Differential Responses of Maize (Zea mays L.) Genotypes to Elevated Plant Density Combined with Deficit Irrigation

High plant density and full irrigation along with the use of high density-tolerant genotype would lead to maximizing maize (Zea mays L.) grain productivity per unit land area. The objective of this investigation was to match the functions of optimum plant density and adequate irrigation with the greatest maize genotype efficiency to produce the highest possible yields per unit area. Six maize inbred lines differing in tolerance to water stress and high density (D) [three tolerant (T); L-20, L-53, Sk-5, and three sensitive (S); L-18, L-28, Sd-7] were chosen for diallel crosses. Parents and crosses were evaluated in the 2013 and 2014 seasons under three plant densities: low (47,600), medium (71,400), and high (95,200) plants ha−1 and two irrigation regimes: water stress (at flowering stage) and non-stress (well watering). The T × T crosses were superior to the S × S and T × S crosses under the water stress–high D environment in most studied traits across seasons. The relationships between the six environments and grain yield per hectare (GYPH) showed near-linear regression functions for the tolerant high yielding group of hybrids with the optimum environment combination was well watering combined with high plant density (95,200 plants ha-1) and a curvilinear relationship for the sensitive low yielding group with the highest GYPH at a density of 71,400 plants ha−1 combined with well irrigation. Cross L20 × L53 gave the highest grain yield in this study under both well watering– high-D (17.05 t ha−1) and well watering–medium-D environment (16.45 t ha−1).