Fertilizer nitrogen uptake efficiencies for potato as influenced by application timing

Estimation of N uptake efficiency of fertilizer applications at different growth stages of crop plants is critical to develop management recommendations that enhance fertilizer use by minimizing N losses. In this study, the N-fertilizer uptake efficiency (FNUE) of two chipping potato (Solanum tuberosum L.) varieties ('Atlantic' and 'FL1867') under three typical fertilizer application timings was investigated. All treatments received a total of 225 kg ha(-1) of N throughout the season, split into three applications of 75 kg ha(-1) as ammonium nitrate (NH4NO3) applied at pre-plant, plant emergence and tuber initiation. FNUE at each application timing was evaluated by the substitution of conventional N-fertilizer by isotope labeled ammonium nitrate ((NH)-N-15 (4) (15) NO3). Total tuber yield was similar between the two varieties at 48.8 and 37.5 Mg ha(-1) in 2013 and 2014, respectively. Likewise, the overall FNUE was also similar at 45 % across both varieties and years. FNUE was 11 % for the pre-plant application, while 62 % for the applications at emergence and tuber initiation stages. Since a small fraction of the N applied at pre-plant was recovered in the plant, N fertilizer application closer to the potato planting may increase the FNUE.