Adequate supply of micronutrients is essential for plant growth in reclaimed sites in the Athabasca oil sands region. The objectives of this study were to determine boron, iron, manganese, copper, and zinc concentrations in peat–mineral mix (PMM), tailings sand (TS), and overburden (OB) materials and to assess whether lodgepole pine (Pinus contorta) planted on PMM over TS and white spruce (Picea glauca) planted on PMM over OB had low foliar micronutrient concentrations. Micronutrient concentrations determined using LiNO₃ and Mehlich-3 extractions were different between PMM and TS in the pine sites while only LiNO₃ extractable boron was different between PMM and OB in the spruce sites (p < 0.05). Micronutrient concentrations varied in the order of boron > iron > manganese > zinc > copper in all soil layers with concentrations ranging from 0.04 to 39.56 µg g^-1. The low foliar concentration of copper in pine and spruce was consistent with low LiNO₃ extractable copper in the soil in both the pine and spruce sites. We conclude that the availability of micronutrients such as copper can become a potential limitation for revegetation of white spruce but not lodgepole pine. Further studies on soil management for improving Cu availability in reclamation materials are needed for improving the growth of spruce in reclaimed soils.

Nitrogen loss through ammonia volatilization is an environmental and economic concern. When acid traps are used with wind tunnels to measure ammonia volatilization, loss of solution volume is observed. As the loss mechanism affects volatilization estimates, a field study was conducted to determine if solution loss from acid traps was due to either selective loss of water through evaporation, loss of bulk solution, or a combination. Two methods for calculating air flow volume through the acid traps were also examined. Solution losses from acid traps averaged 40 mL d^-1 (±9.2 mL) from an initial 100 mL, and ammonium concentration increased in close accordance with the dilution–concentration relationship for aqueous solutions. Hence, solution loss was due to evaporation, with virtually no ammonium loss, confirming that the flux calculations using corrected acid trap volumes are required. Failure to correct for the reduced volumes resulted in 9%–224% overestimation of ammonium concentrations. Air flow volumes through acid traps were underestimated by 18.5% when initial and final air flow rates were used compared with continuous cumulative flow measurements. Using cumulative flows and accounting for evaporation loss from acid traps help ensure that treatment differences are not masked by the inherent variability in field-based measurements.

Little research has been conducted on the influence of land application of stockpiled feedlot manure (SM) containing either wood-chip (WD) or straw (ST) bedding on soil net N mineralization (Nm) and nitrification (Nn) rates during the barley (Hordeum vulgare L.) silage growing season. The stockpiled manure containing ST or WD bedding at 77 Mg (dry weight) ha^-1 yr^-1 was annually applied for 13–16 yr to a clay loam soil in a field experiment in southern Alberta. The net Nm and Nn rates were measured using the “in situ-soil core” method over 30–33 d (Nm1, Nn1) and 46–50 d (Nm2, Nn2) in each of 4 yr (2011–2014). Net Nm1 rates were generally significantly (P ≤ 0.05) greater for ST (1.0–1.9 mg N kg^-1 d^-1) than WD (0.1–0.9 mg N kg^-1 d^-1). Net Nn1 rates were also generally significantly greater for ST (0.9–2.0 mg N kg^-1 d^-1) than WD (0.03–0.9 mg N kg^-1 d^-1). Similar trends were found for Nm2 and Nn2. The Nn rates, however, were limited by NH₄ supply during the incubations as Nm:Nn ratios were typically <1 with relatively low initial ammonium levels. Hence, the nitrification rates reflected the Nm rates and they would have been considerably lower than potential nitrification rates. A shift from ST to WD bedding by feedlot producers may decrease crop N supply 2- to 10-fold by lowering Nm (2- to 10-fold) and Nn (2- to 30-fold), and supplemental inorganic N fertilizer may be required when WD bedding is used.

Accurately accounting for water budgets within regional agroecosystems is becoming an increasingly important practice, as both climate change and water consumption pressures have the potential for influencing agro-productivity and other water use activities. In this study, water budget measurements from 10 rainfed experimental sites across Canada were utilized to evaluate the performance of three models for their water partitioning capabilities: denitrification–decomposition (DNDC), Holos, and versatile soil moisture budget (VSMB). To assess the likely model performance at an upscaled national level, the models were applied at the site level with no water component-specific calibration. Evapotranspiration (ET) was found to be the dominate component of the water budget at the prairie sites (89%–149% of precipitation) (i.e., in comparison to runoff, tile drainage, and deep percolation), while both ET (37%–73% of precipitation) and drainage (19%–61% of precipitation) represented most of the water outflow budget at the sites in eastern and Atlantic Canada. As DNDC integrates daily crop growth dynamics with nitrogen, water, and heat stresses, in contrast to VSMB and Holos, which only utilize a water budget model, it was not surprising to find that DNDC consistently out-performed the other two models across all the statistical performance metrics considered at daily resolution.

Soil organic matter (SOM) is a major driver of key agroecosystem functions. Our objective was to examine the dynamics of organic matter in whole soil, particulate (POM; >53 µm size), and mineral-associated (MAOM) fractions under varying crop rotations and nutrient managements at two long-term experimental sites (Breton and Lethbridge). Soil samples were collected from simple (2 yr) and complex (5 or 6 yr) crop rotations at the 5–10 cm depth. We found associations between SOM pools versus microbial community and soil aggregation. Compared to cropped soils, an adjacent forest exhibited a significantly higher soil total organic carbon (TOC) and a shift in SOM fractions with substantially higher POM. However, the forest soil had the lowest microbial biomass C among all the assessed land use systems (P < 0.05), suggesting that other factors than the amount of labile SOM (i.e., POM-C) were controlling the microbial community. When contrasted to simple 2 yr rotations, the complex rotations including perennials and legumes significantly raised TOC and soil total nitrogen as well as the stable SOM fraction (i.e., MAOM-C and -N) consistently for both Breton and Lethbridge sites. Our findings highlight that varying land managements have profound feedbacks on soil quality as mediated by alterations in long-term SOM dynamics.

Utilization of wood ash as a forest soil amendment in British Columbia could have numerous benefits, including potentially increasing tree growth. Two wood-derived bottom ashes (low-carbon gasifier ash and high-carbon boiler ash) were applied at 5000 kg ha^-1 (dry weight equivalent) with urea (100 kg N ha^-1), in a two-way factorial randomized block design across two (18- and 24-yr-old) hybrid spruce (Picea glauca × engelmannii Parry × Engelm.) plantations in interior British Columbia. Changes in spruce foliar nutrients and selected soil properties were evaluated. After one growing season, foliar Ca and S significantly increased in plots treated with ash, and foliar N significantly increased while foliar Mg and P significantly decreased in spruce treated with urea. In LFH horizons, soil pH, exchangeable base cations (Ca, Mg, and K), strong acid-extractable B, and Ca significantly increased (p < 0.05) with ash addition; soil pH was greatest in plots treated with urea plus gasifier ash. No significant treatment effects were observed in underlying mineral soil. We conclude that gasifier and boiler ash derived from clean wood applied at 5000 kg ha^-1 are effective soil amendments as expressed within 1 yr by changes in nutrient status of LFH horizons and spruce foliage.

This study assesses the water repellency (WR) of aggregated oil sand material (AOSM) from the Athabasca region, Canada, and evaluates the onion-skin weathering hypothesis, which postulates that with increasing depth into the soil profile or into individual AOSM samples, the exposure to and extent of weathering of AOSM decreases and petroleum hydrocarbon (PHC) content and WR increase. WR and PHC content were determined for outer and inner portions of AOSM from depths of 15–200 cm. Results show AOSM displays a wide range of WR, in terms of both contact angle (0°–129°) and water drop penetration time (0 to >3600 s). As salvage depth or depth into AOSM increases, PHC content and WR increase, confirming onion-skin weathering. These findings imply the benefit of discreet salvaging into separate layers, as opposed to composite salvaging of shallow and deep soils. Deep materials, which contain relatively high PHC contents, can be salvaged and replaced as deep layers to avoid the excessive drying and expression of WR which may occur in the near-surface. By controlling the location of AOSM within the soil profile, water storage in the rooting zone may be increased, allowing the establishment of relatively productive ecosystems.

Brunisolic soils developed on sandy deposits comprise a significant portion of the land disturbed by surface mining in the Athabasca Oil Sands Region. These soils support forest communities ranging from nutrient limited jack pine to more productive aspen stands. The objective of this study was to determine if and how the physical properties of these sandy soils influence the accumulation and distribution of soil nutrients. Sixteen sites, selected to capture the natural range in forest productivity of the area, were characterized to assess particle size distribution, total and available nutrient stocks in forest floors, total C and N, and extractable nutrients in B horizons. Under jack pine, relatively small decreases in sand content of the upper soil profiles, from 97% to 88%, were associated with greater total nutrient stocks and lower C/N ratios in the forest floors. In soils under aspen, forest floor nutrient stocks related most strongly with texture of the B horizons, with finer B horizons (from 94% to 78% sand) leading to larger forest floor nutrient stocks. These results indicate that textural characteristics play an important role in nutrient cycling of these sandy soils and should be a primary focus during their reclamation.

Micro-topography and spatial variability of soil properties influence the environmental consequences of site-specific management. This study investigated the spatial structure of soil properties in relation to the micro-topography of an agricultural field in the Canadian Prairies. The geospatial sampling scheme had 178 soil cores to a depth of 120 cm. Soil texture and soil water content (SWC) at 0–120 cm, total nitrogen (TN), total carbon (TC), and soil organic carbon (SOC) at 0–15 cm were measured and spatially interpolated using semi-variograms calculated with GS . The correlation of terrain attributes, calculated from digital elevation models, with soil properties was also assessed. Texture was strongly spatially dependent in the surface layers, and the significance of spatial dependency declined with depth. Spatial autocorrelation of sand content declined from 96% at the soil surface (0–15 cm) to 90% at 30–45 cm, 53% at 75–90 cm. SWC, TC, TN, and SOC were similarly auto-correlated. Elevation, relative slope position, and vertical distance to channel network influenced the distribution of texture and SWC based on analysis with partial least squares, though this relationship decreased with depth. Terrain attributes are correlated with the spatial variability of soil properties and should be considered in environmental analyses at the micro-scale.

Straw return and biochar addition are promising approaches to enhance carbon sequestration and reduce greenhouse gas emission; however, their effect on CO₂-fixing autotrophs remains unclear. Hence, quantitative PCR based on cbbL and cbbM, accC, and hcd, which are marker genes of the Calvin cycle, the 3-hydroxypropionate cycle, and the 4-hydroxybutyrate cycle, respectively, were used to determine the abundance of CO₂-fixing autotrophs in paddy soil. Soils with chemical fertilizers receiving no exogenous carbon amendment, low and high amounts of rice straw, or low and high amounts of biochar were sampled at the tillering, milky, and ripening stages of late rice season. Results showed that both straw and biochar application increased the abundance of CO₂-fixing microbes in paddy soil, whereas more abundant CO₂-fixing microorganisms were observed in HS and LC rather than other treatments. The effects of different amounts of straw and biochar are attributable to the prominent differences in their properties. Redundancy analysis revealed that redox potential, C/N ratio of input fertilizer, and soil content were significantly correlated with the gene abundance of CO₂-fixing microorganisms. Path analysis revealed that gene abundance was causally and indirectly driven by rice growth stage and exogenous C addition. Collectively, our study suggested that adding extra carbon affected the growth of CO₂-fixing microorganisms, which provided novel insights into the effect of straw return and biochar addition in paddy soil.

Phosphorus (P) loss from agricultural land poses a major risk to the environment. The main objectives of this study were (i) to adapt a simple P saturation indicator using 141 soils that had contrasting P levels and to deduct critical environmental P values, and (ii) to identify environmental risk classes and their spatial and temporal distribution at the scale of Prince Edward Island, Canada. The P saturation index (PSI) was greatly influenced by the soil acidity, and two critical P saturation indices were identified (i) a PSI (P/Al)_M-III of 19.2% for very to extremely acidic soils (pH < 5.5), and (ii) a PSI of 14.2% (corresponding to 200 mg P_M-III kg^-1) for slightly to moderately acidic soils (pH > 5.5). Above these critical values, P fertilization should be limited to crop requirements. Six environmental P risk classes from very low to extremely high were identified. Spatial distribution of the identified classes was performed using georeferenced soil data collected between 2003 and 2015. The moderate risk class (P/Al ratio from 7% to 14% for soil pH above 5.5) was the predominant class, covering approximately 70% of the total area. Hot spots in the very high to extremely high range were found in about 10% of the total area, and mitigation strategies are needed to reduce P inputs to control P-related eutrophication risks in surrounding waters.

Long-term application of feedlot manure and inorganic fertilizer to cropland may increase metals and trace elements in soils, and negatively impact agricultural land use. We sampled a surface clay loam soil at Lethbridge in southern Alberta after 16 annual applications (2014) of feedlot manure or inorganic fertilizer, as well as an unamended control. The manure treatments were stockpiled (SM) or composted (CM) feedlot manure with barley straw (ST) or wood-chips (WD), and were applied at 13, 39, and 77 Mg ha^-1 (dry weight). The soil was analyzed for strong-acid extractable concentrations of selected metals (Al, Fe) and trace elements (As, Ba, Cd, Co, Cr, Cu, Li, Mn, Ni, Pb, Sr, Ti, V, and Zn). Manure type (SM versus CM) had little or no significant (P > 0.05) effect on the elements. Significantly greater As, Co, Cu, Fe, Li, and V were found for ST than WD at all or higher rates, and the reverse trend occurred for Cd at the highest rate. Cadmium (ST only), Cu, Sr, and Zn were increased by greater application rates, whereas most of the other elements were decreased. Concentrations were significantly increased by manure (Cu, Sr, and Zn) and inorganic fertilizer (Cd) compared with the unamended soil. Copper, Sr, and Zn were greater for manured than inorganic fertilizer treatments, and the reverse trend occurred for Al, As, Co, Cr, Fe, Li, Ni, and V. Although manure and fertilizer may increase certain elements in the soil, no concentrations exceeded the federal soil guidelines for agricultural land use.

As the focus of soil science education in Canada and elsewhere has shifted towards nonsoil science majors, it is important to understand if and how this has affected the scope of introductory soil science courses. The objectives of this study were to inventory Canadian postsecondary units that offer introductory soil science courses and to document attributes of instructors, students, and teaching approaches in these courses. We surveyed 58% of the instructors of introductory soil science courses across Canada, and most of these courses were offered by geography and environmental science units. The majority of instructors followed a traditional lecture (86%) and laboratory (76%) delivery format, whereas 36% used online teaching resources. Introductory courses were delivered by primarily one instructor, who held a Ph.D. in a tenure track position and in most cases developed the course themselves. Over half of the instructors surveyed used either a required or a recommended textbook, pointing to the need for creation of a Canadian-authored soil science textbook. Several follow-up studies are needed to evaluate teaching methods used in the upper level soil science courses, students’ perceptions of teaching in soil science, and instructors’ knowledge of resources available for online and (or) blended learning.

Landscape-level disturbance is a reality in many parts of the world including the Athabasca oil sands region, Canada, and soils play an essential part in the overall reclamation process. Soils are reconstructed during reclamation to provide a foundation and a nutrient source for the novel ecosystems. However, reclamation is often monitored through structural indicators of soil quality, which may not reflect dynamic ecosystem functions such as nutrient cycling. Our objective was to determine if nutrient cycling was occurring on novel ecosystems and if standard structural measures of soil quality were appropriate indicators. We assessed soil quality and nitrogen cycling in reclaimed, harvested and undisturbed aspen forest sites following the addition of ¹⁵N-labelled aspen (Populus tremuloides Michx.) leaf litter to the soil surface. Structural soil quality indicators, including soil moisture and microbial carbon and nitrogen biomass, were higher on the undisturbed site, whereas soil microbial composition differed among sites. Yet, uptake of ¹⁵N by microbes and plants, which continued throughout the 52 mo field incubation, was comparable across all sites. These results indicate that differences in structural attributes between disturbed and undisturbed soils do not necessarily translate into differences in soil functioning related to nitrogen cycling. Instead, this case study supports exploring the use of stable isotope tracers to assess dynamic soil function indicators in reclaimed ecosystems. Being able to follow biogeochemical cycling as vegetation becomes established and new forests start to develop following reclamation is key to assessing the long-term sustainability of these novel ecosystems.

Increases in oil extraction on public lands in the US northern Great Plains has created an extensive network of access roads that must be removed upon well abandonment. However, the effects of road removal on soil properties are largely unknown. The objective of this study was to determine whether soil properties were altered on removed roadbeds and whether time since road removal has improved soil properties. Soils were sampled (n = 208) on perpendicular transects across removed roadbeds and extending into undisturbed areas on 16 restored roads located on two ecological site classifications such as (i) thin loamy and (ii) sandy. A Bayesian hierarchical mixed model was used to determine posterior predictive distributions and means of measured particle size distribution, gravel content, infiltration rate, pH, electrical conductivity, sodium adsorption ratio, CaCO₃ content, and organic matter. Alterations in the predicted distribution of particle size, pH, CaCO₃ content, and sodium adsorption ratio were attributed to mixing topsoil with subsoil during the road removal process. Soil organic matter decreased on roads. Most importantly, measured soil properties on removed roads did not improve with time since road removal. The alterations in soil properties can have lasting effects on nutrient availability, vegetation dynamics, and ecological resiliency of the native prairie.

L’objectif a été d’évaluer l’efficacité des formes d’engrais azotés dans la culture du bleuet sauvage et de déterminer leurs impacts sur le pH et l’azote (N) du sol. Seul le sulfate d’ammonium a permis de diminuer et de maintenir le pH du sol tout en assurant une grande disponibilité du N à la culture. Les formes de N n’ont eu aucun impact sur la productivité de la culture.

Repeated analysis of soil organic matter (SOM) in the top 0.3 m of a perennial rotation pasture with legumes in Nova Scotia showed a significant increase of SOM from 2007 to 2015 (paired t test; n = 24; P < 0.001). This suggests perennial pastures in cool-humid biomes enhance ecosystem services of dairy farms through SOM storage.