Browsing by Author "Omara, Peter"

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    Biochar Applied with Inorganic Nitrogen Improves Soil Carbon, Nitrate and Ammonium Content of a Sandy Loam Temperate Soil
    (MDPI, Basel, Switzerland, 2022-02-23) Omara, Peter; Aula, Lawrence; Otim, Fred; Obia, Alfred; Souza, Joao Luis Bigatao; Arnall, Daryl Brain
    Biochar is suggested to improve soil properties. However, its combination with inorganic nitrogen (N) fertilizer in temperate soils is not well understood. This study compared the effect of fertilizer N-biochar-combinations (NBC) and fertilizer-N (FN) on total soil N (TSN), soil organic carbon (SOC), soil nitrate (NO3−–N), and ammonium (NH4+–N). Soil samples were taken from experiments at Efaw and Lake Carl Blackwell (LCB), Oklahoma, USA with ten treatments consisting of three N rates (50, 100, and 150 kg N ha−1) and three biochar rates (5, 10, and 15 t ha−1). Results at Efaw showed greater TSN and SOC under NBC compared to FN by 3 and 21%, respectively. No percentage difference was observed for NH4+–N while NO3−–N was lower by 7%. At LCB, TSN, SOC, NO3−–N, and NH4+–N were higher under NBC by 5, 18, 24, and 10%, respectively, compared to FN. Whereas application of biochar improved SOC at both sites, NO3−–N and NH4+–N were only significant at LCB site with a sandy loam soil but not at Efaw with silty clay loam. Therefore, biochar applied in combination with inorganic N can improve N availability with potential to increase crop N uptake on coarse textured soils.
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    Iodine Agronomic Biofortification of Cabbage (Brassica oleracea var. capitata) and Cowpea (Vigna unguiculata L.) Is Effective under Farmer Field Conditions
    (Agronomy MDPI, 2019-11-23) Ojok, Joe; Omara, Peter; Opolot, Emmanuel; Odongo, Walter; Olum, Solomon; Gijs, Du Laing; Gellynck, Xavier; De Steur, Hans; Ongeng, Duncan
    Abstract: 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.