Deficit irrigation effects on adjunct and all‐malt barley yield and quality

Semiarid regions are reliant on irrigation to produce large‐yielding and high‐quality malt barley (Hordeum vulgare L.). Drought in the western United States is of concern as surface and ground water reductions are occurring that affect irrigation water availability. Implementing a seasonal water deficit compared to evapotranspiration (ET) is a potential strategy to reduce water usage if yield and quality can be maintained. Research was conducted in Aberdeen, ID, on the effects of deficit irrigation on yield, grain quality, and malt characteristics. Five genotypes were selected to represent those used for large‐scale adjunct brewing and those targeted at the all‐malt craft industry. Irrigation was managed at three rates (100%, 75%, and 50%) of estimated crop evapotranspiration (ETc) using sprinkler irrigation. Total aboveground dry matter was not affected by irrigation until soft dough (Feekes 11.2). Yield was similar within a genotype with irrigation reduction from 100% ETc to 75% ETc. Averaged across genotypes, yields were 6936 kg ha−1 at 100% ETc and 6297 kg ha−1 at 75% ETc. At 75% ETc, protein remained just below the adjunct target (130 g kg−1) for four of five genotypes while all five exceeded the all‐malt target (120 g kg−1). Reduced irrigation decreased malt extract and increased diastatic power, where β‐glucan either did not differ or increased. Deficit irrigation is promising, particularly for adjunct brewing; however, expected changes to malting quality must be understood and genotype selection, altered fertilizer management, and/or changes to malting criteria may be needed for implementation. Core Ideas Grain yields were similar within a genotype with a reduction in irrigation from 100% to 75% crop evapotranspiration (ETc). Total aboveground dry matter yields at the F10 (boot) stage, when forage is commonly harvested, were unaffected by irrigation rate. Adjunct (130 g kg‐1) but not all‐malt (120 g kg‐1) protein was met with irrigation reduction to 75% ETc. With decreased irrigation, malt extract and soluble protein to total protein ratio decreased, diastatic power increased, and β‐glucan did not differ or increase. Irrigation reductions to 75% ETc are promising for adjunct targets; caution is needed for all‐malt targets.