Effects of Nitrogen Rates on Nitrogen use Efficiency of Low-Nitrogen Tolerant Maize (Zea mays L.) Varieties

Maize is a nitrogen-demanding crop whose productivity is strongly influenced by nitrogen (N) availability. However, the high cost and limited accessibility of nitrogen fertilizers necessitate the development of maize cultivars with improved nitrogen use efficiency (NUE), particularly under low-input systems. This study evaluated the effects of varying nitrogen rates on NUE indices and yield performance of low-nitrogen tolerant maize varieties. Field experiments were conducted during raining period (May to July) 2012 at the Teaching and Research Farm of the Institute of Food Security, Environmental Resources and Agricultural Research, Federal University of Agriculture, Abeokuta (Opeji), and MATKIS Farm, Eruwa, Oyo State, Nigeria. Six maize varieties (M0926-6, M0926-9, M1026-10, OBA 98, SUWAN-1-SX, and OBA SUPER 2) were evaluated under four nitrogen rates (0, 15, 30, and 45 kg N ha⁻¹) in a 6 × 4 × 2 factorial arrangement (variety × nitrogen rate × location) fitted into a randomized complete block design with three replications. Data were collected on physiological efficiency (PE), nitrogen use efficiency (NUE), nitrogen uptake efficiency (NUpE), recovery efficiency (RE), cob yield, grain yield, 100-grain weight, and stover yield. Data were analyzed using analysis of variance (ANOVA) in GenStat (12th edition), and means were separated at p ≤ 0.05. Application of 45 kg N ha⁻¹ significantly increased NUE across varieties, while variety M1026-10 recorded the highest nitrogen uptake efficiency (60.9 kg kg⁻¹). Application of 15 kg N ha⁻¹ significantly improved physiological efficiency (228.0 kg kg⁻¹) and recovery efficiency (0.508). Nitrogen × location interaction significantly affected PE and RE, with the highest values recorded at Eruwa. Overall, application of 45 kg N ha⁻¹ enhanced nitrogen use efficiency and yield performance of low-nitrogen tolerant maize varieties under the studied environments.