May 28,1917 
Influence of Crop , Season , Heater on Soil Bacteria 
33i 
PILOTS RECEIVING 25 INCHES OF IRRIGATION WATER 
The four cropped plots and one fallow plot were in this series, send each 
received 2 5 inches of irrigation water during the season. The summarized 
results are given in Table XXX. 
Table XXX. —Number of colonies of bacteria, milligrams of ammonia, and milligrams 
of nitric nitrogen from soil with various crops receiving a medium application of water 
(25 inches) 
NUMBER OF COLONIES DEVELOPED IN 4 DAYS ON SYNTHETIC AGAR 
Plot No. 
Crop. 
Sampled May 1. 
Sampled Aug. 1. 
Sampled Nov. 
28. 
Average. 
Alfalfa. 
8,933) 000 
5, 700,000 
4, 600,000 
5,666,000 
3,300,000 
7, 066, OOO 
4,866,000 
5,800,000 
7, OOO, OOO 
3,370, ooo 
4,933, ooo 
2, 866, ooo 
3,366, ooo 
4, ooo, ooo 
3,700,000 
6,977,000 
4, 477, ooo 
4, 589, ooo 
5 ) 555 ) 000 
3, 457 )°°° 
Oats. 
48. 
Com. 
^ • * * *.. 
26. . . . .. 
Potatoes... 
Fallow.... 
0“’ * * * ’. 
AO . 
MILLIGRAMS OF AMMONIA PRODUCED IN IOO GM. OF SOIL IN 4 DAYS 
Alfalfa. 
47-9 
5 1 * 2 
39 -° 
46. 0 
Oats. 
53-3 
5 6 - 3 
52.1 
53*9 
Corn. 
55-2 
55 - 8 
44*4 
51.8 
Potatoes. .. 
63.0 
66.3 
48. 5 
59*2 
Fallow. . . . 
66.8 
80.1 
56.1 
67.6 
! 
MILLIGRAMS OF NITRIC NITROGEN PRODUCED IN IOO GM. OF SOIL IN 21 DAYS 
Alfalfa. 
2. 7 
8.6 
3-7 
5 ° 
Oats. 
2. 2 
4*7 
.8 
2. 6 
Com. 
I. O 
2. 1 
. K 
1. 5 
Potatoes... 
7 
4*3 
i 7 .’8 
IO. 4 
10.8 
Fallow. . . . 
. 6 
2. 0 
i *5 
r -3 
The number of organisms in the alfalfa soil is very high during the 
spring and very low and uniform in the fallow throughout the year. The 
greatest difference in the plots is noted in the spring, the numbers being 
more nearly uniform during the summer; especially is this the case in the 
fall. 
A very marked difference is noted in the ammonifying powers of the 
soils in favor of the fallow. Naming the plots in the order of increasing 
efficiency, we have alfalfa, oats, com, potatoes, and fallow, which is about 
the order they have been maintaining in each series. And the difference 
is very pronounced in favor of the fallow soil. But we find the nitrifying 
powers of the fallow soil very low. In this series during the season it is 
high in the potato soil. The alfalfa is high compared with any of the 
other soils, thus showing that alfalfa soil has a high nitrifying power 
when compared with oats, corn, or even fallow. 
