686 
Journal of Agricultural Research 
Vol. XXVII, No. 9 
of the calcium is shown in the second column. The third column shows 
the difference between i and 2, which may be taken as the sum of the 
bases other than calcium existing in the solution in excess of the strong 
acids. 
Table; XXVIII. —Effect of C 0 2 in solution on the solubility of bases in the soil , expressed 
in reacting values based on the soil 
Sample. 
jr Acid required. 
; 
r Ca. 
! Difference. 
1. Untreated.. 
2. {Saturated with CO<>. 
39 - 8 
147 - 5 
15. 0 1 
85. 0 ; 
24. 8 
62. 5 
Increase from CO.,.| 
! 
107. 7 
0 
0 
37 - 7 
In the absence of information to the contrary, it may be assumed that 
the C 0 2 in the solution did not decrease the solubility of any of the mate¬ 
rial in the soil; in other words, that the increase of dissolved bases shown 
in the table represents a real increase in solubility. 
Certain experiments recently reported by Kelley and Thomas (11) 
afford another illustration of the effect of dissolved C0 2 on the solubility 
of soil material. In their experiments they digested the soil for one hour 
with five times its weight of water partially saturated with C 0 2 . The 
results as reported by them are shown in Table XXIX, computed as 
reacting values. These results show that while only a part of the C0 2 
added to the water of digestion is accounted for as carbonate in the 
solutions, there is a consistent increase in the quantity of total dissolved 
bases and in the dissolved calcium with increasing quantities of C 0 2 used. 
Table; XXIX. —Effect of C 0 2 in solution on the solubility of bases in the soil , expressed 
as reacting values based on the dry soil a 
Soil No. 
1 
r CO2 
added to 
solution. 
r Acid 
required. 
Increase. 
| 
r Ca. 
Increase. 
oo< .. 
None. 
5 o 
100 
200 
17. 0 
34 - 5 
42. 2 
60. 5 
0.25 
6. 25 
10. 00 
20. 25 
16. 5 
25. 2 
43 - 5 
6. 00 
9 - 75 
20. OO 
y 0 1 
1 
i 
a From Kelley- and Thomas. 
These illustrations of the effect of carbon dioxid in solution on the 
solubility of the soil material permit the inference that an abundance of 
carbonate in the soil solution may sometimes be beneficial rather than 
harmful. If the soil is rich in calcium carbonate, carbon dioxid in the 
solution brings the calcium into solution. Once in solution this calcium 
is free to react with and replace any sodium that may be combined with 
the soil. It has long been known that the application of organic matter 
to the soil tends to improve its physical condition. It is possible that 
this beneficial effect may be due in part to the enrichment of the soil 
solution in carbon dioxid from the decaying organic matter, followed in 
turn by the solution of calcium and the replacement of combined sodium 
by the calcium. 
