Copper Coating growing Trays

For many years, since the early work of Tinus and McDonald, and the use of copper discs at the bottom of paper pot seedlings, copper has been used effectively to prune roots of containerized forest seedlings and ornamentals (Ruehle, 1985; Arnold and Struve, 1989; Arnold and Young, 1991; Struve, 1993). Without root pruning, the root plug produced on a containerized seedling may be characterized by many roots on the outside of the plug, forming a typical `cage'; few roots in the middle; clustered root tips at the bottom of the container; and a lack of regenerating root tips in the upper portion of the plug (Smith and McCubbin, 1992; Struve et al., 1994). Such a root system may result in all new roots arising from the cluster of root tips at the bottom of the plug which in many soils in Canada, may not grow out due to cool temperatures at that depth, or reportedly result in seedling instability after planting (Ruehle, 1985; Struve et al., 1994). In BC especially, copper tray treatment has been used effectively, to encourage root growth in the upper section of the seedling root system after transplanting into cool soils (Lloyd, 1996).

The use of copper treated containers has been shown to rectify some of these concerns. The presence of a copper coating on the tray results in the inhibition of cell division at the root apex and produces an inhibitory effect on root elongation at the root/container wall interface. This creates an abundance of higher order laterals and their growth is, in turn, stopped at the container wall, resulting in a root system with many branched roots within the plug. Once these seedlings are out planted, root tips resume growth, producing a more branched root system, with more roots in the top section, better able to exploit water and nutrient resources and with better seedling stability (Ruehle, 1985; Smith and McCubbin, 1992; Struve et al., 1994).

Copper treated polystyrene seedling containers have been effectively re-used in Canada, but little work has been done on the activity of the residual copper ions in the coating on the polystyrene. It is important to know whether older, previously used treated trays effectively root prune the seedlings.

Source: http://www.for.gov.bc.ca/nursery/fnabc/Proceedings/EffectOfCopper.htm