37 
Table XIV. — Effect of remaining in the soil on the availability of the phosphoric arid 
of guanos. 
Kind of soil. 
Efficiency of phosphoric acid in 
guanos compared with that of 
acid phosphate= 100. 
(iain( + )or 
loss ( — )in 
ediciency 
caused by 
remaining 
six weeks 
in soil. 
Source of phosphoric acid 
(P2O5). 
Both 
applied 
six weeks 
before 
planting. 
Both 
applied 
just 
before 
planting. 
Guanos 
applied 
six weeks 
before. acid 
phosphate 
just before 
planting. 
Guano No. 797A 
Sand 
30 
57 
39 
15 
37 
50+ 
25 
36 
17 
7 
27 
27 
50+ 
13 
111 
88 
40 
100+ 
38 
4 
40+ 
3 
24 
9 
Do; 
Clay 
50 
30 
9 
22 
48 
15 
19 
11 
6 
29 
23 
50+ 
5 
37 
27 
8 
19 
50+ 
17 
20 
11 
6 
25 
18 
50+ 
9 
80 
58 
21 
84 
25 
2 
40+ 
3 
13 
Do 
Clay, limed 
Sand 
- 3 
Guano No. 811A 
1 
Guano No. 842A 
Guano No. 851 
do 
Clay 
- 3 
+ 2+ 
Do 
Clay, limed 
Sand 
+ 2 
Guano No. 860 
+ 1 
Guano No. 889 
do 

Guano No. 923 
do 

Guano 1N0. 966B 
Clay 
— 4 
. Do....! 
Clay, limed 
Clay 
— 5 
Guano No. 975... ...*. 

Do 
Clay, limed 
Clay 
+ 4 
Guano No. 977 
Do 
Clav, limed 
Sand 
69 
23 
57 
22 
3 
29 
1 
-11 
— 2 
Do 
Clay 
+27 
Do 
Clay, limed 
Sand 
+ 3 
Floats 
- 1 
Do 
Clay 
+ 11+ 
Do 
Clay, limed 
+ 2 
The third column in Table XIV gives the efficiencies of the guanos 
relative to acid phosphate when all materials were added to the soil 
six weeks before planting, and the fourth column gives the efficiencies 
when materials were added immediately before planting. It will be 
noted that relative to acid phosphate nearly all guanos were more 
effective when applied six weeks before planting than they were when 
applied immediately before planting. This does not show that the 
absolute availability of the guanos and other phosphates was in- 
creased by remaining in the soil, as the greater efficiency relative to 
acid phosphate may be merely due to a depression in the availability 
of acid phosphate produced by remaining in the soil. The fifth 
column elucidates this. 
In the fifth column, efficiencies of guanos, bone meal, and floats, 
added to the soil six weeks before planting, are compared with those 
of acid phosphate applied immediately to the crop. The values in 
the fifth column should be greater than those in the fourth, if the 
availability of the other phosphates has really been increased (rather 
than that of acid phosphate depressed) by remaining in the soil. As 
a matter of fact, most of the materials lost in efficiency by remaining 
in the soil, although they lost less than acid phosphate. In the sixth 
column is shown the amount the materials actually gained or lost in 
efficiency by remaining in the soil. 
