Abstract:
Knowledge of the particle size distribution of soil can provide valuable
information on many disciplines of soil science, including, pedology
classification, land evaluation, soil plant relationships and soil fertility. The role
played by CaCo3 on dispersion of soil particle is not clear, and the objective of
this work is to help determine the effect of this component on aggregation and
cementation of soils. For this purpose particle size distribution was carried out
with, and without hydrochloric acid treatment on soil types with different
textures, and calcium carbonate content. The clay content and CaCo3 of the soil
samples selected for this work varied between 7-77% and from 0.2-27%
respectively.
The difference in clay content for the hydrochloric acid treated and untreated
samples was insignificant for soil containing 0.2-14% CaCo3.
The cementation of soil particle is initiated when the content of CaCo3 is about
14%. For those samples with more than 14% CaCo3 the difference in clay
content for hydrochloric acid treated and untreated samples was highly
significant.
The test have shown that for routine mechanical analysis of soils the removal of
CaCo3 with addition of hydrochloric acid is unnecessary unless content of CaCo3
exceeds 14%.
The effect of soil type and mode of occurrence of CaCo3 t needs further research
work.
It is interesting to note that this threshold of above 14% CaCo3 approaches the
same content required for the definition of Calcic horizon as is given in USDA
soil classification system as it seems some important change in the
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physicochemical aspects of soils takes place when soil content of CaCo3 reaches
a value of about 15%.
These findings will help improve the laboratory technique of mechanical
analysis, as well as reducing the cost of the test through saving the amount of
Hcl used to remove CaCo3..
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