246 



LIME 



On the other hand, it frequently happens that soils derived 

 from silicate rocks containing calcium do not become acid 

 readily. This is because the calcium is slowly dissolved 

 out as calcium bicarbonate and but little is wasted due to 

 leaching. Practically all of it neutralizes acids or serves 

 some other valuable function. There is no excess at any 

 one time and, moreover, the total amount of calcium present 

 is very considerable. 



1 ' ■ ■ * 



•*.<., v»„. .„ u\ ,< .' > i\ . . i 



mwrn 





Fig. 59. — Effect of sufficient limestone in the soil to neutralize the acidity 

 from ammonium sulphate. Oats. General fertilizer plats, Department of 

 Agronomy, Pennsylvania Station. ' 



But, nevertheless, the general tendency of all soils is to 

 lose the basic material and to produce acids from various 

 causes. This combination of changes results in an acid or 

 sour soil. 



Virgin soils may be temporarily acid, the latter being due 

 to the accumulation of organic matter. Cultivation will 

 cause further oxidation and destruction of these acids and 

 also will cause increased solution of basic material and hence 

 neutralization of the acids. 



