ORIGINAL RESEARCH
Conversion of Soil pH 1:2.5 KCl and 1:2.5 H2O
to 1:5 H2O: Conclusions for Soil Management,
Environmental Monitoring,
and International Soil Databases
Cezary Kabała, Elżbieta Musztyfaga, Bernard Gałka,
Dorota Łabuńska, Paulina Mańczyńska
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Institute of Soil Science and Environmental Protection, Wrocław University of Environmental and Life Sciences,
Wrocław, Poland
Submission date: 2015-12-31
Final revision date: 2016-01-22
Acceptance date: 2016-01-23
Publication date: 2016-03-17
Pol. J. Environ. Stud. 2016;25(2):647-653
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ABSTRACT
Both the international ISO standard and modern soil classifi cations and databases require soil pH measurement
at a 1:5 soil:solution ratio, while the ratio 1:2.5 is still the most commonly used in Poland and other
European countries. The transformation of laboratory practices is necessary, but it is also necessary to establish
and validate a reliable procedure for converting soil pH at soil:solution ratios of 1:5 and 1:2.5. Based
on 200 soil samples representing typical soil types and soil properties of southwest Poland (including arable
and forested areas, both in the lowlands and mountains), a general conclusion was derived that pH values
measured at soil:solution ratios 1:2.5 and 1:5 in distilled water and KCl solution, respectively, have nearly
identical values and do not require conversion in most practical applications. If precise conversion of pH1:2.5
to pH1:5 is necessary, e.g., for soil database construction or long-term soil quality monitoring, the following
equations are suggested: pHH2O 1:5 = 0.14 + 0.99*pHH2O 1:2.5 and pHKCl 1:5 = 0.09 + 1.00*pHKCl 1:2.5, respectively.
When the direct conversion of pHKCl 1:2.5 to pHH2O 1:5 is required, a simple logarithmic model offer precise and
reliable transformation: pHH2O 1:5 = -1.95 + 11.58*log10(pHKCl 1:2.5). This model makes the archival records still
useful, both for international soil classifi cations, background data in the long-term measurement series, and
as input data for modern international soil databases.