Soybean growth and nitrous oxide emissions in response to tillage and crop rotation

Global climate change is forcing different sectors including agriculture to come up with mitigation strategies. Nitrous oxide is the most potent greenhouse gas that contributes to global warming and is mainly produced from agricultural soil management. Two mitigation strategies to potentially reduce nitrous oxide emissions while maintaining cash crop yields are (i) shifting from conventional tillage to no-till and (ii) incorporating winter rye (Secale cereale L.) into corn (Zea mays L.)-soybean (Glycine max L.) rotation as a typical production system in the Midwest, USA. We harnessed a long-term trial to evaluate soil N dynamics, moisture and temperature, soybean production, and nitrous oxide emissions during 2020 and 2022 growing seasons. Treatments were two tillage factors (no-till and conventional chisel-disk) and two cover crops (winter rye and a no-cover crop control) arranged in factorial design with three replications. Results indicated that in 2020, no-till-no-cover crop had less nitrous oxide fluxes than the winter rye treatments, however it had higher N₂O-N losses than 2022.  A combination of winter rye-no-till provided similar soybean morphology, shoot biomass and grain yield compared to a tillage-based system with no cover crop but promoted soybean root biomass leading to greater carbon inputs. These results indicate the tradeoffs in benefits of winter rye in soybean cropping systems.