Grass/white clover swards could provide a greener path to better farm productivity

Teagasc has published an external review of its grass/clover and multi species swards research program, which was carried out by Dr. Sinclair Mayne, former CEO of the Agri Food and Biosciences Institute (AFBI) in Northern Ireland.

Research from UCD on multispecies swards was also included in the review. Teagasc Director Professor Frank O'Mara commissioned the review to examine the research program and determine the key findings to date, to ensure that the important advisory messages for farmers were being synthesized from across the full research program, and to identify any research gaps and future strategic priorities.

The Irish Government's Climate Action Plan has set out a target to reduce greenhouse gas emissions (GHG) from agriculture by 25% by 2030. One measure that has been highlighted as a method to achieve this target is to reduce chemical nitrogen (N) fertilizer use on Irish farms.

Reducing fertilizer N levels has the potential to, not only reduce the level of greenhouse gas emissions from Irish agriculture, but also to reduce pasture production at national level resulting in increased purchased feed requirement. However, reducing chemical N has the potential to improve farm profitability where biologically fixed nitrogen from legumes replaces chemical nitrogen.

Teagasc and UCD have undertaken a portfolio of research comparing the performance of perennial ryegrass swards with perennial ryegrass/legume swards (ryegrass/white clover for grazing and ryegrass/red clover for silage production) and multispecies swards (grasses that include perennial ryegrass, Cocksfoot, Timothy; legumes that include red and white clover; herbs that include Chicory and Plantain).

The impacts of the differing sward types on herbage production, animal performance, environmental sustainability and farm profitability with dairy cows, beef cattle and sheep have been assessed across a range of different levels of chemical N fertilizer levels.

The review highlighted that perennial ryegrass/white clover swards managed appropriately have the potential to maintain pasture dry matter production, increase animal performance, reduce greenhouse gas emissions, and increase farm profitability.

It concluded that a perennial ryegrass/white clover sward receiving 100 kg per hectare less chemical nitrogen, produced similar pasture production to that of a perennial ryegrass only sward. This was based on the perennial ryegrass/white clover sward having on average 20 to 25% white clover over the grazing season. The biggest challenge identified at farm level was the establishment and maintenance of the white clover content.

In addition to the fertilizer replacement effect, livestock grazing perennial ryegrass/white clover swards had higher milk production/live weight gain. Together with savings on fertilizer, this resulted in higher farm profitability. There was evidence that perennial ryegrass/white clover swards emitted lower nitrous oxide, thereby lowering GHG emissions, with research in relation to nitrate leaching at an early stage.

The results also indicated that the risk of bloat was relatively low where average white clover content over the grazing season was maintained at 20 to 25%, but vigilance is required. However, in situations where clover content was higher than 30%, and/or herbage dry matter content was low, the risk of bloat was much greater and, in these situations, careful monitoring of livestock as well as the use of preventative measures is required.

Additionally, the report highlighted that perennial ryegrass/red clover swards in silage systems have the potential to produce high dry matter yields with low chemical nitrogen, with little impact on animal performance.

The results to date in relation to multispecies swards show that performance is generally similar to perennial ryegrass/white clover swards in terms of herbage production and animal performance. However, the results of more recent studies have shown that lack of persistency is a major issue with multispecies swards, especially with chicory, red clover and plantain largely disappearing within two to three years of establishment.

Multispecies swards may have some environmental advantages over perennial ryegrass/white clover swards in terms of lower nitrate leaching and greater soil biodiversity. There may also be benefits in terms of higher dry matter production in drought conditions, provided herb content is maintained within the sward.

The director of Teagasc, Professor Frank O'Mara, thanked Dr. Sinclair Mayne for the professional manner in which he carried out the review using his vast experience on pasture-based systems. The director emphasized the importance of greater adoption of perennial ryegrass/white clover on grassland farms in Ireland given the benefits highlighted in the report.

Clear, concise and consistent advisory messages based on robust science are needed to provide a clear strategy for farmers in their journey to reduced chemical N use, while increasing legumes in pastures. Likewise, he emphasized the importance of continued research in particular around the areas identified in this review.

More information:
External Assessment of Teagasc's Clover and Mult-Species Sward Research Programme. www.teagasc.ie/publications/20 … search-programme.php

Provided by Teagasc