Impacts of Smooth Pigweed (Amaranthus hybridus) on Cover Crops in Southern Ontario
Guinel, Frederique C.
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Amaranthushybridus is anoxious weed in Ontario, with demonstrated allelopathic properties that can lead to decreased agricultural production. We tested the germination and growth of ﬁve cover crop species exposed to A. hybridus extracts, and to dried or fresh materials in soil. A germination index was calculated, and the dry weight of plant organs were measured to quantify responses to treatments. All species had reduced germination (≤29%) in 100% extract. Trifolium pratense had signiﬁcant root weight reductions in extract (52%) and dried (72%) treatments, whereas shoot weight only decreased (48%) in dried treatment. Medicagosativa shoot weight decreased (52%) in 20g fresh treatment, while root weight decreased (62%) in dried treatment. Shoot weight of Raphanus sativus increased (32%) at mid-extract concentrations, while root weight increased (33%) only with dried treatment; however, both its shoot and root weight decreased (>40%) in fresh treatment. Only the shoot weight of Loliummultiﬂorum increased (41% in 75% extract and 55% in dried treatment). Both Cichorium intybus shoot and root weights decreased (~50%) in fresh treatment. Crop responses to A. hybridus are complex, and material and species-dependant. Further testing in the ﬁeld may provide a more comprehensive understanding of how to improve the management of A. hybridus.