A method to determine the soil bulk density of undisturbed samples with non-isodiametric shape

Abstract

The soil bulk density (ρb) determination is a hard task when large areas are involved and non-isodiametric undisturbed samples analysed. The use of pedotransfer functions (PTFs) can support the estimation of ρb in samples of irregular shape. The objective of this study was to examine three pedotransfer equations in order to estimate ρb of irregular shaped samples taken from a Cambisol, a Nitosol and two Ferralsols and to compare their results to those obtained with other methods, such as excavation, volumetric ring, paraffin sealed clod and computed tomography. In addition, a coefficient of expansion of pores (cp) was introduced to correct the differences that may occur when the total volume of pores is measured in dry or water-saturated conditions. All methods studied generated values of ρb concordant with the most of the evaluated data, while computed tomography presents an exception. The PTF described by a simplified equation exhibited the best correlation with the other methods. The coefficient cp showed up as an appropriate parameter for correcting the total volume of soil samples measured under water-saturated conditions. Thereby, the examined PTFs were efficient as a good alternative for estimating ρb when irregular undisturbed soil samples are utilized.