Precision, accuracy, and efficiency of four tools for measuring soil bulk density or strength.

Abstract

AuthorsMonitoring soil compaction is time consuming. A desire for speed and lower costs, however, must be balanced with the appropriate precision and accuracy required of the monitoring task. We compared three core samplers and a cone penetrometer for measuring soil compaction after clearcut harvest on a stone-free and a stony soil. Precision (i.e., consistency) of each tool at depths of 0-10, 10-20, and 20-30 cm was determined from two adjacent samples at 21 or more sampling points in each harvested location. Because one bulk density (D b ) sampler provided a continuous sample of each decimeter depth, it was designated as the standard; thereby, the relative accuracy and bias of the two shorter core samplers could be calculated. Both shorter samplers overestimated D b as determined by the standard. At least 15 penetrometer samples could be taken and processed in the time required for three D b samples to the same 30-cm depth. Precision of measurements taken by the cone penetrometer, however, was clearly less than that with any of the D b samplers. Based on time requirements and precision of each tool, we examined the efficiency of double sampling (using a combination of penetrometer and core sampler) for estimating D b . Results from the stone-free soil indicated an advantage in both precision and efficiency in applying double-sampling theory to estimate D b rather than sampling exclusively by the more time-consuming core samplers.Keywords: Bulk density, measurement precision, relative accuracy, cone penetrometer, soil strength. SummarySoil bulk density (D b ) is the ratio of mass of dry solids to bulk volume of soil. Bulk density, expressed as Mg•m -3 or g•cc -1 , is commonly used to measure soil compaction. An increase in D b indicates that movement of air and water within the soil has been reduced, and that the soil may be less favorable for plant growth or be more likely to erode. Soil compaction also can be indicated by a penetrometer (PEN), a device forced into the soil to measure its resistance to vertical penetration. Soil strength, as measured in kPa by a PEN, is related crudely to soil resistance as encountered by roots. Because PEN readings can be strongly dependent on soil moisture content, field sampling for comparative purposes should be done when soils are near field capacity.Our general objective was to compare precision and efficiency of four tools conventionally used to monitor soil compaction. We compared three bulk density samplers and a cone penetrometer for measuring soil compaction over a range of sampling conditions in two young forests. Both stands had been planted after clearcutting and yarding by crawler tractors (D-8) in winter on wet silt loam soils. Both study locations were sampled during the spring rainy season; therefore, soils were probably at or near field capacity. Sampling points for each tool were assigned by subdividing each potential sampling plot, a 25-x 100-cm rectangle, into four equal-sized squares and randomly allocating a tool to each square. Two subsamples (replica...

The long-term effects of silvicultural thinning and partial cutting on soil compaction in red pine (Pinus resinosa Ait.) and northern hardwood stands in the northern Great Lakes Region of the United States

“…Penetrometer measurements are used as an index of soil resistance to root penetration, and are inversely related to pore volume. In some soils penetrometer tests can indicate compaction has occurred when no difference in soil bulk density is found (Sands et al 1979;Alban et al 1994;Miller et al 2001). Hydraulic conductivity, which measures the rate of saturated water flow, is also an indirect measure of total soil pore space and pore size.…”

“…High soil moisture contents during our late spring sampling period would also reduce the sensitivity of soil PR measurements to differences in soil compaction (Sands et al 1979), and may have masked treatment effects. Soil PR values inherently have high variability (Fritton 1990, Miller et al 2001, and this would be compounded by the rock-fragment content of the hardwood soil.…”

“…Bulk density, or the mass of soil per unit volume, is the most commonly accepted measure of soil compaction, and is a soil variable that indirectly measures water and nutrient availability, gas exchange and root activity (Miller et al 2001;Powers 2006). However, bulk density alone may not be an accurate metric in some soils, and soil penetration resistance (PR) tests are often used, either alone or in conjunction with bulk density measurements, to estimate soil compaction (Fritton 1990;Powers et al 1998).…”

Light Intensity and Soil Compaction as Influenced by Ecotourism Activities in Pahang National Park, Malaysia

“…Soil compaction is often characterized by changes in soil bulk density, typically expressed in Mg/m 3 or g/cc. Soil density is also related to soil resistance, which can be measured using a penetrometer much more rapidly than bulk density can be obtained [19]. Some soils are difficult to sample consistently due stony, light-textured or highly friable soils by hammer-type bulk density samplers using corers and rings.…”

La regeneración natural del pino silvestre (Pinus sylvestris L.) en el Valle del Lozoya (Madrid): germinación y supervivencia inicial

“…Debido a la presencia de multitud de factores muy intercorrelacionados, esto no implica taxativamente que en un suelo duro las raíces no vayan a desarrollarse o que en uno blando vayan a hacerlo. Sin embargo, a grandes rasgos tiene sentido esperar que, llevando a cabo un muestreo suficientemente intenso de RP (asequible, teniendo en cuenta la facilidad de medición), sea posible caracterizar la superficie de un monte en un momento puntual de acuerdo con un gradiente de idoneidad para el crecimiento radical en relación con su estado de compactación (Miller et al, 2001;Schmalz et al, 2013;Steber et al, 2007). Si el muestreo se lleva a cabo durante el período en el que el crecimiento de la masa debería ser máximo, la imagen obtenida nos proporciona una idea de la idoneidad real del suelo en cuanto a dureza para el crecimiento radical.…”