Methane and nitrous oxide emissions as affected by organic–inorganic mixed fertilizer from a rice paddy in southeast China

Abstract

The effects of commercial compost fertilizer application on trace gas emissions are not well understood due to a lack of field experiments. The objective of this study was to evaluate the emissions of methane (CH4) and nitrous oxide (N2O) along with grain yield from a rice paddy as affected by different organic–inorganic mixed fertilizer (OIMF) treatments. A field experiment was initiated in 2006 with chemical compound fertilizer (CF) and three OIMF amendments including pig manure compost (PMC), Chinese medicine residue compost (CMC), and rapeseed cake compost (RCC), from a rice paddy in southeast China. The emissions of CH4 and N2O were simultaneously measured using the static opaque chamber method over the entire rice growing season in 2011. Soil biotic parameters were measured in soil collected after the rice was harvested in 2011. Relative to the control, the OIMF treatments significantly increased CH4 emissions by 56–99 %, mainly due to exogenous organic substrate input, whereas no difference was observed in the CF treatment. The N2O emissions were stimulated substantially by an average of 40 % due to nitrogen fertilization compared with the control. Consecutive OIMF application tended to increase the grain yield, making it marginally higher than that of the CF treatment (7 %, P = 0.06). Compared with the control, the CF treatment slightly decreased the global warming potential and greenhouse gas (GHG) intensity, while they were remarkably increased in the OIMF treatments. Over the 5-year period of 2006–2011, the annual soil carbon sequestration rate was estimated to be 1.19 t C ha−1 year−1 for the control and 1.73–1.98 t C ha−1 year−1 for the fertilized treatments. Our results suggest that despite the beneficial effects of increasing both grain yield and soil organic matter, OIMF application such as PMC, CMC, and RCC may be responsible for increased global warming due mainly to the stimulated CH4 emissions. This effect should be thus taken into account when balancing agricultural production and GHG mitigation.