2 Russell R. Spafford 
Figs. 1, 2, and 3 illustrate the relative importance of moisture, 
soil fertility, and temperature, as limiting factors in crop pro- 
duction. 
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——s : 
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My, AN 
Fic. 1. Moisture the limiting factor in the Great Plains. 
Climate and soil are best described as natural factors over which, 
in the large, we have little or no control. In contrast with natural 
factors there are so-called artificial factors. These lie to a cer- 
tain extent within the control of individuals or groups of indi- 
viduals. Government, organized commerce, and the organization 
of private business serve as illustrations. 
In an early day people of western Nebraska and similar regions 
were not inclined to look upon climate and soil as fixed. They 
expected them to be greatly modified as a result of breaking new 
land and growing cultivated crops. This idea lasted only so long 
as they lacked actual experience with the country. A few years 
of effort made it plain that to do profitable farming it was neces- 
sary to conform to the natural conditions of the region. This 
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