Ridge–furrow mulched with plastic film increases little in carbon dioxide efflux but much significant in biomass in a semiarid rainfed farming system

Abstract

Plastic film mulching is one of most widely used field management techniques in rainfed agriculture systems in dryland areas of China. Due to its benefits of improved water use efficiency and crop productivity, plastic film mulching has also been rapidly expanding in other geographic regions. However, the potential positive and negative effects to soil organic carbon cycling are still unknown. CO2 efflux is a proxy of the soil carbon decomposition process, and is also largely unknown for fields covered with plastic film. In this study, maize fields in the Loess Plateau were used to conduct an experiment to measure CO2 efflux response to plastic film mulching. Over a four-year experimental period (2011–2014), CO2 efflux exhibited a Lorentz single peak emission pattern during the growing season, reaching maximum emissions at 70–120 days after sowing. The timing of the efflux peak in the full plastic film mulching (PM) field occurred 7 days earlier than the field without plastic film mulching (CK). The CO2 efflux magnitude in PM was higher than that in CK with large variation. However, the difference in magnitude was not significant at the 0.05 level. The four-year mean CO2 efflux during the growing season was 1.321±0.798μmolm–2s–1 and 1.579±0.937μmolm–2s–1 for CK and PM, respectively. The average CO2 efflux rate increased 19.53% and total growing season CO2 efflux only increased 6.8% in PM treatments in comparison with CK; meanwhile PM gained 75% higher biomass than CK. During the entire experimental period, the PM field had significantly higher soil surface temperature and moisture. Soil temperature showed a significant positive exponential relationship with CO2 efflux, and soil moisture content had an insignificant negative relationship with CO2 efflux. However, soil temperature can only explain 28% and 21% of the CO2 efflux variation for CK and PM, respectively. The weak correlation between soil temperature and CO2 efflux under plastic film mulching suggested the plastic film mulching decreased soil carbon temperature sensitivity and induced more complex nonlinear interaction between CO2 efflux and the soil microenvironment. In addition, the process-based model could be applied to trace the changing of soil carbon under the plastic film mulching system.