Maize cultivars with improved grain yields under nitrogen (N) stress are desirable for sub‐Saharan African maize growing environments. This study assesses N uptake, N utilization, and the genotype × environment (G × E) interaction of 16 tropical maize (Zea mays L.) hybrids differing in grain yield under low‐N conditions. Hybrids were evaluated under low‐N, medium‐N, and high‐N at Harare, Zimbabwe, in 2003 and 2004 and at Kiboko, Kenya, in 2003. At maturity, N accumulation in the aboveground biomass ranged from 47 to 278 kg N ha−1 in various experiments. Grain yields ranged from 1.5 to 4.3 Mg ha−1 and 10.6 to 14.9 Mg ha−1 for the same experiments, respectively. Significant G × E interactions were observed which became more pronounced as the difference in N stress intensity between two environments increased. High grain yield under low‐N was consistently associated with higher postanthesis N uptake, increased grain production per unit N accumulated, and an improved N harvest index. Additive main effect and multiplicative interaction analysis identified hybrids with specific adaptation to either low‐N or high‐N environments. Several hybrids produced high yields under both low‐N and high‐N conditions. More detailed studies with these hybrids are required to examine the underlying physiological mechanisms contributing to the N‐use efficiency.

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The cultivation of N‐efficient oilseed rape cultivars could contribute to a reduction of the large N balance surpluses of this crop. To facilitate the breeding process of N‐efficient cultivars, the identification of secondary plant traits correlating with N efficiency is necessary. The objectives of this study were to investigate leaf senescence and N uptake parameters of oilseed rape cultivars and doubled haploid (DH) lines with contrasting N efficiency in a short‐term nutrient solution experiment and to relate these results to their performance in field experiments. In the nutrient solution experiment, genotypes differed in leaf senescence of fully expanded leaves and maximum N uptake rate per unit root length under low N supply. A high maximum N uptake rate seemed to have contributed to delayed leaf senescence by enhancing N accumulation in leaves. Also in the field experiments, genotypes differed in leaf senescence after flowering at limiting N supply. Additionally, the most N‐efficient DH line was able to adapt leaf photosynthetic capacity to the low‐light conditions in the canopy during flowering. N efficiency (grain yield at limiting N supply) was positively correlated with delayed leaf senescence both in nutrient solution and field experiments. It is concluded that important leaf and root traits of N‐efficient cultivars are expressed in short‐term nutrient solution experiments, which may facilitate the selection of N‐efficient cultivars.