On the “Metsubure” symptoms of taro corms

Abstract

Abstract Cultivars of taro (Colocasia antiquorum Schott var. esculanta Engl.), some tolerant to calcium deficiency and some sensitive to it, were cultivated in order to determine the effectiveness of a new fertilization technique (NFT) in volcanic ash soil. The principle of the NFT was to minimize the potassium supply from manures and/or fertilizers and to apply as much calcium fertilizer as possible in acid soils, thereby reducing the occurrence of “Metsubure” corm formation. This technique proved very effective in the Wasehasubaimo cultivar. In the case of the Ishikawawasemaru cultivar, greater applications of potassium promoted growth and resulted in larger yields without physiological disorders. A further experiment was conducted primarily to confirm the effects of potassium and calcium applications with hog manure on the taro yields. The effects of different kinds of nitrogen sources were also observed. Corm yields increased with increasing applications of both potassium and calcium, and the occurrence of “Metsubure” corm formation caused by calcium deficiency was the same as in previous findings. The kind of nitrogen fertilizer applied had no significant effect on yield except in total yield weight. Too much nitrogen application was presumed to stunt the growth of the taro. The yield weight of corms affected by “Metsubure” symptoms ranged from 3,260 to 210 kg/ha. Lime application decreased the incidence of “Metsubure” corm formation, but that of potassium resulted in a more frequent occurrence. The ratios between the NH4-N and K2O content of the taro corms did not show any difference by the treatments, but the K2O/CaO ratios showed large differences both between the corms themselves and between the treatments.