How plastic mulching affects net primary productivity, soil C fluxes and organic carbon balance in dry agroecosystems in China

Abstract Agricultural soil management has a great potential to reduce the anthropogenic emissions of carbon (C), mainly via increasing soil organic carbon (SOC) sequestration. The global use of agricultural plastic mulches has emerged as a widespread soil management practice due to its apparent economic benefits, especially in the dry croplands of China. However, the integrated effects of plastic mulching in China's drylands on net primary productivity (NPP) of staple crops (i.e. maize, wheat, and potato), SOC stocks, and C emissions have rarely been assessed quantitatively. We conducted a meta‒analysis of nationwide dataset and found that compared with traditional non‒mulching farming, plastic mulching on average increased national aboveground NPP by 1.41 Mg C ha−1 y−1, while it led to rising soil CO2 emissions (437 kg C ha−1 y−1 higher than non‒mulching) because of stimulated microbial metabolism, such as higher microbial biomass C and extracellular enzyme activities. Critically, plastic mulching not only enhanced crop‒sourced C inputs into the soil by 0.24 Mg C ha−1 y−1 through improving belowground NPP, but also facilitated soil CH4 absorption by 0.25 kg C ha−1 y−1 across the entire dataset. As a result, a significant increase in SOC storage under plastic mulching was estimated as 0.012 Mg C ha−1 y−1, and crop types, N input, and precipitation seems to be the strongest predictors explaining variability in mulching‒driven SOC sequestration. These results suggest that plastic mulching in dry agroecosystems can have a distinct potential to curtail the anthropogenic emissions of C through significant increases in both SOC sequestration and crop C fixation.