The distribution of SOC in the soil profile in 2014 (Fig. 2B) was slightly different from that in 2013. The SOC in the entire 60 cm soil layer under PM + SL and SL was higher than those under control by 10.64 and 9.40% respectively, while that under PM was 2.71% lower.
In the upper 0–5 cm layer, the SOC under SL was much higher than that in other treatments but no significant differences were observed among PM + SL, PM and CK. In the 5–10 cm layer, PM + SL and PM had much lower SOC than SL and CK, while there was a significant increase for PM + SL in the 10–20 cm layer. There were only marginal differences among treatments at the 20–30 cm layer. At the 30–40 cm layer, PM + SL and SL had much more SOC than CK and PM, being similar with that in 2013. No obvious differences were noted among treatments below the 40 cm depth.