The changing role of perennial ryegrass in dairy pastures in northern Victoria, Australia

Abstract

In the dairy region of northern Victoria, Australia, the performance of temperate perennial dairy pastures is often poor over summer due to a combination of high temperatures and limited water availability that can restrict dry matter production and plant survival. This review summarizes published and unpublished research on perennial ryegrass, mostly undertaken in the northern Victoria region over the past decade, to help determine its future role in this environment. It includes information from a series of field experiments or case studies where the effects of heat and restricted irrigation on the growth and nutritive characteristics of perennial ryegrass were examined. This research involved investigations on whether plant survival under the stressed experimental conditions could be influenced by plant genotype, irrigation, and grazing management strategies, as well as by the presence of endophyte. In conclusion, it was difficult to identify any irrigation, grazing management or plant genotype effect that consistently improved the performance of perennial ryegrass in the hot, dry summers of northern Victoria, Australia. The incidences of extreme heat events and low water availability in this region are increasing, and the role of C3 perennial grasses as major suppliers of feed for dairy cows is diminishing. A major focus for the dairy industry in this region is now to identify new farming systems and alternative species that may be better adapted to the climate environment than perennial ryegrass, as well as be capable of adapting to year‐to‐year variations in irrigation water supply.

Editorial ‐ topics from the XXIV International Grassland Congress held in 2021

“…In this issue, work of Rogers et al (2022) illustrates the effects of climate change on grass productivity and quality in Northern Victoria, Australia. The role of perennial ryegrass will decline if irrigation is reduced and the authors mention a replacement of C3 species with C4 grasses.…”

A cytochrome P450 gene, LpCYP72A15, confers drought tolerance in perennial ryegrass

“…Perennial ryegrass is a rather drought‐sensitive grass (Fry & Huang, 2004). The performance of perennial ryegrass is often poor over summer under a combined stress of heat and drought stresses that restrict dry matter production and plant survival (Rogers et al, 2022). When watered at 33% of the requirement for optimal soil moisture levels, perennial ryegrass suffered a more pronounced leaf dry matter reduction than tall fescue ( Festuca arundinacea ) and cocksfoot ( Dactylis glomerata ) showing that prolonged drought conditions can be a major threat to the persistence of ryegrass pastures (Turner et al, 2012).…”

Root aphid (Aploneura lentisci) population size on perennial ryegrass is determined by drought and endophyte strain

“…The frequency of drought has increased in some agricultural regions (Mullan et al 2005;Strzepek et al 2010), with major impacts on pastoral production and resilience (Rogers et al 2022). Although climate models are highly variable between countries and regions, in temperate grass-producing countries such as New Zealand, Australia, and the USA, the likelihood of soil moisture depletion is increasing (King et al 2020;Trenberth et al 2014).…”