Copper Release from Chemical Root-Control Baskets in Hardwood Tree Production
2002
Kosuta, Sonja | Hamel, Chantal | Dalpé, Yolande | St-Arnaud, Marc
The City of Montreal, Canada, evaluated the environmental impact and usefulness of in-ground copper (Cu)-treated baskets in controlling root growth of hardwood trees in nursery culture. Using baskets planted with 5-yr-old Norway maple (Acer platanoides L.) trees, the amount and temporal pattern of Cu release from the basket surface into soil was determined for two copper formulations: Cu metal powder and Cu(OH)₂ Release of both Cu formulations from the basket surface decreased exponentially over time, with Cu concentration at the basket surface dropping to 2% of the initial Cu applied by the end of the second field season. Total Cu content increased significantly in the soil around the baskets (from 7 to 28 mg Cu kg⁻¹ soil) and in the baskets (from 7 to 50–70 mg Cu kg⁻¹ soil) over the two years of the study. Three levels of phosphorus application (33, 66, and 100% of the regular nursery rate of 465 kg ha⁻¹ yr⁻¹) did not affect release of Cu from the basket surface. The release of Cu metal at 28 and 105 d in the field was significantly increased by inoculation with the symbiotic arbuscular mycorrhizal fungus (AMF) Glomus intraradices Schenck & Smith; however, AMF inoculation had no affect on Cu(OH)₂ release. Trees grown in Cu-treated baskets and inoculated with G. intraradices had similar colonization to non-inoculated trees, suggesting that inoculation was not very effective and that AMF inoculum was already present in the root ball of the trees at planting. After two years, copper basket–grown trees had significantly less root colonization than isolated control trees growing in the open field. This strongly suggests that conditions inside the baskets were not favorable to AMF.
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