Yield and Quality Response of Perennial Ryegrass Selected for High Concentration of Water‐Soluble Carbohydrate to Nitrogen Application Rate

ABSTRACT The expression of elevated water‐soluble carbohydrate (WSC) concentrations in perennial ryegrass (Lolium perenne L.) cultivars selected for high forage WSC concentration can be highly variable across environments. Our aim was to determine whether N application rate influences the expression of the high WSC phenotype. Cultivars AberDart (selected for high WSC concentration) and Fennema (control) were evaluated across four fertilizer N application rates (0, 40, 80, and 120 kg ha−1 per harvest) over four replicates and 2 yr at Grange, Ireland, and Særheim, Norway. Plots were managed for silage production with four cuts per year in Ireland and three cuts per year in Norway. Nine forage traits were measured: WSC, dry matter digestibility, crude protein, buffering capacity, dry matter, ash, dry matter yield, N use efficiency, and apparent N recovery. The response of AberDart and Fennema to N application rate was predominantly similar within and over years and locations for all traits. Differences between cultivars in WSC concentration were largely consistent across N application rates, years, and locations. AberDart had mean WSC concentrations 8 to 12% higher than Fennema depending on harvest. Present results suggest that the evaluation and selection of perennial ryegrass for high concentrations of WSC in cool‐temperate maritime climates may be conducted across a wide range of N application rates and, by extension, soil N supply rates.