Correlation between soil ph measured in two eluents in the case of agricultural land: conclusions regarding soil reaction classes

Soil pH is one of the most important measured soil parameters. It is an indicator of soil quality, establishes the reaction class, fertilizer recommendations, liming necessity and also an index of the soil biological processes. In Romania, the most common measurement of soil pH is carried out in H2O or KCl as eluents in 1:2.5 ratio. The novelty of this research is that a large number of soil samples (911) were investigated from Romanian farmland territories with different soil types and different chemical properties. In order to integrate the results of soil pH in international soil databases, it is necessary to establish and validate a relationship between pHH2O and pHKCl. The obtained value of the correlation coefficient r = 0.983 indicates a strong correlation between the two sets of values. The linear and polynomial functions have a high coefficient of determination R2 = 0.96. The investigated soils of this study are classified in reaction classes from strongly acidic to slightly alkaline. The models proposed by this study can be used in laboratories for intern quality control and for converting pH values in different eluents.