Effect of Calcium Carbonate on Dispersion of Soil Particles

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 6 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.. 7