Elevating plant density and improving N fertilizer rate for high density-tolerant genotype can maximize maize (Zea mays L.) grain productivity per unit land area. This investigation’s objective sought to evaluate the effects of stresses resulting from increasing plant density combined with reducing N application rate on traits of eight inbred lines and their diallel F₁ crosses. Choosing eight maize inbred lines differing in tolerance to low N and high density (D) were samples for diallel crosses. Parents and crosses’ evaluation ensued in the 2020 and 2021 seasons under three plant densities: low (47,600), medium (71,400), and high (95,200) plants/ha, and three N fertilization rates: low (95 kg N/ha), medium (285 kg N/ha), and high (476 kg N/ha). Elevating plant density from 47,600 to 71,400 and 95,200 plants/ha caused a significant decrease in grain yield/plant by 25.43% and 30.15% for inbred parents and 17.92% and 25.65% for F₁ crosses, respectively. This reduction correlated with significant decreases in all yield components but caused a notable increase in grain yield/ha by 13.69% and 27.33% for inbreds and 20.99% and 44.69% for F₁ crosses, respectively. The best combination of plant population density and N level for giving the highest grain yield/ha was high N (476 kg N/ha) × high density (95,200 plants/ha) for all inbreds and all F₁ crosses.

Keywords: Maize (Zea mays L.), high-density, low-N, unit area productivity

Key findings: The results will help maize (Zea mays L.) breeders match the functions of optimum plant density with adequate nitrogen fertilizer application to produce the highest possible yields per land unit area with the supreme maize genotype efficiency.