134 THE PRINCIPLES OF SOIL MANAGEMENT 



Table XVIII. Water Evaporated by Growing Plants for 

 One Part of Dry Matter Produced 



The variation exhibited by the figures for the crop, 

 as well as for different crops, illustrates the influence 

 of climate and soil upon transpiration. Other things 

 equal, more water will be required in an arid region 

 than in one of humid climate; more in a warm region 

 than in a cold region; more on a clay soil than on a 

 sandy soil; more in a windy section than in a region 

 of still atmosphere; more with a high soil moisture 

 content; more on a poor soil; and, finally, more water 

 is used per pound of dry matter produced in a small 

 crop than is required in a large crop. All of these figures 

 agree in indicating the large amount of water used 

 in the production of crops. Not only is the total seasonal 

 requirement to be considered, but the maximum de- 

 mands of the crop at any period of its growth must 

 be met. King observed that a single corn plant during 

 the first week of August, when it was coming into tassel 

 and the ear was forming, used water at the rate of 1,320 



