Tillage is a common agricultural practice that helps prepare the soil and remove weeds. However, it remains unknown how tillage intensity has evolved and its effect on net greenhouse gas (GHG) emissions. Here, using a process-based modelling approach with a multi-source database, we examined the change in tillage intensity across the US corn–soybean cropping systems during 1998–2016 and the impact of tillage intensity on soil GHG emissions. We found that tillage intensity first decreased and then, after 2008, increased, a trend that is strongly correlated with the adoption of herbicide-tolerant crops and emerging weed resistance. The GHG mitigation benefit (−5.5 ± 4.8 TgCO₂e yr⁻¹) of decreasing tillage intensity before 2008 has been more than offset by increased GHG emissions (13.8 ± 5.6 TgCO₂e yr⁻¹) due to tillage reintensification under growing pressure of weed resistance. As weed resistance persists or grows, tillage intensity is anticipated to continue rising, probably increasing GHG emissions. Our results imply that farmers’ choices in managing herbicide resistance may help mitigate agricultural GHG emissions, underscoring the importance of an alternative strategy to control weeds.

耕作是一种常见的农业实践，有助于整地和清除杂草。然而，耕作强度如何演变及其对温室气体 (GHG) 净排放量的影响仍然未知。在这里，我们使用基于过程的建模方法和多源数据库，研究了 1998-2016 年美国玉米-大豆种植系统耕作强度的变化以及耕作强度对土壤温室气体排放的影响。我们发现耕作强度先是下降，然后在 2008 年之后增加，这一趋势与采用耐除草剂作物和出现的杂草抗性密切相关。温室气体减排效益 (−5.5 ± 4.8 TgCO ₂ e yr ⁻¹) 在 2008 年之前降低的耕作强度已经被增加的温室气体排放量 (13.8 ± 5.6 TgCO ₂ e yr ⁻¹ ) 所抵消，这是由于在杂草抗性压力不断增加的情况下耕作再集约化。随着杂草抗性持续存在或增强，耕作强度预计将继续上升，可能会增加温室气体排放。我们的结果表明，农民在管理除草剂抗性方面的选择可能有助于减少农业温室气体排放，强调了控制杂草的替代战略的重要性。