JOURNAL 
OF THE 
WASHINGTON ACADEMY OF SCIENCES 
Vout. 13 Marcu 19, 1923 No. 6 
SOIL CHEMISTRY.—Relations between the active acidity and lime- 
requirement of soils. Epagar T. Wuerry, U. S. Bureau of 
Chemistry.1 
The lime-requirement, or amount of lime needed to bring a soil to a 
neutral reaction, is decidedly less easy to determine with certainty than 
is the active soil acidity, or hydrogen-ion concentration of the aqueous 
extract (also sometimes termed soluble, effective, or ‘‘true’’ acidity). 
If any numerical factor could be discovered connecting the two, it 
would be possible to carry out the simpler acidity determination, 
and then to calculate from it the lime-requirement. From an indirect 
comparison of the active acidity and the lime-requirement of the same 
soils Blair and Prince? have concluded that more or less correlation 
between these quantities does exist; but they did not work out the 
direct relations, nor do any other writers appear to have done so. 
The matter seems of sufficient importance, however, to justify further 
study of the available data. 
In what follows, lime-requirement will be expressed in parts of 
calcium oxide per thousand; this being numerically identical with 
tons per acre, if that area is considered as offering for treatment two 
million pounds of soil (corresponding to a depth of approximately 6 
inches). 
Hydrogen-ion concentration will be stated in the form of specific 
acidity, which has been defined by the writer? as the acidity of a solu- 
1 Presented at the Birmingham meeting of the American Chemical Society, April, 
1922. Contribution from the Laboratory of Crop Chemistry. 
2 Soil Sci., 9: 253. 1920. 
3 Jour. Wash. Acad. Sci., 9: 305. 1920. 
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