Surface Soil Stockpiling Research Trial

When the trial began in 2016, regulations required separate storage of a/b surface soil (ABSS) and d/other surface soil (OSS) to preserve soil quality and maintain distinct seed banks, which was costly and required more space than if combined. Initially, the trial was designed to take 6 years and assess soil quality and vegetation establishment on three stockpile treatments: (1) ABSS, (2) OSS, and (3) ABSS mixed with OSS (MIXED). However, surface soil mixing was approved part way through the trial (2018), so focus shifted towards temporal changes in soil biogeochemistry and physical characteristics, associated reclamation suitability ratings and the establishment of vegetation and native plant communities, and extra time was added to the study with a focus on electrical conductivity (EC).

After eight years of surface soil storage, there was little difference in soil quality and chemistry among stockpile types. In most cases, soil parameters fluctuated over time but ultimately remained within a relatively narrow range of values. MIXED surface soil stockpiles were similar to ABSS and OSS stockpiles in most cases. Results from this trial suggest additional research into whether high EC values in short-duration stockpiled surface soils decrease after soil placement would be beneficial – it hasn’t been be an issue to date in stockpiled surface soil in long-term reclamation monitoring plots, but field trials tracking changes in EC after surface soil placement could confirm this.