360 THE PRINCIPLES OF SOIL MANAGEMENT 



has been increased several hundred per cent by the use 

 of lime at a number of the Experiment Stations. The 

 amount of the acidity determines the injury it occasions. 

 There is always a great waste of fertilizers when they are 

 added to an acid soil. The acidity should be corrected 

 by the application of lime, in order that manuring shall 

 be most effective. 



There are several ways in which an acid condition 

 of the soil operates to render ineffective the natural 

 and applied fertility. 



(1) Bacteria which are concerned in the processes of 

 rendering plant-food available do not usually thrive 

 in an acid media, preferring a neutral or slightly alka- 

 line condition. Acidity for this reason checks nitrifi- 

 cation, as well as the bacteriological processes by which 

 phosphorus is rendered soluble. 



(2) Bacteria concerned in the acquisition of atmos- 

 pheric nitrogen in symbiosis with legumes are greatly 

 injured by an acid condition of the soil. Nitrogen con- 

 servation, one of the most important features of the use 

 of legumes for green manuring, cannot be effectively 

 carried out on an acid soil. 



(3) The liberation of potassium from zeolitic combi- 

 nations is best effected only where there is a basicity 

 that will permit the replacement of one base by another. 

 The presence of at least a small amount of calcium car- 

 bonate in the soil is essential for this, as it is for many 

 other desirable processes, and an acid condition of the 

 soil means that no basicity exists. 



(4) Lime, when present in large amount, reacts 

 with the very insoluble phosphates of iron and alumina, 



