292 Bacteria in Relation to Country Life 



he will appreciably impoverish the potential fertility 

 of his land. 



Organic acids and decomposition of rock fragments. 

 Aside from carbon dioxid, there are other substances 

 generated by bacteria that play a more or less important 

 part in accelerating the decomposition of rock fragments. 

 Among such substances may be included the various 

 organic acids generated in the course of decay, as well 

 as the nitrous and nitric acids produced by the corre- 

 sponding organisms. As yet but little is known of the 

 action of organic acids and of other organic compounds 

 on the decomposition of rock particles and in the for- 

 mation of available potash. In the case of nitric acid, 

 it is known that nitrifying organisms are met with on 

 rock surfaces, and that they contribute to the disintegra- 

 tion of the rock. 



Potash salts and bacteria. Aside from aiding in the 

 formation of available potash in the soil, the bacteria 

 are themselves readily affected by the supply of soluble 

 potash salts. Such salts materially aid nitrification, as 

 is evidenced by both laboratory and field experiments. 

 Similar experiments tend to indicate that decay bacteria 

 proper are favorably influenced by available salts of 

 potash. The same is true of the nitrogen-fixing bacteria, 

 particularly those forming tubercles on the roots of 

 legumes. The stimulating influence of carbonate and 

 of sulfate of lime in the growth of most legumes ascribed, 

 as was already noted, to the increase in the store of 

 available potash, is, undoubtedly, extended also to 

 the tubercle-bacteria. 



Direct applications of potash salts, particularly of 



