Climate change effects on the weed suppressive ability of several cover crop mixtures

Climate change effects, such as rising temperature, carbon dioxide levels and extreme weather events, impact agriculture directly by reduction of crop yields and indirectly by increasing damage of crop pests. Therefore, preventive methods of plant protection, like cover cropping in integrated weed management, gain in importance. Their performance, however, depends on soil moisture and temperature in late summer. This study examined the effects of elevated temperature (+5°C) and increasing drought levels (no, mild and severe drought) on four commercial and two self-composed cover crop mixtures and their weed suppression performance in a split-plot greenhouse experiment from 2020-2022. Cover crop (CC) and weed biomass were assessed, along with weed control efficacy (WCE) and soil coverage. A canonical correspondence analysis (CCA) was performed to identify drought and temperature tolerant species. Both, elevated temperature and increasing drought level, reduced CC biomass and soil cover by 50%, severe drought even by more than 80%. Weed biomass was affected similarly, only severe drought reduced it by more than 90%. Nevertheless, CC mixtures, and the self-composed mixtures in particular, reduced weed biomass further and showed consistently WCE of more than 80% and up to 98%. The CCA revealed that Sorghum bicolor , Brassica carinata and Camelina sativa are promising species for future CC mixtures. Even though their biomass and soil coverage were reduced drastically by the examined climate change effects, CC mixtures still showed a high weed control ability. This resilience might be improved further by adjusted sowing dates and establishment methods and in turn improve CC performance under adverse climate change conditions. • The influence of drought and heat stress on cover crop mixtures was examined • Cover crop and weed biomass was reduced by each stress level by approx. 25-50% • Cover crop biomass was reduced, but weed control efficacy was still at 80-98% • Sorghum bicolor , Brassica carinata and Camelina sativa are promising species • Species diversity in mixtures did not contribute to stress resilience