Assessment of herbage yield and quality traits of perennial ryegrasses from a national variety evaluation scheme

Perennial ryegrass evaluation schemes categorize varieties into three maturity (early, intermediate and late) and two ploidy (diploid and tetraploid) groups, and compare the relative yield, persistence and nutritive quality of varieties within these groups. The present study compared these groups for herbage yield, dry matter (DM) concentration and, using near infrared reflectance spectroscopy (NIRS), four quality characteristics (in vitro content of digestible dry matter (CDDM), water-soluble carbohydrate (WSC) and crude protein (CP) concentrations, and buffering capacity). A total of 1208 plots were sown across 5 years in Irish Recommended List trials and then harvested 6-7 times in each of 2 harvest years. This also allowed an assessment of the effect of sward age. Maturity group had no significant effect on annual herbage yield, quality or DM concentration except for in vitro CDDM (P < 0.01) but differed significantly for in vitro CDDM (P < 0.01), WSC concentration (P < 0.01) and buffering capacity (P < 0.05) at the first silage harvest. Tetraploid swards had greater annual herbage yields (P < 0.001), in vitro CDDM values (P < 0.001) and WSC concentrations (P < 0.01), but lower CP and DM concentrations (P < 0.001) than diploids. Swards in their first full year produced an additional 5.17 t/ha DM (P < 0.001) and had a higher (P < 0.01) WSC concentration at the second silage harvest than in their second year, but did not differ significantly for in vitro CDDM and WSC, CP or DM concentrations. The present study showed that differences exist in yield, nutritive quality and ensilability indices between maturity and ploidy groups. These observations justify their assessment in variety comparative trials and facilitates particular groups being selected for individual farming systems to increase efficiency.