ABSTRACT:

Three trials were conducted during the 2020, 2021 and 2022 rainy season at the Institute for Agricultural Research (IAR) farm, Samaru in the Northern Guinea Savannah zone of Nigeria to evaluate the growth response of two open pollinated and two hybrid varieties to varying nitrogen levels and plant spacing in Kaduna. The treatment consisted of four maize varieties (SAMMAZ 15, 1 SAMMAZ 51, OBASUPER 13 and SC 651) three Nitrogen rates (90, 120 and 150) kg ha- and three plant spacing (75 X 30, 75 X 40 and 75 X 50). The experiment was laid out in a split plot design with a combination of nitrogen and population density in the main plot and variety in the subplot with three replications. The study indicated that maize variety exerted a stronger influence on nitrogen flag leaf content than nitrogen rate or plant spacing across the three years of study. SAMMAZ 15 and SAMMAZ 51 consistently recorded superior nitrogen flag leaf content in most seasons and in the combined analysis, indicating their better efficiency in nitrogen uptake. Nitrogen application levels did not significantly enhance nitrogen flag leaf content, suggesting that moderate fertilization may suffice under the prevailing conditions. Similarly, plant spacing had inconsistent effects across years, implying limited influence on nitrogen accumulation in maize flag leaves. The significant interactions between variety, nitrogen, and spacing in certain years suggest that varietal adaptation and environmental factors jointly affect nitrogen utilization efficiency. Overall, open-pollinated varieties demonstrated stable nitrogen flag leaf content across environments, underscoring their potential for sustainable maize production under variable nitrogen regimes.