Empirical Analysis of Nitrogen Use Efficiency Variation Among Maize Genotypes Under Low-N Soils in the North Central Zone

Nitrogen use efficiency is a critical breeding and agronomic target for reducing fertiliser input costs and environmental nitrogen losses in Nigerian maize systems, and characterising the genetic variation in NUE among diverse maize genotypes under the low-nitrogen soils of the North Central zone provides important data for both breeding programme design and agronomic recommendation. This study empirically analysed nitrogen use efficiency variation among 20 maize genotypes (12 tropical quality protein maize lines, 4 hybrid checks, and 4 local varieties) under two nitrogen supply levels (0 and 90 kg N ha-1) at Abuja (FCT) and Kogi State research farms. A split-plot design with nitrogen as the main plot and genotype as the sub-plot was used over two seasons (2022 and 2023) with three replications. Grain yield, nitrogen uptake efficiency, nitrogen utilisation efficiency, agronomic nitrogen use efficiency, and NUE index were calculated. Results showed significant genotypic variation in agronomic NUE at 90 kg N ha-1, ranging from 8.4 to 24.7 kg grain kg-1 N applied. QPM line TZEQI-45 combined high NUE (22.4 kg kg-1) with high yield at both N levels. Local variety Oloyin had the highest relative yield at zero N (91 percent of its 90 N yield), indicating constitutive low-N adaptation. The study fills a data gap in NUE characterisation for tropical maize in Nigeria and recommends TZEQI-45 as a high-NUE parent for breeding programme crossing and Oloyin for further physiological characterisation of low-N adaptation mechanisms.

Keywords: nitrogen use efficiency, maize genotypes, low-nitrogen soil, North Central Nigeria, NUE variation