MINERAL NUTRIENT DISORDERS OF ROOT CROPS OF THE PACIFIC - PRELIMINARY-OBSERVATIONS ON SWEET-POTATO (IPOMOEA-BATATAS)

Solution culture was used to characterise deficiencies or toxicities o f several essential elements in Ipomoea batatas cv. Wanmun, and to def ine the critical concentrations of these elements in young mature leav es during vegetative growth. Tentative critical concentrations for def iciency, expressed on the basis of dry weight of leaf blade, were: nit rogen 3.8%, phosphorus 0.17%, potassium 2.4%, magnesium 0.12%, mangane se 20 mu g/g and zinc 10 mu g/g. For manganese and zinc toxicities it was possible only to designate the range within which the critical con centration occurred. Visible symptoms are briefly described.