58 PRINCIPLES OF FARM PRACTICE 



relation of each of these factors to crop production, it will be 

 necessary to consider each separately and somewhat in detail. 



How climate affects the choice of crops. In relation to 

 crops climate plays an important part. It affects them 

 chiefly through rainfall and temperature, for these determine 

 the length of the growing season the period from seed- 

 time to harvest. In a temperate climate like that of the 

 Corn Belt, this period continues from about the middle of 

 May until frost appears in the fall. It follows that the grow- 

 ing season is longer in the South than in the North. Since 

 rainfall is abundant in the Corn Belt, temperature becomes 

 the main factor. But in other parts of the country where the 

 temperature is relatively high during the entire year, as in 

 New Mexico, Arizona, and Southern California, rainfall be- 

 comes the chief factor. In these regions the so-called rainy 

 seasons determine the growing season of the crop. By timing 

 the planting so as to take full advantage of the rainfall, it 

 is possible to produce barley, corn, wheat, beans, and many 

 other crops. In many places where the annual rainfall is 

 low, as in the Western States, crops are made independent of 

 rain by the application of water through irrigation. 



Adaptation of crops to climate. By adaptation is meant 

 the use of only such crops as are suitable to climatic con- 

 ditions; that is, whose growing periods correspond to the 

 season of temperature and moisture favorable to the best 

 plant growth. For example, cotton has too long a growing 

 season to be used successfully as a northern crop. The 

 question of selecting crops suited to climate has been pretty 

 well settled by experience, especially in the great farming 

 sections of the Middle West. A study of crop production in 

 any well-established farming region will usually indicate the 

 kinds of agricultural plants best suited to that region. 



