Increasing plant diversity in agricultural grasslands boosts yields, reducing reliance on fertiliser

Higher plant diversity in agricultural grasslands increases yields with lower inputs of nitrogen fertiliser. Under warmer temperatures, the yield benefits of more diverse grasslands further increase. There are headline results from a landmark study across 26 international sites as part of LegacyNet, and published in Science. 

Sown productive grasslands (used to supply forage for livestock or as a ley in a crop rotation) typically comprise low species diversity. Two widely used grassland practices comprise 1) a single grass species (monoculture) managed with high inputs of synthetic nitrogen fertiliser, and 2) a two-species grass-legume combination that receives lower inputs of nitrogen fertiliser.

Webinar on multi-species mixtures: the Swiss experience

Prof. Andi Luescher presented a webinar on 30th April 2024 as part of the Agroecology Transect project. (website: agroecology-transect.net)

Andi has worked on multi-species grasslands for many years, and shared his group's research experience that ranges from basic research to on-farm assessments. 

Andi's webinar is available here on YouTube.

Multi-species grasslands enhanced diversity of soil nematode community

New research from the Teagasc Environment Research Centre, Johnstown Castle shows that higher plant diversity of intensively managed multi-species swards enhances belowground soil biodiversity and health. The study, which has been published in the international scientific journal, ‘European Journal of Soil Biology’, showed that as grasslands increased plant diversity up to six species of grasses, clovers and herbs, soil-dwelling nematode communities also had increased diversity and improved performance across a range of ecological soil health indices.

Plant diversity (and drought) affect legacy effects on soil fertility

We investigated the effect of grassland diversity, drought and higher nitrogen level on legacy effects. Legacy effects (measured as yield of a follow-on crop, which reflect the influence of the preceding crop) were strongly positively affected by the proportion of legumes. Drought can impact legacy effects, but is modest relative to the effect of plant diversity. Aggregated across both ley and follow-on crop phases, the high-diversity, lower-nitrogen grassland community yielded more than the higher-nitrogen grass monoculture. 

Fig. 1. Overhead shot of the field site with the experimental design and plot management to track the effect of plant diversity, drought and fertiliser level on the legacy effect within plots.

Assessing the habitat quality of Irish field margins

 

We developed a methodology to assess the habitat quality of field margins in a set of more intensively managed farms in Ireland. Overall, we found that over half of the field margins surveyed had low or very low levels of habitat quality.

Field margin with very low habitat quality (dominated by negative indicator species)

Semi-natural habitats and Ecological Focus Areas on Irish farmland

HIighlights: We surveyed farmland habitats on tillage and more intensive beef and dairy farms. Habitat area was lower than that found in the general countryside, and was dominated by linear features (especially hedgerows). All tillage farms and the majority of pastoral farms in our sample met the current 5% EFA requirement, and the vast majority (93%) met a scenario with a 7% EFA requirement. There is a considerable amount of a broader range of wildlife habitats already present on intensively managed farms that was not included in EFA in Ireland, and is not reflected in policy or legislation. 

Open Access data: landscape classification of Ireland

The FarmForBio project has developed a landscape classification map of the Republic of Ireland. 

The map and the GIS data are now available on Teagasc’s TStor repository https://t-stor.teagasc.ie/handle/11019/2790