Assistant Professor University of Idaho Aberdeen, Idaho
Nitrogen (N) management remains a critical aspect of potato production, particularly for the effect it has on yield, size profile, and tuber set, all of which need to meet stringent quality demands of processing and table stock industries. This study examined the effects of N rate and application schedule on the total yield of Teton Russet and Russet Norkotah-278 in Aberdeen, Idaho. Four N rates (0, 160, 200, and 240 lb./acre) were applied based on two application schedules: weekly and bi-weekly. The applications were further split based on growth stage with 25% applied during tuber initiation, and 25% during tuber bulking. Fertilizer was applied between 100% crop emergence [35 days after planting (DAP)] and 96 DAP, with vines terminated at 115 DAP. Both cultivars showed similar response patterns across all N rates and application schedules. Teton Russet consistently yielded higher than Russet Norkotah-278 at all N rates with yield advantages of 30.6% at 0N, 22.5% at 160N, 21.0% at 200N, and 27.8% at 240N. Yield increased with N rates of 160, 200, and 240 lb./acre compared to the control (0 N). A bi-weekly application of 160 lb./acre produced higher yields than the same N weekly applications, whereas at 200 lb./acre, weekly applications yielded higher than bi-weekly treatment. However, increasing N to 240 lb./acre resulted in no further yield gains, with yields similar to 160 lb./acre. Teton Russet showed no yield differences at 240 lb./acre across application schedules. With an average residual nitrogen of 38.3 lb./acre at emergence, these results highlight that maximum yields were achieved at 160 lb./acre with bi-weekly application and at 200 lb./acre with weekly application, indicating that while increasing N rate can increase total yield, N effects may depend on cultivar and an optimal balance between N rate and application scheduling for yield optimization.
