EFFECT OF HARVEST DATE AND CULTIVAR MATURITY ON PERENNIAL RYEGRASS (LOLIUM-PERENNE L) YIELD AND DIGESTIBILITY

Three perennial ryegrass cultivars, early (Gremie), intermediate (More nne) and late (Perma) maturity, were each sown as monocultures in eigh t identical groups. These 'groups' were sequentially taken for first s ilage cuts at 10-day intervals, with second cuts after 6 weeks followe d by further cuts to the end of the season. The work was repeated in 3 different years. Delaying the first cut increased dry matter (DM) and digestible organic matter (DOM) yields, despite a lowered percentage of digestible organic matter in the dry matter (DOMD), but caused redu ced DM and DOM yields at the second cut even though DOMD increased. Th erefore, large fluctuations in DM yield were recorded but, due to the counterbalancing effect of DOMD, the DOM yield responses were less ext reme. No significant effects on productivity due to varying timing of the first cut were recorded beyond the second cut. Maturity difference s between cultivars caused similar responses as varying cutting times. Absolute losses in DM yield incurred by early cutting were not fully compensated by the enhanced regrowth rates to the second cut. Cutting early to obtain two cuts within the time period for one late first cut increased yields during that period. However, this advantage was lost due to lower yields at the following cuts. Avoiding cutting at too im mature or mature a growth stage, coupled with selection of cultivars o f specific maturities to allow flexibility in timing of cutting, was g enerally the best strategy for optimising the herbage yield/quality ba lance in both the first and second silage harvests.