Emergence delay effect on maize (Zea mays L.) nitrogen uptake

Spatial and temporal variability in plant emergence may cause differences in nitrogen (N) uptake by crops leading to a mismatch between plant nitrogen requirements and nitrogen supply, with negative environmental and economic impacts. We aimed to understand N uptake and concentration (%) in unevenly emerged plants by conducting experiments in pre-determined yield stability zones (YSZs) in three farmers’ fields planted to maize (Zea mays L.). We found that maize emergence ranged from 64 to 124.1°C day, with significant variability between YSZ in two of three fields. Maize biomass plant-to-plant variation decreased from maize six leaves stage (V6) to maize silking stage (R1). At maize physiological maturity (R6), biomass ranged from 54 to 736 g plant⁻¹ and was significantly affected by YSZ (p < 0.001). In the cases where late-emerging plants accumulated less N than early emerging plants, this led to altered N partitioning within the plant (i.e., nitrogen harvest index decrease). Although N concentration in the grains remained unaffected by late emergence, the N concentration in the biomass increased. This was likely due to a reduced total biomass and the lack of a N sink (i.e., less yield per plant due to less grain per plant). The absence of variations in N utilization across emergence classes, coupled with the significant impact observed in the YSZ, reinforces the advantages of focusing on N management fitted to YSZ. Understanding the impact that the spatial and temporal variation of plant emergence has on maize N uptake is important in helping to improve N input prescription maps, N-use efficiency, and reduce N losses to the environment.