Tine Yi'MA Mksa 



245 



Very little water drained off the tubes under the force of gravity 

 during the first 24 hours, and after that time almost none. If the 

 depth of water equivalent to that retained after 24 hours be com- 

 puted, it is seen that approximately 4 inches of water is retained 

 per foot of soil. The silty surface soil in the old orchard shows a 

 much higher water holding capacity. It would thus appear that 

 under ordinary irrigation, especially with a scant supply, the soil 

 would not be wet very deeply, even though it appears to be sandy. 

 The relatively high water holding capacity of these sands must be 

 attributed to the roughness of the soil particles, which in turn is 

 caused by the calcareous incrustation. 



TABLK XII — PHYSICAL rROPERTlRS OF YUMA MESA SOILS 



The belief has been expressed that great difficulty would be 

 experienced in getting water to penetrate the silt that would be 

 deposited on the surface from the Colorado water, and, when once 

 through the surface blanket, water would sink very rapidly be- 

 yond the reach of crops. In the light of data recorded in Table 

 XII, and the incrusted nature of the said, these fears seem with- 

 out foundation. The soil, which in its virgin state shows good 

 water holding capacity, \\\\\ be improved by the Colorado silt. 

 Silt will probably be deposited at the rate of about .034 inches a 

 year, or 1 inch in 30 years. For many years this silt can be broken 

 and incorporated with the sand by ordinary tillage implements, 

 and for many additional years there will be the possibility of bring- 

 ing sand to the surface with power subsoiling tools. 



