Jan. 13, 1919 Nitrates, Nitrification, and Bacteria of Acid Soils 29 



BACTERIAL NUMBERS 



The conditions under which studies of the number of bacteria present 

 in soils have been made have varied to such an extent that generaUza- 

 tions rather than specific correlations have resulted. Chester (6) was the 

 first to note that applications of lime increased the bacterial content of 

 soils. He concluded that the favorable action was not — 



due to any direct action of the lime, but due to the more favorable reaction which the 

 4ime gave the soil. 



Later F'abricius and Feilitzen (jo), Engberding (9), and Brown (5) 

 reported increased bacterial numbers as the result of liming, Engber- 

 ding showed that in most cases a lack of lime accounted for low bac- 

 terial counts. 



Kossowicz (16) summarizes the results of investigations by Houston, 

 Th. Remy, Fabricius, and Feilitzen and C. Hoffman, as follows: 



Manuring brings about an increased bacterial content and betters the conditions 

 for the development of those organisms already present in the soil. The time of 

 the year and weather conditions influence the bacterial content of the soil. — 

 Translation. 



Koch {15), Adametz {18) and others have shown that the majority 

 of soil microflora consist principally of rod-shaped organisms. That 

 anaerobic bacteria are present in great numbers has been shown by 

 Ucke (24) , who found over 13,000,000 anaerobes present in a garden soil. 



Lohnis {18) states that the multiplication of soil organisms varies with 

 different soil layers, and the number of bacteria present decreases with 

 the depth, air and food being the first considerations. 



PRESENT INVESTIGATIONS 



Many* uncontrolled conditions, such as variations in temperature, 

 moisture, and aeration, are constantly occurring in field practice. The 

 data reported in this paper were obtained in order to ascertain the dif- 

 ferences in bacterial numbers, nitrates, and nitrification of five var- 

 iously treated typical acid soils, after these soils had been kept for 10 

 months under the same temperatures and controlled moisture conditions 

 in pots where nitrates could not be lost by leaching. The soils used were 

 all very acid and varied widely in organic matter. They were: (i) A 

 yellow silty clay containing 0.7 per cent of humus, 0.07 per cent of 

 nitrogen; (2) a whitish silt loam containing 1.3 per cent of humus, 

 0.12 per cent of nitrogen; (3) a brown silt loam containing 3.1 per cent 

 of humus, 0.22 per cent of nitrogen; (4) a black peaty sand containing 

 5 per cent of humus, 0.4 per cent of nitrogen; and (5) a dark-brown peat 

 containing 52 per cent of humus, 2. 04 per cent of nitrogen. More com- 

 plete analyses of these soils and the changes in their acidities due to 

 moisture changes are given by one of us in another paper (7). 



