Management options to recover perennial ryegrass populations and productivity in run-out pastures

In parts of the upper North Island, farmers frequently report perennial ryegrass (Lolium perenne L.) pastures failing within 3 or 4 years post-sowing. This appears to be related to interactions between several factors: climatic (drier, hotter summers), biotic (insect pest), soil (texture, water-holding capacity) and grazing management factors that vary spatially and temporally. The efficacy of three management interventions for recovering ryegrass populations and production in runout pasture was assessed in an experiment initiated in 2018/19 in central Waikato. Treatments were a long-spring rotation (LSR), a longer grazing deferral during late spring and summer (pasture deferral, PD) and under-sowing with perennial ryegrass (US), each applied to pastures of four ryegrass cultivars. In the year after the treatments were implemented, the yield of ryegrass in PD was 2.4 t DM/ha greater than for the control (7-year-old pasture), and ryegrass tiller populations initially doubled but later declined. Yields in US and LSR were intermediate but not significantly different from the control. Ground score changes responded more positively to PD compared with the other treatments. Relative to the baseline prior to initiation of the study, tiller populations increased for PD and US but declined for control and LSR. There were no interactions between management treatment and cultivar for any of the variables measured. Pasture deferral shows promise as an intervention for recovering failing ryegrass pastures through natural reseeding. However, the longevity of the benefits observed here has yet to be determined.