Optimizing Nitrogen Use for Irrigated Waxy Barley

Waxy barley (Hordeum vulgare L.) with high amylopectin has value as a food crop, but information on optimal N fertilization of furrow‐irrigated waxy barley is limited. Furrow‐irrigated field studies were conducted at Parma, ID, and Ontario, OR, with ‘Merlin’ and ‘Salute’ spring genotypes planted fall or spring during the 2006, 2007, and 2008 seasons as the main plots and N treatments as subplots. “Early” N as dry urea was applied preplant or late winter (0, 60, 120, and 180 lb/acre) and “late” N was applied at heading (0 or 40 lb N per acre) to selected early N treatments. Late N was applied as top‐dressed dry urea (DU), foliar fluid urea (FU), foliar urea‐ammonium nitrate (FUAN, Parma only) or FU applied to ethephon‐treated barley (FUE, Ontario only). The optimal early N rate for Salute at Ontario was 0 with severe lodging or 60 lb N per acre, as compared to 60 or 120 lb N per acre for Merlin. At Parma, varieties did not differ in their yield response to N and optimal early N, ranged from 60 to 120 lb/acre. Yield increased as much as 1488 lb/acre with late N and was unaffected by late N source. Late N did not increase lodging or reduce apparent N recovery despite more total fertilizer N available. Ethephon controlled lodging sufficiently to improve yield 1439 lb/acre. Late N may allow producers to reduce the early N that contributes to lodging, and to both reduced yield and apparent N recovery.