12 



Journal of Agricultural Research 



Vol. XIII, No. t 



CLAV-LOAM SOILS 



In Table IV and figure 4 are given the quantities of water held before 

 and after irrigation for five typical farms having clay loam soils as de- 

 termined by 296 six-foot borings, making 1,776 single observations. 



Figure 4 represents average results of the five clay-loam fields. The 

 increase in water content varies from 1.35 in the surface to 0.28 in the 

 sixth foot, as compared to a variation of 1.13 to 0.44 in the silt-loam 

 soils and 1.04 to 0.90 in the silt loams having fine sandy-loam subsoils. 

 The increase in convergence of curves with depth as the texture of the 

 soil increases in fineness is to be noted. The water content after irri- 



Fig. 4. — Graphs of the water content before and after irrigation, moisture equivalent, and pore space of 

 clay-loam soils. Each water-content curve is the average of 148 borings. 



gation seems to decrease appreciably with depth of soil. It is therefore 

 doubtful if the maximum capillary capacities of these soils were satisfied. 

 The average amount of water held by the clay loams after irrigation 

 was 3.49 inches per foot, or enough to fill 58 per cent of the pore space 

 as compared to 40 and 51 per cent, respectively, in the first and second 

 types of soil considered. 



CLAY SOILS 



It was pointed out above that the maximum water-holding powers of 

 clay soils are sometimes limited by their pore space. This condition 

 seems to apply to the soils described below, the volume weights of which 

 were found to be unusually high. The total external surface area of 



