Changes in yellow bristle grass (Setaria pumila) incidence in Waikato dairy pastures over 4 years

Abstract

Thirty-nine Waikato dairy pastures have been surveyed annually each February, for 5 years, to quantify changes in cover of yellow bristle grass and to determine if management factors influence this. After a severe drought, yellow bristle grass ground cover increased from 4 to 11% (2008 to 2009) and has since remained at this level. Ryegrass cover declined after the drought and has not returned to pre-drought levels while clover cover has increased. There was a much higher than average 2011/2012 summer rainfall, possibly causing the reduced summer grass and broadleaf weed cover measured in February 2012. By the end of the survey period, there was no reduction of yellow bristle grass cover from any of the following farm practices aimed to improve pasture performance: summer cropping, undersowing, oversowing and non-selective herbicide applied during summer. © 2012 New Zealand Plant Protection Society (Inc.).