Nutrients Availability in Quality Protein Maize (QPM) Cobs at Various Levels of Nitrogen Application

Background and Objective: The central core of a maize ear (maize cob) represents around 17% of the total biomass of a maize plant. In Sub-Saharan Africa, maize cobs are underutilized even though they are available to most farming households. The study aimed to estimate the proportion of nutrients in various genotypes of Quality Protein Maize (QPM) maize cobs and estimate the variability of these nutrients at different levels of nitrogen application. Materials and Methods: Thirty-two QPM inbred lines were evaluated in a randomized complete block design with two replicates at five nitrogen (N) application rates (0, 30, 60, 90 and 120N) in depleted soil under field conditions. The variances in nutrients estimated among genotypes were analyzed at various levels of treatments using SAS software and Tukey’s test was used for mean separation. Results: Highly significant differences were observed between N levels for all the nutrients estimated except fat, starch and potassium. The total digestible nutrient (TDN) in maize cobs was 76.19 with 1.64% of fat and 34.74% starch at all nitrogen levels. The nitrogen application rate of 30N provided 17% of crude protein, 20% crude fiber, 20% ash, 0.11% P, 0.2% Ca, 0.07% Mg, 180.63 mg kg‾¹ of Fe and 16.44 mg kg‾¹ of Mn. The QPM cobs of genotypes L1, L7, L11, L13, L16, L8, L19, L21 and L27 contained a low amount of Mn, Cu and Mg elements. Conclusion: As 30N application was most effective at the farmer level. The cobs of nine QPM hybrids could be used for animal feeding and mushroom production while the rest could be for soil amendments.