Nitrous oxide emissions during biological soil disinfestation with different organic matter and plastic mulch films in laboratory-scale tests

Nitrous oxide (N₂O), which is a greenhouse gas, may be more emitted as an intermediate product of denitrification during biological soil disinfestation. The biological soil disinfestation is a method to suppress soil-borne pathogens under reductive soil conditions produced by the application of organic matter and water irrigation with plastic film. The objective of the study was to determine the effects of different organic matter and mulch films on N₂O emissions during biological soil disinfestation. Grey lowland soil amended with cattle compost plus rice bran (0.2%), rice husk (0.2%) or dent corn (0.1%, 0.2% and 0.4%) was incubated at 100% water-holding capacity with or without plastic films made of polyvinyl chloride (PVC) and triple-layer polyolefin (3PO) for 72h at 50°C. Permeation of the two films was also measured at 25°C and 50°C. Results showed that incorporation of organic matter increased N₂O emissions compared with no organic matter addition at 50°C. Incorporation of rice bran and dent corn with easily decomposable C and low C:N ratios increased N₂O emissions for the first 12h, but thereafter, available C supply from these amendments suppressed N₂O emissions. Permeability of mulch films increased at a higher temperature and was larger for PVC than for 3PO. Our study indicated that rice husk should not be used for soil disinfestation and that application rates of organic matter must be determined based on their decomposability. Moreover, mulch film covering would not suppress N₂O emission in biological soil disinfestation because of high temperature.