Exudate compositions differ between the cover crops vetch and oat

Enhancing carbon (C) storage in soils through crop management can mitigate atmospheric CO₂ levels and improve soil health. Cover crops like bristle oat (Avena strigosa) and common vetch (Vicia sativa) may contribute to soil C sequestration via root biomass and rhizodeposition, including root exudates, but C storage potential at the species and varietal levels for these plants remain poorly documented, partly due to difficulties in measuring root exudation under field conditions. This study compared four cultivated varieties of bristle oat and common vetch, focusing on their root and exudate C content and metabolic profiles. Distinct metabolite profiles were identified mainly at the species levels. Oat roots had a reduced C content compared to vetch roots although they contained more amino acids, sugars, organic acids and specialized metabolites. On the contrary, C content was higher in oat exudates with more fatty acids and specialized metabolites while vetch exuded more sugars, organic acids and nucleotides. These results suggest that the mixture of these two plants can produce complementary C deposits, enhancing C storage and allowing the construction of a rich (microbial) soil ecosystem.