07 August 2023

Identifying the best perennial ryegrass varieties when reseeding

Regular reseeding of pasture allows farmers to grow increased yields of higher quality grass, thereby increasing feed self-sufficiency and sustainability of their farms.

The Pasture Profit Index (PPI) is used when deciding ‘what varieties to sow in my reseeded sward?’. The PPI outlines, in economic terms, the agronomic differences between varieties for traits that influence the profitability of ruminant production systems. The PPI identifies the best varieties for Irish farms. A variety’s strengths and weaknesses should be noted to make informed decisions when choosing varieties.

Using the PPI

The 2023 PPI list is displayed in Table 1. Variety performance data is collected and assessed by the Department of Agriculture, Food and the Marine Recommended List trials, which take place at five sites across Ireland.

Varieties are ranked based on their overall PPI value, which is calculated by adding its performance in each of the sub-indices or traits that make up the PPI. These sub-indices (and their relative emphasis within the PPI) are Spring (19%), Summer (6%) and Autumn (8%) dry matter (DM) production, Mid-season Quality (measured as DM digestibility; 25%), Silage DM yield (13%) and Persistency (29%). The relative emphasis of a trait within the PPI is based on its economic value and the level of variation between varieties for that trait.

Table 1: 2023 Pasture Profit Index

Aberclyde is the top ranked variety for 2023 with a PPI value of €253. This value indicates that by sowing Aberclyde on your farm, net profit will increase by €253/ha/year relative to the national average sward performance in Ireland. The higher the € value for a trait, the greater the varieties performance. Cognisance should be taken of a varieties strengths and weaknesses as indicated by the PPI. The grazing utilisation sub-index does not contain € values, but ranks varieties on a scale of 1-5 stars, with five stars indicating greatest grazing efficiency.

Selecting varieties

Farmers should select varieties using the PPI to ensure best return on investment when reseeding. Selecting based on the sub-indices allows for system specific seed mixtures to be designed.

When choosing varieties for intensively grazed paddocks on the milking platform, those performing strongly in the grazing utilisation, quality and spring/autumn DM sub-indices should be selected. Variety selection for paddocks destined for regular intensive silage harvesting would benefit from prioritising the silage and spring yield traits. Paddocks located on the grazing platform, but destined to be closed for silage should aim to combine high silage and utilisation traits.

Research investigating variety mixtures found that the trait performance of a mixture could be accurately predicted as the average of the component varieties for all traits.

This article by Tomás Tubritt, Noirín McHugh, Laurence Shalloo and Michael O’Donovan first appeared in the Moorepark 2023 open day book. Tomás also featured in on a recent Let’s Talk Dairy webinar, where he provided more information on the PPI. This webinar can be accessed here.