Abstract
Eight maize (Zea mays L) hybrids were grown under five N levels with or without the nitrification inhibitor, nitrapyrin (2‐chloro‐[6‐trichloro‐methyl] pyridine), to evaluate N interactions relative to yield performance, N use efficiency, grain protein concentration, and kernel texture. Results indicate that maize hybrids can be grouped into three categories based on grain yield: (1) low N‐responsive types which reach their maximum yield with 134 kg ha^−1^ of applied N; (2) intermediate types that respond to moderate N levels (134 to 201 kg N ha^−1^); and (3) high N‐responsive types that respond to higher levels of N (201 kg N ha^−1^). High N‐responsive types, in general, increased yield with nitrapyrin treatment at all levels of N. Crop N utilisation efficiency for high N‐responsive hybrids decreased, but was static for low N‐responsive hybrids as N fertiliser increased. In general, as the grain yield of a hybrid increased in response to N, the concentration of protein in the kernel increased; although grain yields and protein concentration are negatively correlated among hybrids. Increased kernel translucence, an indicator of kernel hardness induced by N fertiliser, correlated highly positive with zein proteins. Isoelectric focusing analysis showed that increases in zein were primarily due to a quantitative increase in α‐ and γ‐zein polypeptides. This study indicates that hybrids are different in their N requirements for maximum yield. Low N conditions not only restrict grain yield but also affect kernel textural quality.