Dry Bulk Density Values Research Articles

Traffic-soil-plant (maize) relations

Twenty-five treatments consisting of three vehicle contact pressures, 62, 41 and 31 kPa (0.63, 0.42, 0.32 kg/cm 2), four numbers of tractor passes (1, 5, 10, 15,) before and after seeding groups, and a control of zero traffic were used to study the effect of soil compaction on corn plant root growth and distribution in a Ste. Rodalie clay soil. The average dry bulk density values for 0–20 cm depths measured during the season varied from a minimum of 0.89 g/cm 3 to a maximum of 1.12 g/cm 3 depending on the severity of the treatment. Root distribution maps were obtained for all the treatments by field measurements coupled with root washing methods. An average root density of 5.7 mg/g of soil in an uncompacted control plot was reduced to less than 2 mg/g in a plot with 15 passes of 0.63 kg/cm 2 contact pressure. Soil penetration resistance values in various plots were compared, and a statistical model was obtained in terms of the traffic treatments, soil moisture content and depth. Yield reductions and penetration resistance were compared to root distrubution density results.

Cole Determination by Thermomechanical Analysis

AbstractThe coefficient of linear extensibility (COLE) is used as a criterion to differentiate vertic from typic subgroups. The ratio, (Lm − Ld) ÷ Ld, in which Lm is the length at 1/3 — bar moisture tension and Ld is the air‐dry length of a soil clod, is used to calculate this coefficient. Length changes can be obtained from measurements of moist and dry soil cores. COLE can also be calculated from moist and dry bulk density values. The objective of the study was to evaluate the use of the thermomechanical analyzer (TMA) for the measurement of soil ped length change as the ped is dried. The TMA unit is available as a plug‐in module for thermal analysis systems. Field moist (approximately at field capacity) and 1/3 — bar soil peds were selected from six soils and analyzed by this method. TMA‐COLE values from 0.126 to 0.010 were calculated from length change values. About 30 min was required for each measurement of field moist peds. This is a rapid procedure for shrinkage estimation since it requires essentially no preliminary preparation.

GAMMA PROBE DRY BULK DENSITIES

The gamma density probe is a useful instrument for measuring water content in small volumes of soil. Essentially, the gamma probe measures the density of the soil and water between a source and a detector. To transpose the gamma densities into water content, the dry bulk density of the soil is needed. A nondestructive method for estimating dry bulk densities for use with the gamma probe is proposed. The procedure is based on the assumption that water content values in a field dry condition were more stable than the dry bulk density values and could be transferred from one point to another. The procedure was successfully used on three areas in Reynolds Creek Experimental Watershed in Southwest Idaho. /Author/