Priming effect intensity of soil organic carbon mineralization under no-till and residue retention

Abstract No-till (NT) and residue retention (RR) are widely adopted techniques to improve soil health and mitigate global warming, but knowledge on the priming effect (PE) intensity of soil organic carbon (SOC) mineralization under NT and RR is still limited. Therefore, a field-cum-laboratory study was conducted to assess the effects of NT and RR as well as their interaction on the basal SOC mineralization and PE intensities. Soil samples obtained for 0–5, 5–10, and 10–20 cm layers, from a factorial experiment of tillage practices (NT and plow tillage (PT)) and residue managements (RR and residue removal (R0)), with and without 13C-labelled maize residues were incubated. The results showed that the contribution of PE intensity to total mineralization increased with the depth of soil layer, but the interaction of NT and RR on the PE was not significant. The PE of NT was lower than that of PT by 12.5–17.9% (30.6–54.3 mg kg−1) under RR and 10.2–11.5% (32.4–39.9 mg kg−1) under R0, because of higher soil water content and compaction under NT than that under PT. Additionally, the ∆POC (particulate organic carbon concentration loss) after incubation was the dominant positive factor; a lower ∆POC was observed under NT than that under PT. Moreover, the PE of RR was lower than that of R0 by 23.8–28.0% (66.7–96.7 mg kg−1) under NT and 21.3–22.3% (68.5–81.6 mg kg−1) under PT due to lower bulk density, higher SOC concentration before incubation, and substantial ∆DOC (dissolved organic carbon concentration loss, 7.7–25.8 mg kg−1) under RR. Furthermore, the basal mineralization of NT was lower than that of PT under RR and R0. Although RR had higher basal mineralization than that under R0, the lowest basal mineralization per unit carbon was recorded in the NT with RR treatment due to a significant interaction between NT and RR. Therefore, a combination of NT and RR synchronously decreased the basal mineralization and PE intensity and enriched the amount of SOC, which can lead to positive feedback against the SOC sequestration.