DID WE UNDERESTIMATE SILT AND CLAY CONTENT IN THE TEXTURAL ANALYSIS?
John Clunes, José Dörner, Andrea Bravo, Roberto Jara, Felipe Zúñiga · Chilean journal of agricultural & animal science · 2022
Particle size distribution (PSD) is a soil physical property influenced by organo-mineral complexes (or-mic) in silt and clay fractions.In Andosols, these fractions are underestimated due to the presence of or-mic in soil micro-aggregates.This study estimated quantitatively the organomineral fraction by comparing two methodologies of granulometric analysis (sequential dispersion and sieve-sedimentation) in Andosols and Fluvisols from southern Chile.Or-mic were calculated through specific dissolution extractions (Al, Si, Fe).In addition, pH NaF , and soil organic carbon (SOC) were determined.Correlations between Al o (0.74), Al p (0.71), pH in NaF (0.41), and the ormic were found.Or-mic were higher in Andosols, varying between 1.5 and 5.2%, which led to an underestimation of silt and clay fractions of the soil in PSD analysis and, thus, an overestimation of soil texture due to the continuous formation of micro-aggregates.Therefore, to properly determine soil PSD, it is essential to estimate or-mic, particularly in highly reactive soils, which are readily capable of binding organic compounds in their mineral fraction.