Dec. 4, 1916 
Nitrification in Sentiarid Soils 
425 
Again, it was found that the lower concentrations of these materials 
were actively nitrified in every case; and when the concentration was 
increased, the percentage of nitrification decreased. One per cent 
dried blood was actively nitrified in every soil except that from Lark 
Ellen, but 2 per cent was toxic in each case. The percentage of dried 
blood nitrified was somewhat greater than that of bone meal; otherwise 
the degrees of nitrification of the different materials were similar. The 
results, therefore, are in harmony with those of the preceding series. 
The preceding data show that each of the soils studied, representing 
quite a wide range of soil conditions, is capable of supporting active 
nitrification of dried blood, bone meal, or ammonium sulphate, provided 
these materials be added in low concentrations. They also indicate that 
the results obtained with the use of such high concentration of dried 
blood as 1 and 2 per cent, or 0.3 and 0.6 per cent of ammonium sulphate, 
do not form a reliable criterion upon which to base practical conclusions. 
NITRIFICATION AT DIFFERENT DEPTHS AS AFFECTED BY CONCEN¬ 
TRATION 
As already stated, differences of opinion are held regarding nitrifica¬ 
tion in the substrata of semiarid soils. The following data are of interest 
in this connection. The soil used was taken from an orange grove near 
Woodlake, in Tulare County. It is a dark-colored clay loam, high in 
organic matter. The subsoil contains considerably less organic matter 
than the surface soil and closely resembles adobe. The samples were 
drawn in foot sections down to 5 feet in depth. Only a few concentra¬ 
tions of nitrogenous materials were employed, owing to the smallness of 
the samples. The incubation period Avas four weeks, as in the previous 
series. (Table IV). 
Table IV .—Nitrification in soil from different depths 
Materials added. 
Nitro¬ 
gen 
added 
per 
100 
gm. 
of soil. 
First foot. 
Second foot. 
Third foot. 
Fourth foot. 
Fifth foot. 
Nitric 
nitro¬ 
gen 
found. 
Per¬ 
cent¬ 
age 
nitri¬ 
fied. 
Nitric 
nitro¬ 
gen 
found. 
Per¬ 
cent¬ 
age 
nitri¬ 
fied. 
Nitric 
nitro¬ 
gen 
found. 
Per¬ 
cent¬ 
age 
nitri¬ 
fied. 
Nitric 
nitro¬ 
gen 
found. 
Per¬ 
cent¬ 
age 
nitri¬ 
fied. 
Nitric 
nitro¬ 
gen 
found. 
Per¬ 
cent¬ 
age 
nitric 
fied. 
None.. 
Mgm. 
0 
132- 0 
13 - 2 
13 - 2 
P.p.m. 
60.0 
32.0 
132.0 
130- 0 
1.i 
P.p.m. 
64.0 
2. 6 
95-0 
92.0 
4-5 
P.p.m. 
46.0 
x. 8 
100.0 
74-0 
2. 5 
P.p.m. 
36.0 
0. X 
40.0 
68.0 
3- 6 
P.p.m. 
35 -o 
9. 2 
34-0 
68.0 
0.6 
Dried blood, r per cent.. 
Dried blood, o.i per cent 
Ammonium sulphate, 
0.062 s per cent...._ 
Original soil. 
0 
54 -S 
53 -o 
0 
23-5 
21. 2 
0 
40-9 
21. 2 
0 
3 *o 
24. 2 
0 
0 
25.0 
Active nitrate formation took place in the check portions from each 
of the 5-foot sections studied, showing that the nitrifying organisms are 
not only present down to 5 feet in depth but that the chemical, physical, 
and biological conditions ensuing in the samples were favorable for nitri- 
