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

Authors: Chatterjee, Amitava; Rivera Santiago, Eric; Dinnes, Dana; Olk, Daniel

Submitted to: Vadose Zone Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2025
Publication Date: 11/20/2025
Citation: Chatterjee, A., Rivera Santiago, E.E., Dinnes, D.L., Olk, D.C. 2025. Can adoption of multispecies cover crop mixtures improve soil water movement in fragipan soils of southern Illinois?. Vadose Zone Journal. https://doi.org/10.1002%2Fvzj2.70046.
DOI: https://doi.org/10.1002%2Fvzj2.70046

Interpretive Summary: Fragipan soils are compacted layers below the soil surface that restrict root penetration and water movement. Roots of annual ryegrass have been observed to penetrate fragipan and improve water flow through soil. This study was conducted to determine the long-term effects of planting annual ryegrass after harvest of the main crop on soil properties and changes in soil water content during a growing season. Two Illinois fields, one at Marion and another at Springerton with fragipan layers, were selected to compare with and without ryegrass. Soils under cover crop had higher silt particle content than without cover crop at fragipan layer. At Marion, soils after cover crop termination had higher water content at 25 cm and 55 cm soil depths probably due to cover crop root take out water from deeper soil depths. Growing cover crop increased soil water storage during winter at Springerton only. These results showed that ryegrass roots might use water ponding over fragipan layer. These results will be useful to improve crop production under fragipan soils. Findings could be of interest to growers and scientists managing soils with restrictive soil layers that slow downward soil water flow and limit root growth.

Technical 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; cm3 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.