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The pore space of soil contains the liquid and gas phases of soil, i.e., everything but the solid phase that contains mainly minerals of varying sizes as well as organic compounds. In order to understand porosity better a series of equations have been used to express the quantitative interactions between the three phases of soil.
Soil structure describes the arrangement of the solid parts of the soil and of the pore spaces located between them (Marshall & Holmes, 1979). [1] Aggregation is the result of the interaction of soil particles through rearrangement, flocculation and cementation.
Pore space is that part of the bulk volume of soil that is not occupied by either mineral or organic matter but is open space occupied by either gases or water. In a productive, medium-textured soil the total pore space is typically about 50% of the soil volume. [55]
In fact the pore space of soil is a uniform fractal e.g. a set of uniformly distributed D-dimensional fractals of average linear size L. For the clay soil it has been found that L=0.15 mm and D=2.7. [20] The surface tension of water explains why the water does not drain out of a wet sand castle or a moist ball of clay.
Atmospheric CO 2 concentration is 0.04%, but in the soil pore space it may range from 10 to 100 times that level, thus potentially contributing to the inhibition of root respiration. [66] Calcareous soils regulate CO 2 concentration by carbonate buffering, contrary to acid soils in which all CO 2 respired accumulates in the soil pore system. [67]
Porosity of a soil is a function of the soil's bulk density, which is based on the composition of the soil. Sandy soils typically have higher bulk densities and lower porosity than silty or clayey soils. This is because finer grained particles have a larger amount of pore space than coarser grained particles.
The samples' total volume and pore space volume were measured in order to calculate the porosities. Measuring pore space volume. A helium pyrometer was used to calculate the volume of the pores and relied on Boyle's law. (P 1 V 1 =P 2 V 2) and helium gas, which easily passes through tiny holes and is inert, to identify the solid fraction of a ...
Porosity of surface soil typically decreases as particle size increases. This is due to soil aggregate formation in finer textured surface soils when subject to soil biological processes. Aggregation involves particulate adhesion and higher resistance to compaction. Typical bulk density of sandy soil is between 1.5 and 1.7 g/cm 3. This ...