LIMESTONE 163 



acids in ensilage and sauerkraut, etc. Souring is usually the first 

 stage in the process of decay of organic matter. 



Thus, there are two principal effects produced by applying lime 

 to soils: one of these is to furnish a base for neutralizing the acids 

 that may exist in the soil or that may form in such necessary 

 processes as nitrification, and the other is a more active decomposi- 

 tion or destruction of the soil itself, especially of its organic matter 

 or humus content. 



To correct the acidity of sour soils is certainly a very desirable 

 and profitable use of lime. Clover, alfalfa, alsike, cowpeas, soy- 

 beans, and most other valuable legumes will not thrive on soils 

 that are strongly acid. To be sure, such crops can be made to grow 

 on acid soils by liberal applications of farm manure or other fer- 

 tilizers, but the nitrogen-gathering bacteria of such legume plants 

 do not properly develop and multiply in acid soils, and consequently 

 the legumes do not have the power which they should have to 

 accumulate large quantities of atmospheric nitrogen by means 

 of the root-tubercle bacteria. Furthermore, the process termed 

 nitrification by which the nitrifying bacteria transform the in- 

 soluble organic nitrogen, in farm manure and plant residues, into 

 soluble nitrate nitrogen, the form in which it becomes available 

 as plant food, is greatly promoted by the presence of limestone and 

 retarded by acid conditions. 



The use of some form of lime for correcting the acidity of soils, 

 and thus encouraging nitrification and the growth of clover and 

 other legumes with their wonderful power to enrich the soil in 

 nitrogen, is certainly good farm practice. Any form of lime which 

 is finely divided and can be thoroughly mixed with the soil will 

 serve this purpose, whether it be ground limestone, marl, or chalk, 

 or fresh-burned lime, water-slacked lime, or air-slacked lime. 



The one effect of lime, due to its basic property, results in a 

 building-up process, through the increased growth of legumes and 

 nitrogen-gathering bacteria; while the other effect, the decompo- 

 sition of the soil, produced by its caustic property, is in all respects 

 a destructive process, serving only to destroy humus and to liber- 

 ate and reduce the stock of plant food stored in the soil. Whether 

 this second effect is desirable, will depend upon the soil itself. On 

 soils which are exceedingly rich in organic matter, such as peaty 



