332 
Journal of Agricultural Research 
Vol. IX, No. 9 
PLOTS RECEIVING 15 INCHES OP IRRIGATION WATER 
The treatments of these plots were, with the exception of the water 
applied (15 inches), the same as the previous series. The average 
results for the three years are given in Table XXXI. 
Table XXXI.— Number of colonies of bacteria , milligrams of ammonia, and milligrams 
of nitric nitrogen from soil with various crops receiving a minimum application of water 
(15 inches) 
NUMBER OP COLONIES DEVELOPED IN 4 DAYS ON SYNTHETIC AGAR 
Plot No. 
Crop. 
Sampled May 1. 
Sampled Aug. 1. 
Sampled Nov. 
28. 
Average. 
33 . 
Alfalfa. 
9, 466, OOO 
6, 566,000 
4,600, OOO 
6, 877, OOO 
45 . 
Oats. 
6, 200, OOO 
5,133, 000 
6,133,000 
5,067,000 
4, 400,000 
5, 244, OOO 
49 . 
Com. 
5 > 933 > 000 
2,967, 000 
5, on, 000 
37 . 
Potatoes. .. 
5,833,000 
4,800,000 
5, 233, 000 
3, 789,000 
4 i. 
Fallow . . .. 
4, 867, 000 
3, 967,000 
2, 533> 000 
MILLIGRAMS OP AMMONIA PRODUCED IN IOO GM. OP SOIL IN 4 DAYS 
33 
45 
49 
37 
4 1 
Alfalfa. 
S *-9 
52.8 
35*2 
46.6 
Oats. 
48. 0 
55-4 
46. 0 
49.8 
Com. 
50.5 
61. 5 
43*2 
51*7 
Potatoes. .. 
Si-2 
57*4 
38-7 
49 * 1 
Fallow. . . . 
61.5 
76.8 
46-5 
61.6 
MILLIGRAMS OP NITRIC NITROGEN PRODUCED IN IOO GM. OP SOIL IN 21 DAYS 
33 
45 
49 
37 
41 
Alfalfa. 
Oats. 
Com. 
Potatoes... 
Fallow. . .. 
4*7 
5*2 
3*6 
4*5 
7 
2 . 0 
2*3 
2 . 0 
2.3 
2 . 2 
2.4 
2*3 
2 . 6 
20 . 6 
6 . 0 
9*7 
i*5 
3*6 
3* 1 
2.7 
Here, again, we find the greater number of organisms in the soil during 
the spring, with a great decrease during the fall. But the greatest num¬ 
ber of organisms are found in the alfalfa and the least in the fallow. 
The ammonifying powers of all the soils are highest in summer and 
lowest in fall. The fallow soil has a higher ammonifying efficiency than 
any of the others, which is the same as the order noted where the maximum 
quantity of water was applied to the soil. 
The nitrifying powers of the fallow soil are very low, and of the alfalfa 
soil high, thus bearing out the observation made for the previous series. 
The quantity of nitrates produced by the potato soil during the summer 
and fall is very high, and is probably due in a degree to the cultivation 
received by these plots. It appears in all of the potato plots and not in 
the corn plots, which were also cultivated; hence, it must be due in a 
measure to the crop. 
