Waxy Barley: Optimizing Nitrogen Use for Yield and Grain Quality.

Little research has evaluated nitrogen (N) management for growing waxy barley varieties to optimize both higher protein and beta-glucan soluble fiber content. A local company has proposed the building of a barley fractionation plant to capitalize on these value-added traits. Research is needed to help producers know how to apply N for optimum yield, protein and beta-glucan under irrigated conditions. Salute and Merlin, two spring waxy barley cultivars, were fall-planted to compare yield and quality under different N treatments applied in late winter and at heading, and to evaluate ethephon growth regulator to reduce lodging. Winter weather in the Treasure Valley reduced stands by 60 to 70% in 2006 and required replanting in the spring of 2007. In 2006, yield of Merlin and Salute were not different and averaged 5.4 Mg ha-1. In 2007, Merlin yielded 6.6 Mg ha-1 whereas, Salute only yielded 4.5 Mg ha-1 and had heavy lodging. In 2007, Salute had 30% lodging even where no late winter nitrogen was applied and it increased to near 98% when only 27 kg ha-1 of N was applied. In 2007, the application of ethephon growth regulator at the full labeled rate increased Salute yield by 1.3 Mg ha-1 and decreased lodging by 28%. Grain protein was influenced by year, variety, N rate, N at heading and ethephon application. Grain protein was 2.2 percent higher in 2006 than 2007. Merlin was 0.8 percent higher in protein content than Salute. Increasing the N rate from 0 to 180 kg ha-1, increased grain protein from 10.0 to 12.9 percent. Applying 45 kg ha-1 N at heading consistently increased protein about 1 percent. Applying Ethephon decreased grain protein content by 0.4 percent. A strong positive relationship between flag leaf N at heading and grain protein was found (R2= 0.79). Ethephon influence on beta-glucan was inconsistent over years. When ethephon was applied in 2006, beta-glucan content dropped from 5.8 to 5.2%, however no difference occurred in 2007. Averaged over years and varieties, 45 kg ha-1 N dry or fluid at heading increased the beta-glucan content from 5.4 to 5.7%.