Development of Mechanical Soil Stability In An Initial Homogeneous Loam And Sand Under In-Situ Field Conditions

Abstract

PurposeSoil structure evolving from physical and biological processes is closely related to soil mechanical characteristics and texture. A soil plot experiment in Bad Lauchstädt, Germany, allowed us to study the influence of substrate and genotype on the initial development of mechanical traits, differences between depths, and changes over the course of two years. MethodsPlots were homogeneously filled with a loam and a sand and planted with two maize (Zea mays L.) genotypes (wild type (WT) and rth3 mutant) with contrasting root hair attributes. Undisturbed soil cores were taken in 2019 and 2020 at 14 and 34 cm depth. Confined uniaxial compression tests were performed to determine pre-compression stress (σpc), compressibility (Cc, Cs) and elasticity index (EI). Mechanical energy was calculated based on penetration resistance tests with a penetrometer needle resembling root geometries. Resultsσpc, Cc and Cs were significantly higher in loam as compared to sand, whereas the factor genotype proved to be negligible. Over time, σpc increased and Cc decreased in loam from 2019 to 2020 and Cs declined in both substrates. Higher mechanical energies were observed in loam and partially in WT. Required energy was higher at 14 cm than at 34 cm depth and decreased from 2019 to 2020 in sand. Airdry sand samples required four times as much energy than those at -50 kPa.ConclusionFor the development of the mechanical traits examined texture proved to be the dominating factor and changes in soil stability could be observed within a short period of time.