Zinc nutrition in tropical tuber crops: A review

Tropical tuber crops are known for their biological efficiency, climate, soil and pest resilience, quantity and quality starch for the preparation of several industrial value added products. Their inherent yield potential results in the uptake of substantial quantum of nutrients from the soil necessitating their replenishment through external sources. In addition to the major and secondary nutrients, the micronutrient requirement of these groups of crops are very high though deficiency disorders are manifested in extreme cases. Depletion of Zn noticed under continu- ous cultivation of cassava (Manihot esculenta Crantz) over 14 years under a permanent manurial experiment re- sulted in the initiation of Zn-nutrition studies in tropical tuber crops. Extensive studies conducted in the Zn-nutrition of tropical tuber crops especially cassava, sweet potato [Ipomoea batatas (L.) Lam] and elephant foot yam [Amorphophallus paeoniifolius (Dennst.) Nicolson] including Zn content in the different plant parts of other tuber crops over the growth period, Zn status of the soils of the State, Zn in value-added fertilizers developed for el- ephant foot yam and enriched manure prepared from cassava starch factory solid waste, sorption characteristics of Zn, significance of the low-input management strategy involving soil test-based application of Zn for cassava and results of the on-farm trials conducted in some of the above studies are reviewed in this paper.