TYPES OF SOILS 



35 



accomplished by flooding with water. In using this means care 

 must be taken to see that proper underdrainage is provided 

 by means of tiles, if the natural drainage is not sufficient. 



Acid soils. Some soils will not support a good growth of 

 cultivated crops because of various acids left in them by the 

 decaying vegetation, which hinder the growth of the bacteria 

 necessary to turn the humus into available plant food. Such 

 soils are called acid, or sour, soils. Though not adapted to ordi- 

 nary crops, sour soils may support a luxuriant vegetation, and 

 some wild plants have become so accustomed to acid soils that 

 they will thrive in no 

 other. Among plants 

 of this kind may be 

 mentioned huckleber- 

 ries, cranberries, trail- 

 ing arbutus, and many 

 other plants of the heath 

 family. Most of the 

 plants found in peat 

 bogs are lovers of acid 

 soils. On the other 

 hand, clover, beans, 

 peas, and other legumes are very intolerant of such soils and 

 cannot live in them. Lettuce, beets, spinach, and timothy are 

 other plants that will not grow in sour soils. The majority of 

 sour soils are found in low and poorly drained districts, but 

 the proper combination of conditions will turn any soil acid, 

 and many upland soils are of this kind. The bird's-foot violet, 

 sorrel, and beard grass (Andropoyori) are regarded as indica- 

 tors of acid soils in uplands. When mosses grow on the lawn 

 or in the fields it is also a pretty sure indication of a sour soil. 



A test for acid soils. To discover whether a given soil is 

 acid or not, make it into a tnin mortar with water and test 

 with blue litmus paper, or inclose a piece of the paper in a ball 



FI<J. 17. A pitcher plant (Sarracenia), a char- 

 acteristic plant of acid soils 



