328 
Journal of Agricultural Research 
Vol. IX, No. 9 
Table XXVIII. —Average bacterial activities in soil with various water treatments 
NUMBER OF COLONIES OF BACTERIA 
Water applied (inches). 
Spring. 
Summer. 
Fall. 
Average. 
6, 546, 000 
5, 640, 000 
6, 260, 000 
6, 206, 600 
7, 600, 000 
5, 606, 000 
5, 173, 000 
6, 060, 000 
3,400,000 
3 » 773 > 000 
3,86o, 000 
4,807,000 
5, 849, OOO 
S, 006, 000 
5, 098, OOO 
5, 691, 000 
0 / * 0 * 
i tr.o. 
None. 
MILLIGRAMS OF AMMONIA PRODUCED IN IOO GM. OF SOIL 
37-5 . 
25.0. 
None. 
54*8 
57*2 
52. 6 
55*o 
62. 3 
6l. 9 
60.8 
58.2 
46.3 
48. 0 
40.9 
47*5 
54- S 
55- 7 
5i-4 
53-6 
MILLIGRAMS OF NITRIC 
i NITROGEN PRODUCED IN 
IOO GM. OF SOIL 
37*5 .. 
2.7 
8-4 
i*7 
4-3 
25*0 . 
2*3 
7.0 
3*4 
4- 2 
*5° . 
2. 5 
7 
3*8 
4*3 
None... 
2. O 
7.0 
3*9 
4*3 
If we take all the results into consideration, it is clear that the irriga¬ 
tion water had increased all of the bacterial activities of the soil; but it 
will be noted that the numbers of organisms, the ammonifying powers, 
and nitrifying powers of all the plots are extremely low; and it would 
appear that in all these plots the limiting factor is the organic matter. 
Had there been more organic matter present, the effect of the water 
would have been more pronounced, as it was found by one of us (21) in 
other experiments to be the case. 
Furthermore, the difference which actually exists in the bacterial 
activities must have been greater than is brought out by these results, 
for during one season we made determinations of the number of organ¬ 
isms in the soil, and the ammonifying powers and the nitrifying powers 
of the soil both the day before irrigation and the day after irrigation. 
The results for the day before irrigation averaged one-fourth higher 
than did the results for the day after irrigation, thus clearly indi¬ 
cating that many of the organisms and the different species in about 
the same proportion had been carried below the first foot by the irriga¬ 
tion waters. This being the case, in order that an increase for the bac¬ 
terial activities for the season is obtained, the remaining organisms 
must have multiplied much faster, or their physiological efficiency have 
become much greater in the irrigated than in the unirrigated. There is 
the possibility that the organisms would rapidly be brought to the sur- 
