MICRONUTRIENT TOXICITY BUFFALOGRASS

The growth responses of buffalograss [Buchloe dactyloides (Nutt.) Enge lm.] to elevated micronutrient levels in the fertilizer solution were investigated. Seedling plants established in peat-lite mix in 11-cm (0 .6 L) pots in the greenhouse were irrigated with solutions containing 0.5, 1, 2, 4, 6, 8, or 12 mM of boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), or zinc (Zn). The control solution contained (in mu M): 20 B, 0.5 Cu, 40 Fe, 10 Mn, 0.5 Mo, and 4 Zn. A standard macronutrient concentration was used for all treatme nt solutions. Boron and Mo induced visual toxicity symptoms more readi ly than other micronutrients. Boron toxicity was characterized by chlo rosis often accompanied by bleached leaf tips, while Mo toxicity resul ted in leaf necrosis. The lowest levels that induced visual foliar tox icity were 0.5 mM B, 2 mM Cu, 4 mM Fe, 6 mM Mn, 1 mM Mo, and 4 mM Zn. Chloride did not induce foliar abnormalities in the concentration rang e tested. Biomass yield was reduced when the nutrient solution contain ed 2 mM B, 6 mM Cu, or 2 mM Mo. Elevated levels of Cl, Fe, Mn, and Zn did not alter dry matter yield. The relationship between the nutrient and tissue concentrations was determined for each microelement.