ACTION OF MANGANESE IN SOILS. 11 
distilled water was taken as 100, the poor soil extract was 103 and 
the good soil extract 275. It was also pointed out that treating the 
poor soil extract with an absorbent agent benefited oxidation, that 
the presence of toxic organic substances in solution was deleterious 
to the oxidizing power of plants, and that the oxidizing power of the 
plants, especially in the presence of chemicals which promoted oxida- 
tion, was able to alleviate the toxicity of such solutions. 
In more recent work harmful organic compounds have been found 
in soils and isolated. 1 The harmfulness of some of these soil com- 
pounds are overcome by fertilizers which promote root oxidation. 
Other harmful organic compounds have been worked with in this 
laboratory which are overcome by fertilizers which check root 
oxidation. 2 
CULTURAL AND OXIDATION METHODS. 
In order to study the oxidation by manganese and its effect on 
soil improvement, aqueous extracts of soils were used as culture 
solutions. The aqueous extract was made by stirring 2 parts of soil 
with 5 parts of distilled water for 3 minutes and filtering after 30 
minutes through a Pasteur-Chamberland filter tube. It has been 
found that soil extracts prepared in this manner possess a plant- 
producing power similar to that of the soil from which they were 
made. That is, fertile soils give extracts which promote good plant 
growth and infertile soils give extracts which grow poor plants. 
The effect of manganese salts was studied by adding the substance 
to the soil extract. The water used in making soil extracts was 
distilled water, further purified by treating with carbon black and 
filtering. 3 
Salt-mouth bottles having a capacity of 250 c. c. were used as 
containers of the solution and served as culture jars in which to 
grow the plants. 
Wheat was used in these experiments. The seeds were germinated 
on floating perforated aluminum plates, according to the method 
described in Bulletin 70 of this bureau. The seedlings were trans- 
ferred from the germinating plates to the cultures when they were 
about an inch high, or just when the first true leaf was beginning 
to emerge from its sheath. Ten wheat plants were used in each 
culture. They are held in place by a cork which has had triangular 
wedges cut from its circumference. These wedges are truncated 
at their inner angle and are held in place by a rubber band around 
the cork. 
iSchreiner, O., and Shorey, E. C, The isolation of harmful organic substances from soils. Bui. 53, 
Bureau of Soils (1909). Chemical nature of soil organic matter. Bui. 74, Bureau of Soils, U. S. Dept. 
Agr. (1910). 
2 Schreiner, O., and Skinner, J. J., Organic compounds and fertilizer action. Bui. 77, Bureau of Soils, 
U.S. Dept. Agr., (1911). 
SBuls. 36 and 70, Bureau of Soils, U. S. Dept. Agr. 
