A ground-contact field test was installed to evaluate the effect of wrapping the below-ground portion of a post on the decay resistance of a carbon-based preservative system. After two years of exposure at two locations in Canada, the unwrapped untreated Pacific silver fir 4x4 posts showed significant decay, with half the posts failing at one location. In contrast, all the wrapped untreated posts remained sound at both test sites. Treated posts were in excellent condition, with no visible decay.