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

Muhandiram, N. 2023.


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 not detected for any of the soil health indicators (24-hour CO2 respiration, permanganate-oxidizable carbon [POXC], and bioavailable [ACE protein]) N tested. However, partial least squares (PLS) analysis showed that baseline soil properties measured prior to treatment establishment in 2019 explained > 72% of the variation in the three soil health indicators and > 79% of the variation in number of spikelets/head, average number of florets/head and head count. Results from this study indicate the potential of a legume intercrop as an alternative source of N for an IWG perennial forage-grain system. The results also demonstrate the potential of PLS analysis to model short-term soil productivity and crop attributes in an IWG perennial forage-grain system.

Key Words

cold-tolerant forage species, Intermediate Wheatgrass, Thinopyrum intermedium, Kernza®, soil chemical properties, soil health, partial least squares analysis