Botanical survey of perennial ryegrass‐based dairy pastures in three regions of New Zealand: implications for ryegrass persistence

Abstract

A botanical survey of 24 commercial dairy pastures ranging in post‐sowing age and perennial ryegrass type (mid‐season diploid, late‐season diploid, tetraploid) was undertaken in each of Waikato‐Bay of Plenty (BoP), Taranaki and Canterbury during autumn/winter. The mean perennial ryegrass proportion (85% of total DM) and tiller density (3252 m −2 ) was greatest in Canterbury and the broadleaved weed proportion lowest (2%). Conversely, Waikato–BoP had the lowest ryegrass proportion (59%), tiller density (1817 m −2 ) and greatest proportion of broadleaved weeds (15%), with Taranaki intermediate. Tiller density was greater in pastures sown with diploid rather than tetraploids (averaging 3033 vs. 1784 m −2 ). Grass grub ( Costelytra zealandica , 11 m −2 ) populations were lowest in the youngest age category pastures where nematode populations were highest (80 g −1 dry soil). The soil seedbank was dominated by unsown species (with total species emergence averaging 4594 seeds m −2 ), with negligible ryegrass emergence.