ACTION" OF MANGANESE IN SOILS. 19 
sive oxidation was noticeable ; the leaves were yellow at the tips and 
appeared bleached. The natural processes of oxidation in the pro- 
ductive soils were good, and the addition of manganese caused exces- 
sive action, and thus injured the culture as a medium for growth. 
The life processes in the unproductive soils were probably bad, and 
the addition of this substance aided the needed function and therefore 
overcame its bad qualities and made it a better medium for plant 
growth. 
In relation to the beneficial effect of manganese on poor soils by 
stimulating root oxidation where oxidation is naturally poor, and the 
harmful effect by causing additional oxidation by plant roots in good 
soils where the oxidation processes are already good, it is interesting 
to note the effect of different fertilizers, which increase or check 
oxidation on the action of organic compounds. Quinone, which has 
been shown to be toxic to wheat seedlings in a former research, 1 is an 
oxidizing substance. Its harmful effect is partly overcome by potash 
salts, which check oxidation processes. On the other hand, those 
harmful soil organic compounds that have reducing properties — that 
is, are themselves readily oxidized — such as vanillin and dihydroxy- 
stearic acid, have an inhibiting effect on root oxidation and on root 
growth generally, and their harmful effects are overcome by fertilizers 
such as nitrate, which increase root oxidation to the greatest extent. 
EXPERIMENTS WITH MANGANESE IN THE FIELD. 
The tests with manganese sulphate made at the department farm 
at Arlington, Va., were laid out in the spring of 1907 and are a part of 
a larger experiment, which includes the testing of a number of other 
compounds and fertilizers. Five crops are concerned in each treat- 
ment. The crops grown were wheat, rye, corn, cowpeas, and potatoes. 
Describing only the manganese plots in this series, it should be said 
that these consisted of two parallel strips of land, each 1 rod wide 
and separated by a 3-foot path. Each strip is divided into 5 plots 
of 1 square rod, with 2J-foot paths separating the plots. One strip 
or series of 5 plots is treated with manganese sulphate, the other strip 
is not treated and serves as a control or check. The five different 
crops are grown on both the treated and untreated plots, which lie 
side by side in the two strips. 
The soil on which these experiments were made is a silty clay loam, 
low in organic matter. The physical condition of the soil is rather 
poor. Great care had to be practiced in cultivation to keep the soil 
in a good physical condition. The ground on which the manganese 
experiments were made is level and has surface drainage. The soil 
throughout these manganese plots and their controls is uniform, so 
i Schreiner, O., and Skinner, J. J., Organic compounds and fertilizer action. Bui. 77, Bureau of Soils, 
U. S. Dept. Agr. (1911). 
