BIOPAR

Hemiparasitic plants for less competitive and more diverse ground covers

In vineyards and orchards, ground covers protect the soil, support biodiversity and contribute to the functioning of agroecosystems. However, they can become dominated by highly competitive grasses that produce large amounts of biomass, potentially compete with the crop for water and nutrients, and reduce plant diversity. Their management may then require frequent mowing, mechanical interventions or herbicide use.

The BIOPAR project explores an original approach to address these two challenges simultaneously: using native hemiparasitic plants, in particular greater yellow-rattle (Rhinanthus alectorolophus), to reduce the vigour and biomass of dominant grasses while promoting more diverse plant communities. Hemiparasites remain photosynthetically active, but connect to the roots of neighbouring plants and draw part of their water and nutrients from them. In doing so, they can reduce the competitive ability of dominant species and free up resources and space for other plants.

BIOPAR combines field trials, controlled-environment experiments and the prospecting of wild Swiss populations to characterise the effectiveness of yellow-rattle, its establishment requirements and the diversity of available plant material.

The first results are encouraging. Under controlled conditions, greater yellow-rattle significantly reduced the biomass of all five grass species tested under two fertilisation levels. This supports its potential to reduce ground-cover biomass and, ultimately, competition with grapevines or fruit trees. The experiments also show that seed origin strongly influences germination capacity. Complementary observations in a natural meadow further indicate that higher yellow-rattle abundance is associated with lower grass cover and lower total plant biomass.

Prospecting has also produced several documented seed lots of greater yellow-rattle (Rhinanthus alectorolophus), yellow-rattle (Rhinanthus minor) and common eyebright (Euphrasia rostkoviana). These resources will make it possible to compare different seed sources and broaden the range of hemiparasitic plants studied.

BIOPAR therefore aims to lay the foundations for ground covers that produce moderate biomass, are less competitive with the crop, and support greater plant diversity. The next steps will refine sowing and management protocols and prepare the transfer of this approach to viticulture and fruit-growing systems.