar »
ment of the individual plants, it made no material difference in the development of the individual plant, the size of the ear, the yield of grain or of stover, and hence the proportion of grain to stover, whether one, two, three, four or five grains were planted in a place, provided the number of grains planted per acre was the same, the least distance between hills being three inches, and the greatest being forty-eight inches, in rows three feet eight inches apart. The following table shows the yield of grain for five years, plats having been averaged so as to eliminate the influence of rate of seeding.
At the Maryland Station experiments have been conducted during five years with one stalk each twenty-two and a half inches in rows three feet nine inches apart as compared to two stalks per hill three feet nine inches apart. The following table shows the yield to have been slightly in favor of drilling every year both in yield of grain and stover:
The Connecticut Station1 found the composition of the crop practically the same, whether planted in hills or drills. Doubtless in some instances increased yields which have been attributed to planting in drills have been due to increased rate of seeding and not to the method of distribution. Where deep culture is practiced, however, drilling doubtless lessens the injury from root pruning (311), although at the same time tending to increase the growth of weeds. (309)
307. Distance Apart of Rows.—While a large number of experiments have been made to determine the advisability of planting in hills or drills, but few experiments have been made to determine the best distance or the limit of distance between rows. The distance apart of rows usually varies from three feet six inches or less in the extreme North to six feet or more in the South. Probably more maize planters are sold which plant three feet eight inches apart than any other distance. From experiments which have been conducted it is doubtful whether greater yields of dent maize can be obtained with rows three feet six inches apart than with rows three feet eight inches apart, provided the same amount of grain is planted per acre. On the other hand, the labor of cultivation is increased about five per cent .
The Georgia Station spaced single plants of dent maize four by three feet, five by two and four-tenths feet, and six by two feet, thus securing the §ame number of plants per acre, and obtained seventeen, sixteen and five-tenths, and sixteen and one-tenth bushels per acre respectively.2 At the Alabama Station3 slightly better yields were obtained with single plants three feet nine inches apart in rows four feet apart than with single plants three feet apart in rows five feet apart. The station, however, recommends rows five feet apart, both on account of the cheapness of cultivation and because it facilitates the raising of a row
1 Conn. Ept. 1890, p. 183.
2 Ga. Bui. 46, p. 68.
s Ala. Bui. 88, p. 500.
cf cowpeas between the rows of maize, which practice is recommended for poor land.
308. Intercultural Tillage.—The cultivation of maize during its early development prevents the growth of weeds and stirs the soil. The destruction of the weeds is made necessary by the fact that comparatively few plants are raised per acre and that it takes these plants from four to eight weeks to occupy the soil and shade the ground sufficiently to check the growth of weeds. The small grains quickly occupy the soil and prevent the growth of weeds. The tillage of these cereals has not in most instances been found to increase the yield. (136) This fact, in itself, suggests that killing the weeds is the most important purpose of tillage.
309. Injury Due to Weeds.—At the New Hampshire Station1 on an uncultivated plat on which weeds grew luxuriantly, the yield of grain was 17.1 bushels per acre, while on a plat cultivated shallow five times, the yield was 79.1 bushels, and when cultivated deep five times it was 69.7 bushels per acre. The injury due to weeds may be attributed to three causes:
(1) They consume plant food. The plant food removed by the largest possible crop can easily be supplied in fertilizers. As good a crop could not be raised in this way as would be obtained if no fertilizer were applied and the land kept free of weeds. Hence, weeds must do something else.
(2) Weeds shade the ground. They obstruct the sunlight and perhaps keep the soil cooler. The author, however, mulched a plat sixteen days after planting, with sufficient coarse, strawy manure to keep the weeds in subjection, and obtained forty-eight bushels of grain and 5,009 pounds of maize fodder, as compared with forty-six bushels of grain and 4,686 pounds of fodder when cultivated one to two inches deep, and forty-one bushels of grain and 4,224 pounds of fodder when cultivated four inches deep. Hence, weeds must do something else.
1 N. H. Bui. ji, p. 47.
(3) Weeds evaporate water. The demand of the maize plant for water is so great at certain periods of its growth that the possibility of development and yield is fixed by the supply of water available. (280) If this supply of water is in any way reduced by the growth of weeds, the yield of maize must be reduced. Sturtevant observed the difference in practice among the vineyardists in New Jersey. Those on the low lands allow weeds to grow: on the uplands the soil is kept free of weeds. The inference is that the weeds pump the water out of the wet land to the advantage of the grape, which prefers a dry soil.
310. The Effect of Stirring the Soil is to break the roots in the area stirred and to make the soil in this area looser, otherwise change its structure and to bring particles of soil into different relations one to another. This allows air, water and roots to enter more freely. The amount of water, the temperature, and probably the salts in solution are affected thereby. (297) King found that cultivating three inches deep made the soil .4 to 1.10 F. cooler than cultivating 1.5 inches deep.1
311. Root Pruning.—It has been clearly demonstrated that any mutilation of maize roots has an injurious effect. At the Illinois Station2 pruning three to four times during the ordinary season on all sides six inches from the center of the hill to a depth of four inches reduced the yield of grain from ten to thirtytwo per cent, the average decrease for five years being twenty per cent. The greater percentages of decrease were during seasons of least rainfall. Pruning three inches deep one season caused a decrease of five per cent. The Oklahoma Station3 found during one season no injury from running a knife three inches deep six inches from the hill, or six inches deep twentytwo inches from the hill, but when the knife ran six inches deep six or twelve inches from the hill the yield was much reduced.
1 Wis. Rpt. 1893, p. 190; 1894, p. 283.
2 11i. Buls. 13, 25, 31. 8 Okla. Bui. 36.
The New York State Station found a decrease in grain of twenty-eight per cent and in stover of twenty per cent during a dry season, pruning three inches deep three to four inches from the hill. During a rainy season pruning in the same manner the second and last time when plants were only ten inches high decreased the yield of grain seventeen per cent and the stover twenty-three per cent.
312. Depth of Cultivation.—While the experiments in root pruning suggest that decided injury would result from deep culture, they do not show what influence stirring the soil might have in counteracting such injuries. Not less than nineteen