Wood ash application in a managed Norway spruce plantation did not affect ectomycorrhizal diversity or N retention capacity

Ectomycorrhizal (ECM) fungi are key players in N cycling in coniferous forests, and forest management such as application of wood ash can affect their functionality. The aim of this study was to determine the effects of wood ash application on ECM fungal mycelial production, capacity to retain N, diversity and community composition. In-growth mesh bags were installed in control and treated plots. After 6 months, ¹⁵N labeled ammonium and nitrate were applied into the mesh bags, and 24 h later extramatrical mycelium (EMM) was extracted and analyzed. Wood ash had no effects on EMM in-growth, N retention capacity, diversity or community composition. In contrast, there were significant seasonal differences in the amount of EMM produced. These results demonstrate that applying up to 6 t ha⁻¹ of wood ash in this type of plantation forest is a safe management practice that does not increase N leaching or negatively affect ECM fungi.     

Pore Water Quality in the Upper Part of the Vadose Zone under an Operating Canadian Small Arms Firing Range Backstop Berm

Canadian military small arms firing range (SAFR) backstop berm soils contain high concentrations of Pb, Cu, Sb, and Zn. Three Teflon® cylindrical lysimeters were installed in the vadose zone of the backstop berm in order to characterize the pore water quality. Copper-Zn concentrations were below their respective Québec drinking water thresholds, and Pb-Sb concentrations were above the criteria in many cases, indicating that a metal vertical migration occurs in the vadose zone. Metal concentrations in pore water were, in decreasing order, Zn > Pb > Sb > Cu. Calculated annual metal leaching rates showed that a rather small portion of the metals in the soil were mobilized in the vadose zone, and that metals were a potential source of contamination for extremely long periods of time, highlighting the importance of finding ways to remediate such soils in order to limit metal mobility in SAFR backstop berms.     

Chemical Fate and Transport of Atrazine in Soil Gravel Materials at Agrichemical Distribution Facilities

The gravel commonly used to cover parking lots and roadways at retail agrichemical facilities may contain relatively large concentrations of pesticides that resulted from past management problems. These pesticides may threaten groundwater quality. Previous studies, however, suggested that the pesticides had not moved from the gravel in several sample profiles. Excavations at a closed facility revealed tremendous variability in pesticide distribution within the site. Pesticides were present below the gravel in two profiles, but the mechanism(s) for their movement were not clear. The objectives of this study were to investigate how the physical and chemical properties of the gravel influence the environmental fate of atrazine. All of the gravel samples collected and characterized contained atrazine and sufficient organic C to adsorb significant amounts of atrazine, thus retarding its movement through the gravel. Laboratory column leaching experiments, however, suggested that much of the atrazine should leach from the gravel within a year or two. A field-scale test plot was constructed to study how atrazine moves through the gravel under controlled conditions. Atrazine was “spilled” in the test plot. Atrazine moved from the gravel both vertically and horizontally. It appears that formulated product spilled on gravel will leach. A single discrete spill can give rise to phantom spills whose occurrence and distribution is not related to any specific pesticide-management practice. The apparent lack of atrazine leaching from gravel appeared to be a transient phenomenon and/or the result of sampling limitations in previous studies. The contaminated gravel clearly poses a risk to groundwater quality.     

Some observations on surface soil pH,base saturation and leaching of cations under three contrasting orchard soil management practices

Summary Observations from a soil management trial conducted on a previously grassed down orchard showed that after 3 years the pH of the surface soil (0–10 cm) whether measured in distilled water or 1N KCl was significantly lowered in herbicided and cultivated treatments in comparison with plots under continued grass sod. The drop in pH was accompanied by a decrease in base saturation and a consequent increase in exchange acidity. This was attributed to the leaching of Ca and also Mg from the surface soil of the non-grassed plots.In a subsequent laboratory leaching study, cubic soil blocks (16 cm³) were leached with distilled water at two weekly intervals for 24 weeks. It was found that over the experimental period, the cumulative quantity of cations leached (in milli-equivalents) per soil block from the herbicided and cultivated treatments was approximately 3.5 times that leached from the grassed treatment.     

Deepened snow cover increases grassland soil carbon stocks by incorporating carbon inputs into deep soil layers

Climate-induced changes in snow cover can greatly impact winter soil microclimate and spring water supply. These effects, in turn, can influence plant and microbial activity and the strength of leaching processes, potentially altering the distribution and storage of soil organic carbon (SOC) across different soil depths. However, few studies have examined how changes in snow cover will affect SOC stocks, and even less is known about the impact of snow cover on SOC dynamics along soil profiles. By selecting 11 snow fences along a 570 km climate gradient in Inner Mongolia, covering arid, temperate, and meadow steppes, we measured plant and microbial biomass, community composition, SOC content, and other soil parameters from topsoil to a depth of 60 cm. We found that deepened snow increased aboveground and belowground plant biomass, as well as microbial biomass. Plant and microbial carbon input were positively correlated with grassland SOC stocks. More importantly, we found that deepened snow altered SOC distribution along vertical soil profiles. The increase in SOC caused by deepened snow was much greater in the subsoil (+74.7%; 40–60 cm) than that in the topsoil (+19.0%; 0–5 cm). Additionally, the controls on SOC content under deepened snow differed between the topsoil and subsoil layers. The increase in microbial and root biomass jointly enhanced topsoil C accumulation, while the increase in leaching processes became critical in promoting subsoil C accumulation. We conclude that under deepened snow, the subsoil had a high capacity to sink C by incorporating C leached from the topsoil, suggesting that the subsoil, originally thought to be climate insensitive, could have a higher response to precipitation changes due to vertical C transport. Our study highlights the importance of considering soil depth when assessing the impacts of snow cover changes on SOC dynamics.     

Leachant pH effects on the leachability of metals from fly ash

The leachability of metals from fly ash produced by a coal‐fired electric plant and a municipal waste incinerator under acidic conditions was experimentally investigated. The results of these column‐leaching experiments show that a decrease in the pH of the leachant favors the extraction of metal ions from solid particles of both coal combustion fly ash and municipal waste incinerator fly ash. The significant increase in the extraction of cadmium, chromium, zinc, lead, mercury, and silver ions from the ash is attributed to the instability of the mineral phases that contain these metals under acidic conditions.