Independence of dry matter yield and leaf yield among perennial ryegrass varieties differing in seasonal yield distribution

Four varieties of perennial ryegrass ( Lolium perenne L.), (Ba11316, Merlinda, Morgana and Talbot), with similar ear emergence dates but differing in seasonal yield distribution were compared over two harvest years (1992 and 1993) in a small plot trial employing six levels of fertilizer N (100 to 600kg Nha⁻¹ year⁻¹ applied monthly as split dressings). In each year, a conservation cut in May was followed by five further harvests at monthly intervals. Herbage samples from each of the twelve harvests were separated into leaf lamina and other tissues, and the yield of leaf lamina calculated. The percentage of flowering tillers was determined in May and July of each year, Ba11316 produced significantly more dry matter (DM) than the other three varieties at six of the twelve harvests, but its total DM yield over all twelve harvests was 5% less than Merlinda and 3% less than Morgana, owing to lower yields of reproductive growth in May of both years. Varieties also varied in mean leaf content of the herbage over all harvests, Ba11316 being 69 g kg⁻¹ higher than that of Merlinda. Differences among the varieties in leaf content were primarily because of difference in proportion of flowering tillers, Ba 11316 having a lower proportion of flowering tillers than the other three varieties. However, the mean leaf content of the tetraploid Merlinda was significantly lower than that of Morgana although these two varieties had a similar mean percentage of flowering tillers. Despite its lower total DM yield, Bal 1316 produced 16% and 14% more leaf over the two harvest years than Merlinda and Morgana respectively. Total leaf yield of Talbot was significantly higher than that of Merlinda and Morgana, although Talbot had been developed twelve years earlier than the other two varieties.