Effects of Soil Sample Grinding Intensity on Carbon Determination by High‐Temperature Combustion

Abstract

Recently, many studies related to carbon (C) sequestration by soils have been reported. However, little information has been reported related to the need for and effects of grinding soils on C analysis by high‐temperature combustion. We studied the effects of grinding five glacially derived soils of varying textural composition and organic matter content to 2‐mm, 1‐mm, 0.5‐mm, 0.25‐mm, and 0.15‐mm particle sizes on the measurement of total, inorganic, and organic C content using a high‐temperature combustion technique. Medium‐textured soils showed significantly higher total and organic C values for the 2‐, 1‐, and 0.5‐mm particle sizes than for the 0.25‐ and 0.15‐mm particle sizes compared to soils that were high in sand or clay. Grinding did not appear to affect inorganic C values. Grinding the soils to 0.15 mm, in all cases, greatly reduced the variability of C values by as much as two‐ to six‐fold when compared to 2‐mm soils. We recommend that soils be ground to pass a 0.15‐mm (100‐mesh) screen prior to C analysis by high‐temperature combustion.