Manganese and iron toxicities dependent on soybean variety

Abstract

Tolerances to Fe and Mn were determined with ''Bragg'' and ''Forrest'' (Mn intolerant) and ''T203'' and ''Lee'' (Mn tolerant) soybean (Glycine max. (L.). ''Bragg'' was Fe efficient; ''Forrest'' and ''T203'' were equally Fe-inefficient plants. The soybeans were grown in nutrient solutions with 1.0 and 2.0 mg Fe/l, and with 0.33 and 5.1 mg Mn/l as variables, respectively. ''Bragg'' soybeans developed Fe toxicity symptoms with 2.0, but not with 1.0 mg Fe/l. ''Forrest'', ''Lee'' and ''T203'' did not develop Fe toxicity symptoms on either treatment. ''Bragg'' and ''Forrest'' soybean developed more severe Mn toxicity symptoms than ''Lee'' or ''T203'' soybean when grown on nutrient solutions with 5.1 mg Mn/l. Approach grafts showed that Mn tolerance apparently is controlled in the plant tops. Both Mn intolerant and tolerant soybean tops contained about the same concentration of Mn, but Mn tolerant tops contained more K and roots contained less Fe than Mn intolerant tops and roots. When Fe and Mn toxicities are not economically correctable, tolerant soybean varieties may be selected in order to make the plant compatible with the soil.