LAUSR

ABSTRACT Sodium calcium ratios are often sufficiently high to limit root growth and result from lower calcium rather than high sodium, and was the focus of this study. A simple model of complex ion formation by magnesium and carbonate was derived, which adequately explained the relationship between pH, calcium, and magnesium, particularly the typical supersaturation of calcium with respect to calcium carbonate. Concentrations of magnesium and calcium declined when excess bicarbonate was applied, and the frequency of adverse sodium/calcium ratios increased. Calcium and magnesium declined proportionately until low concentrations when the proportion of calcium increased. Increased carbonate concentrations could depress calcium and magnesium concentrations to low levels with magnesium being buried in calcium carbonate and unable to redissolve once carbonate levels return to normal. Magnesium soil amendment may be the key to addressing adverse sodium calcium ratios. Plant selection for tolerance to adverse sodium calcium ratios is warranted.