Grain Quality and Starch Characterization of Waxy Barley as Influenced by Nitrogen and Ethephon.

Waxy barley (Hordeum vulgare L.) with high amylopectin has value as a food crop, but information on optimal nitrogen (N) fertilization of furrow-irrigated waxy barley is limited. Furrow-irrigated field studies were conducted at Ontario, OR with 'Merlin' and 'Salute' spring genotypes planted fall 2006 and spring 2007 as the main plots and N treatments as subplots. “Early” N as dry urea was applied preplant or late winter (0, 67, 134 and 201 kg /ha) and “late” N was applied at heading (0 or 45 kg N/ha) to selected early N treatments. Late N was applied as top-dressed dry urea (DU), foliar fluid urea (FU) or FU applied to ethephon-treated barley (FUE). Grain yield influenced total production (kg /ha) of protein, starch, and beta glucan more than kernel concentrations of protein, starch and beta glucan. Early N linearly increased concentrations of protein, linearly decreased starch, but did not affect beta glucan. Added N reduced peak viscosity and peak time more for Merlin than Salute but N increased the final viscosity more for Salute than Merlin. Averaged over years, the treatment combination that maximized yield (6.5 Mg/ha) of Salute was 67 kgN /ha late winter in combination with FUE. Higher N rates reduced yield due to severe lodging. Under this treatment grain composition of Salute was 11.1% protein, 51.3% starch and 5.6% beta glucan. The milled flour was characterized for pasting properties which resulted in a peak viscosity of 510 Rapid Visco Analyzer Units (RVU), trough viscosity of 188 RVU, and final viscosity of 386 RVU, time to pasting was1.6 minutes (MIN) and time to peak was 4.8 MIN. In comparison, averaged over years, Merlin yield was maximized (7.2 Mg/ha) with 134 kg N/ha late winter in combination with FU. Lodging did not limit yields of Merlin. With optimal N, Merlin grain composition was 13.0% protein, 54.0% starch, 5.6% beta glucan, peak viscosity of 652 RVU, trough viscosity of 172 RVU, final viscosity of 345 RVU, time to pasting of 1.9 MIN, and time to peak of 4.9 MIN. Waxy barley variety selection and N management can affect grain quality depending on the end use.