Stacking and intersecting nitrogen 4Rs on potato: Nitrogen use efficiency

Abstract The 4Rs of nutrient management are agronomic guidelines with an aim to balance the economic, social, and environmental outcomes of major cropping systems. The objective of this study was to evaluate individual and stacked 4R management practices and their effect on nitrogen use efficiency (NUE) in “Russet Burbank” potato ( Solanum tuberosum L.) at a field trial near Grace, Idaho, in 2020 and 2023. Nitrogen (N) fertilizer treatments included all combinations of two sources (urea or polymer‐coated urea [PCU]), two rates (82% or 100% of the recommended rate), and/or two timing/placements (all applied at emergence or 84% at emergence + 16% fertigation simulation) compared to an untreated control. Overall, potato was responsive to N for plant biomass and N concentration. There were efficiency increases in four NUE metrics for the reduced rate compared to the full rate of urea with a single application timing. There were no observed differences between any of the 4R treatments for any of the 16 NUE metrics determined. Treatments with PCU had a significant increase in internal efficiency over uncoated urea. The split application timing showed no increase in any NUE metric compared to the single application timing. These data reinforce the 4R principles and suggest that stacking some methods may not be necessary to increase overall NUE.