If it's copper or zinc, there will be a clear change in the plant's appearance. Recently the products of the taro field of farmer Chen Shui-lien of Ta-chia in Taichung showed changes of color, while the stems and leaves withered.
如果是銅、鋅，作物外表會有明顯變化，近來台中大甲農民陳水連的芋田發生莖、葉枯萎，果實變色，就被台中農改場判定為「鋅中毒」。