Agricultural soil plastic as a hidden carbon source stimulates microbial activity and increases carbon dioxide emissions.

• The DOC released from plastic that can be used by microorganisms in soil. • Plastic carbon participated in soil carbon cycle was confirmed. • PE plastic farmland in northwest China, 1.39 × 10⁵ tons of excess CO 2 emissions. • Replace PE plastic film with biodegradable film, 7.5-fold more excess CO 2 emissions. Plastic film mulching is an important agricultural practice, but its accumulation in soil threatens soil health. Here, we explored the effects of plastic film on soil carbon cycling through microcosmic incubation and estimated the excess carbon dioxide (CO 2) emissions of farmland soils through Meta-analysis. The results showed that plastic film released dissolved organic carbon (DOC) into the soil, which was rapidly used by microorganisms and accelerated the decomposition of soil organic carbon (SOC), increasing CO 2 emissions. Soil moisture content and soil carbon content affected the rate of DOC release from plastic. We estimated that residual plastic film farmland in six northwest provinces of China, 1.39 × 10⁵ tons of excess CO 2 emissions in 2020. The soil excess CO 2 emissions was influenced by polyethylene (PE) plastic concentration and soil type. Replace PE plastic film with biodegradable film, 1.05 × 10⁶ tons of excess CO 2 emissions, 7.5 times that of PE plastics. [Display omitted] [ABSTRACT FROM AUTHOR]