Do the benefits of diversity hold in agriculture?
It is well established that species-rich grasslands achieve more than species-poor ones. For over twenty years, biodiversity experiments such as the [Jena Experiment](LINK TO JENA PROJECT PAGE) have shown that yield and many other functions increase with the number of plant species. However, these experiments run under very extensive conditions, without fertiliser and with only two cuts a year, and with wild plants. Whether their results also apply to agriculture is therefore often questioned. Intensively used forage grasslands in Germany consist mainly of a few heavily fertilised grass species bred for high yield.
This is exactly where the international network LegacyNet comes in. It studies diversity under agricultural conditions: with bred forage plants, with fertilisation and with frequent use.
The experiment: grassland leys and what they leave behind
The same experiment was set up at every site in the network. The plots contain grasses, legumes (such as clover) and herbs, ranging from single species to mixtures of six species. Heavily fertilised grass monocultures serve as a comparison. Because the design is identical everywhere, we can test whether the results hold under very different climate and soil conditions.
But the experiment does not end with the ley. In crop rotations, leys are ploughed up after a few years and followed by an arable crop. After the grassland phase, the same follow-on crop is therefore sown on all plots. This makes it possible to measure what a ley leaves to its successor, its legacy: Does a diverse mixture pass on more nitrogen to the next crop? Does it improve the soil? Can fertiliser also be saved in the subsequent arable phase? This legacy-effect across the crop rotation is at the core of the network and gives it its name.
Results
Higher yields with less fertiliser. The first major analysis, from 26 sites on four continents, has been published in the journal Science. Mixtures of grasses, legumes and herbs produce higher yields than intensively fertilised grass monocultures while requiring considerably less nitrogen fertiliser. Legumes in particular reduce fertiliser demand because they fix nitrogen from the air. Under warmer conditions, the benefits of diversity become even greater. Read the publication · TUM press release (German)
Diversity delivers more than yield. At the Freising site, we studied how the mixtures perform seven different ecosystem functions at the same time, known as their multifunctionality. Multifunctionality increases with the number of species and functional groups, even under intensive management. The groups contribute different things: legumes and herbs increase yield and improve water availability, while grasses make the plots more resistant to invasion by unwanted species. Mixtures of legumes and herbs performed particularly well overall, pure grass stands the worst. Targeted plant mixtures can thus benefit both agriculture and sustainability. Read the publication
Our contribution: the Freising site
From 2020 to 2023, we ran one of the network's experimental sites at Dürnast near Freising. On a total of 60 plots, the grassland leys of different diversity grew first, followed by two years of wheat. The work at the site was part of Laura Argens's doctoral thesis. The data from Freising feed into the network's joint analyses, including the Science publication. Now that the fieldwork is complete, we are involved in a series of further analyses and publications, among them on the legacy-effects of the leys on the follow-on crop. Sebastian T. Meyer is also a member of the LegacyNet publication committee, which coordinates the network's joint publications.
Key facts
Site lead: Sebastian T. Meyer · Network coordination: Caroline Brophy (Trinity College Dublin), John Finn (Teagasc) and Carsten Malisch (Aarhus University) · Funding: Voluntary research network, field experiment in Freising supported by IGSSE (Technical University of Munich) · Duration of the Freising site: 2020–2023 · More: LegacyNet