26 
BULLETIN 42, U. S. DEPARTMENT OF AGRICULTURE. 
Table XVII. — Relative oxidation in plots treated with manganese sulphate and in the 
corresponding check plots growing the same crop {wheat soil in April tal:en as 100). 
Crop. 
April. 
June. 
August. 
Check 
plots. 
Manganese 
plots. 
Check 
plots. 
Manganese 
plots. 
Check 
plots. 
Manganese 
plots. 
Wheat 
100 
131 
110 
66 
87 
95 
105 
100 
64 
60 
110 
131 
130 
105 
91 
130 
105 
131 
110 
78 
55 
78 
87 
53 
53 
64 
Rye 
60 
Corn 
Cowpeas 
53 
Potatoes 
55 
With the exception of the wheat plot, where there is shown a 
slight increase as an average of the three determinations, the addi- 
tion of manganese sulphate has not increased the oxidative power 
of the soil, and in a number of instances it has lessened oxidation. 
The soil in general has a tendency to be acid in character and at best 
has not a strong oxidizing power. If the first determination, made 
in April, is considered (that is, the oxidative power of the plots at a 
time when there is little or no growth) the oxidation in the manganese 
plot is less in every instance than that of the check plot. This period 
is the best one for testing the oxidation effect of manganese unmodi- 
fied by plant growth. The lessened oxidation produced by manga- 
nese sulphate agrees roughly with the lessened yields on the same 
plots under treatment with manganese. In 1912, for instance, the 
year in which the oxidation was tested, the yield, as previously 
shown, of wheat, corn, and potatoes was less on the manganese plot 
than on the untreated plot, while rye showed a slight increase and 
the yield of cowpeas was practically the same. 
In the second determination, made in June, the oxidation power 
of the manganese plot is on the average more like that of the check 
plot. 
In the third determination, made in August, shortly after wheat 
and rye had been taken off, the manganese plot was on the average 
again less than the check plot. 
As previously pointed out, the manganese plots, with the exception 
of the potato plot, showed a higher lime requirement than the check 
plots. Under acid conditions the formation of organic compounds 
capable of acting as oxygen carriers or as activators of inorganic 
oxidizing compounds such as manganese salts is much lessened 
or entirely inhibited. This is indicated from the results with the acid 
soil under investigation, for the addition of manganese did not in- 
crease the oxidizing power of the soil nor indeed of plants growing 
therein. This oxidizing power of the plants was tested in the case of 
wheat. By carefully removing the soil from the young wheat plants 
growing on the plots, the oxidizing power of the intact roots when 
placed in aloin solution was found to be no greater in the case of the 
