Have multi species swards a role on Irish farms?

Multi species swards have the ability to grow 11Ton of dry matter with no chemical nitrogen, but have they a role on Irish farms? Joe Kelleher, Teagasc Advisor, Newcastle West, Co. Limerick addresses this question here and discusses what is known so far about Multi species swards

Key target to reduce Chemical N

The Department of Agriculture, Food & Marine published the Ag Climatise document before Christmas last. This document sets out a roadmap for Irish Agriculture towards 2030. One of the key targets in the document is the reduction in the volumes of chemical Nitrogen on Irish farms. “Chemical nitrogen use on Irish farms peaked at 408,000 tonnes in 2018. This must be reduced to a target level of 350,000 tonnes by 2025, with a further reduction to an absolute maximum of 325,000 tonnes 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 Nitrogen including clover, building our soil fertility status, more efficient use of slurry and incorporating mixed species sward s into our farms. 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?

Multispecies swards are swards that have a variety of plants from various families of plants including grasses, clovers, brassicas and herbs. 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 the end result is often greater than the sum of the individual parts often ends. 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 on-going at present investigating the potential of these swards on Irish farms. Teagasc, Johnstown Castle and the UCD Smartswards programme are two examples of where in-depth research is currently being undertaken. 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. This mixture grew 11.6Ton of DM with no chemical fertiliser applied and this increased to 13.1Ton when 240kgs of chemical Nitrogen was added. When you compare this to the monoculture of perennial ryegrass which grew 5.9Ton with no nitrogen and 11.4Ton with 24okgs of chemical nitrogen. With these results, should we all be rushing out to sow these on our farms?

Unanswered questions

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.

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, the multi species sward only 4% of the mixture comprised of 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?