Straw return influences the structure and functioning of arbuscular mycorrhizal fungal community in a rice-wheat rotation system

Straw return is a sustainable soil fertility-building practice, which can affect soil microbial communities. However, how straw return affects arbuscular mycorrhizal fungi (AMF) is not well explored. Here, we studied the impacts of different straw management treatments over eight years on the structure and functioning of AMF communities in a rice-wheat rotation system. The straw management treatments included no tillage with no straw (NTNS), rotary tillage straw return (RTSR), and ditch-buried straw return (DBSR). The community structure of AMF was characterized using high-throughput sequencing, and the mycorrhizal functioning was quantified using an in situ mycorrhizal-suppression treatment. Different straw management treatments formed unique AMF community structure, which was closely related to changes in soil total organic carbon, available phosphorus, total nitrogen, ammonium, and nitrate. When compared with NTNS, RTSR significantly increased Shannon diversity in 0--10 cm soil layer, while DBSR increased it in 10--20 cm soil layer; DBSR significantly increased hyphal length density in the whole ploughing layer (0--20 cm), but RTSR only increased it in the subsurface soil layer (10--20 cm). The mycorrhizal responses of shoot biomass and nutrient (N and P) uptake were positive under both straw return treatments (RTSR and DBSR), but negative under NTNS. The community composition of AMF was significantly correlated to hyphal length density, and the latter was further a positive predictor for the mycorrhizal responses of plant growth and nutrient uptake. These findings suggest that straw return can affect AMF community structure and functioning, and farmers should manage mycorrhizas to strengthen their beneficial effects on crop production.