EFFECT OF MAGNESIUM ON EARLY TARO GROWTH

Little research has been conducted on magnesium (Mg) nutrition of tare [Colocasia esculenta (L.) Schott cv. 'Bun Long']. In this study, we e valuated the effects of varying levels of Mg (0.0, 0.05, 0.1, 0.2, 0.4 , and 0.8 mM) on tare plants grown hydroponically for 33 days. Magnesi um treatment effects were evaluated for dry matter biomass, leaf area, and N, P, K, Ca, Mg, Na, Mn, Fe, Cu, Zn, and B concentrations of old and young leaves. Dry matter of leaves (young, old, and total), roots, corms, petioles, and total biomass were significantly higher in all p lus-Mg treatments than in the zero-Mg treatment. These same biomass pa rameters were not different among treatments with Mg (0.05 to 0.8 mM). Leaf area (young, old, and total) did not differ significantly with v arying levels of Mg. A quadratic model described the relationship betw een Mg levels in leaves and solution Mg (r(2) = 0.99). Young and old l eaf Mg concentrations did not differ. Total leaf Mg concentration rang ed from 0.07% to 0.42% for the lowest and highest Mg levels in solutio n, respectively. Leaf Mg effects on total leaf DM was best fit using s egmented regression (r(2) = 0.95), with a corresponding critical leaf Mg concentration (95% of maximum predicted leaf DM) of 0.14%. No signi ficant interactions were observed between Mg and other mineral nutrien ts. Critical leaf Mg concentration is based on the vegetative growth s tage of taro and could be a key index for taro producers who emphasize vegetable leaf, rather than corm production.