Wood and soils are important natural resources of the land, the former widely used as structural supports in contact with the latter. Many low durability wood species exposed to soil contact has reportedly high incidence of decay failures in poorly treated and untreated materials depending on soil types, properties and soil microbial virulence. This paper probes the relationship of the main soil types in Sarawak (i.e. red-yellow podzolic, grey-white podzolic, gley, podzols and peat) on untreated wood durability in soil-contact. In this study, soils used in laboratory decay testing were maintained at 130% of their water holding capacities (WHC) according to ASTM2017 decay test method, yielding 84, 51, 110, 43 and 160% soil moisture content (MC) for red-yellow podzolic, grey-white podzolic, gley, podzols and peat, respectively. Also compared were all soils conditioned to 70% MC. Significant (P<0.05) variations in decay rates in rubberwood (Hevea brasiliensis) and kelempayan (Neolamarckia cadamba) were detected among these different soil types, soil MCs and decay types, with statistically significant interactions. Among soil types, red-yellow podzolic at 84% MC had the highest (20%) while grey-white podzolic at 70% soil MC the lowest (13.6%) overall mean mass loss. Highest mean mass loss (34%) was due to white rot on podzols at 43% soil MC, while the lowest (5.7%) was due to soft rot on podzols at 70% soil MC. In addition, rubberwood had the highest mean mass loss (25.2%) on red-yellow podzolic at 84% soil MC while kelempayan had the lowest mean mass loss (12.1%) on gley soil at 110% soil MC. At comparable soil MCs (i.e. 70%), (i) peat had the highest (19.3%) and grey-white podzolic the lowest (13.6%) overall mean mass loss; (ii) overall, most severe wood decay mass loss was due to brown rot (21.6%) and soft rot was the least severe (8%); and (iii) overall, both wood species had comparable decay rates (respectively, 16.8 and 16.1%). Besides soil MC, soil physical (microbial counts test and organic matter content) and chemical (pH and soil total elements) properties associated with soil types, were determined as other likely causes of variations in wood decay rates with strong correlations for some of these.

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