244 LIME 



show the effect of the same treatment on corn and oats, 

 but in soil that contains enough limestone to neutralize the 

 acidity. Sulphate and particularly the muriate of potash 

 also tend to leave an acid residue, due to the absorption of 

 potassium by plants or colloids and the presence of the acids 

 sulphuric and hydrochloric. This of course is the same 

 phenomenon described under natural acidity, except that 

 it is more pronounced. 



* * is n <■ i rrnnuvj 



/* r . It ox , , 



I. ,.},„■ i',,-, ^„ 



w» 



< j -" *■' 



Fig. 57. — Effect of acidity resulting from use of ammonium sulphate. 

 Oats. General fertilizer plats, Department of Agronomy, Pennsylvania 

 Station. 



Whether or not a soil becomes acid from any or all of the 

 above mentioned causes depends on the absence or presence 

 of sufficient bases to neutralize the acids as they are formed. 

 In other words the causes above enumerated produce acids. 

 The effect is noticed if insufficient bases are present to 

 neutralize the acids (Figs. 56, 57, 58, and 59). The principal 

 base in the soil is calcium carbonate resulting from limestone 

 or from silicates containing calcium. Soils derived from 



