Crop Management Options to Help Increase Maize Grain Carotenoid Levels

Despite breeding advancements in high carotenoid maize, impacts of common crop management on carotenoid levels remain unclear. Our objective was to identify possible crop management options, other than genotype selection, for increasing maize grain carotenoid concentration and to relate them with the resulting flour color. We were also interested in understanding what environmental factors help explain variations in grain carotenoid concentration. The effects of plant population, sowing date, genotype selection, and N fertilization on total grain carotenoid concentration and flour color were tested in different field experiments under rainfed conditions. Genotypes had 25% higher values when sowing date was delayed. However, the response to sowing date was genotype dependent (p < 0.05; an increase from 6 to 57%). Plant populations higher than 8.5 plant m-2 decreased carotenoid concentration by 5% (p < 0.05), while N fertilization showed inconsistent effects (+5 or-12% depending on the environment). The higher concentrations in later sowings were associated with cooler temperatures and a better water balance during grain filling. The impact of management over carotenoid concentration also affected the resulting flour color, modifying its lightness and chromaticity. Results suggest that, in addition to genotype selection, late sowing dates and moderate plant populations can help increase grain carotenoid concentrations.