MANGANESE UNDER ACID AND NEUTRAL SOIL CONDITIONS. 5 
OXIDATIVE POWER OF PLATS WITH AND WITHOUT MANGANESE UNDER 
ACID CONDITIONS. 
Bertrand * showed that manganese played an essential part in the 
oxidation by the so-called oxidizing enzym laccase. Further, since 
manganese increased the oxidizing power of a number of soils tested 
by the Office of Soil-Fertility Investigations and it has been found 
that a number of soils of strong oxidizing power contain considerable 
manganese, some of which was in the highly oxidizing form of Mn0 2 , 
it became of interest to determine whether the manganese had any 
accelerating effect on the oxidation in the soil of the field plats 
planted with wheat, rye, corn, cowpeas, and potatoes. 
In 1912 composite samples from five borings to the depth of 6 
inches were taken of the manganese plats and check plats (1) early 
in April, (2) late in May, and (3) in August. The oxidation readings 
were made on the air-dried samples within two weeks after collection. 
When 10 or 20 grams of soil are shaken two or three times with 50 
to 70 c. c. of a 0.125 per cent water solution of aloin, the aloin solu- 
tion is changed in a few minutes from a bright yellow to a cherry red. 
After the soil has stood for about an hour and has settled, the some- 
what turbid solution is decanted and centrifuged, the supernatant 
liquid drawn off, and the depth of color of the different solutions com- 
pared by means of a Schreiner colorimeter, either with each other or 
with colored glass of a shade of red matching the oxidized solutions. 
In the present experiment the oxidation reading was made against a 
glass standard which matched in tint the red color produced in the 
aloin solution by the sample of wheat soil collected in the spring. 
Ten grams of soil were employed for each test. The relative oxida- 
tion in the manganese plats and the check plats is given in Table III. 
Table III. — Relative oxidation in plats treated with manganese sulphate and in the 
corresponding check plats groiving the same crops {wheat soil in April being taken 
as 100). 
April. 
June. 
August. 
Crop. 
Un- 
treated 
plats. 
Plats 
treated 
with 
man- 
ganese. 
Un- 
treated 
plats. 
Plats 
treated 
with 
man- 
ganese. 
Un- 
treated 
plats. 
Plats 
treated 
with 
man- 
ganese. 
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 
60 
Rye 
Com 
75 
53 
Cowneas 
Potatoes 
55 
'Bertrand, Gabriel. Sur les rapports qui existent entre la constitution chimiques des composes organi- 
ques et leur oxydabilite sous l'influence de la laccase. In Compt. Rend. Acad. Sci. [Paris], t. 122, no. 20, 
p. 1132-1134. 1896. 
Sur I'intervention du manganese dans les oxydations provoquees par la laccase. In Compt. 
Rend. Acad. Sci. [Paris], 1. 124, no. 19, p. 1032-1035. 1897. 
