Table 3.
Seasonal cumulative N2O and CO2 emissions and global warming potentials (GWPs) under different fertilization treatments during the maize growing seasons in 2021 and 2022.
| Treatment | N2O emission (kg N ha−1) | CO2 emission (t C ha−1) | GWP (t CO2-eq ha−1) | ||||||
|---|---|---|---|---|---|---|---|---|---|
| 2021 | 2022 | Avg. | 2021 | 2022 | Avg. | 2021 | 2022 | Avg. | |
| CK | 0.78 (0.03)a db | 0.54 (0.02) c | 0.66 (0.03) | 1.45 (0.27) | 3.01 (0.25) | 2.23 (0.21) e | 5.66 (1.01) | 11.25 (0.90) | 8.46 (0.77) e |
| CN | 2.09 (0.18) a | 1.53 (0.08) a | 1.81 (0.11) | 2.48 (0.24) | 4.63 (0.32) | 3.55 (0.28) d | 9.97 (0.88) | 17.63 (1.20) | 13.80 (1.03) d |
| CNM | 1.46 (0.11) c | 1.14 (0.05) b | 1.30 (0.08) | 3.10 (0.14) | 4.93 (0.50) | 4.02 (0.29) cd | 12.00 (0.57) | 18.57 (1.84) | 15.29 (1.11) cd |
| CNS | 1.58 (0.08) c | 1.15 (0.07) b | 1.36 (0.07) | 3.01 (0.34) | 4.75 (0.39) | 3.88 (0.18) cd | 11.71 (1.26) | 17.90 (1.41) | 14.80 (0.68) cd |
| CM | 1.52 (0.08) c | 1.08 (0.04) b | 1.30 (0.04) | 3.52 (0.09) | 5.19 (0.43) | 4.36 (0.25) bc | 13.56 (0.38) | 19.51 (1.57) | 16.53 (0.93) bc |
| CT | 1.86 (0.14) ab | 1.15 (0.11) b | 1.51 (0.04) | 4.17 (0.57) | 6.10 (0.61) | 5.13 (0.58) a | 16.07 (2.02) | 22.85 (2.28) | 19.46 (2.11) a |
| NT | 1.61 (0.16) bc | 1.14 (0.05) b | 1.38 (0.10) | 3.82 (0.14) | 5.93 (0.54) | 4.87 (0.22) ab | 14.69 (0.53) | 22.22 (1.97) | 18.45 (0.83) ab |
| F and p values of fixed effects | |||||||||
| Treatment | F(6, 12) = 79.19, p < 0.001 | F(6, 12) = 54.31, p < 0.001 | F(6, 12) = 58.23, p < 0.001 | ||||||
| Year | F(1, 14) = 257.22, p < 0.001 | F(1, 14) = 388.67, p < 0.001 | F(1, 14) = 369.97, p < 0.001 | ||||||
| Treatment × Year | F(6, 14) = 4.31, p = 0.011 | F(6, 14) = 0.80, p = 0.589 | F(6, 14) = 0.73, p = 0.634 | ||||||
aNumbers in brackets are standard deviations (n = 3).
bDifferent letters indicate Tukey-adjusted differences among treatments at the level of 0.05 based on linear mixed-effects model. For N2O emissions, letters compare treatments within each year due to significant Treatment × Year interaction; for CO2 emissions and GWP, letters compare treatment marginal means averaged across two years due to insignificant Treatment × Year interaction.
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.