326 Journal of Agricultural Research v 0 i. xxxi, no. 4 
Table Y. —Temperature changes in degrees centigrade occurring in soil under a steam 
pan , showing the temperatures 1 , 4) and 7 inches below the surface in the treated 
soil during and following steam-pan treatments , at different pressures and for 
different lengths of time. Rates of rise and fall in temperatures and maximum 
temperatures sustained for 30 minutes are included 
95 pounds pressure, with outlet closed, 0 25 minutes h 
[ Depth of soil covering tem- 
| perature bulbs 
Initial temperature of soil 
Maximum temperature of 
| soil 
Time to attain maximum 
temperature 
Temperatures after maxi¬ 
mum had been reached 
Average last temperature 
taken 
Average time from maximum 
to last temperature 
Average time required per de¬ 
gree of increase from initial 
to maximum temperature 
Average time required per de¬ 
gree of decrease from maxi¬ 
mum to last temperature 
Maximum sus¬ 
tained temper¬ 
atures main¬ 
tained for one- 
half hour 
Sets averaged 
10 
min. 
20 
min. 
30 
min. 
45 
min. 
60 
min. 
Min. 
Max. 
Aver. 
In. 
°C. 
°C. 
Min. 
°C. 
°C. 
°C. 
°C. 
° C. 
°C. 
Min. 
Min. 
Min. 
°C. 
°C. 
°C. 
No. 
1 
22 
88 
29 
81 
75 
70 
58 
50 
33 
215 
0.45 
3.6 
70 
89 
81 
5 
4 
23 
48 
72 
47 
47 
45 
43 
41 
33 
172 
2.9 
11.9 
44 
53 
47 
4 
7 
22 
29 
134 
29 
28 
28 
29 
29 
28 
107 
19.1 
107 
27 
30 
28 
4 
95 pounds pressure, with outlet closed, 40 minutes 
1 
22 
98 
32 
96 
92 
88 
77 
63 
37 
225 
0.42 
3.3 
86 
99 
95 
4 
4 
20 
74 
54 
71 
70 
69 
65 
63 
45 
188 
1.0 
6.5 
47 
99 
71 
5 
7 
19 
38 
151 
37 
37 
37 
37 
36 
35 
110 
7.9 
40 
33 
47 
37 
4 
10 pounds pressure, with outlet open,® 25 minutes 
1 
21 
96 
20 
91 
88 
85 
74 
54 
34 
212 
0.27 
1 
3.4 
85 
100 
94 
5 
4 
20 
74 
57 
73 
71 
68 
63 
59 
35 
209 
1.1 
5.6 
41 
99 
73 
5 
7 
19 
56 
100 
53 
51 
50 
47 
46 
34 
I 
161 
2.7 
8 
26 
89 
53 
5 
10 pounds pressure, with outlet open, 40 minutes 
1 
19 
99 
29 
98 
95 
90 
78 
63 
35 
209 
0.36 
3.3 
91 
99 
97 
13 
4 
17 
72 
62.5 
68 
65 
63 
60 
57 
41 
187 
1.1 
6 
38 
89 
68 
17 
7 
16 
38 
155 
38 
37 
37 
36 
32 
31 
131 
7.0 
58 
23 
58 
37 
14 
10 pounds pressure, with outlet open, 75 minutes 
1 
14 
100 
47 
100 
99 
99 
97 
91 
40 
291 
0.55 
4.8 
100 
100 
100 
3 
4 
14 
100 
62 
99 
98 
96 
92 
87 
54 
276 
0.72 
6 
98 
100 
99 
3 
7 
15 
100 
70 
97 
! 
95 
92 
85 
79 
52 
268 
0.82 
5.6 
96 
99 
97 
3 
20 pounds pressure, with outlet open, 40 minutes 
1 
14 
100 
15 
100 
99 
98 
97 
96 
39 
152 
0.17+ 
2.5 
98 
100 
99.5 
6 
4 
13 
100 
32 
99 
98 
96 
94 
84 
61 
134 
0.37- 
3.4 
99 
100 
99 
9 
7 
13.5 
100 
38 
98 
90 
85 
79 
75 
64 
119 
0.44 
3.4 
94 
98 
96 
6 
° 95 pounds pressure with outlet closed means that a gauge on the steam line registered 95 pounds before 
the steam outlet was opened. 
b The number of minutes during which steam was allowed to run into the steam pan is indicated. In 
each case the steam pan was removed 30 minutes after steam was shut off. 
c 10 pounds pressure with outlet open means that a reducing valve was used and the valve so adjusted 
that a gauge on the steam line between the valve and the outlet registered 10 pounds pressure, while steam 
was allowed to run freely into the open air. 
