Jan. 13, 1919 Nitrates, Nitrification, and Bacteria of Acid Soils ^2> 



The results given in Table II show that the amount of water present 

 in a soil is concerned with its nitrification, and further, that soils fully 

 saturated with moisture do not contain nitrates either before or after 

 incubation with ammonium sulphate. This table shows even more 

 strono-ly than Table I that nitrification takes place in an acid soil, for 

 the nitrates contained in the soils when sampled varied directly with the 

 organic matter content of the different soils, but did not increase with 

 lower soil acidities. The many instances where the nitrates in the soil 

 when sampled were greater than those after incubation show that the 

 nitrates present in these uncropped soils were near the maximum that 

 could be present under the conditions of the experiment. 



METHOD OF OBTAINING COUNTS 



Field conditions are variable, and the results of these variations are 

 apparent in the soil processes, due to bacterial agencies. It was believed 

 that bacterial counts properly made would show some correlations 

 among these different acid soils, the lime and fertilizer treatments, and 

 the variable moisture contents they were kept under. Not only the 

 nitrifying organisms but all classes of organisms had been given 10 

 months to respond to the different treatments, and an enumeration of 

 both aerobes and anaerobes should show the types of bacteria predomi- 

 nating under the different treatments. 



Plate counts were made from plates of high bacterial dilutions of each 

 treatment according to the technic of Noyes and Voigt(2o). Unpub- 

 lished work by one of us on aerobic and anaerobic soil bacteria has 

 shown that the average of five plates of a bacterial dilution high enough 

 so that all bacteria from i cc. of the dilution will have a chance to 

 develop into colonies in 10 days, gives accordant results. The media 

 used was Lipman and Brown(i7) modified synthetic agar, which exten- 

 sive tests have proved to be satisfactory for the development of soil 

 microorganisms. The carbon dioxid and hydrogen incubations were 

 carried out in an atmosphere of flowing hydrogen or carbon-dioxid gas. 



AEROBIC AND ANAEROBIC COUNTS ON CROPPED, LIMED, AND FER- 

 TILIZED SOILS 



The number of bacteria present under the different lime and fertilizer 

 treatments are given in Table III. 



Table III shows that large increases in bacterial numbers result 

 from the use of lime. These increases are largely in the aerobic organ- 

 isms, although with the soils that contain considerable partially decom- 

 posed organic matter the anaerobic count is also increased. 



Representative aerobic plates obtained from the yellow silty clay 

 are shown in Plate i. The numbers of colonies per plate are small, 

 allowing for maximum development;, yet no striking differences in kinds 

 of microorganisms are apparent under the different treatments. Neither 



