Background and aims In environments with low potential for maize production, late sowing and low plant densities can encourage the expression of vegetative (tillering) and reproductive (prolificacy) plasticity. However, limited nitrogen (N) fertilization often restricts the expression of these mechanisms. This study aimed to compare N uptake, internal N efficiency for biomass and grain (NIEB, and NIEG), N harvest index, grain harvest index (HI), and grain yield (GY) among maize phenotypes that differ in vegetative–reproductive plasticity under contrasting growth conditions during the tillering and prolificacy expression periods.Methods Three irrigated field experiments were conducted across different growing seasons using four maize hybrids, including plastic phenotypes exhibiting tillering, prolificacy, and a combination of prolificacy + tillering, and a non-plastic phenotype. These treatments were grown at a density of 3 plants m− 2 under a soil N availability of 370 kg N ha− 1. Shading treatments (growth-limited conditions) were applied for approximately two weeks at different phenological stages, alongside a non-shaded control (potential growth conditions).Results Under potential growth conditions, crop N uptake at R6 did not differ among phenotypes. However, the tillering phenotype showed the highest NIEB, whereas the prolific phenotype had the highest NIEG. In contrast, the flex phenotype had the lowest NIEG. Similarly, under early vegetative growth restrictions, the flex phenotype achieved the lowest NIEB, whereas the prolific phenotype maintained higher values of NIEG and HI values around flowering.Conclusions Vegetative and reproductive plasticity differentially shaped maize N economy. Tillering enhanced NIEB under favorable conditions, whereas prolificacy stabilized NIEG and HI under growth restrictions around flowering.