SOIL ACIDITY AND THE HYDROLYTIC RATIO IN SOILS 1 
By C. H. Spurway, 
Assistant Professor of Soils Physics , Michigan Agricultural College 
HISTORICAL REVIEW 
Recent investigations pertaining to soil acidity indicate a relationship 
between iron and aluminium compounds in soils and their reaction to 
litmus-paper-phenolphthalein indicator. Abbot et al. ( i ) 2 found that 
soil acidity in certain marsh soils may be due mainly to the presence of 
aluminum nitrate, and the quantity of aluminum found in an unpro¬ 
ductive marsh soil was directly proportional to the amount of alkali 
required to neutralize the soil solution. Veitch (9) and Harris ( 6 ) 
found that when acid soils were treated with certain salt solutions iron 
and aluminium salts came from these soils and the iron and aluminium 
could be precipitated from the solutions as hydroxids by the addition 
of alkali. Daikuhara (4), working on soils of Japan found a relation¬ 
ship between the acidity of soils and their content of iron and aluminium 
compounds and concludes that these acid compounds are absorbed by 
soil colloids. In drawing conclusions from his work Rice (7) states: 
much aluminum was present in extracts from soils of the highest acidity, 
and Connor (5) also concludes that— 
much of the harmful acidity of acid soils is due to the presence of toxic acid salts 
of aluminum and iron. 
Ames and Schollenberger ( 2 ) state in their conclusions on the 
subject— 
for the several soils investigated there was found to be an approximately quantitate 
relationship between the bases soluble in fifth-normal nitric acid (excluding car¬ 
bonates) and differences in lime requirement by the vacuum method. 
A further list of references concerning effects and other causes of 
soil acidity may be found in the publications already cited and also in 
those of Frear (5) and Truog (<£), and to avoid repetition the reader is 
referred to these papers for a more complete discussion of the subject. 
THE PROBLEM 
From studies on glacial-formed soils the author has for some time 
observed an apparent relationship between iron and aluminium salts in 
these soils and their reaction to litmus paper and phenolphthalein indi¬ 
cator. Yellow and brown colored soils of the Glacial Province are often 
acid to litmus paper. Small, well-marked, highly colored areas of soil 
1 Approved for publication in the Journal of Agricultural Research by the Director of the Michigan 
Agricultural Experiment Station. 
2 Reference is made by number (italic) to “ literature cited,” p. 672. 
(659) 
Journal of Agricultural Research, 
Washington, D. C. 
If 
Vol. XI, No. 13 
Dec. 17, 1917 
Key No. Mich. 7 
