Apr. 1, 1918 



Capacities of Soils for Irrigation Water 



II 



are based upon 174 borings and 1,044 moisture determinations, while 

 those of the depth from 7 to 9 feet are based upon 36 borings and 108 

 single observations. 



The curves of the silt-loam soils converge from the surface of the soil 

 downward. This seems to be due in large measure to the fact that these 

 soils do not dry out as rapidly at great depths as do the more porous fine 



00 OS IC 15 



^ 40 



% 



^ 5.0 

 O 



70 

 75 



Fig. 3. — Graphs of the water content before and after irrigation, moisture equivalent, and pore space of 

 silt-loam soils. Each water-content curve is the average of 87 borings. 



sandy-loam subsoils, since the observations after irrigation show very 

 little decrease of water content with depth. As the soils are very uni- 

 form, it seems reasonable to conclude that their maximum capillary 

 capacities were satisfied. The average amount of water held after irri- 

 gation was 3.20 inches per foot,' or enough to fill 51 per cent of the pore 

 space, as compared to 2.73 inches per foot, or enough to fill 40 per cent 

 of the pore space for the loam soils having fine sandy loam subsoils. 



