Empirical Relationships Between Prismatic SoilStrength Index and Cone Index

摘要

We developed a horizontally operating on-the-go soil strength profile sensor (SSPS)to measure within-field spatial variability in soil strength at five depths up to 50 cm. Forcedivided by the base area of the sensing tip of the SSPS was defined as a prismatic soil strengthindex (PSSI, MPa), analogous to the cone index (CI, MPa) of a vertically operating conepenetrometer. This study was conducted to obtain empirical relationships between PSSI and CIdata collected in an indoor soil bin and two research fields. In the soil bin tests, linearrelationships were found between CI and PSSI. Field data showed that both CI and PSSI weregenerally greater with higher bulk density, lower apparent soil electrical conductivity (ECa, wherelower values indicate coarser soil texture), and lower gravimetric soil water content.Relationships were different when the data were classified into sub-groups by operating depthand ECa range. CI prediction models with the highest coefficients of determination wereobtained at 30-cm and 40-cm depths. The effects of PSSI and its interaction with other variableswere major factors in the models obtained at these depths . Including operating depth in theregression model increased coefficients of determination from 0.35 to 0.45 and from 0.51 to0.53 for the two test sites.