Discipline: Ecology, Environmental & Earth Sciences
Subcategory: STEM Research
- Alcorn State University
Co-Author(s): Ari Jumpponen, Kansas State University; Girish Panicker and Ananda Nanjundaswamy, Alcorn State University
In an agricultural landscape, management practices — crop rotation, tillage, cultivation of cover crop, planting densities — can change soil and plant microbiomes. Continuous cover crops with minimal or no tillage are central to Conservation Agriculture (CA), the core principle of sustainable crop production. Switchgrass (Panicum virgatum) is a perennial C4 grass native to North America and used in soil conservation. To better understand the impact of plant varieties and planting densities on CA, four switchgrass varieties (Alamo, Bomaster, Colony and Kanlow) were grown as cover crop under high and low planting densities since 2012 in a split plot randomized complete block design at Alcorn State’s Center for Conservation Research in Mississippi. The overall objective was to compare the switchgrass fungal and bacterial rhizobiomes before and after harvest. Roots were sampled in November 2015 right before harvest of aboveground biomass and again in March 2016 immediately after the grass had all regenerated. Bacterial (16S) and fungal (ITS) amplicon libraries were generated for Illumina sequencing. The rhizobiomes were not influenced by switchgrass varieties but varied before and after harvest. Additionally, bacterial rhizobiomes were also influenced by planting densities before harvest but not after. In contrast, fungal rhizobiomes were influenced neither by variety nor planting density either pre- or post-harvest. Among the major bacterial phyla, Actinobacteria, Chloroflexi and Aramatimonadetes were more abundant before harvest, whereas Firmicutes, Planctomycetes, Bacteroidetes were more abundant after harvest. Proteobacteria, Nitrospirae and Acidobacteria remained unchanged pre and postharvest. Among fungal phyla, Glomeromycota and Basidiomycota were more abundant before harvest, whereas Ascomycota and Chytridiomycota were more abundant after harvest. Basal taxa formerly assigned to Zygomycota remained unchanged before and after harvest. A large number of indicator species and common (core) communities of both bacteria and fungi were identified and their potential functional relevance will be discussed in the context of CA.
Funder Acknowledgement(s): This project was funded mainly by NSF HBCU UP Research Initiation Award to KM
Faculty Advisor: None Listed,