ACID SOILS ARE EXTENSIVE 



237 



generally not acid, or only slightly so; whereas those in sections 

 where limestone is absent are generally strongly acid. 



How Soils Become Acid. — Soils become acid when they lose 

 carbonate of lime and other substances of a similar chemical 

 nature. In mineral soils, deficiency of carbonate of lime is brought 

 about by leaching and cropping. Leaching is the greater factor. 

 Certain determinations have shown that on ordinary cropped 

 fields the total amount of lime removed annually by leaching is 

 equivalent to 300 to 500 pounds of carbonate of lime per acre to 

 a depth of four feet. From uncropped, cultivated fields the losses 

 may double these amounts. 



f^' 



4. 



Fig. 152. — Soil acidity is increased by dust from zinc-ore roasters. Vegetation in back- 

 ground destroyed by sulfur fumes. (Wisconsin.) 



In undrained peat and muck soils, acidity develops through the 

 accumulation of acids resulting from the decomposition of the 

 organic matter; and in drained and cropped peats, deficiency of 

 lime may be brought about in the same manner as in mineral soils. 



Acid Soils Are Extensive. — The great majority of soils of the 

 East, South and portions of the Middle West are in immediate 

 need of liming, not to mention extensive areas elsewhere. Three- 

 fourths and more of the soils of New York, Wisconsin and Indiana 

 are acid; most of the soils of Massachusetts have not sufficient 

 Ume for highest productivity; the soils of the greater portion of 

 Tennessee are acid; large areas of Missouri and Oregon are in need 

 of liming; the same may be said of Georgia, Mississippi and 

 other states. 



