Measuring cover crop benefits from a fungal perspective

Diversified cropping systems that incorporate year-round ground cover, are known to maintain healthy soils. Plenty of information is available for producers regarding the benefits of specific cover crop species for soil fertility, weed and pest management. Even though it is widely recognized that cover crops promote microbial biomass and activity, the specific responses of particular microbial groups to various cover crop treatments are yet to be understood. Hence, we describe fungal communities associated to roots of four cover crop species grown in a soil inoculum originating from a prairie remnant. We analyzed total fungal community composition using amplicon sequencing of a) universal fungal and b) arbuscular mycorrhizae (AM) -specific ribosomal markers from total DNA of root extracts. Fungal communities enriched by each cover species are distinct from each other and from the original prairie soil. Individual cover crops not only enrich for a different subset of the AM fungi community found in prairie soils, but they also show differences of enrichment between AM and other fungal groups. For instance, using fungal specific markers, greater proportion of Glomeromycota and Early diverging fungal lineage sequences (relative to total Fungi) are recovered from vetch and clover roots. Wheat and oats, however, show greatest proportion of Ascomycota and oomycetes. Within AM fungi, wheat roots are colonized in higher proportion by taxa within Glomeraceae, whereas vetch, oats (and clover), by taxa within Diversisporaceae (Acaulospora in particular).  Differences in enrichment of fungal taxa appear to be related to higher plant taxonomic rank (legumes vs. grasses) or greater crop management history in wheat and oat, as compared to vetch and clover. From a fungal perspective, the direct benefits of the cover crop species in the cash crop will relate to the life history characteristics of fungal communities preferentially colonizing each cover crop host.