Table 1.
Input values utilized to the validated DNDC model for baseline scenario and the sensitivity tests.
Table 2.
Measured and simulated data of cumulative emissions of CH4 and N2O from a winter wheat – single rice rotation system from November 13, 2009 to October 10, 2010.
Figure 1.
Dynamics variations of field observed (in dot) and simulated (in line) emissions of CH4 (A, B, C) and N2O (D, E, F) for the treatments of CK, N, and NS, respectively.
CK, without both N fertilization and straw incorporation, N, with N fertilization, NS, with both N fertilization and straw incorporation. The vertical line in each panel divided the whole rotation into wheat (left) and rice (right) seasons. The vertical bars indicate the standard deviation of three replicates for each treatment. The dotted and solid arrows represent midseason or final drainage and N fertilization, respectively.
Table 3.
Impacts of alternative scenarios on averaged annual GHG emissions, soil organic carbon sequestration rate (SOCSR), N loss, grain yield, net GWP, and GHGI over the 45-year simulation.
Figure 2.
Cumulative emissions of CH4 (A, B, C) and N2O (D, E, F) for the treatments of CK, N, and NS, respectively. CK, without both N fertilization and straw incorporation, N, with N fertilization, NS, with both N fertilization and straw incorporation.
The slopes and determination coefficients were calculated by the linear regression of observed and simulated cumulative emissions of CH4 and N2O.
Figure 3.
Sensitivity tests of GWP of CH4 and N2O emissions to environmental factors and alternative management practices.
Starting from the baseline management conditions, change in (A) soil texture, (B) initial SOC content, (C) total precipitation, (D) annual mean temperature, (E) soil pH, (F) N fertilizer input, (G) straw return, (H) manure amendment, (I) tillage, and (J) split application ratio altered the GWP for the rotation system. Abbreviations for soil texture are as follows: LS, loamy sand; SCL, sandy clay loam; SC, sandy clay.
Figure 4.
Long-term (45-year) impacts of alternative management scenarios on (A) CH4, (B) N2O, (C) SOC content, (D) N loss, (E) net GWP, and (F) GHGI.
See Table 1 for the baseline scenario, N300 and N700, total N fertilizer rate of 300 and 700 kg N ha−1 yr−1,respectively, S1.5 and S6, straw return rate of 1.5 and 6.0 t ha−1 yr−1, respectively, OM250, replacing half of the annual inorganic N fertilizer (250 kg N ha−1) with an equivalent N amount of bean cake (C:N = 6.8∶1) used as manure and incorporated as basal fertilizer for each season, No-tillage, zero-tillage.