S20 - Session P1 - Copper phytoextraction ability of green manure plants in vineyard soils

Authors: Pierre Eon *, Thierry Robert, Jean-Pascal Goutouly, Laurent Delière, Violette Aurelle, Laurence Denaix, Jean-Yves Cornu

Many vineyard soils are contaminated by copper (Cu) due to the long-term use of Cu-based fungicides to prevent downy mildew. Soil Cu contamination in vineyard soils has consequences for the sustainability of vineyard ecosystems since it has chronic effects on the population dynamics of the soil fauna, which is important for maintaining the soil structure and completing the biogeochemical cycles of nutrients. Ways to reduce the Cu contamination of vineyard soils are thus needed along with alternatives to Cu to protect vines against downy mildew. Phytoextraction is a phytotechnology that reduces the concentration of metals in soil by accumulating metals in harvestable plant parts. Phytoextraction trials are underway to reduce the Cu contamination of vineyard topsoils by growing specific cover plants in the inter-row (Fig. 1). The aim of this work was to assess the Cu phytoextraction ability of green manure plants using different approaches: (i) individual screening of green manure plants through hydroponic and soil pot experiments, (ii) in situ cultivation of one green manure mixture on different vineyard soils, and (iii) in situ cultivation of different green manure mixtures on one vineyard soil. Plants tested were selected among the grasses, legumes and crucifers most commonly sown as green manure plants in vineyards. Their phytoextraction potential was assessed from their dry matter production and from the concentration of Cu in their shoots. First results showed that (i) clover has a higher Cu extraction potential than other green manure plants, (ii) Cu extraction by green manure plants varied among vineyard soils together with Cu phytoavailability, and (iii) Cu phytoextraction yields remained lower than 1 kg Cu/ha/year regardless of the soil and the green manure plants used. This work will get new insights into how green manure plants can be used to alleviate Cu ecotoxicity in vineyard soils. Figure 1. Mixed crop green manure plants made of rough oats (Avena strigosa) and clover (Trifolium incarnatum, Trifolium michelianum and Trifolium resupinatum) sown in vineyard inter-rows (Courpiac, Gironde, France).