Can adoption of multispecies cover crop mixtures improve soil water movement in fragipan soils of southern Illinois?

Abstract Crop production on fragipan soils can be severely limited due to restrictive root growth and perched water table. We hypothesized that roots of multispecies cover crop mixtures containing annual ryegrass (ARG, Lolium multiflorum L .), hairy vetch ( Vicia villosa ), and crimson clover ( Trifolium incarnatum ) can improve soil physical conditions for main crop root growth, and roots of ARG can penetrate through the fragipan layer to remove excess moisture. Two on‐farm sites, Marion and Springerton, in southern Illinois were established in 2019 and 2013, respectively. Depth from surface to fragipan layer was 70 cm and 50 cm for Marion and Springerton, respectively. Both sites had replicated trials in a corn ( Zea mays L.)–soybean ( Glycine max L. Merr.) rotation with two treatments: with cover crop (CC) and without cover crop (NCC) mixes having ARG as the dominant species. In spring of 2023, intact soil cores were collected and analyzed for soil water retention characteristics and particle size distributions. Volumetric water contents (VWCs; cm 3 cm −3 ) of the soil through 90‐cm depth were monitored during corn phase and during cover crop growth of 2023–2024. At Marion, NCC had higher VWC at 25‐ and 55‐cm depths than CC most of the time during summer. At Springerton, CC soils within 15‐ to 35‐cm depths had higher VWC than NCC during cover crop growth in winter. Inclusion of cover crop mixtures can improve soil water movement, but the magnitude depends on the length of adoption and depth to the fragipan layer.