Jan. 31,1916 Bacterial Activity in Soils and Crop Production 
867 
If the results secured in the ammonification tests are examined, it is 
seen that the effects of the manure were the same whatever method was 
employed. It is unnecessary, therefore, to consider the different results 
individually. Similarly in the case of nitrification, the fresh-soil and 
air-dry-soil methods yielded similar results, and general conclusions only 
need be drawn. 
If the bacterial results as a whole are compared with the cfop yields, it 
is found that there was exact agreement. Applications of manure in¬ 
creased the ammonifying and nitrifying powers of the soil, and the crop 
yield was also increased. Further gains in bacterial action and also in 
crop yields were obtained as the amount of manure applied was increased, 
but the maximum effect was obtained with the use of 16 tons of manure 
per acre. Beyond that point increasing the quantity of manure de¬ 
creased both bacterial action and crop yields. 
These results therefore check the previous observations that ammoni¬ 
fication and nitrification tests may often run parallel. Previous results 
are also confirmed regarding the relation between crop yields and cer¬ 
tain bacterial activities. Tests of the ammonifying power of soils or of 
their nitrifying powers apparently indicate quite accurately their crop- 
producing powers. 
TESTS ON LIMED PLOTS IN 19H 
The three plots in this series were sampled during 1911 on June 21, 
, July 6, September 14, and October 24. Ammonification tests were made 
by the dried-blood and cottonseed-meal methods, nitrification by the 
ammonium-sulphate and dried-blood methods, and azofication by the 
mannite method. Crop yields were secured as in the other series studied. 
Complete results of these tests have been reported, 1 and only average 
results are given here. 
The ammonification results appear in Tables XXI and XXII, the 
nitrification results in Tables XXIII and XXIV, the azofication results 
in Table XXV, and the crop yields in Table XXVI. 
Table XXI .—Ammonification of dried blood on limed plots in 1911 
Quantity of nitrogen. 
Plot No. j 
Test 1. 
Test 3. 
Test 3. 
Test 4. 
trio. 
Mgm. 
207. 17 
208. 12 
Mgm, 
206. 60 
Mgm, 
128. 06 
Mgm. 
129. 78 
140. 05 
149. 32 
coo. 
207. 30 
235. 22 
144 . 51 
* 55 - 59 
tro8. 
214. 13 
1 Brown, P. E. Bacteriological studies of field soils. I. The effects of lime. Iowa Agr. Exp. Sta. 
Research Bui. 5. p. 187-210. 1912. 
17212°—16 - 4 
