Apr. I, 1918 



Capacities of Soils for Irrigation Water 



In Table II are presented the number of irrigations v/hich each tract 

 was given annually, and the average depths of water applied per irriga- 

 tion. These were found to decrease rapidly with the increase in fineness 

 of the soil texture, averaging 15.02 inches for the silt-loam soils having 

 fine sandy-loam subsoils and only 4.72 inches for the clay soil. The 

 quantity of water retained by the upper 6 feet of soil also decreased 

 with increase in fineness of texture. 



Fig. 2. — Graphs of the water content before and after irrigation, moisture equivalent, and pore space of silt- 

 loam soils having fine sandy-loam subsoils. Each water-content curve is the average of 62 borings. 



SILT-LOAM SOILS HAVING FINE SANDY-LOAM SUBSOILS 



In Table III and figure 2 are presented the results of 108 6-foot and 

 16 9-foot borings, thus making a total of 792 moisture determinations. 

 It is of special interest to note that when these soils contained all of the 

 water they would hold against gravity, an average of 2.73 inches for 

 for each of the upper 6-foot sections, only 40 per cent of the pore space 

 of the soil was filled. Apparently the maximum water capacity is 



