Jinyang Wang

Combined effects of nitrogen deposition and biochar application on emissions of N2O, CO2 and NH3 from agricultural and forest soils

Abstract Both nitrogen (N) deposition and biochar can affect the emissions of nitrous oxide (N2O), carbon dioxide (CO2) and ammonia (NH3) from different soils. Here, we have established a simulated wet N deposition experiment to investigate the effects of N deposition and biochar addition on N2O and CO2 emissions and NH3 volatilization from agricultural and forest soils. Repacked soil columns were subjected to six N deposition events over a 1-year period. N was applied at rates of 0 (N0), 60 (N60), and 120 (N120) kg Nh a−1 yr−1 without or with biochar (0 and 30 t ha−1 yr−1). For agricultural soil, adding N increased cumulative N2O emissions by 29.8% and 99.1% (p < 0.05) from the N60 and N120 treatments, respectively as compared to without N treatments, and N120 emitted 53.4% more (p < 0.05) N2O than the N60 treatment; NH3 volatilization increased by 33.6% and 91.9% (p < 0.05) from the N60 and N120 treatments, respectively, as compared to without N treatments, and N120 emitted 43.6% more (p < 0.05) NH3 than N60; cumulative CO2 emissions were not influenced by N addition. For forest soil, adding N significantly increased cumulative N2O emissions by 141.2% (p < 0.05) and 323.0% (p < 0.05) from N60 and N120 treatments, respectively, as compared to without N treatments, and N120 emitted 75.4% more (p < 0.05) N2O than N60; NH3 volatilization increased by 39.0% (p < 0.05) and 56.1% (p < 0.05) from the N60 and N120 treatments, respectively, as compared to without N treatments, and there was no obvious difference between N120 and N60 treatments; cumulative CO2 emissions were not influenced by N addition. Biochar amendment significantly (p < 0.05) decreased cumulative N2O emissions by 20.2% and 25.5% from agricultural and forest soils, respectively, and increased CO2 emissions slightly by 7.2% and NH3 volatilization obviously by 21.0% in the agricultural soil, while significantly decreasing CO2 emissions by 31.5% and NH3 volatilization by 22.5% in the forest soil. These results suggest that N deposition would strengthen N2O and NH3 emissions and have no effect on CO2 emissions in both soils, and treatments receiving the higher N rate at N120 emitted obviously more N2O and NH3 than the lower rate at N60. Under the simulated N deposition circumstances, biochar incorporation suppressed N2O emissions in both soils, and produced contrasting effects on CO2 and NH3 emissions, being enhanced in the agricultural soil while suppressed in the forest soil.

Modeling Impacts of Alternative Practices on Net Global Warming Potential and Greenhouse Gas Intensity from Rice–Wheat Annual Rotation in China

Background Evaluating the net exchange of greenhouse gas (GHG) emissions in conjunction with soil carbon sequestration may give a comprehensive insight on the role of agricultural production in global warming. Materials and Methods Measured data of methane (CH4) and nitrous oxide (N2O) were utilized to test the applicability of the Denitrification and Decomposition (DNDC) model to a winter wheat – single rice rotation system in southern China. Six alternative scenarios were simulated against the baseline scenario to evaluate their long-term (45-year) impacts on net global warming potential (GWP) and greenhouse gas intensity (GHGI). Principal Results The simulated cumulative CH4 emissions fell within the statistical deviation ranges of the field data, with the exception of N2O emissions during rice-growing season and both gases from the control treatment. Sensitivity tests showed that both CH4 and N2O emissions were significantly affected by changes in both environmental factors and management practices. Compared with the baseline scenario, the long-term simulation had the following results: (1) high straw return and manure amendment scenarios greatly increased CH4 emissions, while other scenarios had similar CH4 emissions, (2) high inorganic N fertilizer increased N2O emissions while manure amendment and reduced inorganic N fertilizer scenarios decreased N2O emissions, (3) the mean annual soil organic carbon sequestration rates (SOCSR) under manure amendment, high straw return, and no-tillage scenarios averaged 0.20 t C ha−1 yr−1, being greater than other scenarios, and (4) the reduced inorganic N fertilizer scenario produced the least N loss from the system, while all the scenarios produced comparable grain yields. Conclusions In terms of net GWP and GHGI for the comprehensive assessment of climate change and crop production, reduced inorganic N fertilizer scenario followed by no-tillage scenario would be advocated for this specified cropping system.