A comparative evaluation of the Mississippi soil test method for determining available manganese, magnesium, and calcium

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Abstract
Soil Samples (72) were collected from the Delta, Hill, and Northeast Blackland areas of Mississippi. Chemical analyses for manganese, magnesium, and calcium were made using the Mississippi Soil Test Solution (MSTS) and several other extracting solutions chosen for comparison. For the determination of available soil manganese, the MSTS proved to be as effective as either the Double Acid (0.025 N HCl in 0.05 N H2SO4) or 0.1 N H3PO4. The acid extractants removed more manganese than 1 N NH4OAc (pH 7.0) and therefore included forms that are not exchangeable. The methods studied for magnesium determinations were equilibrium extraction with 1 N NH4OAc, MSTS, Double Acid, 0.25 N CaCl2, and leaching with 1 N NH4OAc. All methods were highly correlated and therefore would be equally effective in determining available soil magnesium. Since MSTS and equilibrium extraction with 1 N NH4OAc removed similar amounts of magnesium from the soil, the same calibration can be used. Calcium determinations were made using equilibrium extraction with 1 N NH4OAc, MSTS, and Double Acid, and by leaching with 1 N NH4OAc. All methods proved effective in measuring available soil calcium on acid soils.

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