The University of Western Australia: Nedlands, WA. Hunt N and Gilkes R (1992) Farm Monitoring Handbook. NJ McKenzie, HP Cresswell and KJ Coughlan) CSIRO Publishing: Collingwood, Victoria. In: Soil Physical Measurement and Interpretation For Land Evaluation. Please refer to Bulk Density-On Farm Use fact sheet for information on interpreting bulk density results and using this in total nutrient and carbon calculation.Ĭresswell HP and Hamilton (2002) Particle Size Analysis. Both the intact clod and excavation methods are described in detail by Cresswell and Hamilton (2002). The excavation or water replacement method is useful for soils that are too loose to collect an intact core or clod, or for soils containing gravel. This is important to recognise when using bulk density measurements to calculate nutrient levels on an area basis, as an over-estimation will occur. If soil has >10 % gravel or the stones are >2 cm conventional bulk density readings will be inaccurate, as most coarse fragments have bulk densities of 2.2–3.0 g/cm 3 (McKenzie et al., 2002). Total pore space is reduced in soil with abundant gravel and plants are more susceptible to the effects of drought and waterlogging. The presence of gravel has a significant effect on the mechanical and hydraulic properties of soil. It is generally desirable to have soil with a low BD (2 mm) are the coarse fragments and gravel. Both BD and porosity (V pores) give a good indication of the suitability for root growth and soil permeability and are vitally important for the soil-plant-atmosphere system (Cresswell and Hamilton, 2002 McKenzie et al., 2004). Soil BD and porosity (the number of pore spaces) reflects the size, shape and arrangement of particles and voids (soil structure). The average values of air, water and solid in soil are easily measured and are a useful indication of a soils physical condition. The total soil volume is the combined volume of solids and pores which may contain air (V air) or water (V water), or both (figure 1). The soil bulk density (BD), also known as dry bulk density, is the weight of dry soil (M solids) divided by the total soil volume (V soil). Bulk density can be used to calculate soil properties per unit area (e.g.Sandy soils are more prone to high bulk density.Bulk density increases with compaction and tends to increase with depth.Soils with a bulk density higher than 1.6 g/cm3 tend to restrict root growth.Bulk density is the weight of soil in a given volume.
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