Hot water extraction of boron from soils using sealed plastic pouches

Abstract

Logistically, the determination of available B in soils is one of the most difficult analysis routinely performed in soil testing laboratories. The purpose of this study was to examine the feasibility of using sealed plastic pouches in place of the traditional glass refluxing apparatus for the hot water extraction of B in soils. Seven northern Idaho soils were collected, spiked with B levels of 0.25, 0.5, 1.0, 1.5, 2.0, and 4.0 μg/g, and analyzed for extractable B using both types of vessels. When extraction time was five minutes, extraction of B from soil using glass refluxing apparatus yielded from 0.03 to 0.16 μg/g more extractable B than when sealed plastic pouches were used. This was true for all soils at all B levels. It was determined, however, that equivalent B values were obtained with both procedures when the boiling time with the plastic pouches was increased from 5 to 7 minutes.

A procedure for B extraction is proposed using the sealed plastic pouches as extraction vessels. The plastic pouches have several advantages over the glass refluxing apparatus including: (1) cost, (2) labor, (3) repeatability, (4) sample turn‐around time, and (5) the actual number of samples which can be run concurrently.

Key words:

• Soil boron
• soil extraction
• soil testing
• soil test correlation