Other considerations
Meat & Livestock Australia December 13, 2021
Seedling recruitment in Italian ryegrass and hybrid ryegrasses
Hybrid and Italian ryegrass (Lolium multiflorum) types are short-lived but valued for their high production. Can seedling recruitment techniques be used to increase their longevity in these pastures?
Anecdotal information is that 20–30% of Italian ryegrass might be expected to survive if the plant was able to form viable seed and the seed re-establish. However, many flower late and have low-aftermath heading, meaning the chances of setting and shedding viable seed are less than perennial varieties. Shorter‑season cultivars are more likely to achieve this than late-season cultivars.
Endophyte in perennial ryegrass seed
Endophytes are microscopic fungi which live within perennial ryegrass plants and can transfer through seed. If perennial ryegrass has endophyte this will be transferred into the recruited seedlings.
Endophytes can enhance persistence, protecting the plant against insect and soil-borne diseases, but toxins produced by some cultivars, especially older varieties, can cause staggers, heat stress and death.
A numbers game
New pastures of mixed species are typically sown with 8–12kg/ha of perennial ryegrass seed or 3–4kg/ ha of cocksfoot seed. Estimated seed yields for thinning ryegrass or cocksfoot within mixed pasture could be 130kg/ha and 50kg/ha for cocksfoot. This equates to approximately 7,000 seeds/m2 for ryegrass and 9,500 seeds/m2 for cocksfoot.*
* Results based on crop seed production of 1.3t/ha perennial ryegrass and 0.5t/ha cocksfoot. In a mixed poor perennial pasture, it is estimated that seed yields could be approximately 10%. One kilogram of perennial ryegrass seed equals 320 seeds/m2 and one kilogram of cocksfoot is 760 seeds/m2.
Where does all this seed go?
In a grazed pasture most is ingested by animals, which makes the seed unviable. If not removed by grazing, the main source of loss is ant predation. However, even achieving a 3% success rate with the high amounts of available seed equates to 200–300 seedlings/m2.