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' Author:Kwong Ym Chan <br /> Pages: 128- 130 <br />' DOI: 10 1081!1~-ESS-120001632 <br /> Published on: 171Jun12002 <br /> http 11www dekker cornlsdeklabstract--content=a713571738-db=enc <br />' Bulk density(Pb) is defined as the ratio of the mass of a given soil sample(111)to its bulk volume <br />' M The mass is obtained by <br /> drying the sample to a constant weight at 105°C, and the bulk volume is that of soil particles3Plus <br /> pore space at the time of sampling (1) The commonly used SI unit for bulk density is Mg m- <br /> which <br />' which is numerically the same as g on 3 Bulk density Is a key sod physical property and is <br /> required for 1) determining the degree of compactness and hence as a measure of soil structure, <br /> 2) using as an indicator of sod aeration status (together with sod water content), and 3)converting <br /> soil water content and nutnent values from the gravimetnc to the volumetnc basis <br />' Bulk density of sod is dependent on the composition as well as the structural conditions It <br /> therefore tends to vary with the sod's texture,which determines the packing of the soil particles <br /> Sandy sods tend to have higher bulk density(ranged 1 4-1 9 Mg m )than clogs (0 9-1 4 Mg m �} <br /> (Table 1) Volcanic sods and peaty soils tend to have bulk density<1 0 Mg m" because of the <br />' high organic matter levels and special clay minerals for the former and higher organic matter levels <br /> for the latter Furthermore, as field sods are not lust mixtures of primary particles in different <br /> degrees of packing, bulk density is also modified by soil aggregation (sod structure) and soil <br />' organic matter levels Organic matter tends to reduce the degree of compaction For 58 samples <br /> of surface sods in Scotland, a highly significant effect of organic matter is represented statistically <br /> tem=, = I ".055 x ONI r 2) <br />� . by the relationship where is <br /> the maximum bulk density over a range from 1 3 to 1 8 Mg rri 3 and OM is the content of organic <br />' matter over a range of 2%to 10%was obtained (3) <br /> Table 1. Range of bulk density and porosity values in drfferent sods and particle mixtures <br />' Bulk density <br /> Soil/particles mix (Mg m-3) Porosity <br /> Surface soil of wet clay 1 12 0 58 - - <br />' Surface soil of loam 1 28 052 <br /> Sandy subsoil 161 039 <br /> Sandy loam compacted by heavy traffic 19 028 <br />' Spheres of uniform size in open packing 1 39 048 <br /> Spheres of uniform size in dose packing 196 026 <br /> Sandstone 212 02 <br /> Peaty soil 03 - <br /> Volcanic soil <0 9 <br /> 1 <br />