In northern Victoria, Australia, perennial pastures for the dairy industry have historically been based on perennial ryegrass. However, perennial ryegrass does not perform well under high summer temperatures and water stress. We investigated irrigation, renovation and grazing management strategies for improving the resilience and survival of perennial ryegrass over summer on two farms in northern Victoria over 2.5 years. At each farm, two irrigation bays were sown in March 2015. During summer (late December–mid-March), one bay was not irrigated and the other bay received a single mid-summer irrigation. Each bay was sown to 12 ryegrass cultures: five cultivars of perennial ryegrass either oversown or not oversown, and two oversown cultivars of short-lived ryegrass (SLRG). A mid-summer grazing treatment was applied to one-half of each of these plots. All plots at both sites received the same irrigation and grazing management at other times of the year. There were significant variations in dry matter (DM) production, nutritive characteristics and plant frequencies across sites and seasons, and across renovation, irrigation and grazing management strategies. Cumulative DM yields were higher in the perennial ryegrass than the SLRG cultivars. Summer DM removal was very low at both sites; the ungrazed plots recovered and produced more DM in the following cooler period than the grazed plots in the first year but not the second. Metabolisable energy concentration was higher for perennial ryegrass than SLRG cultivars and was also higher in plots that had been grazed over the summer. There were large differences in plant frequency between species, and there were some differences among perennial ryegrass cultivars. The effect of summer grazing on plant frequency varied at each site and was not significant within an irrigation treatment. This research confirms that perennial ryegrass is not well suited to the hot, dry summers of northern Victoria and suggests that, under conditions of limited summer irrigation, farmers should focus on plant survival rather than summer yield if they are to maximise annual DM production.

在澳大利亚维多利亚州北部，历史上乳制品业的多年生牧场一直以多年生黑麦草为基础。但是，多年生黑麦草在夏季高温和水分胁迫下表现不佳。我们调查了灌溉，翻新和放牧管理策略，以提高夏季维多利亚州北部两个农场2.5年内多年生黑麦草的复原力和生存能力。每个农场在2015年3月播种了两个灌溉海湾。在夏季（12月下旬至3月中旬），一个海湾没有进行灌溉，而另一个海湾则接受了盛夏的一次灌溉。每个海湾播种了12种黑麦草文化：5个过度播种或未过度播种的多年生黑麦草栽培种，以及两个短命黑麦草（SLRG）过度播种的栽培种。对每个样地的一半进行了仲夏放牧处理。在一年中的其他时间，两个站点的所有地块均接受相同的灌溉和放牧管理。在不同地点和季节，以及翻新，灌溉和放牧管理策略中，干物质（DM）的生产，营养特性和植物频率存在显着差异。多年生黑麦草的DM累积产量高于SLRG品种。两个站点的夏季DM去除率都很低。在接下来的凉爽时期，未湿润的地块比第一年放牧的地块恢复并生产更多的干物质，但第二年没有。多年生黑麦草的可代谢能量浓度高于SLRG品种，并且在夏季放牧的地块中也较高。物种之间的植物频率差异很大，多年生黑麦草品种之间存在一些差异。夏季放牧对植物频率的影响在每个地点都不同，并且在灌溉处理中并不显着。这项研究证实，多年生黑麦草不太适合维多利亚州北部炎热干燥的夏季，并建议，在夏季灌溉有限的条件下，如果农民要最大限度地提高DM的年产量，应着重于植物的生存而不是夏季的产量。