Influence of annual ryegrass (Lolium multiflorum) as cover crop on soil water dynamics in fragipan soils of Southern Illinois, USA

Authors: Chatterjee, Amitava; Dinnes, Dana; Olk, Daniel - Dan; O'Brien, Peter

Submitted to: Soil Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/29/2024
Publication Date: 12/3/2024
Citation: Chatterjee, A., Dinnes, D.L., Olk, D.C., O'Brien, P.L. 2024. Influence of annual ryegrass (Lolium multiflorum) as cover crop on soil water dynamics in fragipan soils of Southern Illinois, USA. Soil Systems. 8(4). https://doi.org/10.3390/soilsystems8040126.
DOI: https://doi.org/10.3390/soilsystems8040126

Interpretive Summary: Fragipans are compacted layers below the soil surface that restrict root penetration and water movement. Roots of annual ryegrass plants have been observed to penetrate fragipans and improve water flow through soil. This study was conducted to determine the long-term effects of planting annual ryegrass after harvest of corn or soybean on soil properties and changes in soil water content during a growing season. Two Illinois fields with fragipan layers, one at Marion and another at Springerton, were selected to compare soil properties with and without ryegrass. At Marion, soils under ryegrass had increased plant available water at the 45-60 cm depth. Soil water storage to 60 cm depth during the peak growing season was not different between with and without ryegrass. These results showed that including ryegrass in rotation might improve soil water movement. These results will be useful to improve crop production on fragipan soils. Findings could be of interest to growers and scientists managing soils with hard soil layers that slow downward soil water flow and limit root growth.

Technical Abstract: A fragipan is a dense subsurface soil layer that severely restricts root penetration and water movement. The presence of shallow fragipan horizons limits row crop production. Roots of annual ryegrass (Lolium multiflorum) have been observed to penetrate fragipans to facilitate drainage and increase effective soil depth for greater long-term soil water storage. On-farm studies were conducted at Marion and Springerton in southern Illinois to evaluate annual ryegrass as one component of a cover crop (CC) mix as a management option to improve the characteristics and distribution of soil moisture. Soil samples were collected at 15-cm increments to the 60 cm (Marion) and 90 cm (Springerton) depths using a hydraulic probe during autumn 2022. Both sites had low total soil carbon (1.17-11.7 g kg-1) and nitrogen (0.35-1.40 g kg-1) contents and acidic soil pH (= 6.4). A soil water retention curve was fitted using the van Genuchten equation. At Springerton, the CC treatment increased saturated (thetaS) and residual (thetaR) soil water contents above those of the no cover crop (NCC) at the 60-75 cm and 75-90 cm depths. Changes in volumetric soil moisture content were measured using a multi-depth soil moisture sensor for the Springerton site during late July to early August of the soybean growing phase of 2022. NCC had higher soil moisture than did CC within the 0-15 cm depth, but CC had higher soil moisture than NCC at the 30-45 cm depth. These findings indicate that ryegrass increased soil water content at deeper depth, possibly through root penetration of the fragipan, and reduced soil hydraulic gradient between the surface and fragipan layers.