The Efficacy of Management Interventions to Restore Perennial Ryegrass Tiller Populations, Content and Production in Dairy Pasture

Three interventions aimed at restoring perennial ryegrass populations and the herbage production of run‐out dairy pastures based on mid‐season or late‐season heading perennial ryegrass cultivars were compared with a control (CON) treatment over 3 years in Waikato. The treatments were: short deferral of grazing (47–48 days) in spring (SD); long deferral (112–123 days) in spring/summer (LD) and undersowing in autumn (US). Compared with all other treatments, LD increased ryegrass ground score and tiller density in year 1 post‐treatment but there were few differences thereafter. Compared with CON over all 3 years, LD led to: 2260 kg DM/ha/yr greater ryegrass herbage accumulation (HA); lower content of white clover (−50%), other grass species (−60%) and broadleaf weeds (−20%); higher metabolisable energy (ME) content (+5%); but no difference in total pasture HA. The ryegrass HA advantage of LD declined over time but was still significantly greater than other treatments by the third response year. Short deferral and undersowing had little effect on any variables, though a small benefit to ryegrass HA was detected when SD was applied to mid‐season cultivars but not to late‐season cultivars. Implications of net differences between CON and LD in total harvestable ME supply are analysed and discussed.