SOME SOILS ARE DROUGHTY 



99 



Moisture Supply Better in Silt Loams Than in Sand. — Sandy 

 soils give up their water much more easily and completely than silt 

 loams and clays, nevertheless the latter soils generally furnish to 

 crops a much better moisture supply. 



The figures in the last column of the table seem to indicate 

 that crops would suffer less for want of water on a coarse sand 

 than on a light colored silt loam during a drought. On the con-/^, 

 trary, crops suffer much more on the sand, for two main reasons : 



Fig. 42. — A droughty soil. A fine loam about 14 inches deep underlaid by coarse sand 



and gravel. 



(1) Sand gives up its water more easily than silt loam and 

 hence plants are more lavish with it. 



(2) In the coarse sand, roots cannot secure moisture by capil- 

 larity from depths below the root zone. 



Thus it is that corn on sand grows faster than on a silt loam 

 and shows no injury because of lack of rain during the beginning 

 of a dry period, but suffers much for want of water later on as 

 the dry weather continues. 



Some Soils are Droughty. — Soils which are unable to furnish 

 crops with sufficient moisture during short dry periods are called 

 "droughty'' — a deep coarse sand is a good example (Fig. 42). 

 Often the best appearing loam or silt loam proves droughty, because 

 it is underlaid at a shallow depth by a coarse and porous subsoil, 



