Effects of plastic film mulching with drip irrigation on N₂O and CH₄ emissions from cotton fields in arid land

SUMMARY To evaluate the effects of a modern cultivation system of plastic film mulching with drip irrigation (MD) on soil greenhouse gas fluxes, methane (CH 4 ) and nitrous oxide (N 2 O) fluxes were quantified and contrasted in an MD system and a traditional system of mulch-free flood-irrigated (MFF) cotton ( Gossypium hirsutum L.) in fields of northwest China. The results showed that soil N 2 O flux and the absorption rate of CH 4 were lower in the MD than the MFF sites. A possible reason for the higher CH 4 emissions at MD sites was that the relatively low gaseous oxygen (O 2 ) availability and high ammonium (NH 4 + ) content in the MD soil increased CH 4 generation by methanogens and decreased CH 4 oxidation by methanotrophs. The lower N 2 O in the MD sites may be due to an increase of soil denitrification by Thiobacillus denitrificans that reduced some nitrous compounds further into nitrogen gas (N 2 ). Taking into account the global warming potentials of CH 4 and N 2 O in a 100-year time horizon, during the entire growth period, the contribution of CH 4 to the greenhouse effect was significantly lower than N 2 O in these two treatments. Considering these two greenhouse gas fluxes together, a transition from non-mulching cultivation to mulching cultivation could reduce atmospheric emissions by c . 20 g CO 2 e m 2 /season. Based on these findings and previous studies, it can be concluded that mulched-drip irrigation cultivation is a good way to decrease the emission of greenhouse gases and reduce the global warming impact of arid farmlands.