32 



SOILS OF THE TRUCKEE-CAESON IRRIGATION PROJECT. 



Table IX shows the difference between the good and poor soils in 

 regard to total numbers and distribution of bacteria. The difference 

 in the floras is more strikingly brought out when we consider the 

 difference in the colonies from the different soils. The plates from 

 the 6-inch and 12-inch layers of plats 300 and 310, which show low 

 numbers, chiefly contained peculiar colonies surrounded by a wine- 

 colored diffusible pigment. The colony itself was but slightly colored 

 and, surrounded as it was by this pigment, produced a very striking 

 appearance on the plates. One plate from plat 310 was apparently a 

 pure culture of this organism. Such a plate obtained from soil where 

 the growth or flora is almost always rich and varied is very rare, and 

 is the only unusual condition thus far encountered that seems to cor- 

 relate consistently^ with the unusual conditions of infertility. This 

 peculiar colony was never seen on soils from the fertile spots, and the 

 fact that it was so predominately present in the infertile soils and in 

 those strata in which the peculiar black layer occurred certainly in- 

 dicates that further study should be made of this point. ^Microscopic 

 examination of the colony showed that it was a micrococcus associated 

 with a mold. 



Table IX. — Total number of bacteria present in 1-gram samples of soil from plats 

 SOO, SIO, .1^0, SSO, 340, and 350, Truckee-Carson Experiment Farm. 



CONCLUSIONS. 



(1) Nitrifying, denitrifying, and ammonifying bacteria are well 

 distributed and universally present in the soils of the Truckee-Carson 

 Irrigation Project and become physiologically active if favorable con- 

 ditions are provided for their development. 



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