Table 1.
Soil organic carbon sequestration in the 0–20 cm and 20–40 cm soil layers under different water management strategies over the period 1998–2014.
| Soil layers | Treatments | γ1998 (g cm−3) | γ2014 (g cm−3) | C1998 (g kg−1) | C2014 (g kg−1) | ΔCS (kg C ha−1) | SOCSR (kg C ha−1 yr−1) |
|---|---|---|---|---|---|---|---|
| 0–20 cm | F-RF | 1.02 ± 0.01 a | 0.99 ± 0.01 a | 13.12 ± 0.44 a | 16.96 ± 0.09 b | 8013 ± 998 b | 501 ± 62 b |
| F-D-F | 1.04 ± 0.01 a | 0.96 ± 0.02 a,b | 12.47 ± 0.22 a | 17.81 ± 0.13 a | 11074 ± 470 a | 692 ± 29 a | |
| CF | 1.04 ± 0.01 a | 0.90 ± 0.02 b | 12.03 ± 0.23 a | 18.07 ± 0.17 a | 11854 ± 705 a | 741 ± 44 a | |
| 20–40 cm | F-RF | 1.34 ± 0.02 a | 1.33 ± 0.01 a | 8.78 ± 0.35 a | 9.62 ± 0.37 c | 2259 ± 207 c | 141 ± 13 c |
| F-D-F | 1.33 ± 0.01 a | 1.26 ± 0.01 b | 8.43 ± 0.10 a | 10.71 ± 0.20 b | 6077 ± 245 b | 380 ± 15 b | |
| CF | 1.33 ± 0.01 a | 1.19 ± 0.01 c | 8.50 ± 0.19 a | 11.82 ± 0.25 a | 8816 ± 636 a | 551 ± 39 a |
Mean ± SE. The different letters following each value in the same column indicate significant differences among the treatments in each soil layer (P < 0.05). γ1998 and γ2014 refer to soil bulk densities, and C1998 and C2014 refer to the SOC contents in 1998 and 2014, respectively. ΔCS refers to the changes in carbon stocks, and SOCSR refers to the SOC sequestering rate from 1998 to 2014. CF means continuous year-round flooding with 2–10 cm water layer, F-D-F means flooding in rice season, except drainage at midseason and harvest time, and F-RF means flooding for transplanting and tillering, with no further irrigation.