Continued No‐Till and Subsoiling Improved Soil Organic Carbon and Soil Aggregation Levels

Tillage and crop residue inputs are important factors that impact soil aggregation and soil organic C (SOC) decomposition. This study evaluated the impacts of tillage and 10 yr of crop residue removal on aggregate stability, distribution, and associated C. The research was conducted in North China between 2002 and 2011. The treatments were five tillage systems that included conventional tillage (CT), subsoiling (ST), harrow tillage (HT), rotary tillage (RT), and no‐till (NT) in combination with crop residue retention (P) or residue removal (A). The results indicate that 74 to 82% of aggregates were macroaggregates (0.25–5 mm) and that these aggregates contained from 53 to 87% of the SOC in the 0‐ to 30‐cm depth. Tillage and residue removal reduced macroaggregates and SOC levels, especially under the RT treatment, but residue inputs slowed down the rate of SOC depletion in the soil. The treatments of no‐till with residue retention (NTP) and subsoiling with residue retention (STP), accumulated more C in stable macroaggregates and significantly increased SOC levels, which increased 13.37 and 9.59 Mg C ha–1, respectively, in 10 yr. Crop residue input combined with an appropriate tillage system is an effective method for maintaining and improving low‐quality soil and SOC levels in the widespread wheat (Triticum aestivum L.)–maize (Zea mays L.) cropping system of North China.