Multi-species swards have the ability to grow 11t of dry matter (DM) with no chemical nitrogen (N), but have they a role on Irish farms?
Joe Kelleher, a Teagasc advisor based in Co. Limerick, has outlined what is known so far about multi-species swards.
Key target to reduce chemical N
The Department of Agriculture, Food and Marine (DAFM) published the Ag Climatise document before Christmas 2020.
This document sets out a roadmap for Irish agriculture towards 2030. One of the key targets in the document is the reduction in the volume of chemical nitrogen (N) used on Irish farms.
Joe said: “Chemical nitrogen use on Irish farms peaked at 408,000t in 2018. This must be reduced to a target level of 350,000t by 2025, with a further reduction to an absolute maximum of 325,000t by 2030, equivalent to the usage in 2013.”
Tools to reduce chemical N
”We have numerous tools available to help us reduce our reliance and usage of chemical N including clover, building our soil fertility status, more efficient use of slurry and incorporating mixed-species swards into our farms,” Joe explained.
”The latter is a relatively new concept to most of us, but the reality is that if we go back a few generations, mixed-species swards were common on most Irish farms.”
What are multi-species swards?
Multi-species swards are swards that have a variety of plants from various families including grasses, clovers, brassicas and herbs.
Joe explained: ”When combined in a sward setting, the various species root at varying depths, allowing them to access more nutrients and moisture in the soil.
“The interaction between the plants in the swards allows them to work off each other and the end result is often greater than the sum of the individual parts.
”Red and white clover are often the engine of these swards that provides the nitrogen to produce high quantities of dry matter production.
”There are numerous trials ongoing at present investigating the potential of these swards on Irish farms. Teagasc, Johnstown Castle and the University College Dublin (UCD) Smartswards programme are examples of where in-depth research is currently being undertaken,” he added.
”One research project that has reached a conclusion was a trial undertaken in Teagasc Grange between Teagasc and UCD.
”The results of this trial, which began in 2012, were published last year, and show huge potential for these swards on Irish farms.
”One mixture used in this trial contained timothy, perennial ryegrass, red clover, ribwort plantain and chicory,” he continued.
”This mixture grew 11.6t of DM with no chemical fertiliser applied and this increased to 13.1t when 240kgs of chemical N was added.
”Compare this to the monoculture of perennial ryegrass which grew 5.9t with no N and 11.4t with 240kg of chemical N.”
Unanswered questions
Joe finished by stating: ”While the early results show great promise, there are still a lot of unanswered questions.
”The Grange trial was carried out by cutting trial plots, but how will these mixtures perform in a grazing situation?
“Will they suit a 21-day rotation? Will they be taken over by other weed species? Will they last in the mixture or will they all disappear in a few years?
”These and other areas are being currently investigated in trials at UCD, Johnstown Castle and Moorepark amongst other venues, and while it is early days in these trials, the early data looks strong,” he added.
”One of the early results from the Johnstown Castle trial shows that they are very good at out-competing other weed species, and when compared against unsprayed ryegrass plots, [with] the multi-species sward, only 4% of the mixture comprised weed species versus 30% for ryegrass plots.
“The persistency of multi-species swards in a grazing situation is the area that we know least about at this stage, but even if the chicory and plantain were to die out after a few years and you were left with a field of perennial ryegrass with good levels of clover, then that may be not such a bad outcome.
”The ability of these mixtures to grow large quantities of herbage with little or no chemical nitrogen cannot be ignored and yes, there are still some questions that need to be answered.
”Sometimes the best way to find out these answers is to find out for yourself.
”If you are reseeding a paddock this year, perhaps sowing a few acres of multi-species mixture might be worth a go,” he concluded.