New Zealand dryland pastures: effects of sown pasture species diversi on the ingress of unsown species

摘要

Botanical composition was assessed in spring in 30 paddocks in each of four New Zealand regions: Northland (beef, sheep), Waikato (dairy), Taranaki (dairy) and North Canterbury (beef, sheep, deer). The hypothesis tested was that increasing flinctional diversity of sown species reduced ingress of unsown species as pastures age. Paddocks selected ranged in age and diversity of the sown mix (grasses + legumes, or grass + legumes + herbs). In all regions except for Taranaki, sown species declined and unsown species increased over time. This was mainly due to an increase in unsown grasses, although unsown herbs also increased. There was little unsown legume. In Northland, unsown herb ingress was less where herbs were sown, but only in older pastures. Percentage of unsown species in total dry matter in 4-6 year old pastures was: 35% (Waikato), 16% (Taranaki) and 15% (North Canterbury), while in 5-6 year old Northland pastures it was 30%. Most unsown species were undesirable. However, productive unsown species were also present (e.g. ryegrass, commercial plantain, white clover, subterranean clover).