Effect of grazing management and stockclass on Chilean needle grass ('Nassella neesiana') seed production

Concern about the invasion of pastures in south-eastern Australia by Chilean needle grass (CNG, 'Nassella neesiana' (Trin. & Rupr.) Barkworth) began to mount in the 1970s. CNG infestations can reduce stock carrying capacity during late spring and summer. This is because of the production of large numbers of unpalatable flower stalks. These flower stalks are actively avoided by stock, and have sharp seeds that can penetrate the hides of sheep. Research into CNG management in Australia has shifted towards using grazing as a tool to both manage and utilise CNG. This paper describes an experiment that commenced in spring 2004, comparing methods of set stocking and rotational grazing using both sheep and cattle as grazing species. Grazing (by sheep or cattle) significantly reduced the occurrence of standing CNG panicle and stem seed during 2004 when compared to ungrazed plots. However, grazing did not reduce the occurrence of standing CNG panicle and stem cleistogenes during 2005 and did not significantly affect the viability of harvested panicle seed. Cattle tended to graze more standing CNG panicle seed than sheep did during the 2004 season. This did not re-occur during the 2005 season. Panicle seed viability and cleistogene production were not significantly affected by the type of grazer during 2004 and 2005. Grazing management did not significantly affect the number of panicle seeds, panicle seed viability or number of stem cleistogenes harvested in 2004 and 2005.