Submitted to: Journal of Environmental Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/15/2018
Publication Date: 3/1/2018
Citation: Altland, J.E., Boldt, J.K. 2018. Influence of substrate physical properties on container weed germination. Journal of Environmental Horticulture. 36(1):1-6.
Interpretive Summary: Container substrate components can have a measurable impact on substrate physical properties and water relations, which in turn impacts weed germination and herbicide longevity. Despite this, relatively little work has addressed the impact of substrate components of the germination and establishment of weeds in container crops. The objective of this research was to determine how pine bark substrate amended with sphagnum peatmoss, and its resultant substrate physical properties, affects creeping woodsorrel (Oxalis corniculata L.) germination in containers with or without applications of pendimethalin herbicide. Additions of peatmoss to the pine bark substrate increased water holding capacity of the bulk substrate. However, water is not equally distributed in the vertical profile of a container. Volumetric water content on the container surface was similar regardless peatmoss amendment. As a result, weed germination and herbicide efficacy was similar across the wide range of peatmoss amendment rates used in this study.
Technical Abstract: Container nursery substrates in the central and eastern U.S. are composed primarily of pine bark with lesser percentages of other amendments, including sphagnum peatmoss. Peatmoss is often amended from 0% to 40% (by vol.) to increase the water holding capacity of the substrate. The objective of this research was to determine how a pine bark substrate amended with sphagnum peatmoss affects creeping woodsorrel (Oxalis corniculata L.) germination in containers with or without applications of pendimethalin herbicide. Increasing percentage of peatmoss increased the water holding capacity of the substrate, however, water availability on the substrate surface where weed seed germinate and establish was the same in all substrates. Substrates with varying levels of sphagnum peatmoss only slightly affected weed germination. While sphagnum peat moss can be used to increase the water holding characteristics of a substrate in order to provide an optimum growing environment, changes in bulk substrate physical properties will not affect herbicide performance on the substrate surface.