Irrigated malt barley nitrogen management: Insights from historical and modern cultivars

Barley (Hordeum vulgare L.) is the primary grain used for malting and brewing in the United States. Idaho accounts for upward of 40% of US production with the largest share grown under irrigation in the Snake River Plain. Cultivar and agronomic advancements occurred in the past century but, N-supply research has lagged behind. We addressed this with N-response trials of historical and modern malt barley cultivars from 2015 to 2019. Six N-supplies (applied fertilizer-N + soil inorganic-N) were tested, allowing critical nitrogen supply (CNS) determination, that is, N-supply at yield plateau. Site-by-site analysis of variance (ANOVA) and linear plateau (LP) models were used to determine ANOVA CNS, which ranged from 110 to 149 kg N ha⁻¹. At ANOVA CNS, modern barley yields were 10%–20% greater than historical cultivars. Combined-site LP and quadratic plateau (QP) models resulted in CNS ranges of 117–152 kg N ha⁻¹ for historical cultivars and 141–170 kg N ha⁻¹ for modern cultivars; both model results are below the current maximum recommendation of 235 kg N ha⁻¹. Grain yields for Klages were 20%–35% greater than reported from research in the 1970s and 1980s; however, CNS were similar. Grain protein was more negatively affected by N-supply for Klages, but all cultivars remained below malting thresholds across their CNS ranges. Our data support lower fertilizer-N applications and expenditures compared to current recommendations and evidence the importance of synergistic enhancement of malt barley production through breeding and agronomic advancement to optimize crop and farm business performance.