Nutritional Deficiencies of Yams (Dioscorea spp.) and Related Effects on Yield and Leaf Composition

Abstract

Deficiencies in the nutrition of the yam (Dioscorea rotundata) cultivar Habanero were studied in the greenhouse using sand culture. Symptoms were produced by the omission in the nutrient solution of one of each of the following elements: nitrogen, phosphorus, potassium, calcium, sulfur, magnesium, iron, manganese, and boron. Lack of nitrogen, phosphorus, potassium, calcium, or sulfur restricted growth and tuber yield significantly. The most striking foliar symptoms were produced in plants lacking potassium. Necrotic spots, which appeared along the margins of well developed leaves, soon coalesced and produced rolling of margins and tips. In advanced stages, the whole plant showed a burnt appearance followed by shedding of foliage. Plants lacking magnesium showed an exhuberant growth despite developing a marked interveinal chlorosis in the older leaves on the bottom half of the plant and tuber formation was negligible. Lack of calcium caused deformation and severe damage to the skin of tubers which were rough and corky. Lack of iron, manganese, and boron resulted in significantly reduced growth and tuber formation. Mild chlorosis appeared in leaves of minus iron and manganese treatments. Lack of boron caused brown rot inside the tubers. Leaf analyses indicated that omission of some nutrient elements influenced the absorption of others and/or their accumulation in the leaves.