This paper highlights major activities and achievements in soil science by professors at the University of Alberta (U of A), which provide incredible benefits to society, provincially, nationally, and globally. Evolution of the soils profession in Alberta commenced in 1919 with the hiring of F.A. Wyatt, who developed the Department of Soil Science (DSS) and initiated a soil survey program in Alberta. J.D. Newton joined the department in 1922, teaching and supporting soil surveys that led to a fertilizer program greatly benefitting agriculture. With time, opportunities and problems were encountered with utilization of soils. U of A soil scientists conducted inventories, conducted innovative research, developed superior management techniques, and through evolving education and extension, continuously helped bring improvements to how we utilized and managed soil resources. The DSS 100 yr evolution is chronicled under the themes of pedology (including soil survey), soil fertility, soil sustainability (conservation, land reclamation, and contaminant remediation), with embedded specialized studies within these themes.

For the past 70 yr, researchers in the Soil Science/Renewable Resources Department at the University of Alberta have used isotopes to study topics of ecological importance. This review highlights the soil isotope research conducted within our department over this time, including an historical overview of studies of interest. Analytical techniques and advances in instrumentation are discussed, focusing on the measurement of light stable isotope ratios (i.e., for C, H, N, S, and O) using isotope ratio mass spectrometry (IRMS). Early soil isotope work (1950–2000s) focused on agricultural soils and soil fertility issues. These studies included the use of radioactive isotopes such as ¹⁴C and ³⁵S, and (or) artificially enriched stable isotopes including ¹⁵N-labelled fertilizers. More recently (2000–present), the scope of research widened to include natural-abundance stable isotope ratio studies as higher-sensitivity IRMS systems became more prevalent. Current isotope research topics include N biogeochemistry in natural and managed ecosystems, land management effects on greenhouse gas emissions, carbon cycling in northern landscapes, paleo-reconstruction in peatlands, carbon sequestration in boreal forests, and biodegradation of petroleum hydrocarbons. Further technological progress also enabled new techniques such as compound-specific IRMS analysis, including δ¹³C and δ²H measurements of soil n-alkanes and phospholipid fatty acids. In conclusion, current IRMS instrumentation presents unparalleled opportunities for multidisciplinary research to track carbon, plant nutrients, and pollutants as they move through soils.

Stable isotope probing of phospholipid fatty acids (PLFA-SIP) is useful when studying bacterial contributions to soil processes, and it is an effective way to separate fungal and bacterial activity by linking ¹³C enrichment to specific PLFAs. Distinguishing bacterial contributions to soil processes often employs selective inhibitors; however, studies demonstrating their efficacy when using PLFA-SIP are less common. Here, we determined the effect of the fungal inhibitor cycloheximide (4.8 mg g⁻¹ dry soil) and the bacterial inhibitor bronopol (0.48 mg g⁻¹ dry soil) on microbial communities white spruce [Picea glauca (Moench) Voss] forest floor by measuring the uptake of ¹³C-enriched glucose (2 mg g⁻¹ dry soil) in microbial PLFAs. We targeted [¹³C]glucose uptake by the bacterial community conditioned to a stable soil environment of 23 °C for over 2 wk rather than new bacteria generated from active colony growth caused by glucose addition. Nearly all bacterial PLFAs exhibited pronounced inhibition of ¹³C enrichment in the presence of bronopol. Limited inhibition of ¹³C enrichment in the presence of cycloheximide was observed as bacterial PLFA affected by cycloheximide had roughly one third less ¹³C enrichment than samples emended with [¹³C]glucose alone. Inhibitory effects only reduced ¹³C enrichment and did not affect total PLFA concentrations, implying that the inhibitors in the concentrations applied were impeding bacterial activity without causing cell death. Based on this work, we conclude that bronopol is an effective inhibitor for bacteria. Additionally, non-targeted effects of cycloheximide on soil bacteria must be accounted for when it is used in soil incubations.

Peat bogs are valuable archives of environmental change, including climate history, landscape evolution, and atmospheric deposition of trace elements, fallout radionuclides, and organic contaminants. Maintaining the fidelity of peat samples during collection and handling can be challenging, given that bogs consist mainly of fossil plant materials that typically have a very low density and are easily compressed. The surface layers of bogs, which are dominated by living plants and poorly decomposed fibrous peats, are especially problematic. To extract peat monoliths, we use a Belarus corer for deep layers and a Wardenaar device for surface layers. Both corers are constructed using titanium alloys to improve strength, reduce weight, and minimize the risk of contamination by the trace metals of environmental relevance. In this review, we include detailed drawings of the Belarus corer and photographs of the modifications to the Wardenaar corer. Modifications to the motorized Noernberg corer for frozen peat are described, and a complete set of drawings provided. A summary is given of simple procedures to minimize the risk of metal contamination in the laboratory from slicing and subsampling the peat cores and milling the dried samples.

The distributions of dissolved (<0.45 μm) trace elements (TEs) amongst major colloidal forms in soils have implications for their availability, accessibility, and toxicity to plants and animals. The size-resolved distributions of TE species in soil solutions were collected using lysimeters and were measured using asymmetrical flow field-flow fractionation (AF4) coupled to ultraviolet absorbance (UV) and inductively coupled plasma mass spectrometry (ICP-MS). Using this AF4-UV-ICPMS system, dissolved TEs were separated by size, and concentrations in major forms were quantified: “truly dissolved” primarily ionic and small molecules <ca. 1 kDa, organic-dominated colloids, and primarily inorganic colloids. The soil solutions were collected under vacuum using a novel surgical (316L) stainless steel (SS) lysimeter with a 5 μm pore size. Analyses were performed in the metal-free, ultraclean SWAMP laboratory. The acid-cleaned lysimeters yielded excellent blank values for TEs of environmental interest (i.e., Li, Al, V, Mn, Co, Cu, As, Mo, Ag, Cd, Ba, Pb, Th, and U). Lysimeter sampling offers the major advantage that it can minimize disturbances to the natural TE concentrations and distributions amongst major dissolved colloidal forms in soil solutions and thus provides information that is relevant to plant uptake.

A robust and reliable analytical procedure for the determination of trace (mg∙kg⁻¹) and ultra-trace elements (μg∙kg⁻¹) in soil and sediments by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) was optimized. Aliquots of ∼200 mg of two certified reference materials (IAEA Soil-7, soil and IAEA SL-1, lake sediments) were digested in nitric acid (HNO₃) purified twice by sub-boiling distillation using a microwave-heated high-pressure autoclave. Incremental addition of tetrafluoroboric acid (HBF₄, 0.1–2 mL) to HNO₃ was evaluated for yield. The selection of appropriate proportions of digestion acids was crucial to obtain accurate results. Digested samples were analyzed for a range of trace elements including those that are potentially toxic (Ag, Cd, Pb, Sb, and Tl), plant micronutrients (Cu, Fe, Mn, and Zn), those enriched in bitumen (Mo, Ni, and V), and lithophile elements (Al, Ba, Co, Cr, Rb, Sr, Th, Ti, Y, and Zr). Nitric acid alone proved to be sufficient to completely liberate Cd, Co, Cr, Fe, Mn, Ni, Pb, V, and Zn in both soil and sediments (87%–120% recovery). For almost all the other elements, addition of HBF₄ was needed for improved recovery. A combination of 3 mL of HNO₃ and 1.5 mL of HBF₄ was optimal to fully liberate an extended list of elements including Ba, Sb, and Sr from both the reference materials. Conservative lithophile elements (Th, Ti, Y, and Zr) could not be completely recovered with the proposed method, requiring hydrofluoric acid for complete dissolution of recalcitrant minerals.

Perennial legumes in crop rotations increase soil C sequestration from greater productivity with N₂ fixation. Here, we corroborated increases in soil organic carbon (SOC) and harvests modelled in 5 yr wheat–oats–barley–alfalfa/brome–alfalfa/brome (5Y) vs. 2 yr wheat–fallow (WF) rotations with those measured from 1929 to 2018. Harvest and SOC gains of 100–150 g C m⁻² yr⁻¹ and 15–25 g C m⁻² yr⁻¹ were modelled and measured in 5Y vs. WF rotations with different fertilizer and manure amendments. Modelled gains were closely related to annualized rates of N₂ fixation by alfalfa of 8–10 g N m⁻² yr⁻¹. However, N₂ fixation also drove increases in modelled N₂O emissions of ca. 0.06 g N m⁻² yr⁻¹, which partially offset gains in SOC. Gains in harvest, SOC, and N₂O emissions of 60–90 g C m⁻² yr⁻¹, 15 g C m⁻² yr⁻¹, and 0.05 g N m⁻² yr⁻¹ were modelled and measured in both rotations with amendments of N + P relative to unamended treatments. Harvest and SOC gains were smaller, and leaching and N₂O losses larger, with amendments of N without P. After 100 yr of RCP 8.5 climate change, harvests in WF changed little from those in baseline runs, whereas those in 5Y rose with N + P because of increased N₂ fixation. SOC declined in WF with all amendments and could only be raised in 5Y with N + P amendments. These model findings indicated the importance of N₂ fixation and P amendments in determining responses of agroecosystem productivity and C sequestration to climate change.

Over the last 20–30 yr, increased intensification and diversity of crop rotations, along with increasingly higher yielding crop cultivars on the Northern Great Plains, has increased nutrient removal from cropping systems, but also increased crop residues returned to the soil, affecting soil nutrient cycling, soil carbon (C) and nutrient balances. The University of Alberta Breton Classical Plots, established in 1929, consist of two crop rotations of varying diversity and intensity: (1) wheat–fallow (WF); and (2) 5 yr, cereal–forage. Superimposed on these rotations are eight fertility treatments, including a check (control), manure, balanced (NPKS), and nutrient exclusion treatments. Soil total C, nitrogen (N), phosphorus (P), potassium (K), and sulfur (S) levels were measured on soil samples (0–15 cm) collected from both rotations in 2013. Wheat yields and N uptake for the 2007–2018 growing seasons from both rotations were compared. In the 5 yr rotation, soil total C, N, and S, wheat yield and wheat N uptake were greater than the WF rotation. Soil total P levels were not different between the two rotations, but soil total K was higher in the WF rotation. Despite higher soil S and comparable soil P, wheat yield and N uptake response to applied P and S was greater in the 5 yr rotation compared with the WF rotation. Response to applied N in the 5 yr rotation was muted because of significant inputs of biologically fixed N. Wheat also responded to applied K in the 5 yr rotation. These results highlight the need to replace exported nutrients.

Little research has compared land application of stockpiled (SM) or composted (CM) beef feedlot manure with straw (ST) or wood-chip (WD) bedding on loss of dissolved organic carbon (DOC) in runoff. We conducted a 6 yr (2013–2018) rainfall simulation-runoff study and utilized surface (0–5 cm) soil collected from a long-term (since 1998) field experiment on a clay loam soil in southern Alberta, Canada. The treatments consisted of SM or CM with ST or WD bedding applied at 13, 39, and 77 Mg·ha⁻¹ (dry weight), as well as an unamended control and mineral fertilizer treatment. Surface soil was collected from all treatments after 15–17 (C15, C16, and C17; 2013–2015) continual annual applications and then after one to three legacy years (L1–L3, 2016–2018) after manure applications were first discontinued in 2015. The soil was packed into runoff trays, and flow-weighted mean concentrations (FWMCs) and mass loads of DOC in runoff water were determined during rainfall simulations. Mean DOC losses were generally significantly (P ≤ 0.05) lower for CM with ST bedding compared with the other manure type – bedding treatments in certain years and were consistent with this amendment having the lowest total carbon (C) content. The total C content of the amendments explained 92% of the variation in DOC concentration. Termination of long-term manure applications reduced FWMCs by 85%–91% and mass loss by 76%–89% from the C17 to L3 year. Therefore, our findings suggested that composting manure with ST or discontinued long-term manure application may reduce DOC loss in runoff.

The reduction in net CO₂ emissions from increased carbon sequestration in soil and slower decomposition of soil organic matter under most long-term no-till (NT) situations can potentially be offset by a concomitant increase in nitrous oxide (N₂O) emissions after tillage reversal on long-term NT soils. The objective of this work was to quantify N₂O emissions after tillage reversal on two contrasting western Canadian Prairie soils managed under long-term (∼30 yr) NT. We measured one growing season (2010) of soil N₂O emissions on a Black Chernozem and Gray Luvisol at Ellerslie and Breton, AB, respectively, following 30 yr of NT and N fertilizer application at two rates (0 and 100 kg N ha⁻¹) subjected to tillage reversal and no disturbance (i.e., continuing NT). Tillage reversal after long-term NT was associated with higher N₂O emissions in both soils but was significant only in the Gray Luvisol with 0 kg N ha⁻¹. Long-term N fertilizer applications of 100 kg N ha⁻¹ were associated with higher growing season soil N₂O emissions and higher levels of soil N (i.e., a positive, long-term soil N balance) at both sites. Regardless of tillage, the difference in growing season nitrous oxide emissions from the 0 and 100 kg N ha⁻¹ plots on the Gray Luvisol were much greater than the Black Chernozem. A modest increase in N₂O emissions upon tillage reversal on a long-term NT soils could translate to a significant increase to agricultural greenhouse gas inventories in the event of large-scale tillage reversal on agricultural land in western Canada.

Soil quality (SQ) indicators such as plant available water (PAW), soil organic carbon (SOC), and microbial biomass carbon (MBC) can reveal agroecological functions; however, their spatial variabilities across contrasting land uses need to be better understood. This study examined the spatial variation of these key SQ indicators as a function of two land-use systems and using topography covariates. We sampled a total of 116 point locations in a native grassland (NG) site and an irrigated cultivated (IC) site located near Brooks, Alberta. Compared with NG, cultivation altered soil pore-size distribution by sharply reducing macroporosity by 25%. However, conditions in the IC soil supported greater accrual of microbial growth (MBC of 601 vs. 812 nmol phospholipid fatty acids g⁻¹ soil) probably due to more availability of water and nutrients. Focusing on the effects of topography on SQ indicators, terrain elevation (by light detection and ranging) and estimated depth-to-water were found to be key controllers of SQ at the two land-use systems. Also, there were gradual increases in both SOC and MBC where estimated water table was deeper, and higher SOC also associated with lower elevation. A comparison of ordinary kriging and cokriging (coK) geostatistical mapping indicated that the coK method performed better as demonstrated by improvements in the accuracies of spatial estimations of PAW, SOC concentration, and MBC. Thus, implementing coK using the aforementioned topography covariates enhances the capability for predictive mapping of SQ, which is particularly useful when spatial data for key SQ indicators are sparse and challenging to measure.

A 12 wk laboratory incubation examined the effects of application of various nitrogen (N) and sulfur (S) fertilizers on soil plant-available nutrient levels and nitrous oxide (N₂O) gas emissions with respect to soil fertilization history using soils sampled from the University of Alberta Breton Classical Plots. Fertilization history and added fertilizer treatments showed significant effects on N₂O emissions and NO₃⁻-N and SO₄⁻-S recovered on ion-exchange resins over the 12 wk. Mean cumulative N₂O emissions ranged from 0.43 to 1.18 kg N₂O-N ha⁻¹. The relationship between observed total resin-recovered NO₃⁻-N and N₂O emissions was not consistent for soils receiving long-term applications of various combinations of N, phosphorus, potassium, and S fertilizers. The N₂O emission from two soils with a history of long-term N fertilizer applications but different S fertilization histories was significantly different even though resin-recovered NO₃⁻-N levels were similar. When grouped according to added fertilizer treatments, mean cumulative N₂O emissions showed a strong linear relationship with mean resin-adsorbed NO₃⁻-N production. We hypothesize that the differences in the relationship between NO₃⁻-N production and N₂O-N emissions for soils with different long-term fertilization histories may be a result of the interaction of N and S oxidation processes. Further, soil fertilization history may significantly influence soil N₂O emissions in response to N fertilizers added within the growing season of observation but isn’t often considered in short-term experiments, and this may be a significant source of uncertainty in the estimation of greenhouse gases inventories from agricultural soils.

Forest stand age can affect ecosystem carbon (C) cycling and net ecosystem productivity (NEP). In Canada, establishment of short-rotation plantations on previously agricultural lands has been ongoing, but the effect of stand development on soil respiration (R_s) and NEP in such plantations is poorly understood. These types of data are essential for constraining ecosystem models that simulate C dynamics over the rotation of a plantation. We studied R_s (including autotrophic, R_a, and heterotrophic, R_h) and NEP in 2008 and 2009 in a chronosequence of 5-, 8-, 14-, and 16-yr-old (ages in 2009) hybrid poplar (Populus deltoides × Populus × petrowskyana var. Walker) plantations in northern Alberta. The highest R_s and NEP were generally found in the 14-yr-old stand. Seasonal variations in R_s were similar among the plantations, with most of the variation explained by soil temperature at the 10 cm depth in 2008 with far less explained in 2009, a much drier year. In diurnal measurements, hysteresis was found between soil respiration and soil temperature, with the patterns of hysteresis different among stand ages. Soil respiration in the 14-yr-old plantation had the greatest sensitivity to temperature changes. Stand age did not affect the R_h:R_s ratio, whereas the NEP exhibited strong inter-annual variability. We conclude that stand age was a major factor affecting R_s and NEP, and such effects should be considered in empirical models used to simulate ecosystem C dynamics to evaluate potentials for C sequestration and the C source–sink relationship in short-rotation woody crop systems.

Boreal peatlands are major sources of dissolved organic carbon (DOC) to downstream aquatic ecosystems, where it influences carbon cycling and food web structure. Wildfire and permafrost thaw alter peatland vegetation and hydrology and may affect the quantity and chemical composition of exported DOC. We studied the influence of wildfire and thaw on microbial and photochemical lability of near-surface porewater DOC, assessed through 7 d incubations. We carried out these incubations in spring, summer, and fall but only found differences in spring when DOC biodegradability (% loss during dark incubations) increased with lower DOC aromaticity and C/N ratios. During spring, the most labile DOC was found in recently formed thermokarst bogs along collapsing peat plateau edges (25% loss), which was greater than in mature sections of thermokarst bogs (3%), and peat plateaus with intact permafrost (9%). Increased DOC lability following thaw was likely linked to high DOC production and turnover associated with productive hydrophilic Sphagnum mosses and sedges, rather than thawed permafrost peat. A wildfire (3 yr prior) reduced DOC biodegradability in both peat plateaus (4%) and rapidly collapsing peat plateau edges (14%). Biodegradability of DOC in summer and fall was low across all sites; 2% and 4%, respectively. Photodegradation was shown to potentially contribute significantly to downstream DOC degradation but did not vary across peatland sites. We show that disturbances such as permafrost thaw and wildfire have the potential to affect downstream carbon cycling, particularly as the largest influences were found in spring when peatlands are well connected to downstream aquatic ecosystems.

Copper (Cu) is essential for all organisms but is commonly deficient in organic soils or found locally in excess. Natural and anthropogenic inputs of Cu were examined using 32 peat cores from bogs in Europe, North America, New Zealand, Greenland, and Antarctica. The natural abundance of Cu in ombrotrophic (rainwater-fed) peat was studied using (1) samples from pre-industrial periods (representing background values), (2) bromine (Br) concentrations and the background Cu/Br ratio, and (3) cores from remote locations. Etang de la Gruère in Switzerland provides a record of 15 000 yr of peat accumulation. The lowest Cu concentrations (1.0 ± 0.20 mg·kg⁻¹) are found in 18 peat layers dating from ca. 6000 to 9000 cal yr BP, when atmospheric deposition of soil-derived dust was at a minimum. Similar background values occur in peat bogs from other regions. Recent peat layers from bogs in developed areas reveal much greater concentrations. Using the Cu/Br ratio, “excess” Cu in peat profiles can be calculated and attributed either to anthropogenic inputs in recent peats or natural inputs from mineral–water interactions in deeper layers. Peat cores from remote regions of northern Alberta show little or no evidence of anthropogenic Cu.

Microbial research for maintaining soil productivity, health, and environment as well as for ecosystem function has been one of the main research focuses in the Department of Renewable Resources (formerly Department of Soil Science) during the last 100 yr. In recent years, microbial research has been expanded to effectively reclaim disturbed land, remediate contaminated sites, and manage soft sediments such as huge volumes of oil sands tailings. This article highlights the microbial processes in tailings ponds that can affect strategies to manage growing inventory of oil sands tailings and reduce associated environmental footprint. Enormous volumes of fluid fine tailings produced during bitumen extraction from oil sands are retained in tailings ponds. Some tailings streams contain residual labile hydrocarbons originated from the hydrocarbon solvents used in the extraction process. Indigenous microorganisms acclimated to the pond environment metabolize certain fractions of the fugitive labile hydrocarbons into biogenic greenhouse gases (GHG) such as methane (CH₄) and carbon dioxide (CO₂). Long-term (1–7 yr) biodegradation studies conducted using mature fine tailings (MFT) collected from different tailings ponds reveal that the microorganisms sequentially and preferentially biodegrade hydrocarbons under methanogenic conditions. The stoichiometric mathematical model developed on these biodegradation studies can predict GHG emissions from tailings ponds. Production of biogenic gases also affects the porewater and solid-phase chemistry of MFT and accelerates their de-watering and consolidation during active methanogenesis, which is beneficial for recovery of porewater for reuse in the bitumen extraction process and for effective reclamation of consolidated material.

Managing fluid fine tailings (FFT) present a major cause of industrial and environmental concerns in oil sands surface mining production. A potential management solution is to dewater and cap the FFT solids for use in land reclamation. A 16 wk greenhouse study was conducted to assess whether FFT centrifuge cake with caps of various reclamation soil mixes (forest floor mineral mix, peat mineral mix, and a mixture of both) and depths (0, 5, 10, and 20 cm) would support growth of trembling aspen (Populus tremuloides — native broadleaf tree) and beaked willow (Salix bebbiana — native broadleaf shrub). Beaked willow had a much greater survival rate (100%) when grown directly in FFT cake compared with trembling aspen (16.7%). Plants grown directly in FFT cake were negatively impacted by high water content, low nitrate supply rates, and high metal concentrations with beaked willow seedlings having 10 times higher foliar concentrations of Al, Cr, and Ti compared with any other treatments. Adding soil caps substantially increased aboveground biomass for both species, but differences among soil cap types and depths did not have as significant of an effect on plant growth. Results from this study show that capping FFT substantially improves woody plant growth, and S. bebbiana and P. tremuloides are potentially suitable species for tailings reclamation.