32 
Efficiency of the phosphoric acid as affected by the ~kind of soil. — To 
gain some idea of the extent to which the efficiencies of the guanos 
might vary with the oharacter of the soil, acid phosphate was com- 
pared with bone meal, slag, floats, and 12 guanos in the red clay 
soil and river sand. 
Table X gives the results of a comparative test of 8 of the guanos 
in the two soils. In this test 25 millet plants per pot were grown, 
the experiment running from December 30, 1915, to February 17, 
1916, with a basic fertilizer consisting of 8.4 grams sodium nitrate, 
6 grams ammonium sulphate, and 8 grams potassium sulphate per 
pot given in two applications. 
Table X. — Effect of soil on immediate availability of phosphoric acid in guanos. 
RIVER SAND NO. 213 (46 LBS. DRY SOIL PER POT, WATER CONTENT 18 PER CENT.) 
Source of phosphoric acid 
(P2O5). 
Phos- 
phoric 
acid 
applied 
per 
pot. 
No phosphate 
Acid phosphate . . 
Do 
Do 
Do 
Basic slag 
Bone meal 
Floats 
Guano No. 917.. . 
Guano No. 92S... 
Guano No. 936... 
Guano No. 957... 
Guano No. 966 A.. 
Guano No. 977... 
Guano No. 981... 
Guano No. 982... 
Grams. 
"6." 40 
.80 
1.28 
1.92 
1.60 
3.00 
8.00 
2.00 
3.50 
3.50 
2.50 
3.00 
1.30 
6.00 
1.60 
Oven-dry yield of individual pots. 
Grams. 
Grams. 
Grams. 
Grams. 
11.6 
12.5 
8.2 
12.9 
26.9 
26.9 
25.1 
27.0 
34.3 
42.7 
35.6 
39.5 
53.8 
46.9 
46.3 
47.9 
57.2 
56.5 
57.9 
60.5 
46.5 
48.1 
47.8 
42.7 
36.5 
37.3 
36.0 
34.8 1 
26.7 
21.3 
18.2 
18.2 i 
12.1 
12.0 
14.0 
18.6 '■ 
28.8 
30.4 
28.0 
30.0 
47.5 
47.7 
44.0 
52.7 1 
41.1 
41.6 
39.6 
43.2 1 
31.0 
31.0 
32.0 
35.5 ! 
43.5 
44.2 
40.2 
46.3 
19.5 
17.8 
17.2 
19.8 
30.9 
29.4 
30.1 
30.7 
Grams. 
13.3 
Average 
oven-dry 
yield and 
probable 
error. 
Grams. 
11.7±0.8 
26. 5± .3 
38. Oil. 2 
48.7±1.2 
58. 0± .6 
46. 3± .8 
36. 2± .4 
21.1±1.3 
14.2±1.0 
29.3± .4 
48. Oil. 2 
41.4± .5 
32. 4± .7 
43. 6± .8 
18. 6± .4 
30. 3± .2 
Efficiency 
of phos- 
phoric acid 
as com- 
pared with 
that of 
acid phos- 
phate= 
100. 
RED CLAY (41 LBS. DRY SOIL PER POT, WATER CONTENT 35 PER CENT). 
No phosphate . . . 
Acid phosphate . 
Do 
Do 
Do 
Basic slag 
Bone meal 
Floats 
Guano No. 917.. 
Guano No. 928.. 
Guano No. 936.. 
Guano No. 957.. 
Guano No. 966 A. 
Guano No. 977.. 
Guano No. 9S1.. 
Guano No. 982.. 
.40 
.80 
1.28 
1.92 
1.60 
3.00 
8.00 
2.00 
3.50 
3.50 
2.50 
3.00 
1.30 
6.00 
1.60 
12.2 
42.7 
53.5 
67.8 
71.9 
60.9 
57.5 
54.8 
9.3 
55.7 
66.3 
46.9 
42.5 
65.2 
55.8 
54.5 
16.2 
42.0 
47.8 
55.9 
73.6 
55.6 
66.5 
65.5 
15.7 
53.3 
62.2 
47.8 
43.5 
63.0 
58.9 
60.3 
14.4 
43.5 
45.7 
62.4 
65.9 
61.2 
71.9 
72.5 
14.9 
52.7 
65.5 
59.4 
58.9 
51.8 
64.8 
60.4 
15.3±0.6 
40.7±1.4 
50.5±1.5 
61.4±1.7 
72.3±1.6 
59. 5± .8 
64.1±2.1 
63.0±2.6 
15. 5 ±1.7 
53. 2± .6 
67.9±2.2 
49.6±2.2 
49.6±2.6 
58.6±2.2 
59.8±1.2 
58. 1± .9 
A summary of all data which show the efficiencies of the different 
materials as affected by the kind of soil is given in Table XI. The 
figures given in this table are averages of the efficiencies of the 
different materials as given in Tables VIII, X, and XIII. 
