HUMID AND DRY-FARM SOILS 63 
B 
, MASS j 
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i Me 
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ARID SOIL 
— 
Fic. 18. Difference in structure between humid and arid soil. The third 
section. though arid, is questionable for dry-farming. The gravel 
streaks break the continuity of the soil mass. 
gard.) 
(Adapted from Hil- 
