Potato Uptake and Recovery of Nitrogen‐15‐Enriched Ammonium Nitrate from Periodic Applications

Abstract

Abstract There is a trend in potato ( Solanum tuberosum L.) production to make repeated additions of N fertilizer in sprinkler irrigation water for an extended part of the season. More information is needed on scheduling (rate and timing) these N supplements. A 3‐yr study on the use of frequent supplements of 15 NH 4 ‐ 15 NO 3 by ‘Russet Burbank’ potato was conducted on Quincy loamy sand (mixed, mesic Xeric Torripsamment). The purpose of the experiment was to trace changes in the uptake and partitioning of 15 N in vines and tubers from starter and periodic additions totaling 336 kg N ha −1 . Labeled N fertilizer was sprayed on a different set of replicated potato plots according to the application schedule. Plant tissue samples were taken and analyzed regularly for labeled N uptake. Whole potato plants over the season recovered a maximum of 61 to 67% of the 15 N‐enriched increments of fertilizer applied, as compared to a maximum of 42 to 54% partitioning of the labeled N in tubers at final harvest. Recovery of 15 NO 3 was significantly higher on the average than recovery for 15 NH 4 . Furthermore, in many cases the average recovery was highest from labeled N applied during tuber bulking early in July, which suggests that this is a crucial time for maintaining adequate N fertility.