Particle density of soils refers to the density of the solid particles collectively. It is expressed
as the ratio of the total mass of the solid particles to their total volume, excluding pore spaces
between particles. Convenient unit for particle density are megagrams per cubic meter (Mg/m3), or the
numerically equal grams per cubic centimeter (g/cm3).
Particle density of a soil sample is calculated from two measures quantities, namely, the mass and
volume of the sample. The mass is determined by weighing; the volume, by calculation from the mass and
density of water (or other fluid) displaced by the sample.
Soil bulk density is the ratio of the mass of dry solids to
the bulk volume of the soil. The bulk volume includes the volume of the solids and the pore
space. The mass is determined after drying to constant weight at 105°C, and the volume is
that of the sample as taken in the field.
The method in our laboratory is using core method.
Particle-size analysis (PSA) is a measurement of the size distribution of individual particles in a soil sample. The major features of PSA are the destruction or dispersion of soil aggregates into discrete units by chemical, mechanical, or ultrasonic means and the separation of particles according to size limits by sieving and sedimentation.
Sedimentation analysis relies on the relationship that exists between
settling velocity and particle diameter. It include the pipet method and hydrometer method.
he pipet method is often used as a standard method from which other PSA methods are compares.
Particle-size analysis can be done conveniently with a hydrometer which allows for
nondestructive sampling of suspensions undergoing settling.
An aggregate is a group of primary particles that cohere to each other more strongly
than to other surrounding soil particles. Stability of aggregates is a function of
whether the cohesive forces between particles withstand the applied disruptive force.
The retention between the soil water
content and the soil water suction is a fundamental part
of the characterization of the hydraulic properties of a
soil. The relationship is identified in the literature by
various names, including water retention function, moisture
characteristic, and the capillary pressure-saturation curve.
Soil is mainly composed of minerals and organic matter, like decaying plants and animals, as well as living organisms.
The organic matter in soil derives from plants and animals. When it decays to the point it is no longer recognizable it is called soil organic matter.
The hydraulic conductivity is a measure of a soil's ability to transmit
water. Water movement, whether under saturated or unsaturated
conditions, is highly dependent on the hydraulic conductivity.