Applying DeNitrification-DeComposition model to investigate methane emission processes through nitrogen path in paddy field soil, Lampung Province, Indonesia

บทคัดย่อ

Importance of the work: Alternative methods are required for fertilizer application recommendations
and irrigation schemes in paddy cultivation to mitigate CH4 emission.
Objectives: To investigate whether CH4 emission and its processes from the field are related to
fertilizer dose and irrigation scheme.
Materials and Methods: Three doses of N fertilizer recommendations (no fertilizer, 50 kg N/ha and
100 kg of N/ha) were applied to continuous flooding and intermittent irrigation schemes in paddy
fields. CH4 flux was measured using a static closed-chamber and simulated using the DeNitrificationDeComposition (DNDC) model to investigate the processes of emissions in the soil.
Results: Soil organic carbon decreased quickly with continuous flooding at all fertilizer doses. Total
N and soil organic carbon were higher in the N fertilizer application than without N. The C-to-N ratio
was in the range 18–26; the mineralization rate was 0.024–0.0245 kg C/kg soil in the topsoil and the
NH4
+
level was 16.5 parts per million (ppm). The maximum oxygen content was 10 ppm, while the
soil Eh reached −300 mV. Methane emission was higher in the submerged fields. Fertilizers did not
affect the amount of either methanogens or methanotrophs. Methanogens had a strong correlation to
methane emission (correlation coefficient, r = 0.7–0.8) in all nitrogen doses under submerged soil
and a weak correlation under the intermittent flooding treatment (r = 0.48–0.71). The DNDC methane
emission simulation was lower than the observed values.
Main findings: Methane emissions from continuous flooding were 0.797–1.048 kg C/ha/d, which
were higher than with intermittent irrigation (0.03–0.401 kg C/ha/d). Model simulations and crop
growth showed that intermittent irrigation was effective in paddy cultivation for mitigating methane
emissions.