Nitrous oxide emissions and productivity of irrigated potato: Effects of nitrogen fertilization options

Improved N management is needed in intensive agriculture to mitigate nitrous oxide (N2O) emissions while sustaining high yields. We assessed the effectiveness of polymer‐coated urea (PCU); nitrification inhibitor 2,4‐dimethylpyrazol succinic acid (DMPSA), a biostimulant; and their combinations with granular urea and ammonium sulfate nitrate (ASN) fertilizers to reduce N2O emissions and to improve potato (Solanum tuberosum L.) productivity under irrigation. Sites were located in Lethbridge and Brooks, Alberta, Canada over two growing seasons. Tuber yield, grade, specific gravity, and N uptake were quantified. We used the chamber method to measure N2O fluxes from potato hills and furrows. The N2O emissions from furrow positions were at least two‐fold greater than those from hills at the Lethbridge site. Peak N2O emissions and increased N concentrations in potato petiole and soils occurred shortly after fertilizer applications. The overall average emission factor (EF) of N2O was 0.056% kg N2O–N kg−1 N fertilizer (accounting for emissions from unfertilized controls). Urea alone commonly exhibited the highest N2O fluxes. Admixing DMPSA with either urea or ASN lowered N2O emissions in only certain cases. For instance, in one growing season at the Brooks site, adding DMPSA to urea reduced the N2O emissions by 57%. Likewise, in one of the four site‐years in the study, 36% higher potato marketable yields were obtained when applying either ASN treated with DMPSA or PCU compared with the unfertilized controls (45 vs. 33 Mg ha−1). Results showed that under specific conditions, N application strategies using DMPSA admixed with either urea or ASN can maintain high potato yields while reducing N2O emissions relative to soils receiving these fertilizers without this additive. Core Ideas Adding the inhibitor DMPSA to urea reduced N2O emissions in only one of four site‐years. Potato yield was increased 36% in one site‐year by the fertilizers ASN with DMPSA or PCU. Fertilizer options did not influence the overall nitrogen use efficiency or harvest indices. Nitrate concentrations in potato petioles were closely associated with availability of soil N. Nitrous oxide emissions from furrow positions were often greater than those from potato hills.