Dec. 24,1917 Decomposition of Green and Stable Manures in Soil 695 
It is seen that in every case except where the soils were treated with 
50 tons of manure the lime enhanced the rate of decomposition of the 
organic matter. As already mentioned, the soil treated with 50 tons 
of manure and lime developed a mold, which was later removed. There¬ 
fore, not much dependence should be placed on the results for that soil. 
The figures as a whole given in column 8 are not very consistent. The 
excess carbon from the soils treated with both stable manure and green 
manure is greater than where the similar amounts of manure were used 
separately. Yet, where no manure was used, the excess carbon was 
greater than in any other case. It seems that the original organic matter 
in a soil needs lime for its decomposition, while the organic matter of 
manures used here does not need lime. 
The values given in columns 9 and 10 are extremely interesting. 
On considering the percentage of carbon lost from the various manures, 
it is seen that more than half of the carbon of the stable manures has 
been evolved in the course of the experiment. Thus, more than 10 
times as much of the manure in this experiment has been decomposed 
as in the earlier experiment reported in this paper. This is a far greater 
difference than can be accounted for by a consideration of the time the 
two experiments ran—namely, 53 and 216 days, respectively. It 
should be recalled that in the first experiment dry, well-rotted manure 
was used, whereas in the latter fresh, moist manure was used. As 
stated above, in the discussion of the curves the reasons for this difference 
are that the physical condition of the fresh manure was in favor of its 
more rapid decomposition, more bacteria were added with it, and it 
contained more easily available organic matter. 
Another noteworthy circumstance is that with the limed soils less 
organic carbon has been evolved than from the corresponding unlimed 
soil. Here, again the only explanation seems to be that the organic 
matter of the manures does not need lime for its decomposition. Pos¬ 
sibly the lime, together with the organic matter, causes such a high 
percentage of carbon dioxid in the soil atmosphere and soil solution that 
it becomes slightly toxic to the bacteria. Our apparatus was of such a 
nature that cultivation of the soil during the course of the experiment 
was not feasible. Possibly with cultivation, which would have tended 
to diminish the concentration of carbon dioxid, the results would have 
been different. Particularly to be noticed is the very large percentage 
of the green manures which were decomposed. There were evolved 
as carbon dioxid 78.9 per cent of the carbon of the oats and 95 per cent 
of that of the clover. It should be recalled that the respective figures 
for the experiment which ran 53 days were 52.4 per cent and 62.3 per 
cent. Therefore it seems that the physical condition of the green 
manures did not greatly influence the rate of decomposition. While 
the manner of application of the oats and clover in this last experiment— 
