Prior to termination, the rye cover crop increased the soil methane sink

Even though the impact of cover crops on soil moisture has been well documented, little work has investigated the resulting impact on methane emissions. Therefore, the objective was to determine the influence of a dormant seeded rye ( Secale cereale ) cover crop on soil temperatures, soil moisture, inorganic N, and total CH 4 ‐C emission in a well‐drained frigid soil from the start of growth in April/May through corn's ( Zea mays ) V4 growth stage. In this study, soil moisture, temperature, CH 4 ‐C, and N 2 O‐N fluxes were measured near‐continuously. The rye cover crop: (1) reduced the water‐filled porosity in the surface 5 cm in 2018 and 2020; (2) did not influence soil temperature prior to corn's V2 growth stage, increased the soil temperature between the V2 and V4 growth stages in 2019, and reduced the soil temperature in 2020; and (3) reduced ( p < 0.01) the CH 4 flux prior to corn seed emergence (VE) in 2018, 2019, and 2020. Over the 3 years, rye reduced ( p = 0.04) CH 4 flux (increased soil methane sink) by 6.4 g (ha × day) −1 prior to VE and reduced ( p = 0.02) carbon dioxide equivalence (CO 2 e) from −1.9 to −11.9 kg CO 2 e ha −1 . These decreases accounted for 22.3% of the CO 2 e derived from N 2 O (53.4 kg CO 2 e‐N 2 O) and suggest that the rye cover crop induced reductions in CH 4 emissions need to be considered in carbon intensity calculations.