Comparison of the effect of different soil sources on the type and rate of decay of CCA-treated pine exposed in a soil-bed
J A Drysdale
The types of decay observed in CCA-treated pine posts in horticultural situations in New Zealand can be reproduced using a soil-bed exposure. Radiata pine stakelets, untreated or treated to 1.4, 2.7, or 5.4 kg/m³ with Tanalith NCA, were exposed to six different soil sources. The local nursery soil used for all standard laboratory tests was found to represent the greatest decay hazard to untreated pine. Poverty Bay horticultural soils were more hazardous than the local field test site soil to CCA-treated pine. Soil collected from adjacent to a 'decaying' post could decay treated wood faster than soil collected from around a 'sound' post. Brownrot, softrot, and bacterial degrade was observed. All failures of untreated pine and early failures of CCA-treated pine were caused by brownrot.