jan. 3 i, 1916 Bacterial Activity in Soils and Crop Production 
865 
prime importance. It will be noted, however, that the rotation of crops 
increased in every case both the crop yield and the bacterial activities. 
The use of green manure in the 2-year rotation sometimes proved more 
valuable than the 3-year rotation, and sometimes was of less value. 
This was probably due also to the moisture conditions. The point of 
importance here is, however, the fact that, regardless of seasonal condi¬ 
tions or of the effect on crops under particular conditions, bacterial 
activities and crop production were relatively similar. 
TESTS ON MANURED PEOTS IN 1912 
The manured plots were studied in 1912. Ammonification results were 
obtained by the casein-fresh-soil method, the dried-blood-air-dry-soil 
method, and the dried-blood-fresh-soil method; and nitrification tests 
were carried out by the ammonium-sulphate-air-dry-soil method and the 
ammonium-sulphate-fresh-soil method. Four samplings were made dur¬ 
ing the season—on August 2, August 15, August 22, and September 9. 
The moisture conditions in the soils varied so slightly that they could not 
be considered of significance, and they are not included here. Crop 
yields were secured, corn being grown on the plots as in the other series. 
Complete data from these experiments have been reported in another 
place 1 and only summarized results are given here. 
The ammonification results are given in Tables XV, XVI, and XVII, 
the nitrification results in Tables XVIII and XIX, and the crop yields 
in Table XX. 
Table XV .—Ammonification of dried blood in the fresh soil of manured plots in igi2 
Plot No. 
Quantity of nitrogen. 
Test 1. 
Test 2. 
Test 3. 
Test 4. 
1004. 
Mgm. 
66. 90 
84. 76 
86.32 
97. 90 
86. 72 
Mgm. 
83- 97 
92. 21 
I06. 34 
IO9. 47 
95 - 74 
Mgm. 
73 - 57 
83- 97 
98. 88 
98. 88 
87. 50 
Mgm . 
66. 71 
70.63 
85- 54 
84-95 
76.91 
100 c. 
1006. 
1007 . 
IO08. 
Table XVI .—Ammonification of casein on manured plots in IQI2 
Plot No. 
Quantity of nitrogen. 
Test 1. 
Test 2. 
Test 3. 
Test 4. 
1004. 
Mgm. 
37 - 87 
46. 89 
Si- 79 
5 1 * 99 
48.78 
Mgm. 
68. 27 
73 - 57 
77 - 5 ° 
78. 48 
75 - i 4 
Mgm. 
67.49 
72.79 
78.87 
79.46 
74-75 
Mgm. 
51. 60 
58. 86 
66. 32 
65.72 
60. 42 
100 K . 
IO06. 
1007. 
IO08.. 
1 Brown, P.E. Bacteriological studies of field soils. III. The effects of barnyard manure. IowaAgr. 
Exp. Sta. Research Bui. 13, P- 421-448. 1913. 
