Campbell's 1902 Soil Culture Manual. 



43 



Measurements and records by the government weather bureau have shown 

 that in the more westerly portions of the semi-arid belt the average rainfall 

 is more than twice as much as is needed, while a little farther east it is 

 three and four times the necessary amount. 



The usual difficulty, if such we may call it, is the fact that this rain 

 does not always come just at the time the plants most need it. This is the 

 reason crops have failed and the average investigator or observor of the 

 existing conditions in this great belt has drawn the conclusion that there 

 is not rain enough. We have lived in this belt of country twenty-two 

 years, and have experienced all of the pros and cons, and ups and downs,, 

 that the country is heir to. Ten years of this time has been entirely spent 

 in the study of the soil, the movement of the moisture in the soil, and that 

 all-important question of storing the rain waters. Our experiences in 

 these ten years have been quite varied, but each and every year some new 

 and important fact has been brought out, all leading to the one conclusion, 

 that the rainfall can be stored in the ground and its evaporation prevented 

 by a proper manipulation of the soil, thus enabling us to secure, not only 

 fair, but remarkably good crops any year. 



The present and most modern methods of irrigation have been the 

 result of study along the same lines that we have been working, to wit; 

 that of conserving the moisture in the ground by cultivation after once 

 thoroughly saturating by turning the waters in from the ditches. The most 

 successful farmer today by irrigation, secures better results with one-fourth 

 as much water as was used by the average irrigator some years ago. 



The wonderful rapidity with which moisture rises by capillary at- 

 traction 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 heavy rains, when the surface soil par- 

 ticles are dissolved and settled closely together. Prof. King has conducted 

 some very extensive experiments in ascertaining the amount of moisture 

 that would evaporate from a square foot of ground in twenty-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 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 consecu- 

 tive 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 attraction when the loss was a little over one 

 quart. It was then lifted to three and then four feet, and when rising four 

 feet by capillary attraction the loss was a little over a pint to the square 

 foot. This shows clearly why our crops may suffer so quickly even aftei" 

 we have had considerable rain. 



