Nitrogen (N) is often the most limiting mineral nutrient for taro growth. Two experiments were carried out under hydroponics conditions to determine the effects of varying solution N levels and N form on taro ( Colocasia esculenta L. Schott cv. Bun Long) growth and foliar nutrient concentrations for 42 days. In the first experiment, taro plants were grown at six NH 4 NO 3 levels (0, 0.25, 0.5, 1.0, 2.0, and 4.0 m m N). In the second experiment, taro plants were grown at a total N level of 3 m m with five nitrate (NO 3 -): ammonium (NH 4 +) percent molar ratios (100:0, 75:25, 50:50, 25:75, and 0:100). In the N level experiment, dry matter and leaf area increased up to 2 m m N and then decreased at the highest N level. The reduced growth of taro at the highest N level was attributed in part to a high NH 4 + level that reduced uptake or translocation of cations, such as Ca 2+ , Mg 2+ , and Mn 2+ . Nitrogen concentration in leaf blades increased with increasing N levels. The critical foliar N concentration that coincided with 95% of maximum growth based on a quadratic model was 40.4 g·kg -1 (dry weight basis). In the N form experiment, NO 3 -: NH 4 + ratios of 75:25 or 100:0 favored greater plant growth compared to other treatments. Taro plants grown in NH 4 +-rich solutions drastically acidified the solution pH, and had retarded growth and smaller leaf area compared to those grown in NO 3 --rich solutions.