Hydrochar and microplastics disturb soil dissolved organic matter and prominently mitigate ammonia volatilization from wheat growing soil.

The impacts of microplastics (MPs) pollution on the nitrogen (N) cycle in soil ecosystems have attracted worldwide attention. Meanwhile, dissolved organic matter (DOM)-rich hydrochar (HBC) is being tried as an emerging soil conditioner for gaseous N reduction load to the atmosphere. However, the influence of MPs and HBC on soil DOM and ammonia (NH 3) volatilization in wheat soils remains poorly understood. In this study, a soil column experiment was established in wheat growing soils to determine the impacts of HBC, MPs (i.e., polyethylene and polyacrylonitrile), and the co-occurrence of HBC and MPs (HBC + MPs) on soil NH 3 volatilization, physicochemical properties and wheat growth. In comparison with the control (CK, without MPs or HBC), HBC, MPs, and HBC + MPs reduced cumulative NH 3 volatilization by 45.4%, 66.7–67.4% and 29.8–58.7%, respectively. Soil DOM fulvic acid-like and humic aid substance abundances of the other treatments were increased by 18.5–56.2% and 12.7–39.3%, respectively, compared to CK. Besides, soil NH 3 fluxes were positively correlated to soil NH 4 +-N concentration at basal fertilization and soil NO 3 −-N concentration at first supplementary fertilization. HBC, MPs and HBC + MPs treatments promoted soil urease activity and plant N uptake by 6.5–24.2% and 31.9–74.3%, respectively, compared to CK. This study provides an insight into the variation of NH 3 volatilization caused by anthropogenic carbon in wheat soil ecosystems. [Display omitted] • Hydrochar and microplastics reduced cumulative NH 3 volatilization in wheat soils. • Hydrochar and microplastics increased soil DOM fulvic and humic aid-like substance. • Soil NH 3 fluxes were correlated to soil inorganic nitrogen at different stages. • Hydrochar and microplastics increased soil urease activity. • Wheat nitrogen uptake was enhanced in the presence of hydrochar and microplastics. [ABSTRACT FROM AUTHOR]