Soil analysis procedures using 0.01 <i>M</i> calcium chloride as extraction reagent

TLDR

This CaCl₂ extraction method is simple, inexpensive, and increasingly adopted as an alternative to traditional single‑nutrient procedures, using a solution with ionic strength comparable to typical soil solutions. The study presents detailed laboratory procedures for measuring bioavailable nutrients and pollutants in 0.01 M CaCl₂ soil extracts, facilitating simultaneous multi‑element analysis. Soil samples are extracted for two hours at 20 °C with a 1:10 (W/V) 0.01 M CaCl₂ solution, after which pH and concentrations of numerous nutrients and pollutants are measured in the clear filtrate using techniques such as segmented‑flow analysis, ICP‑OES, and ICP‑MS.

Abstract

Abstract This publication gives details of laboratory procedures for the determinations of bioavailable (e.g., plants) quantities of nutritional and polluting inorganic elements in 0.01 M CaCl2 extracts of air‐dry soil samples. Air‐day soil samples are extracted for two hours with a 0.01 M CaCl2 solution of 20°C in a 1:10 extraction ratio (W/V). After measuring the pH in the settling suspension, the concentrations of nutritional and polluting elements are measured in the clear centrifugate or filtrate. The procedure is simple, easy to perform, and cheap (labor, chemicals) in daily use in routine soil laboratories. The method receives internationally more and more attention as an alternative for the many extraction procedures for a single nutrient or pollutant that are still in use nowadays. The soil is extracted with a solution what has more or less the same ionic strength as the average salt concentration in many soil solutions. Various nutrients and metals can be measured in a single extract that allows considering relationships between them during interpretation of the data. For most elements, different detection techniques are described in detail in this publication. Detailed laboratory procedures are described for the determination of pH, total dissolved organic carbon, nitrate, ammonium, total dissolved nitrogen, sulphate, total dissolved sulfur, ortho‐phosphate, total dissolved phosphate, sodium, potassium, magnesium, cadmium, copper, nickel, lead, aluminum, iron, arsenic, boron, and phenols. Since only one extract of soil samples is used, profitable use can be made of multi‐element detection techniques like segmented‐flow analysis spectrometry, ICP‐OES, and ICP‐MS.