Poor persistence of perennial ryegrass swards is a common problem; however, there is a lack of long‐term studies to understand the mechanisms associated with poor persistence. This study describes an experiment to test the hypothesis that high ryegrass seeding rates (>18 kg seed per ha) reduce long‐term population persistence because of smaller plant size and poorer survival during the first year after sowing. Four cultivars, representing four functional types of perennial ryegrass, were sown at five seeding rates (equivalent to 6, 12, 18, 24 and 30 kg seed per ha) with white clover in three regions of New Zealand. Swards were monitored for 5 years. No evidence was found to indicate a lack of persistence of ryegrass‐based swards sown at higher seeding rates. During the first year, swards sown at higher seeding rates had greater herbage accumulation (except at the Waikato site), greater ryegrass tiller density and greater ryegrass content. This initial impact of high seeding rates had largely dissipated by the fourth year, resulting in swards with similar annual herbage accumulation, tiller density and botanical composition. Similarly, there were relatively few differences among cultivars for these variables. Although high seeding rates did not negatively impact sward persistence, geographical location did, with strong evidence of ryegrass population decline at the Waikato site for all treatment combinations, some decline in Northland, and stable populations in Canterbury. It is possible that productive perennial ryegrass pastures can only be sustained for 4–5 years in some situations, even when the best ryegrass technology and management practices are used.

Failure of perennial ryegrass swards to persist is a key issue on dairy farms in many areas of the world. This study describes an experiment conducted to test the hypothesis that high ryegrass seeding rates (>18 kg seed ha À1 ) reduce plant size and physical survival during the first year after sowing, with negative implications for population persistence. Four cultivars representing four functional types of perennial ryegrass were sown at five seeding rates (equivalent to 6, 12, 18, 24 and 30 kg seed ha À1 ) with white clover in three dairying regions of New Zealand. Plant establishment rates, size and survival were measured for the first 13 months after sowing. Herbage accumulation, botanical composition and perennial ryegrass tiller density were also monitored. Increasing seeding rate reduced plant survival in the seven weeks after sowing, reflecting likely differences in germination and very early mortality of small seedlings. Thereafter, plant survival was relatively high and consistent across seeding rates at two sites but was consistently greater in the 6 kg ha À1 treatment compared with the 24 and 30 kg ha À1 treatments at one site. Higher seeding rates also increased ryegrass tiller density and the contribution of ryegrass towards total herbage biomass but reduced the contribution of white clover. Very few cultivar 9 seeding rate interactions were detected for any of the measured variables. Many of the seeding rate effects dissipated by the end of the first year after sowing, indicating that high seeding rates did not predispose swards to poor persistence in the longer term, irrespective of ryegrass functional type.

Plots were established on three farms in Northland in April 2009 and were monitored from May to December for differences in total pasture dry matter (DM) yield after direct-drilling Italian ryegrass (Lolium multiflorum) into kikuyu (Pennisitum clandestinum) following mulching. Pesticide-treated or untreated Italian ryegrass was drilled at 10, 15, 20 and 30 kg seed per hectare. Plot DM yields were estimated pre- and post-grazing using a rising plate meter. Daily pasture growth rates and total DM yields varied between sites but tended to increase with increased sowing rate. There was no significant pasture yield response to pesticide treatment of seed. This work suggests that sowing Italian ryegrass into kikuyu increases total pasture DM yield during winter and spring. Keywords: kikuyu, Italian ryegrass, sowing rate, pesticide

Three options for controlling surplus pasture on Northland dairy farms were modelled to determine the impact of each on production and operating profit. The three options were a) Light cut, fixed break size (LCFB): Paddock cut for silage as soon as surplus was identified. No effect on rotation length. b) Bulk cut, fixed break size (BCFB): Paddock closed until cover of 4000 kg dry matter (DM)/ha was reached then cut for silage. Rotation length was shortened. c) Bulk cut, variable break size (BCVB): Paddock closed until cover of 4000 kg DM/ha was reached then cut for silage. Rotation length was maintained thus reducing available grazing area. The hypothesis was that LCFB would translate into the most profitable option as pasture is being cut as soon as a genuine surplus is realised, optimising silage feed quality. Results showed LCFB to be $100/ha more profitable (operating profit) compared with BCFB and BCVB at only one of the three sites investigated (P