Annual and hybrid ryegrass cultivars in New Zealand

Results are presented for 16 National Forage Variety Trials of annual and short-term hybrid ryegrass cultivars conducted in Waikato, Taranaki, Manawatu, Canterbury and Southland. In all, 30 cultivars (17 named, 13 experimental) were included. Cultivar effects were significant in all seasons, and for the annual totals. Cultivar differences were greatest in summer. Spring production accounted for over 40% of annual totals and summer production less than 20%, but it was summer production that was more closely correlated with the individual cultivar annual total. Over all trials and cultivars, regrowth in the second autumn accounted for 11% of the total for 12 months beginning in the winter following sowing. Comparing North Island sites with Canterbury sites, there was some indication of cultivar × region interaction, particularly in summer. Patterns of interaction of cultivars with trials were examined, and indicated that some cultivars can be grouped as having similar responses. Repeated trials at the same site were sometimes but not always consistent in ranking cultivars. The results indicate that some cultivars do perform consistently better than others, for particular seasons or for annual totals, so that the trials are a reliable indicator of which new experimental cultivars should be released to the market. The results also indicate that several trials are necessary to determine the merit of a wellperforming cultivar. The error associated with the mean of cultivars present in only one or two trials is high (standard deviation approaching 20% of the mean in some seasons). This may, however, be sufficient to eliminate poorer experimental lines from further consideration. Keywords: Italian ryegrass, hybrid ryegrass, cultivars, Lolium × boucheanum, Lolium multiflorum, pasture agronomy