Long-term reduced tillage does not enhance crop yield, soil organic carbon stocks or greenhouse gas mitigation under ambient rainfall and rainfall exclusion in a temperate Luvisol

Reduced tillage (RT) is widely promoted as an agroecological practice to enhance soil organic carbon (SOC) sequestration and mitigate greenhouse gas (GHG) emissions. However, its long-term effects on SOC stocks, crop yields, and soil GHG fluxes remain debated, particularly under changing climatic conditions. We investigated the impacts of RT and conventional tillage (CT) in the Garte-Sued field trial established in 1970 in Goettingen, Germany on a silt loam Haplic Luvisol under a humid temperate climate. Over two years, we assessed crop yield, SOC stocks and fractions, soil mineral N, and soil CO 2 and N 2 O fluxes under ambient rainfall and 50 % rainfall exclusion (via rainout shelters). After 53 years, RT resulted in a stratification of SOC within the plough layer, but SOC stocks at 0–90 cm did not differ between tillage practices. Crop yields were, in general, lower under RT compared to CT but the significance of the effect depended on crop species. Rainfall exclusion did not significantly affect yields or cumulative CO 2 and N 2 O fluxes, likely due to high soil water retention and moderate water deficit. Soil CO 2 and N 2 O fluxes were mainly driven by soil temperature, water-filled pore space, and mineral N, with emission peaks following management events. Reduced tillage did not affect soil CO 2 efflux, while it tended to increase N 2 O fluxes, especially under reduced rainfall. Our findings suggest that, in humid temperate and medium-textured soils, RT does not enhance crop yield, SOC stocks, or GHG mitigation relative to CT under ambient and reduced rainfall. • Crop yields were slightly lower under reduced tillage than conventional tillage. • Reduced tillage led to a stratification of soil organic carbon in the plough layer. • Soil organic carbon stocks at 0–90 cm did not differ between tillage practices. • Reduced tillage tended to increase N 2 O fluxes compared to conventional tillage. • Reduced tillage tended to increase greenhouse gas emissions under reduced rainfall.