Iodine Agronomic Biofortification of Cabbage (Brassica oleracea var. capitata) and Cowpea (Vigna unguiculata L.) Is Effective under Farmer Field Conditions

Iodine (I) is an essential micronutrient, which plays a critical role in human metabolism. However, its concentration is known to be low in most soils, making it deficient in crops. With most I agronomic biofortification studies conducted under controlled environments, limited information currently exists on this approach of enriching I deficient crops under farmer field conditions. Two-year field experiments were conducted in 2017 and 2018 to examine efficacy of cowpea and cabbage in the uptake of foliar applied potassium iodide (KI) and potassium iodate (KIO3), each with 0, 5, 10, and 15 kg I ha−1 under farmer field conditions. Results indicate that KI was 34% more efficient than KIO3. Iodine concentration increased with application rate. In cabbage, the lowest I concentration (8.2 mg kg−1) was registered at 5 kg I ha−1 with KIO3 while the highest was 109.1 mg kg−1 at 15 kg I ha−1 with KI. Cowpea registered the lowest I concentration of 531.5 mg kg−1 at 5 kg I ha−1 with KIO3 while the highest (5854.2 mg kg−1) was registered at 15 kg I ha−1 with KI. Therefore, cowpea and cabbage can be effectively biofortified through foliar application of both KI and KIO3 under farmer field conditions.