Effects of Iodine Agronomic Bio- fortification on selected Physiological Characteristics of Cassava in Calabar, Southeastern Nigeria

Field experiments were conducted between November 2011 and May 2014 at the Crop Science Teaching and Research Farm of the University of Calabar, (Southeastern rainforest agro-ecological zone of Nigeria) to determine the effectiveness of Iodine agronomic fortification of cassava. The field experiment was a 2x3x4 factorial experiment arranged in randomized complete block design replicated three times, conducted using two cassava varieties,( TME 419 and TMS 30555); four iodine rates( 0, 2.5, 5.0 and 10.0) kg/ha KI; applied at 8, 10 and 12 WAP. Physiological data were obtained by determination of Iodine content [in cassava tuber]; tuber cyanide content (HCN); Carbohydrate content of tuber; starch content of tuber and tuber protein contents. Iodine absorption and retention in cassava tuber flesh was significantly positively correlated with Iodine doses at the times of application (p0.05 and 0.01). TME 419 retained more Iodine in tissues than TMS 30555 and recorded highest correlation co-efficient at 10WAP. Iodine doses and time of application did not significantly control (P≥0.05) contents of cyanide, carbohydrate and starch in cassava tubers. Protein content was significantly varied in cassava varieties and rate and time of Iodine application influenced tuber protein content. TME 419 produced more tuber protein, Iodine doses of 2.5kg/ha KI and 0kg/ha KI had higher protein content than 5kg and 10kg/ha KI. Application at 8WAP and 10WAP were not significantly different. For favourable physiological cassava characteristics, 2.5kg/ha KI is recommended applied 10 weeks after planting (WAP).