Strategic tillage achieves lower carbon footprints with higher carbon accumulation and grain yield in a wheat-maize...

Continuous single tillage has the potential to increase greenhouse gas (GHG) emissions and decrease the accumulation of soil organic carbon (SOC), thus increasing carbon footprints (CFs). However, in a wheat-maize cropping system, limited information was available about the effects of strategic tillage on CFs. Thus, a four-year field experiment was conducted, including continuous rotary tillage (RT), continuous no-till (NT), RT + subsoiling (RS), and NT + subsoiling (NS), to investigate the effects of NS (strategic tillage) on the unit area and unit yield. The results showed that CO₂ emission was the highest contributor to CFs (73.92%) in a winter wheat-summer maize cropping system, following the order of NS < NT < RS < RT. The direct N₂O emissions from fertilizers and residues were 4.43-4.51 t CO₂-eq ha^-1 yr^-1 during the wheat and maize seasons, and indirect N₂O emissions from irrigation and fertilizer inputs had a proportion of >80% from total agricultural inputs. The differences in SOC storage significantly affected the CFs. Although the NS treatment increased the amount of GHG emissions from the residues returned and consumption of diesel, the enhancement of SOC storage by deeper SOC increased. Thus, lower area-scaled CFs were observed in the NS treatment. Furthermore, a higher grain yield and an annual change of SOC storage compared with other treatments were observed under the NS system, which helped to reduce the CFs. The yield-scaled CFs followed the order of RT > RS > NT > NS when considering the changes in SOC storage. Therefore, the NS treatment resulted in a higher grain yield and SOC sequestration with lower CFs, and thus, it could be recommended as the best tillage method to achieve sustainable production and environmental balance in a wheat-maize cropping system.