ACTION OF MANGANESE IN SOILS. 31 
In wheat and rye plots, the catalytic power is greater in the manga- 
nese-treated soils than in the untreated soil. In the corn and cowpea 
plots the untreated soil is on the average slightly the better cata- 
lyzer. In the case of potatoes, the check plot is slightly the better 
catalyzer. The soil of the plots is not a strong catalyzer, and the 
differences between the plots is slight, with the exception of the wheat 
plots. 
Catalysis has been shown 1 to stand in closer relation to the man- 
ganese content of the soil than oxidation, though even in the case 
of catalysis the nature of the associated organic matter is of great 
importance. Addition of manure leachings and of manure ash in- 
creased the catalytic power of the soil of the experiment plots, but 
their effect was not studied in connection with manganese. 
In general, soils of high productiveness previously studied have 
had strong catalytic power, while poor soils have had, as a rule, weak 
catalytic power. The catalytic power, however, does not stand in 
as close relationship to soil fertility as the oxidation power does, 
though in general the presence of a strong catalytic power in a soil can 
be taken as a priori evidence that the many factors making for soil 
fertility, such as suitable organic matter, bacterial activity, oxidation, 
etc., would be prominent and the soil would be a productive soil. 
Factors which favor fertility and oxidation, such as liming and addi- 
tion of manure, also favor catalysis. Though crop production is 
dependent on many factors, no one or two of which can be taken 
as an absolute criterion, it is interesting to note that the soil of 
the experiment plots is a poor oxidizer and catalyzer and is also of 
mediocre productiveness. Its poor oxidation and catalysis and like- 
wise yields of the ordinary cultivated crops may be connected with 
the acid character of the soil. In a similar way the lack of favorable 
response in oxidation, in catalysis, or in crop growth to treatment 
with manganese may be connected with the acid reaction and small 
organic content or the nature of the latter. 
SUMMARY. 
The effect of manganese on poor and good soils was studied by 
growing wheat in pots. Manganese chloride, sulphate, nitrate, car- 
bonate, and dioxide had a stimulating effect in the case of an unpro- 
ductive sandy loam soil. The best results were obtained when the 
salt was applied in amounts from 5 to 50 parts of manganese per mil- 
lion. Quantities higher than this gave no correspondingly larger 
increase and in some cases were even harmful. On a productive loam 
the various salts of manganese had no stimulating effect. 
Further work was done by growing the crop in treated aqueous 
extracts of soils and studying the oxidizing power of the plants. The 
i Bui. 86, Bureau of Soils, U. S. Dept. Agr. 
