Relative contribution of roots and symbiotic fungi to wheat nitrogen uptake and N₂O emissions under straw burial

Ditch-buried straw return (DB-SR), as a novel soil tillage practice, has shown the yield improvement in recent studies in comparison to rotary tillage with straw return (RT-SR). However, the underlying mechanisms are not well known. One field and two greenhouse experiments were conducted to compare the effects of DB-SR on grain yield and nitrogen (N) cycling with other straw managements [RT-SR and straw removal (CK)], and to identify the relative contribution of roots and arbuscular mycorrhizal fungi (AMF) to N cycling in a wheat based cropping system. The field experiment and literature reviews showed that DB-SR can significantly improve annual yields by 19.1% and 15.5% compared with CK and RT-SR, respectively under different cropping systems. The pot experiments supported the findings of field experiments that DB-SR can improve wheat N uptake and decrease N2O emissions driven by trade-offs between AMF and roots depending on soil textures. Roots showed larger impacts in promoting N uptake for wheat and N loss from N2O emissions compared with AMF in clay soils under DB-SR. However, a contrasting pattern was detected in sandy soils where AMF improved N uptake and reduced N2O emissions. Our results highlight that trade-offs between roots and AMF under DB-SR can affect wheat N uptake, and DB-SR could be a practical measure to increase grain yield by improving N uptake and mitigate N2O emission.