Comparability of Electroultrafiltration and Ammonium Acetate–Lactate Extraction Data for Phosphorus and Potassium in Pseudogley Soils

Abstract

The aim of this research was to compare two standardized soil extraction methods [electroultrafiltration (EUF) and ammonium acetate–lactate (AL)] regarding potassium (K) and phosphorus (P) availability in pseudogley soils. In total, 60 pseudogley soil samples from 12 agricultural sites in eastern Croatia (each represented by five soil samples—replicates) were simultaneously analyzed by both methods. The relations of K and P with other important soil traits [pH, selective mineral clay content (SMC), humus content] were established by multiple regression analyses. Furthermore, a highly significant regression equation (P ⩽ 0.01) was established for AL–phosphorus pentoxide (P2O5), using EUF‐P‐I and EUF‐P‐II separately as well as soil pH value determined in 1 M KCl as independent variables. The actual P amount extracted by AL differed by 9% from the value predicted by the regression function. According to the highly significant multiple regression function (P ⩽ 0.01), AL‐extractable dipotassium oxide (K2O) can be approximated using EUF‐K (sum of EUF‐K‐I and EUF‐K‐II fraction), SMC, and the EUF‐K‐Q (ratio of EUF‐K‐II and EUF‐K‐I) as the independent variables. A deviation of calculated AL‐K2O value from the extracted amount of K was 4%. These results point out the possibility of the comparison of EUF and AL extraction data in the evaluation of K and P availability in pseudogley soils. The necessity of more comprehensive research regarding the comparison of the EUF and AL method, taking into account plant nutrient acquisition specificity and a great number of interrelated soil and climate factors, was suggested.