16 BULLETIN 42, U. S. DEPARTMENT OF AGRICULTURE. 
was able to alleviate the toxicity of such solutions. 1 The oxidizing 
power of plants grown in extracts of productive soils is greater than 
that of plants grown in extracts of unproductive soils. Harmful 
organic compounds upon proper conditions suffer change in the soil. 
This change may occur under conditions of thorough aeration and 
oxidation, which is promoted by thorough tillage and good drainage 
and also by the addition of substances to increase oxidation in the soil. 
This seems to be a function of manganese. Its addition to extracts 
of soils of low fertility increases the oxidation, and by so doing may 
change the organic material of the solution and make it a better 
medium for plant growth. 
EFFECT OF MANGANESE IN EXTRACTS OF PRODUCTIVE SOILS. 
The next experiments are concerned with the action of manganese 
in good soils where harmful conditions are necessarily at their mini- 
mum or entirely wanting. One of the soils tested was the Hagers- 
town loam from a productive plot in the experimental field of the 
Pennsylvania experiment station. The soil is naturally productive 
and in the field has been subjected to a four-year rotation. When 
tested in pots, this soil did not respond to manganese. 
An extract of the soil was made in the usual way and wheat seed- 
lings grown. Manganese chloride, sulphate, and nitrate were used 
in concentrations of 10 and 25 parts per million. Two cultures were 
used in each treatment. The experiment was run from December 9 
to December 23. The results are given in Table VII. 
Table VII. — Effect of manganese on growth and oxidation in extracts of a productive 
loam soil. ( untreated extract = 100.) 
Relative 
Treatment. gto^h. 
Relative 
oxidation. 
E xtract untreated 
Extract+MnCl 2 , 10 parts per million 
Extract+MnCl 2 , 25 parts per million 
Extract+MnS0 4 , 10 parts per million 
Extraet+MnSOj. 25 parts per million 
Extract+Mn(N0 3 )2, 10 parts per million. 
Extract+Mn(N0 3 )2, 25 parts per million. 
100 
98 
97 
100 
102 
101 
100 
As seen in the table, there was no increased oxidizing power of 
the plant roots in the manganese cultures. The oxidation in the 
untreated solution was very good, as might have been expected in 
this highly fertile soil, and the addition of manganese produced no 
additional oxidation by the plants. The growth was not increased. 
In several instances it was decreased. Only in one treatment, and 
that with the nitrate, was the growth as good as in the untreated 
solution. 
1 Schreiner, O., and Reed, H. S., The rdle of oxidation in soil fertility. Bui. 56, Bureau of Soils, U. S. 
Dept. Agr. (1909). 
