Soil Microbial Community Dynamics over the Growing Season of a Corn Agroecosystem after Winter Cover Cropping.

Cover crop adoption in the U.S. Corn Belt region is a rapidly emerging management practice being used as a tool to reduce nitrate loading from tile-drainage in corn (Zea mays) agroecosystems. However, little is known about the inclusion of cover crops on the soil microbial community composition and its relation to subsequent nitrogen release from cover crop residue, and the use of next-generation sequencing technologies in cover crop studies is limited. The objective of this study was 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 6” spring tillage following cover crop termination. Soil samples were collected at five dates over the corn growing season during cover crop decomposition. Soil microbial communities (Bacteria) were characterized using the small subunit (16S) rRNA gene sequences determined using the Illumina MiSeq system, and sequences were analyzed using the QIIME pipeline. A distance matrix between samples was created through a beta diversity analysis using a phylogenic weighted_normalized_unifrac metric. Permutational multivariate analysis of variance (perMANOVA) of the distance matrix revealed that the main effect of cover crop species (p<0.001) was a significant determinant of soil microbial community composition. Linear discriminate analysis effect size (LEfSe) analysis indicated that as cereal rye began to decompose the relative abundance of specific taxa contributed to the difference between hairy vetch and cereal rye based treatments (LDA>2.0). Data generated from this study enhances our understanding of the impact of residue management practices and cover crop species on the short-term dynamics of microbial communities in soil of winter cover-cropped agroecosystems.