Seed Yield and Quality of Italian Ryegrass as Affected by Harvesting Date

There is a lack of applied research in Croatia on optimum harvesting date in Italian ryegrass (Lolium multiflorum Lam.) crop for maximizing seed yield and seed quality. Thus, seed yield, yield components, and seed quality were determined for Italian ryegrass crop from the primary growth (pure-seed crop) and from the regrowth after first cut for forage (forage-seed crop). Both crops were harvested at early-, mid-, and late harvesting dates that were 19, 24 and 29 Jun in the pure-seed crop and 3, 6 and 10 July in the forage-seed crop. In spite of significantly lower density of fertile tillers (ears), average seed yield was significantly higher in the pure-seed than in the forage-seed crop. Both crops had similar ear length and floret site utilization, but ears from the pure-seed crop had more spikelets per ear, florets per spikelet as well as heavier seed weight than those from the forage-seed crop. Maximized seed yields were produced at mid-harvesting dates for both crops when seed moisture was 44.1% for the pure-seed crop (552 growing degree days following anthesis) and 40.4% for the forage-seed crop (505 growing degree days following anthesis). Depending on crop management and harvesting date, seed moisture loss ranged from 1.2% to 3.6% per day. Seed germination was not affected by crop management or by harvesting date despite differences in 1000-seed weight. In conclusion, harvesting crop with seed moisture content around 40-45% maximized seed yields for the pure-seed as well as the forage-seed crop, while harvesting date had no effect on seed germination