Perennial to annual system conversion: Implications for soil physico-chemical and biological properties

Land management practices dictate soil physico-chemical and biological functions, and consequently, the agroecological benefits of soils. While several studies exist detailing the effects of cover crops on soil health parameters in annual systems, there is no clear understanding of microbial responses under perennial systems, especially after conversion to annual systems. A 20-year perennial fescue ( Schendonorus arundinaceus ) field was converted to annual systems including two levels of cover crops (cover crop vs no cover crop) and two levels of tillage (tillage vs no tillage). The cover crop included a mix of winter wheat ( Triticum aestivum ) and crimson clover ( Trifolium incarnatum ), while the tillage included disc plowing. Three and four years after conversion, soil samples were collected from no-till with cover crop (NT-CC), no-till with no cover crop (NT-NC), tillage with cover crop (Till-CC), and tillage with no cover crop (Till-NC) plots. Additional samples were also collected from an adjacent field under perennial fescue grass (PER). Soil physico-chemical properties were greater ( p < 0.05) under PER and NT-CC than other management practices evaluated. As a result, total microbial biomass and the composition of microbial community were greater under PER and NT-CC than other management practices. Four years after conversion, the Gr- bacteria and fungi populations under PER were 49% and 59% greater than the average of all CC, and 51% and 133% greater under the average of all tillage managements, respectively. Further, the predato:prey ratio was 38% greater under PER than Till-CC and Till-NC managements. While a conversion from perennial to annual systems can result in soil health parameter degradation, NT-CC is a better annual alternative to perennial systems than other annual practices evaluated.