SOILS 



289 



Norfolk sand is one of the common soils of the Atlantic 

 flood plain. Miami silt loam is found in the corn belt of 

 the central west. Wabash clay occurs along most of the 

 river bottoms of the Mississippi valley. 



Experiment 74. Arrange several lamp chimneys as shown in 

 Figure 250 each containing a different kind of soil. Pour water in 

 the pan, and after 

 allowing it to stand 

 for an hour note the 

 height of the water in 

 each chimney. The 

 capillary action of 

 each soil may be de- 

 termined in this way. 



Importance of 

 Size of Soil Parti- 

 cles. The water- 

 holding power of 

 soils depends 

 largely upon the 

 surface area of the particles composing the soil. The 

 finer the particles the greater will be the amount of 

 water that this kind of soil will hold. The finest soil 

 particles are less than one-thousandth of a millimeter in 

 diameter. The total surface area of a cubic foot of such a 

 soil would be enormous. Such soils have a high water 

 capacity ; that is, they will still hold a large amount of 

 water after the free water has been allowed to drain out t 

 Clay soils have the highest water capacity, sometimes as 

 high as forty per cent ; and sandy soils have the lowest 

 water capacity. In addition to influencing the water 

 capacity of soils, the size of the particles also affects the 

 movements of the soil air, the amount of food that can be 



FIG. 250. 



