Factors Affecting the Determination of pH of Some Mediterranean Soils

MEDITERRANEAN SOILS I a previous article, the authorI dealt with the question of how KC1/N is influencing the pH of soils. The present investigation shows that by adding KC1/N as a soil solvent, hydrolysis is prevented, and any soil-solvent ratio can be used without any change occurring in the pH. The soil samples used for this experiment represent four profiles, two light, soils (one with and one without CaCO~) and two heavy softs (one with and one without CaCO3). The soil samples were taken at the arbitrary depths of o to 25 em, 25 to 50 cm, 50 to 75 cm, and 75 to ioo cm. The pH values of these soils have been determined, using air-dried soil extracted in varying soil-solvent ratios and with different solvents and shaking them for 3 minutes according to the method adopted by Gedroiz.2 The pH was determined in colorimetric measurements as described by the author. In order to confirm results obtained in our laboratory, the pH was determined electrometrically on parts of the same soil samples by the Chemico-Physical Department of the Hebrew University. The results obtained were similar to ours. It will be observed from Fig. i that by using distilled water as a medium the pH increases with dilution. This increase may be attributed to the fact, as expressed by McGeorge, ~ that by increasing dilution the potential alkaline reaches a higher hydrolysis. On the other hand, by using tap water or KC1/N as a solvent very little change in the pH occurs. This is probably due to the buffer action of KC1/N