Mehlich extractable and total elemental concentrations in South Carolina soils
2006
Franklin, R.E. | Duis, L. | Smith, B.R.
Mehlich-1 and Mehlich-3 extracts of soils collected from two depths at 50 sites distributed across South Carolina were compared with total soil digests to determine whether either soil extract would serve as a reliable indicator of total elemental concentration. Eighteen elements, including several of environmental concern, were measured. The sites were located in five different land-resource regions of the state and had different cropping histories. Compared to the total concentration, recovery ranged from less than 1% of the iron (Fe) to almost 50% of the sodium (Na) for Mehlich-1. Mehlich-3 recovered larger amounts of all elements than did Mehlich-1, but neither extract was a good indicator of total concentration. Although correlations of Mehlich and total concentration were significant for aluminum (Al), cadmium (Cd), copper (Cu), magnesium (Mg), manganese (Mn), and zinc (Zn), only for Cu and Mn was more than 50% of the variation accounted for (R2 > 0.50). There were regional differences in Mehlich concentrations for a few of the elements, but unlike total concentrations, Mehlich concentrations were not correlated with clay content. There were indications that Mehlich-3 is more effective than Mehlich-1 at extracting recently applied Zn, whereas Mehlich-1 is more effective in extracting indigenous Zn. Land cropped for long time periods to cotton had significantly higher Mehlich-3 concentrations than land used for production of other field crops, pasture, or forest products. Pastures had significantly higher concentrations of Cu than other sites. Forest sites had lower concentrations of calcium (Ca), Mg, potassium (K), phosphorus (P), and Zn than other sites, as would be expected because these elements are routinely applied to cropland.
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