A novel 15N tracer model reveals: Plant nitrate uptake governs nitrogen transformation rates in agricultural soils

► A new model for 15N tracer studies including plant N uptake is presented. ► The analytical model is superior to commonly used pool dilution-based calculations. ► 14 processes of the N cycle, including plant uptake of NH4+ and NO3−, were estimated. ► Plant NO3− uptake was governing the overall N cycle over prolonged time periods. ► Nitrification was the main fate of NH4+ although kinetics differed between soils.