Influence of Substrate Physical Properties on Container Weed Germination

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, changes in bulk substrate physical properties will not affect herbicide performance or weed germination on the substrate surface.Index words: Herbicide, irrigation, substrate, porosity, weed control.Chemicals used in this study: pendimethalin (Pendulum 2G).Species used in this study: creeping woodsorrel (Oxalis corniculata L.) (OXACO).