Plastic film mulching affects N2O emission and ammonia oxidizers in drip irrigated potato soil in northwest China

In soil, ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) are regarded as key factors mediating nitrous oxide (N2O) production and emission. However, there are scarce reports about the effect of film mulching on ammonia oxidizers, and the biological nitrification process of N2O emission is unclear. This study was based on potato field experiments under different mulching films, including polyethylene mulching film (PM), transparent degradable mulching film (TDM), black degradable mulching film (BDM), and bare land (CK). AOB and AOA abundances were estimated using real-time PCR, and their diversity and community structure were measured using high-throughput sequencing. Result revealed that the total N2O emission from CK was 12.32%-41.03% higher than that from film mulching soil. Under film mulching, according to total N2O emission from soil and N2O concentration in soil treatments were ordered as PM > BDM > TDM, and N2O production was closely correlated with copy numbers of the amoA gene. BDM significantly increased the number of amoA-AOB gene copies (P < 0.01), and PM significantly increased the those of amoA-AOA (P < 0.01). BDM and TDM increased AOB operational taxonomic units (OTUs), Chao1, Simpson, and Shannon indices, while PM increased the AOA OTUs and Chao1 index. Variations in AOA abundance and diversity were closely related to soil mineral N and temperature changes induced by polyethylene film mulching (P < 0.05), whereas AOB showed no significant association with soil properties. Meanwhile, we did not find a distinct treatment effect on AOB community structure. Our findings indicate that (i) degradable film mulching increased AOB abundance and diversity and N2O concentration, but obviously reduced N2O emissions, and (ii) AOA were more sensitive than AOB to polyethylene mulching film.