jan. 31,1916 Bacterial Activity in Soils and Crop Production 
857 
The study of these plots was carried out in 1912, the crop grown that 
year being corn. 
The third series of plots was composed of 3 one-twentieth-acre plots 
located on the same soil type as the other series. 
Special treatment on these soils consisted in the application of lime as 
follows: 
Plot No. Treatment. 
510.Check. 
509. 2 tons of ground limestone per acre. 
508.3 tons of ground limestone per acre. 
The lime was applied to these plots just prior to the corn planting, and 
the tests of the soils were carried out later in the same season. 
BACTERIOLOGICAL METHODS 
The solution method for testing bacterial activities in soils has been 
studied in some detail by several investigators, and, while results of much 
value have been secured by its use, there are certain difficulties attendant 
upon it which have not yet been obviated. These difficulties have been 
discussed in another publication 1 and need not be entered upon here. 
The use of soil itself as a medium for studying bacterial activities in field 
soils seems at the present time the most logical method. Modified solu¬ 
tions such as have been suggested in recent work 2 can hardly be con¬ 
sidered as satisfactory as soil itself in representing the physical and 
chemical conditions in field soils, leaving out of account entirely the 
bacteriological factor. 
The addition of various materials to soils in laboratory tests to permit 
the accumulation of the particular products of bacterial action which it 
is desired to measure has been studied. Dried blood, cottonseed meal, 
and casein have proved the best for ammonification; dried blood and 
ammonium sulphate for nitrification; and mannite for azofication. 
In this work various modifications of the soil method were employed 
for the reason that the tests were carried out during a period of several 
years through which experiments on methods were also being conducted. 
The results, using the different methods, are all included, however, as they 
all tend in the same direction, and conclusions are based on a study of the 
entire mass of data secured. 
EXPERIMENTAL WORK 
TESTS ON ROTATION PLOTS IN 1911 
Four samplings were made during 1911—on June 26, July 8, September 
16, and October 25—and tests made of the soils for their ammonifying, 
nitrifying, and azofying powers. The yield of corn was secured from 
the plots examined. 
1 Brown, P. E. Methods for bacteriological examination of soils. Media for quantitative determination 
of bacteria in soils. Iowa Agr. Exp. Sta. Research Bui. n, p. 379-407. 1913. 
2 Tohnis, Pelix, and Green, H. H. Methods in soil bacteriology. VII. Ammonification and nitrifica¬ 
tion in soil and solution. In Centbl. Bakt. [etc.], Abt. 2, Bd. 40, No. 19/21, P- 4S7~479- 1914- 
