The case for static‐range nitrogen management for irrigated feed barley in Idaho

Abstract

Barley ( Hordeum vulgare L.) is an important component of animal rations in regions with colder climates and shorter growing seasons. US production is concentrated in higher latitude and/or elevation areas of the west and Great Plains. Idaho is the largest barley producing state, but its fertilizer‐nitrogen (N) recommendations are dated and supported by scant published data. Research investigated feed barley (Altorado and Claymore) response to fertilizer‐N (more than five rates), and developed recommendations based on N‐supply = [soil total inorganic N (TIN) + applied fertilizer‐N]. Eight site‐years of N‐response trials were conducted from 2021 to 2023 allowing the determination of the N‐supply at which grain yield plateaued, that is, critical N‐supply (CNS). Individual site‐year ANOVA and linear‐plateau (LP) analysis resulted in a mean grain yield of 8006 kg ha ⁻¹ at an ANOVA CNS of 212 kg N ha ⁻¹ . N‐requirements (Nr) at ANOVA CNS ranged from 14.9 to 41.7 g N kg grain ⁻¹ . Utilization of the corresponding Nr at yields ranging from 5000 to 11,000 kg ha ⁻¹ resulted in CNS of 195 to 220 kg N ha ⁻¹ . Combined site‐year analysis by LP and quadratic‐plateau (QP) resulted in CNS of 223–262 kg N ha ⁻¹ at 95% RGY (relative grain yield). These results support a non‐yield goal based static range N management (SRNM) approach that is narrower than the current yield goal N management (YGNM) approach. Statewide adoption of the recommendations from this work would indicate a range of total fertilizer‐N costs from a savings of $1.25 million to an increase of $430,000 annually. Our data support a practical SRNM recommendation from 220 to 260 kg N ha ⁻¹ for irrigated feed barley production in the region.