6 BULLETIN 441, U. S. DEPARTMENT OF AGRICULTURE. 
With the exception of the wheat plat, where there is shown a slight 
increase as an average of the three determinations, the addition of 
manganese sulphate has not increased the oxidative power of the soil, 
and hi a number of instances it has lessened oxidation. The soil hi 
general has a tendency to be acid in character and at best has not a 
strong oxidizing power. If the first determination, made hi April, 
is considered (that is, the oxidative power of the plats at a time when 
there is little or no growth) the oxidation in the manganese plat is 
less in every instance than that of the check plat. This period is the 
best one for testing the oxidation effect of manganese unmodified by 
plant growth. The lessened oxidation produced by manganese sul- 
phate is in harmony with the lessened yields on the same plats 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 plat than on the 
untreated plat, while rye only showed a slight increase and the yield 
of cowpeas was practically the same. 
In the second determination, made in June, the oxidative power of 
the manganese plat is on the average more like that of the check plat. 
In the third determination, made in August, shortly after the wheat 
and rye had been taken off, the manganese plat was on the average 
again less than the check plat. 
As previously pointed out, the manganese plats, with the exception 
of the potato and the wheat plats, showed a higher lime requirement 
than the check plats. 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 also indicated from the results 
with the acid soil under investigation, for the addition of manganese 
did not increase 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 plats, the oxidizing power of the intact 
roots when placed in an aloin solution was foimd to be no greater in 
the case of the plants from the manganese plat than from the check 
plat. The relative oxidation was 97 and 100, respectively. 
EFFECT OF MANGANESE ON ARLINGTON SOIL UNDER NEUTRAL 
CONDITIONS. 
As the manganese had no beneficial effect on the soil under acid con- 
ditions, the experiment was continued and the soil neutralized as 
nearly as possible by applying lime from year to year. Three years' 
results have now been secured. Each year before planting, the lime 
requirement of the plats was determined by the Yeitch method and 
an excess of lime added to both the check and manganese plats. The 
