It is generally recognized that plant growth is affected by the acidity of the medium in which the plant is grown. The relationships between pH and growth are not simple and need additional clarification. The bulk of evidence available in this field indicates that the indirect effects of soil Ph on plant growth are much more important than any direct effects, and it is at only the very high and very low pH values that plants are directly affected. Magistad (12), Wilson (24) and McGeorge (8) found that root injury was not obtained in culture solutions at pH values as low as those found in very acid soils.
McComb, A. L. and Kapel, Frank J.
"Growth of Seedling Black Locust and Green Ash in Relation to Subsoil Activity and Fertility,"
Ames Forester: Vol. 29
, Article 7.
Available at: https://lib.dr.iastate.edu/amesforester/vol29/iss1/7