Mulching practices altered soil bacterial community structure and improved orchard productivity and apple quality after five growing seasons

• Dominant groups in bacterial communities differred significantly among treatments.
• Changes in bacterial communities were associated with plant performance.
• Trees in the cornstalk mulch treatment had higher yield and fruit soluble solids.

Agricultural management influences soil characteristics, which may in turn affect the soil microbial community and composition based on microbial characteristics and biological functions. The effects of different mulching practices (grass mulch, cornstalk mulch, film mulch, CK) on the soil bacterial community structure, and their implications for orchard productivity and fruit quality were studied in an apple orchard in the Loess Plateau. Treatments were established and sustained in the apple orchard since September 2006. The soil bacterial community structure, soil physicochemical properties, apple size and fruit quality were determined in 2011. A total of 383 clones from libraries were recovered and analyzed. The results demonstrated that the predominant groups in the bacterial community were Alphaproteobacteria (12.27%), Betaproteobacteria (12.79%), Acidobacteria (13.58%) and Bacteroidetes (11.48%). The ratios of the phyla Alphaproteobacteria, Betaproteobacteria, Deltaproteobacteria and Actinobacteria differed significantly (P < 0.05) among treatments. PCoA and Parsimony tests indicated that bacterial communities in mulching treatments were significantly different compared with the CK treatment. It was suggested that changes in the soil bacterial community structure and composition were associated with differences in organic material input and soil physicochemical conditions. Furthermore, stepwise regressions and principal component analyses indicated that changes in the soil bacterial community structure were associated with both orchard productivity and fruit quality in this region. Bacterial traits, i.e. ACE, were found in all of the regression models. Overall, the cornstalk mulch treatment resulted in better plant performance and soil fertilization than the other treatments. This study aimed to provide fundamental information for the scientific application of mulching practices and to serve as a theoretical foundation for maintaining the sustainability of agriculture in the ecosystems of the Loess Plateau.