Short-term dynamics of soil chemical and health properties under an intermediate wheatgrass (Thinopyrum intermedium) forage-grain system

Overwintering of beef cattle on pasture during the late fall/winter is a common practice in western Canada due to the reduced cost compared to feeding in confinement. However, producers rely on single-purpose annual and perennial forage species. Intermediate wheatgrass (IWG, Thinopyrum intermedium (Host) Barkworth & D. R. Dewey) exhibits superior characteristics as a forage species for cattle grazing during the cold season compared to other forage species currently in use in western Canada. As such, it offers potential as a dual-purpose forage for both grain for human consumption and cattle feed within the same growing season. After introducing a novel plant species into a diverse agricultural cropping system, it is crucial to evaluate the impact of incorporating that species on the resilience and diversity of the soil ecosystem. Therefore, this 3-yr study examined the dynamics of soil chemical and health properties under three IWG-based perennial forage treatments: IWG with no fertilizer post-establishment (IWGP), IWG with synthetic fertilizer applied after the first grain harvest (IWGF), and IWG in a mixed stand with a legume (Alsike clover, Trifolium hybridum L.) (IWGL). A forage-only perennial crop consisting of a 50:25:25 mix of Coutenay tall fescue/Algonquin alfalfa/Oxley II cicer milkvetch was included as a control. The experiment was laid out in a randomized complete block design with a one-way treatment structure at each of four field sites in Manitoba and Saskatchewan, Canada. Available nitrate-nitrogen (NO3--N) supply rates were measured in situ using plant root simulator (PRS) probes while all other nutrient analyses were conducted in the laboratory. Soil NO3--N concentrations in the 0-15 and 15-60 cm soil layers during the growing season were similar for the IWGL and IWGF treatments in 2020 and 2021. Soil NO3--N supply rates were also similar for IWGF and the IWGL following urea application after grain harvest in 2021. Significant treatment effects were