Manganese Deficiency and Toxicity Levels for ‘Bragg’ Soybeans1

Abstract

AbstractThe lower and upper critical Mn levels in soybeans [Glycine max (L.) Merr.], which are not documented, were determined to provide guideline values for estimating the Mn status from deficiency through toxicity. Soybean (‘Bragg’) was grown in Hoagland nutrient solution with 14 Mn levels from 0 to 50,000 μg/liter. The plants were grown in the greenhouse for 33 days, harvested and analyzed for Mn.The lower critical levels where Mn is required at minimum concentration for maximum growth ranged from 9 to 11 μg/g in blade 1 (young) and blade 5 (old), respectively. Blade 3 was the most recently matured leaf and is suggested as the tissue to sample for plant analysis. The lower critical Mn level for blade 3 is 10 μg/g. The upper critical level where maximum Mn concentration in blade tissue can be tolerated for maximum growth ranged from 100 to 250 μg/g in blade 1 to 5, respectively. The upper critical Mn level for blade 3 was 160 μg/g. For the ‘Bragg’ cultivar maximum growth was attained from 10 to 160 μ/g Mn in blade 3. The distribution of Mn was low (3 to 7 μg/g) and uniform when plants were under Mn stress. With adequate Mn, the Mn concentration in blade increased with tissue age.