44 Bacteria in Relation to Country Life 



a few instances, bacteria will develop vigorously in 

 distinctly acid media. This is particularly true of the 

 acetic-acid bacteria. On the whole, however, acid media 

 are not acceptable to the bacteria, and, in the struggle 

 for existence, they are replaced in such media by molds 

 better adapted for growth in acid substances. 



Importance of reaction of the soil. — The reaction of 

 the soil is of vital importance in crop production, be- 

 cause it determines what species shall predominate. 

 It determines, also, the rate of decomposition of the 

 soil-humus and the rate of nitrification, or, in other 

 words, it determines the rate at which available nitro- 

 gen is supplied to the crop. 



The application of Hme frequently stimulates plant 

 growth because of the correction of acid conditions, and 

 the favorable influence on decay and nitrifying bacteria. 

 A similar favorable effect may be produced by liming 

 on other desirable bacteria, among them the nodule 

 organisms of clover and other legumes. It should not 

 be supposed that excessive alkalinity is harmless. A 

 large number of experiments have been recorded which 

 show that excessive applications of caustic lime injures 

 the decay and nitrifying bacteria in the soil. This 

 conclusion is further reinforced by the fact that carbon- 

 ate of lime, which is not so caustic as the burned lime, 

 has been found to be less injurious to the soil bacteria. 



