Characterization of microbial community response to cover crop residue decomposition

Cover crop adoption in the U.S. Corn Belt region is a rapidly emerging management practice in corn (Zea mays) agroecosystems. However, little is known about the impact of the inclusion of cover crops on the soil microbiome and its relation to the decomposition of the cover crop residue during the cash crop growing season. Therefore, this study sought to determine the impact of cover crop species and residue management practices on soil microbial community composition and structure during winter cover crop decomposition over the corn growing season. Cover crop treatments included hairy vetch (Vicia villosa Roth), cereal rye (Secale cereal), a hairy vetch/cereal rye mixture, and a no cover crop control. Residue management practices included no-tillage and a 15 cm reduced spring tillage following cover crop termination. Soil samples were collected at five dates during cover crop decomposition that corresponded to an accumulated number of calendar days from cover crop termination, and soil bacterial communities were characterized using the small subunit (16S) rRNA gene sequences. Statistical analyses revealed that sampling date, cover crop treatment, and residue management treatment were significant determinants of soil microbial community composition (p < 0.05) and the effect of cover crop treatment increased as the decomposition period progressed. As cereal rye began to decompose and soil β-glucosidase (EC 3.2.1.21) potential activity increased, the relative abundance of bacteria previously identified as cellulolytic, including Agromyces, Agrobacterium, and Bacillus, contributed to the difference among the cover crop treatments (LDA score > 2.0). Data generated from this study leads to a deeper understanding of bacterial responses to cover crop decomposition in corn agroecosystems.