Subsoiling during summer fallow in rainfed winter-wheat fields enhances soil organic carbon sequestration on the Loess Plateau in China

Scientific management of the soil organic carbon (SOC) pool, e.g., through a reasonable tillage system, is a potential way to mitigate global climate change. There is scarce information about the effect of tillage during the summer fallow period on the SOC pool in rainfed winter-wheat fields. The present study was designed to evaluate the effects of tillage practices, i.e., plow tillage (PTF), subsoiling (STF) and no tillage (NTF), during the summer fallow period on SOC sequestration in winter-wheat fields in the rainfed area of the eastern Loess Plateau of China. The SOC, mineral-associated organic carbon (MOC), permanganate-oxidizable organic carbon (POxC) and particulate organic carbon (POC) concentrations were determined after four years of tillage implementation during the summer fallow period. Our results showed that in comparison to the adoption of NTF, the adoption of STF significantly increased POxC, POC and MOC concentrations by 56.6-111.2%, 45.7-118.7% and 26.2-29.4%, respectively, at the 10-20 and 30-40 cm soil depths before sowing (P < 0.05). The POxC and MOC concentrations under STF at depths of 0-10, 10-20, 20-30 and 30-50 cm were significantly greater than those under PTF and NTF after harvesting (P < 0.05). In addition, the SOC concentration and SOC stock under STF were significantly greater than those under NTF at the 0-10, 10-20, 20-30 and 30-40 cm soil depths before sowing and after harvesting (P < 0.05). Furthermore, in comparison to PTF and NTF, STF resulted in significantly higher SOC stocks by 12.0-25.3% and 7.1-19.2% than PTF and NTF, respectively, in the 0-10, 0-20, 0-30, 0-40 and 0-50 cm soil profiles at harvesting (P < 0.05). In summary, the adoption of STF could be beneficial to the management of the SOC pool in the 0-50 cm soil profile in the rainfed area of winter-wheat on the Loess Plateau of China.