Soil sampling bulk-density in the coastal lowlands of South-East Queensland

Abstract

Bulk density is commonly measured in compaction, cultivation, land evaluation and site classification studies in forestry. Typically, measurements are made using a small-diameter core sampler (an integral open drive sampler) which is manually driven into the soil profile. The study reported in this paper was designed to determine the effects of sampler size on bulk density estimates, and to identify optimal sampling intensities for the coastal lowlands of south-east Queensland. Four sampler sizes were tested (internal diameters of 3.48, 4.83, 5.98 and 9.12 cm, and all approximately 10 cm in length). All sampler sizes provided consistent estimates of bulk density for a range of soil types and conditions. The accuracy of bulk density assessment was not improved by increasing sampler diameter beyond 5.98 cm. The results suggested that the core sampler technique can be used efficiently in a wider range of soil conditions than that recommended in the literature. Comparison of variances estimated for the four sampler sizes indicated no significant differences between either sampler size or site, and no significant 'site by sampler size' interaction. A single pooled estimate of variance was therefore used to recommend sampling intensities for coastal lowland soils. With any of the samplers used in this study, five replications will provide a point estimate of bulk density with a precision of ± 0.1 g cm ^-3; at the 95% probability level.