This uneven distribution of the rainfall is a sufficient incentive to cause the farmer to take every precaution for storing and holding the moisture in the soil before the crop is planted by preparing a deep, mellow seed bed, or for carrying off quickly excessive amounts of rain. Corn should receive an average of at least 2.5 inches of rainfall per month during the three months of its growth. The effects of rainfall during June, July, and August upon corn yields are shown by the records of the old continuous corn plot at the University. Corn has been grown on this plot since 1879, but there is no record of the yield previous to 1SS9 Summer rainfall I,ess than 7 inches 25.3 bu. per acre ( 8 yr. ay.) Between 7 and 10 inches 32.4 bu. per acre ( 9 yr. ay.) Over 10 inches 39.8 bu. per acre (11 yr. ay.) When the rainfall was less than two inches per month, the yield was reduced for a four-year average to 24.4 bushels per acre, and when the rain fall was over thirteen inches. the yield was 45,9 bushels per acre for a seven year average. This is a difference of 21.5 bushels between yields produced with what might be called the maximum rainfall and those produced with the minimum at the University of Illinois. It is evident from this that a month during which there is less than two inches of rainfall may be regarded as a dry month.' Importance of corn.—Corn is by far the most important crop of the United States. The acreage and also the value of the corn crop are greater than that of wheat, oats, barley, rye, buckwheat, rice, fruits, and nuts com bined. The geographic conditions which are essential to large yields of corn are found in only a few regions of the world, and most extensively in the United States.
Corn is pre-eminently the American crop, grown on three-fourths of all the farms of the United States, which produces nearly three-fourths of all the corn in the world. Within the United States three-fourths of all the corn produced is grown in the Missis sippi Valley. There are two centers of heavy production—one in central Illinois and the other in the Mis souri Basin of western Iowa and eastern Nebraska. The total corn acreage of Illinois in 1909 was 10.046,000, or 10 per cent of that for the country as a whole; Iowa had 9,229,000 acres in corn; Kansas, S,109,000 acres; Nebraska, 7,226,000 acres; Missouri, 7,114,000 acres; and Indiana, 4,901,000 acres; these six states combined having 47 per cent of the corn acreage of the United States and 57 per cent cf the produc tion. In this region of concentrated production there has developed a system of live-stock farming adapted to the utilization of corn. Nearly half of the swine of the country are in these six states and one-third of the beef cattle.
The acreage devoted to corn constitutes over 75 per cent of the total acreage in crops in some of the mountainous counties of eastern Kentucky, where a moderately dense rural population derives its meager livelihood largely from the cultivation of small patches of corn, averaging from 10 to 15 acres per farm. The production of corn is small also in Florida and in the southern parts of Alabama and Mis sissippi, where most of the land is still in forests, yet corn constitutes in this region over 50 per cent of the total land in crops.
Corn is the principal source of food supply of the American people, but outside of the South very little of the corn is directly consumed by man.
Most of the crop is fed to cattle and hogs, and consumed as beef, a pound of which represents 10 or 12 pounds of corn, or as pork, to produce a pound of which 5 or 6 pounds of corn are required. Much of the corn raised in central and northern Illinois, as well as a considerable portion of that grown in Iowa, is shipped to Chicago, where it is made into starch, glucose, and corn meal, or is exported, but outside a radius of about 200 miles from that city the corn is fed to cattle and hogs whose concentrated value can better bear the cost of transportation to market. The corn grown in the South is practically all consumed at home, being made into "hog, hominy, and hoe-cake," the staple food products of that region) Leading corn states.—Illinois and Iowa are in a class by themselves as corn-producing states. They are rivals for first place, but they have no rival state for second place. A table at the close of this chapter shows, in round numbers, the acreage, production, and value of corn, oats, wheat, hay, and forage for Illinois, and for the United States for nine years, 1909 to 1917 inclusive. For these nine years the corn acreage of Illinois exceeded that of Iowa each year except 1917, and the production of Illinois exceeded that of Iowa in five years of the nine. These two states with a combined area of only 112,000 square miles produce more than one-fourth of the corn crop of the United States and about one-fifth of the world's crop.
One-half of the land in Illinois devoted to crops is planted to corn, and the value of the corn is equal to that of all other crops of the state. Corn is raised in every county of Illinois, and on 90 per cent of all the farms of the state.
Corn production for the ten leading counties in 1909, with acreage and average yield per acre, is shown in the table at the close of this chapter. The average yield per acre for the state was 38.8 bushels.
Oats.—The oat crop occupies more than one-fifth of the total crop acreage of Illinois and is second in acreage and value. Oats are grown in every county of the state, but the heavy prochktion is in the corn belt, where the crop is especially important in crop rotation with corn. Oats arc not limited in distribution so closely as corn by conditions of soil and climate. They grow well on a wide variety of soils, giving good yields on rather poor soils if there is abundant moisture. They thrive best in a cool, moist climate, but do well in warmer regions if the rainfall is abundant. In Illinois they are sown in the early spring before corn planting time, and get a good start before the season is warm enough for the growth of corn. They are harvested in the summer after the corn has been laid by. They are commonly sown on land which was given to corn in the previous season. They are a good crop with which to sow clover or other grass seed in the spring. Thus oats fit into the crop rotation and the seasonal require ments of farm labor of the corn belt in a most satisfactory way. With the common practice of raising two crops of corn followed by oats, then by clover or other grasses, the acreage of the oat crop is about one-half that of corn.