Removal of ferrous iron from field drainage waters by conifer bark

Iron ochre deposition in field drainage systems is produced as a result of chemical and microbiological oxidation of ferrous iron in soil solution to the insoluble ferric form. Conifer bark, from several plant species, will absorb ferrous iron from solution quickly and irreversibly, the bark changing colour from brown to blue in the process. This bark, unlike that from deciduous trees, contains only small quantities of soluble phenolic components so it does not create an environmental problem under field conditions. Trials carried out at a test farm, where bark was placed within nylon mesh sacks and incorporated into the drainage system, were very successful, and drainage pipes which had previously blocked twice yearly remained relatively free of ochre. The use of bark from conifers can offer an inexpensive method of ameliorating the problem of ochre formation without producing environmental pollution.