SOIL pH MEASUREMENT AND ITS APPLICATION TO ORGANIC SOILS

Abstract

The average soil pH of 10 organic soils was significantly influenced by drying and the salt concentration of the suspending media. Accordingly, mean soil pH of field-moist and oven-dried soils was pH 5.0 and 4.5, 4.1 and 3.9, and 3.8 and 3.6 for soils suspended in water, 0.015 M CaCl 2 and 1 M KCl. A significant treatment–soil interaction indicated that the soils responded differently to the treatments. No junction potentials were found when the ionic strength of the solution was 0.01 M CaCl 2 equivalent or greater. Milli-equivalents exchangeable hydrogen (−0.984**), percent hydrogen saturation (−0.966**) milli-equivalents extractable bases (0.937**) and percent base saturation (0.957**) were more closely correlated with 1 M KCl pH values than with values in the other media. Liming influenced soil pH significantly on all field sites and within 8 h after application on two field sites. The influence of liming on soil pH tended to diminish the year after applications were made. Measured soil pH variability among treatments and replicates at various sampling dates ranged up to 1 pH unit during the growing season. However, it was about 0.2 pH unit on the control treatments with undetectable quantities of residual limestone. The quantity of reacted limestone was established at 25 and 40%, between 23 May and 31 July, on two sites (J.I.V. and S.B.). The reacted limestone was found to be proportional to the application rate.