N2O fluxes and direct N2O emission factors from maize cultivation on Oxisols in Thailand

Abstract

The application of nitrogen (N) fertilizers to agricultural soils is a primary source of nitrous oxide (N2O) emissions to the atmosphere. The default emission factor (EF) suggested by the Intergovernmental Panel on Climate Change (IPCC) is 1.0% of fertilizers–N applied to agricultural soils. This EF has been found to vary significantly in time and space and country specific EF is needed to improve the reliability of greenhouse gas inventory. In this study, direct N2O emission factor in a silt loam soil cultivated with maize was investigated using the static chamber method. Daily N2O fluxes from three treatments: control (T1), and two N application rates of 97 (T2) and 155 (T3) kg N ha−1 were studied in the field experiments. Results indicated that the average N2O fluxes (average ± S.E.) in T1, T2 and T3 treatments for three cropping cycles were 0.54 ± 0.26, 0.81 ± 0.26 and 0.98 ± 0.27 mg N2O m−2 day−1, respectively. N2O emissions increased sharply after 5–7 days of N fertilization application, with the highest value corresponding to 18–32% of total N2O emissions. The average EFs for three crops were 0.0082 ± 0.0022 kg N2O–N kg−1 N for T2 (0.82% of N applied) and 0.0059 ± 0.0014 kg N2O–N kg−1 N for T3 (0.59% of N applied). It was found that the total N2O emissions as well as maize yields varied between wet and dry seasons. It is thus recommended that at least both wet and dry croppings are included when country specifics EFs are developed.