This method determines the pH of soil, using a saturated paste prepared from the soil and a pH meter. It is most applicable to soils with a pH ranging from 4.0 to 9.0. It is not possible to determine the total acidity or alkalinity of the soil from pH because of the nature of the colloidal system and junction potential. This method does however provide information on the disassociated H-ions affecting the sensing electrode. The method is generally reproducible within 0.2 pH units.
U.S. Salinity Laboratory Staff. 1954. pH reading of saturated soil paste. p. 102. In: L. A. Richards (ed.) Diagnosis and improvement of saline and alkali soils. USDA Agricultural Handbook 60. U.S. Government Printing Office, Washington, D.C.