Effects of biochar and arbuscular mycorrhizal fungi on winter wheat growth and soil N(2)O emissions in different phosphorus environments

INTRODUCTION: Promoting crop growth and regulating denitrification process are two main ways to reduce soil N(2)O emissions in agricultural systems. However, how biochar and arbuscular mycorrhizal fungi (AMF) can regulate crop growth and denitrification in soils with different phosphorus (P) supplies to influence N(2)O emission remains largely unknown. METHOD: Here, an eight-week greenhouse and one-year field experiments biochar and/or AMF (only in greenhouse experiment) additions under low and high P environments were conducted to characterize the effects on wheat (Triticum aestivum L.) growth and N(2)O emission. RESULTS: With low P supply, AMF addition decreased leaf Mn concentration (indicates carboxylate-releasing P-acquisition strategies), whereas biochar addition increased leaf Mn concentration, suggesting biochar and AMF addition regulated root morphological and physiological traits to capture P. Compared with low P supply, the high P significantly promoted wheat growth (by 16-34%), nutrient content (by 33-218%) and yield (by 33-41%), but suppressed soil N(2)O emissions (by 32-95%). Biochar and/or AMF addition exhibited either no or negative effects on wheat biomass and nutrient content in greenhouse, and biochar addition promoted wheat yield only under high P environment in field. However, biochar and/or AMF addition decreased soil N(2)O emissions by 24-93% and 32% in greenhouse and field experiments, respectively. This decrease was associated mainly with the diminished abundance of N(2)O-producing denitrifiers (nirK and nirS types, by 17-59%, respectively) and the increased abundance of N(2)O-consuming denitrifiers (nosZ type, by 35-65%), and also with the increased wheat nutrient content, yield and leaf Mn concentration. DISCUSSION: These findings suggest that strengthening the plant-soil-microbe interactions can mitigate soil N(2)O emissions via manipulating plant nutrient acquisition and soil denitrification.