agriculture

1. THE RAINFALL

In the Northern Hemisphere, the western portions of con-tinents are especially favored by the prevailing winds. This is because the western lands gather the rains as they come off the ocean, blown by storms that circle from west to east.
Unfortunately, the Cascade Mountains and the Sierra Nevada Mountains, so dose to the west coast, catch the largest share of the rain off the Pacific Ocean before it can go further Inland. As a result, there is too little rain for almost the whole western half of the United States, which lies in the ,,rain shadow” of the mountains. In a great part of that territory, therefore, farmers must depend on irrigation water from the snows or rains that are trapped by the mountains.
One of the most important geographic boundaries in the United States 15 the 50-centimeter rainfall line, which runs north and south almost through the middle of the country. East of the line, farming is relatively easy, and the popula-tion is relatively large. West of the line, one finds man-made irrigation systems, dry-farming, grazing, and fewer people. West of the Rocky Mountains, running all the way from the Canadian border to Mexico, there are vast areas where almost no trees grow. In this section of the country are the deserts which receive as little as 12.7 centimeters of rainfall a year. Yet, west of the Sierra Nevada Mountains, there are places in which 250 centimeters of ram falls annually.

2. THE TEMPERATURE

If there were no mountains or oceans, and if the winds circled the earth with perfect regularity, then the amount of heat and the length of the farmer's growing season would progress uniformly from north to south. Instead there are all kinds of unexpected differences in climate. For instance, all along the western coast, the temperature changes little between winter and summer. In some places, the average difference between July and January is as little as 10 degrees centigrade. The climate along the northern part of this coast is similar to that of England. But in the north central part of the country, summer and winter are worlds apart. There the average difference between July and January is 36 degrees centigrade and more violent extremes are common. The coldest days of a typical January may be –40 degrees centigrade, and the hottest July day may be 45 degrees. This is the sort of climate that is found far from the moderating influence of the oceans. In the eastern part of the United States, the differ-ence between summer and winter is also very distinct, but not nearly so extreme. Near the southwestern corner of the country, the climate is mild and springlike in winter, but in summer the temperature may reach equatorial intensity. In Alaska, almost continuous daylight in summer makes the short growing season an intense one.
The variations in temperature within the United States have had a marked effect on the country's economy and living standards. As the Growing Season Map on page 13 shows, there is a long crop-growing season along the south-east coast where cotton is a principal product. This 18 also true in several small strips and pockets to the west where crops like grapes grow well during a large part of the year. In some of the cooler climates or in climates which combine coolness and humidity, animals and produce such as apples, wheat and corn thrive, thus giving the United States a large range of agricultural products.
These variations, combined with a fast transportation sys-tem, have meant that there can be a rapid interchange of agricultural products from one part of the country to another. Thus, not only is there a greater market for what otherwise would have been strictly regional products, but this expansion of markets has meant great employment op-portunities in all areas.

3. THE PLANT LIFE

When early voyagers approached the land that is now the United States, they noticed a sweet and surprising ,,land smell," a clue that they were near the shore. This ,,land smell" came from the great, thick forest that covered all the eastern part of the country and stretched about 1,600 kilometers westward until it met the tall grass of the prairies.
No one knows just why the woods ended where they did, or why the tall grass of the prairies - the wide rolling and almost treeless plains - began at that point. The reason still remains shrouded in mystery, for the eastern part of the prairies’ tall grasslands have soil that will support tree life. One explanation has it that the Indians burned off the forest in order to force game animals out to the hunters. Another reason given is that perhaps some early special conditions of soil and rainfall were responsible. This has been accepted as a more plausible explanation, but nobody really knows. Nevertheless, the early settlers wrote that the prairie grass was very beautiful, interlaced with flowers in the spring, and so tall that a man on foot could not see over it.
It is clear why the tall grass became short grass farther west - lack of rainfall.
Still farther west, the Vegetation Map looks quite mixed. Forests cover the slopes where mountains catch enough rain. A few favored grassy meadows lie in the high mountain valleys. On the dry lowland -and on high tablelands - dry, harsh bushes grow; so do kinds of grass common to and regions, with places here and there too dry or too full of salt for even this poor desert growth.
The greatest wonder of all are the forests of sequoia and fir trees on the northwest coast, where the mountains catch the heavy Pacific rains. These great trees, some of which are 3,000 years old, are among the largest and oldest living things known. Some were seedlings when Troy fell, and already giants when Rome was founded. The silent forests are filled with columns of great trunks lighted dimly by sun filtered through leaves far above. Most of these forests are protected by law and preserved as a national treasure.

4. THE CORN BELT

On hot, still midsummer nights in the Corn Belt, the farm-ers insist they can hear the corn growing. This facetious claim points tip the fact that this crop grows fast, sometimes five centimeters during a night. By late summer, it may be three or four meters high. It is easy to get lost in a large field of full-grown corn because there is no way of looking over it or through its tall, heavy growth of thick stalks and broad leaves. The only thing to do is to follow the straight line between two rows of the plants which may stretch for a kilometer or more to reach a road at the edge of the field.
Corn is the most important of all American crops, as basic to American agriculture as iron is to American industry. In the United States, two farmers out of every three, and one hectare out of every four cultivated, grow corn. The annual crop is greater than the nation's yield of wheat, rice and other small grains combined, and probably one of the United States' greatest resources is its ability to grow great quan-tities of corn.
However, the only corn most Americans see is ,,sweet corn”, a garden vegetable that is eaten either fresh or pre-served, or is ground into meal for baking. But these uses account for only a small fraction of the crop.
Most of the yield - some three-fourths of it - is used as animal feed and reaches the table in the form of milk, cream, cheese, butter, eggs, beef, lamb, pork or poultry. Much of the remainder is processed into oil, syrups and starches.
Corn also has proven to be an astonishingly versatile industrial material. From a com distilling process manufacturers extract alcohol-fuel, or gasohol, used in many farm vehicles and growing numbers of cars. Corn soaked in warm water for 2 days produces ,,steepwater”, which can be con-verted into drugs, vitamins and minerals. Scientists have derived a biodegradable plastic film from corn starch that could replace plastics made from petroleum. Another tech-nological offspring of corn starch is called the ,,Super Slurper”, a dust that can absorb 2,000 times its weight in water. And corn starch itself has become such a popular sweetener in soft drinks and other prepared foods that it now rivals sugar.
There are two main reasons why corn has become the basic crop of American agriculture. One is that it grows so well. A hectare of corn requires only one-twelfth as much seed as a hectare of wheat, for instance. Yet the yield of grain from the hectare of corn is several times as high as that from the hectare of wheat. The other reason is that farmers have worked out high-yield mechanized product ion methods in all the important corn-producing areas. The Corn Belt farmer uses machines for every step of his operation-planting, en-riching the soil, cultivating, spraying, killing weeds, harvest-ing the ears, removing the thick natural wrappings, shelling the kernels from the long cobs on which they grow, and cutting the stalks. Because of this extensive use of machin-ery, the average farmer can cultivate as many as 140 hectares and care for a large herd of livestock with no more help than perhaps a son who spends several hours a day in school. On a Corn Belt farm, the most impressive buildings are the large barns and machine sheds which may dwarf the farmer's house itself.
Farmers first began to keep reliable records of corn pro-duction in 1866. Between 1866 and 1939, the corn yield in the United States averaged between 700 and 1,000 liters of shell-ed grain per hectare. Suddenly, in 1940, it began to increase greatly each year; by 1948, it was about 1,500 liters per hectare; and, by 1972, it reached about 3,400 liters per hectare. (The highest recorded yield is about 7,000 liters per hectare, produced in the State of Iowa.) Such a vast and rapid change in the most basic crop represents a real agricul-tural revolution.
This has been a quiet sort of revolution, however, because the chief difference between the older corn agriculture and the new is simply that the farmer plants a different kind of seed. Instead of saving the best ears from each year's crop for the next year's planting, the traditional method, the farmer now buys new seed every year. The increased value of the crop more than pays for the extra cost.
Corn grown from the new kinds of seed is called a ,,hy-brid”, that is, a corn which results from the mating of differ-ent types of the same grain. Different kinds of hybrids are developed for such basic qualities as higher yields, stronger stalks and hydrotropic roots. As with other grains, different strains have been developed for different soil and climate conditions and for different purposes. For instance, some contain twice as much oil as ordinary corn; others are rich in certain minerals.
Producing hybrid corn is a lengthy process which must be done by hand, during 12 or more years of crossbreeding among different varieties. This process, difficult and com-plex as it is, is simple compared to the job of discovering that new kinds of corn could be developed, or to the job of discovering how to develop them. With other grains, all or nearly all the plants are like the parents. But corn is different. American plant scientists began working on the problem of controlling corn qualities very early in the 2Oth century and it was only after many years of trial and error that they were able to master the theory and practice of growing hybrids.
Like farmers everywhere, American farmers did not like to throw away anything that experience had taught them. They did not like to risk an untried new idea, no matter how good it sounded. To the eye, hybrid corn did not look as impressive as the prize ears of ordinary corn they were so proud of growing. So, even after the first hybrids were developed, farmers were unwilling to use them. The corn breeders had to spend some 20 years more improving the value of the new strains before a few farmers were convinced it was worth risking. After that, the revolution in the Corn Belt took only a few years as the greater yields proved the value of the new grain.