Relation of the Hydrogen-Ion Concentration of the Soil to Plant Distribution

Abstract

WITH reference to Dr. W. R. G. Atkins's interesting communication in NATURE of September 15, may I be allowed to submit the following comments? The importance of the study of hydrogen-ion concentration in physiology and biochemistry, soil science, and other branches of research cannot be over-emphasised, and is rapidly becoming appreciated by workers. There appears, however, to be a tendency to apply methods of measurement that have been standardised in one branch of study to other departments—soils, for example—with a minimum change of technique. With the exception of Gillespie's pioneer, but by no means exhaustive, work in America, the colorimetric method of measuring the hydrogen-ion concentration of soils has never been critically examined. After considerable preliminary work with this method—an account of which has been published elsewhere—the present writer feels that the conditions under which it can be applied in soil work so as to yield accurate and reproducible results have not yet been fully worked out. As an example may be cited the fineness of division of the soil sample which is often a factor influencing the apparent pH as determined colorimetrically. Until much more work has been done from this point of view the data being accumulated by ecologists can scarcely have the strict quantitative significance often attached to them, although when regarded as provisional only they are undoubtedly of great interest and no little importance.