126 CAMPBELL'S SOIL CULTURE MANUAL 



and its evaporation prevented by a proper manipulation 

 of the soil, thus enabling us to secure, not only fair, but 

 remarkably good crops any and every year. 



The irrigator must consider this question of evapora- 

 tion. As a matter of fact he has discovered that his great 

 loss of water is from evaporation and he has studied to 

 offset this. Placing water on the surface of the ground 

 simply invites loss of the water at once. What must be 

 done and what is done where irrigation is well understood 

 is to place the water deep in the soil, and store it where 

 it can be made use of at the right time and in the right 

 way. 



LOSS AT THE SURFACE. 



The wonderful rapidity with which moisture rises by 

 capillary attraction to the surface and is evaporated is 

 not commonly understood. The most favorable condition 

 for this rapid, upward movement of moisture is the natural 

 condition found after irrigation or heavy rains, when the sur- 

 face soil particles are dissolved and settled very closely to- 

 gether. Professor King has conducted some very extensive 

 experiments in ascertaining the amount of moisture that 

 would evaporate from a square foot of ground in twentv-four 

 hours. This work was accomplished by placing a metallic 

 tube one foot square in a tank of water so protected that 

 there could be no evaporation or loss of water, except 

 through this tube. The tube was five feet long, filled 

 with soil from top to bottom, and submerged into the 

 water four feet, so that the moisture to reach the surface 

 to evaporate had to pass up one foot through the soil by 

 capillary attraction. The rate of evaporation for ten con- 

 secutive days was a quart and a-half of water to the square 

 foot. The tube was then lifted one foot higher, making 

 it necessary for the moisture to rise two feet by capillary 



