Long term ditch-buried straw return affects soil fungal community structure and carbon-degrading enzymatic activities in a rice-wheat rotation system

As a novel soil tillage practice to build fertility, ditch-buried straw return (DBSR) can affect soil carbon sequestration, nitrogen availability and hydrothermal processes in rice-wheat rotation systems. However, it is still not well-known how DBSR influences soil fungal community. A 6.5-year's field experiment was conducted to test the effects of DBSR on soil fungal community via comparing with rotary tillage straw return (RTSR) and no tillage with no straw (NTNS). Our results showed that soil fungal species composition under DBSR was significantly different from NTNS and RTSR. Also, DBSR showed distinctive impacts on soil fungal composition at the order level. DBSR significantly increased Shannon diversity index and evenness, decreased dominance, but did not affect species richness. Moreover, DBSR significantly increased the abundance of symbiotrophic fungi, but reduced the abundance of pathotrophic fungi. Especially, DBSR largely increased the abundance ratio of arbuscular mycorrhizal fungi to plant fungal pathogens. DBSR significantly reduced β-D-glucosidase activity but increased peroxidase activity while RTSR increased both cellobiohydrolase and peroxidase activity. Our results suggest that long term ditch-buried straw return can structure a unique soil fungal community from that of RTSR and NTNS, increase soil fungal diversity and promote the dominance of beneficial fungi over soil-borne plant fungal pathogens. These findings can provide solid evidence for future large-scale extension of ditch-buried straw return in practical agriculture.