Graze on end
Grass varieties can now be evaluated on commercial grassland farms in Ireland; this system gives grassland farmers more relevant information regarding how varieties can contribute to their farms over time.
On Irish grassland farms, perennial ryegrass is the most important forage as it provides large quantities of high-quality forage to grazing animals at a relatively low cost compared to other feed sources.
Production of perennial ryegrass varieties, which may provide yield and/or quality advantages over older varieties, is a crucial part of the Irish grassland farming system. Currently, varieties are only evaluated, and given economic values, based on data from two-year plot trials. Further, these plot trials only include limited exposure to grazing animals and any effects that they may have on a varieties suitability for grazing-based production systems.
Hence, very little data exists that describes the performance of perennial ryegrass varieties in permanent pastures – i.e. five or more years post-sowing – on commercial grassland farms. Previously, research work has assumed a connection between grass sward production and ground score: this link has been used as a proxy for the persistence of grass variety performance over time.
Assessing persistency
The limitations of the current system are of major concern when it comes to predicting the true value of new grass varieties to commercial farmers, explains Ciaran Hearn, a Research Officer at Teagasc Moorepark’s Grassland Department.
“Grass growth potential and pasture reseeding costs are two major factors in determining farm profitability and long-term farm sustainability — both of which are directly affected by the long-term persistence of sward productivity. As such, there is a need on commercial farms for measuring the persistency of increased grass growth of perennial ryegrass varieties over time. Such a measurement would more accurately describe real conditions.”
The development of PastureBase Ireland has led to agronomic data of individual paddocks being made available for analysis over multiple years. This has allowed for the long-term assessment of varieties sown as monocultures on commercial farms. A trial was developed to evaluate the production and persistency of eight perennial ryegrass varieties sown on over 100 farms across various locations in Ireland. Each of these farms was allocated a subset of varieties from the Pasture Profit Index to be sown as monocultures in different paddocks across multiple sowing years. The grass production in each paddock was monitored via farmer data entered into PastureBase Ireland over the ten-year period of the study (2013–2022).
“The results of this 10-year analysis showed little association between a grass variety's ground score and grass production on farm as swards aged to seven years post-sowing,” explains Ciaran. “This finding is contrary to the current standard, which uses ground scores of varieties to predict long-term grass production. Ongoing monitoring of this data set may lead to a re-evaluation of how long term grass growth is predicted for new grass varieties on the Irish market.”
Production and performance
The best indication of grass production in permanent grasslands was the average grass production of one- to four-year-old swards. All swards had a clear drop-off from year one to year two post-sowing but all swards also showed similar production in years one, six and seven post-sowing.
Similar to the current evaluation systems, clear differences in total grass growth were observed between varieties on commercial farms under grazing conditions. Generally, varieties that produced the most grass in younger swards also did so in permanent pasture swards, Ciaran explains.
“Over longer-term periods these variety differences can manifest into large differences in grass produced and consumed on commercial farms. For example, there was a difference of 1,461kg DM/ha per year between the highest and lowest producing varieties in the current study; this represents an extra grazing per year solely due to variety selection when reseeding a paddock.”
Such differences will have a direct and lasting impact on the environmental and financial sustainability of Irish grassland farms.
“This study provides evidence, and a template, for how the inclusion of commercial grass production data can be used for future analysis of grass varieties. Further, with some modification, similar analysis could be used to evaluate the potential of other pasture species and varieties at farm level,” concludes Ciaran.
“This type of analysis provides a more robust picture of pasture performance for Irish farmers than what is currently available. Greater co-operation between researchers and the grassland industry will be required if this potential avenue of pasture evaluation is to be made full use of in the future.”
Funding
This work was funded by VistaMilk (Science Foundation Ireland) (16/RC/3835).
Contributors
Ciaran Hearn, Research Officer, Grassland Department, Teagasc Moorepark. ciaran.hearn@teagasc.ie
Michael O’Donovan, Head of Grassland Science Research Department, Teagasc Moorepark.
Further reading
This article was first published in TResearch. Read more from TResearch