Temporal nitrogen dynamics in intensively managed loblolly pine early stand development

•Competing vegetation accounted for more N than loblolly if not controlled.•Herbicide was crucial to increase N uptake by loblolly pine.•Expedited growth and N uptake depended upon fertilization early in the rotation.•Increases in N content were not proportional to increases in planting density.•Controls on age-development N use efficiency during early stand development are demonstrated.