High carbon use efficiency and low priming effect promote soil C stabilization under reduced tillage

Abstract Increasing the accumulation of organic carbon (C) in soils is a crucial challenge both for soil fertility and for climate change mitigation. Heterotrophic microbial communities are key drivers of C cycling in the soil and are influenced by cultural practices, among other factors. However, whether changes in microbial communities in turn affect their C degradation functions is not well understood. Here, we studied the effects of prior soil management on the microbial taxonomic composition and activity of soils amended with wheat litter. Prior soil management was either conventional (CONV) (i.e., full inversion ploughing) or reduced tillage (RT) during a 5-year period in the same loamy soil in northern France. Soil samples taken from the top 5 cm of field plots were incubated with 13 C-labelled litter of either flowering wheat or mature wheat for 29 days at 15 °C. We measured the C-CO 2 and 13 C-CO 2 , microbial biomass C (MBC) and 13 C, and hydrolytic enzyme activities during decomposition. The initial bacterial and fungal community diversity was studied via high-throughput sequencing of ribosomal genes. The results showed that the MBC in the RT soil was initially 1.5-fold greater than that in the CONV soil; contrasting taxonomic compositions were also recorded. The soil biotic legacy impacted the degradation functions when the soils were amended with wheat litter. Compared with that in the CONV soil, the enzymatic efficiency of microorganisms in the RT soil increased by 49% and 61% in the presence of mature and flowering wheat litter, respectively. Enzyme efficiency was positively correlated with microbial litter C use efficiency (CUE) (r = 0.92, P-Value