The role of flowering intensity in adapting perennial ryegrass to different production systems

Most current cultivars of perennial ryegrass vary markedly in productivity between harvests during the growing season. Such varieties produce high annual yields of dry matter when harvested infrequently and are suitable for animal production systems which rely heavily on grass silage. New varieties such as cv. Aberelan have been produced which are much better suited to grazing systems. They grow more evenly through the season and maintain dry matter production better when harvested frequently. One such variety (Ba11316) was compared with three commercial cultivars (Merlinda and two others) in a replicated field plot trial with six levels of fertiliser. Merlinda gave the highest total dry matter yields over two harvest years (5% more than Ba11316), but Ba11316 yielded significantly (16%) more leaf lamina than Merlinda. This substantial discrepancy in varietal ranking between total dry matter yield and total leaf yield was mainly because Ba11316 significantly outyielded Merlinda at several of the lower-yielding harvests, which all had high leaf contents, whereas Merlinda significantly outyielded Ba 11316 only at harvests with a low leaf content. The mean percentage of flowering tillers over four sampling dates was significantly lower in Ba11316 than in the three cultivars. This, together with other circumstantial evidence already published, suggests that flowering intensity may be the primary factor controlling seasonal yield distibution of perennial ryegrass varieties and their suitability for different production systems.