Abstract
ABSTRACT To reduce tobacco production suggested by the Chinese government, a 12-year field experiment was established by planting other crops in a traditional tobacco growing system every 2 years. Thus, tobacco-wheat, tobacco-canola, tobacco-wheat-maize, and tobacco-canola-maize rotations were implemented to compare the changes in soil properties. Compared to the initial soil, available N, P, and K increased or changed little after 12-year cropping except for decreased available N in the tobacco-wheat rotation soil. Compared with two-crop rotations, soil organic matter, available N, microbial biomass, enzyme activities (urease, phosphatase, and dehydrogenase), and bacterial community indexes (16S rDNA sequences, operational taxonomic units (OTUs), and richness and diversity indexes) increased in the three-crop rotations. The return of voluminous maize stubble should be the important reason for the change of these soil properties. All cropping soils were dominated by five bacteria (Proteobacteria, Acidobacteria, Firmicutes, Actinobacteria, and Bacteroidetes) accounting for 53.5–62.3% of the 16S rDNA sequences. Among the top 20 predominant bacteria, 10 were commonly found in all soils and only 2–5 were unique. Therefore, maize incorporation into the traditional two-crop systems increased stubble return and improved soil properties. However, bacterial community composition was more influenced by the soil itself than cropping systems.
Published Version
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