that there is a relation between climate and existing varieties of maize. The time that it has taken to fix these types is, however, a matter of much difference of opinion and about which the evidence is obscure. The variations as to size and maturity existed when this country was discovered. It is a common observation that the varieties of a given region tend to assume a common type. When dent varieties are introduced in a region growing flint varieties, or the reverse, the introduced variety tends to take on the characters of the other type. This has been attributed to climatic influences, but may be explained upon the grounds of crossing and unconscious selection. The current cross would not, ordinarily, show in the seed, but would show in the resulting crop. Varieties sufficiently distinct to escape cross-pollination have been grown continuously without modification.1

The author had a standard variety of maize grown about 120 miles north of the Illinois Station for three years. The first season it barely ripened in its new location. The ripest ears were selected for seed, and in subsequent years it was believed by the grower to have ripened earlier. After three years seed was returned to the Illinois Station and on the fourth year grown beside seed continuously grown at the station. When thus grown side by side there was no difference in the time of ripening. The evidence concerning the influence of climate upon varieties is not as clear as might be desired, but it is probable that much that has been ascribed to climate has been due to selection.

279. Influence of Climate Upon Composition.-Analyses so far reported do not indicate any material difference in composition in maize grown in different sections of the country covering a wide variation in soil and climate. An average of thirty-five northern and forty-nine southern grown samples of dent maize has shown the following composition:

1 Cf. Bul. Torr. Bot. Club Vol. XXI (1894), No. 12, p. 521.

280. Need of Water.-At the Illinois Station, from eighteen varieties of maize on eighteen tenth-acre plats, the author obtained thirty-two bushels of dry shelled grain per acre. The next season, with the same varieties on the same plats, with cultural methods as nearly identical as possible, and without the addition of any fertilizer, ninety-four bushels per acre were obtained. During the first season, the rainfall for the five growing months (May to September) was thirteen inches; during the second, twenty-two and a half inches. During the same period the average temperature for the first season was 73° F.; the second, 69° F. (276)

The amount of water evaporated from the maize plant and the surrounding soil has been determined by King1 to be in Wisconsin 270 pounds for each pound of dry matter grown, equivalent to a rainfall of 2.4 inches for each ton. This is only about half that required by oats and clover. Maize is, however, very greatly influenced by the water supply in July and August, since during that time the period of growth is very rapid. The author has determined the growth of maize in one week in July in Illinois to be equal to 1,300 pounds of dry matter per acre, which would require, according to the experiments of King, 1.5 inches of rainfall. (350) At such times, unless the physical conditions of the soil are the best, the plant is apt to suffer from a lack of water, or, in other words, from drouth.

281. Influence of Rainfall.-Everything points to the importance of water in the successful culture of maize. Beale has

1 King: Physics of Agriculture, p. 139.

shown that while no relation could be traced between tempera ture 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 5.25, and a June, July 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. For its best growth, maize requires a friable 1 Ga. Bul. 46, p. 73.

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. Bul. 35, p. 1,211.

* Ind. Bul. 55, 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