Effects of straw return on C2-C5 non-methane hydrocarbon (NMHC) emissions from agricultural soils

The effect of crop straw return on C2-C5 non-methane hydrocarbon (NMHC) emissions from agricultural soils is investigated using a laboratory-controlled incubation of agricultural soils amended with crop straw for a period of 56 days. The average emission fluxes of total C2-C5 NMHCs from amended agricultural soils are 304 and 173 ng kg−1 h−1 under non-flooded and flooded conditions, respectively. Alkenes are the principal emitted C2-C5 NMHCs from amended agricultural soils, where a predominance of ethene, propene and 1-butene together shared 65% and 59% of the total C2-C5 NMHCs under non-flooded and flooded conditions, respectively. The emissions rates of the above top three alkenes and the total C2-C5 alkenes from amended agricultural soils under non-flooded conditions are one to four times those under flooded conditions, and these average values are 14-89 and 5-34 times those in their corresponding control treatments, respectively. These results imply that straw return contributes substantially to the emissions of light alkenes from agricultural soils, particularly under non-flooded conditions. The high correlation between microorganisms and C2-C5 NMHC fluxes from amended agricultural soils suggest that microbes play an important role in C2-C5 NMHC emissions from straw-amended agricultural soils. A rough estimate indicates that crop straw return could contribute insignificantly to global C2-C5 hydrocarbon budgets.