182 
Journal of Agricultural Research 
Vol. XXV, No. 4 
The plants responded very markedly to phosphoric acid in all the 
soils, the yields being increased from 2 to 20 times by the largest quanti¬ 
ties of acid phosphate applied. In all soils, both limed and unlimed, the 
larger applications of acid phosphate produced relatively less increments 
in yield than did the smaller applications, which, of course, is the normal 
effect of increasing any limiting factor. In the case of soil No. 1810, 
however, the larger applications of acid phosphate were markedly less 
efficient in the unlimed soil than they were in the limed soil, although 
the smaller applications were about equally efficient in both series. 
In soil No. 1529 all the quantities of acid phosphate applied were less 
efficient in the unlimed series than in the limed, the differences in effi¬ 
ciencies in the two series being greater with the larger quantities of acid 
phosphate applied. Obviously, the maximum yields in these two soils 
were not to be obtained with acid phosphate as a source of phosphoric 
acid without the use of lime. 
Table V summarizes the results obtained in these experiments. 
Table V .—Summary of the results obtained in Experiments I to VIII, inclusive , 
phosphates mixed with limed and unlimed soil 
UNLIMED SOIL 
Time of 
application. 
Kind of 
phosphate applied. 1 
Soil 
No. 
1524- 
Soil 
No. 
1578- 
Soil 
No. 
1257. 
Soil 
No. 
1810. 
Soil 
No. 
1811. 
Soil 
No. 
1716. 
Soil 
No. 
1529. 
Soil 
No. 
1796. 
Soil 
No. 
213. 2 
Immediately before 
Add phosphate. 
100 
100 
100 
100 
100 
100 
53 
100 
100 
planting. 
Do. 
Bloats. 
10 
20 
22 
34 
15 
8 
79 
46 
4 
Do. 
Bone meal. 
105 
72 
51 
43 
33 
72 
78 
98 
27 
Do... 
Basic slag. 
hi 
94 
71 
92 
69 
105 
no 
80 
59 
Do. 
Double superphosphate. 
85 
IOI 
87 
83 
97 
100 
56 
86 
6 weeks before plant¬ 
Add phosphate. 
77 
58 
48 
61 
57 
79 
39 
49 
54 
ing. 
Do. 
Bloats. 
12 
18 
24 
32 
13 
7 
16 
25 
2 
Do. 
Bone meal. 
81 
60 
38 
52 
44 
30 
60 
66 
55 
21 
Do. 
Basic slag. 
62 
57 
37 
55 
118 
83 
43 
Do. 
Double superphosphate. 
72 
57 
57 
44 
66 
93 
35 
46 
LIMED SOIL 
Immediately before 
Add phosphate. 
ixi 
72 
75 
119 
96 
128 
ZOO 
61 
90 
planting. 
Do. 
Bloats. 
2 
1 
3 
2 
5 
4 
I 
3 
0 
Do. 
Bone meal. 
46 
19 
31 
35 
32 
70 
34 
23 
4 
Do. 
Basic slag. 
93 
60 
40 
117 
59 
120 
98 
47 
3 * 
Do. 
Double superphosphate. 
87 
80 
ci 
81 
128 
140 
47 
6 weeks before plant¬ 
Acid phosphate. 
70 
AA 
56 
74 
54 
H 3 
59 
33 
ing. 
Tf 
Do. 
Bloats. 
2 
I 
5 
5 
4 
13 
1 
2 
Do. 
Bone meal. 
39 
12 
32 
20 
21 
83 
29 
16 
Do. 
Basic slag. 
53 
38 
55 
41 
43 
148 
63 
35 
Do. 
Double superphosphate. 
59 
48 
5 <> 
5 i 
65 
123 
54 
35 
1 The values given for acid phosphate are averages of the results yielded by several different quantities 
of this material. 
2 The results obtained in the river sand. No. 213, are the averages of several experiments described in a 
previous publication (7, p. 25-29). 
Floats (finely ground rock phosphate) was a fairly efficient source of 
phosphoric acid in some of lie soils when no lime was used. It was 
practically without effect, however, when applied to limed soils imme¬ 
diately before planting was done. The uniformity of the very low effi¬ 
ciencies of floats under these conditions, from o to 5 in the different 
soils, is doubtless significant. In quartz sand, floats usually has about 
