A procedure for the determination of soluble boron in soils ranging widely in boron concentrations,sodicity, and pH.

Abstract

Soils in southern Australia within the Mediterranean‐type climate zone vary widely in boron concentrations, from potentially deficient to toxic for plant growth. A general method is needed for the determination of boron in soils ranging from acidic to alkaline, with wide ranges of clay content and sodicity.

The amounts of boron extracted were compared following boiling in 0.01M CaCl₂ in test tubes in temperature‐controlled programmable digestion blocks, or in Erienmeyer flasks on hot plates under different analytical conditions. Comparisons were also made between CaCl₂, hot water, and mannitol extractable boron. All analyses of boron were made by inductively coupled plasma spectrometry (ICPS).

The extraction of boron was dependent on extraction time and temperature of the heating block. Addition of 20 ml of 0.01M CaCl₂ to 10g of soil in 250 ml test tubes fitted with air condensers and placed in a pre‐heated temperature‐controlled digestion block set at 140°C and boiled for 30 minutes. This method was found to be a suitable extractant of boron in soils with a wide range of sodicity, pH and extractable boron (from concentrations potentially deficient to toxic for plant growth).