Table 4.
Soil organic carbon (SOC) sequestration rate, seasonal SOC sequestration efficiency and seasonal net global warming potential (GWP) under different fertilization treatments during the maize growing seasons in 2021 and 2022.
| Treatment | SOC sequestration rate (t ha−1 yr.−1) | SOC sequestration efficiency (%) | Net GWP (t CO2-eq ha−1) | ||||||
|---|---|---|---|---|---|---|---|---|---|
| 2021 | 2022 | Avg. | 2021 | 2022 | Avg. | 2021 | 2022 | Avg. | |
| CK | - | - | - | - | - | - | 12.10 (5.22) | 8.01 (3.44) | 10.05 (3.29) a |
| CN | 0.16 (0.05)a | 0.11 (0.08) | 0.13 (0.01) db | 6.0 (0.8) | 5.5 (2.7) | 5.8 (0.9) c | 4.24 (4.63) | 1.58 (3.07) | 2.91 (3.77) ab |
| CNM | 0.36 (0.15) | 0.33 (0.10) | 0.34 (0.08) c | 13.9 (4.2) | 9.3 (3.2) | 11.6 (2.7) b | −4.72 (3.86) | −5.48 (2.89) | −5.10 (0.69) bcd |
| CNS | 0.58 (0.14) | 0.60 (0.11) | 0.59 (0.03) ab | 12.4 (3.2) | 12.7 (2.0) | 12.5 (0.8) b | −6.76 (6.13) | −7.78 (5.84) | −7.27 (0.74) cd |
| CM | 0.67 (0.03) | 0.74 (0.07) | 0.71 (0.05) a | 16.2 (0.6) | 18.5 (1.7) | 17.4 (1.1) a | −11.14 (3.38) | −12.36 (2.55) | −11.75 (1.56) d |
| CT | 0.37 (0.07) | 0.50 (0.08) | 0.44 (0.08) bc | 9.8 (1.9) | 10.6 (1.7) | 10.2 (1.8) bc | −1.51 (4.57) | −3.26 (4.21) | −2.39 (3.48) bc |
| NT | 0.38 (0.04) | 0.53 (0.03) | 0.46 (0.03) bc | 10.2 (1.6) | 11.4 (0.4) | 10.8 (1.0) b | −3.01 (1.91) | −4.34 (3.06) | −3.68 (1.68) bcd |
| F and p values of fixed effects | |||||||||
| Treatment | F(5, 10) = 30.98, p < 0.001 | F(5, 10) = 16.00, p < 0.001 | F(6, 12) = 18.10, p < 0.001 | ||||||
| Year | F(1, 12) = 2.82, p = 0.119 | F(1, 12) = 0.01, p = 0.909 | F(1, 14) = 2.10, p = 0.169 | ||||||
| Treatment × Year | F(5, 12) = 1.43, p = 0.282 | F(5, 12) = 1.62, p = 0.227 | F(6, 14) = 0.12, p = 0.992 | ||||||
aNumbers in brackets are standard deviations (n = 3).
bDifferent letters indicate Tukey-adjusted differences among treatment marginal means averaged across two years due to insignificant Treatment × Year interaction at the level of 0.05 based on linear mixed-effects model.
CK, no N fertilizer; CN, conventional urea; CNM, 75% urea N plus 25% composted poultry manure N; CNS, 75% urea N plus 25% composted slurry N; CM, 100% composted poultry manure N; CT, 75% urea N plus 25% straw N with deep tillage; NT, 75% urea N plus 25% straw N with no tillage.