Maize Straw Deep-Burying Promotes Soil Bacteria Community Abundance and Improves Soil Fertility

In order to evaluate the potential responses of deep-burying and mulching on soil bacteria community abundance and soil fertility in the same cropping systems, we designed a field experiment as follows: (1) no straw residue (CK), (2) straw mulching (M); (3) straw residue placed in 20–40 cm (DS); and (4) straw residue placed in 20–40 cm with decomposing agent plus (DSP). The results showed that straw deep placement could increase soil organic matter and improve soil microbial community by Illumina HiSeq high-throughput sequencing approach and real-time quantitative PCR (qPCR). Straw deep-burying reduced soil pH (2%) and increased soil total organic carbon (TOC), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN) by 27–339%, as well as soil enzyme activities (urease, dehydrogenase, and cellulase) by over 7%. Thereafter, we found that the deep buried straw residue increased the soil bacteria abundance by 175%, especially Proteobacteria, Bacteroidetes, and Acidobacteria. The family of Xanthomonadaceae and Chitinophagaceae had achieved remarkable growth. In canonical correspondence analysis (CAA), soil organic matter increasing and pH reducing were the main reasons to shift soil bacterial community. A positive correlation was found between straw deep-burying and soil bacteria community (P < 0.01). Therefore, our results highlight that deep-buried maize straw residue changes soil bacteria community abundance and improves soil fertility. Deep placement could potentially be an effective use of straw residues for the future sustainable cropping systems.