Information on the spatial distribution of soil pH is essential for assessing soil quality and soil productivity. Digital soil mapping (DSM) is commonly used to predict soil characteristics over various types of landscapes. Over the past decade, researchers have made progress using machine learning techniques to provide reliable predictions of soil properties with limited data. DSM studies often use a single learning approach, which is constructed with a machine learner that systematically extracts soil–environment relationships from a large database, whereby a fitted model is used to predict soil information in an unmapped area. The practice of using an ensemble learning approach, especially one that combines several base learners, has rarely been tested in DSM. We developed a workflow for using an ensemble learning algorithm to predict soil properties for the Thompson-Okanagan region of British Columbia, Canada. Here, we focused on soil pH and tested a variety of base learners. Base learners with high prediction accuracies were then used to construct a SuperLearner (SL) to extract the complex relationships between soil properties and environmental variables. The fitted SL was then used to predict soil properties at 25 m spatial resolution at three depth intervals (0–5, 5–15, and 15–30 cm). Prediction accuracies were assessed using an independent test dataset, which indicated that the SL had a similar prediction accuracy to the best individual base learners. Using the heterogeneous ensemble learning approach with a weighted average stacked generalization process eliminated the need to choose the best base learner.

Although British Columbia (BC), Canada, has a rich history of producing conventional soil maps (CSMs) between 1925 and 2000, the province still lacks a detailed soil map with a comprehensive coverage due to the cost and time required to develop such a product. This study builds on previous digital soil mapping (DSM) research in BC and develops provincial-scale maps. Soil taxonomic classes (e.g., great groups and order) and parent material classes were mapped at a 100 m spatial resolution for BC (944 735 km²). Training points were generated from detailed and semi-detailed soil survey maps. The training points were intersected with 26 topographic indices for mapping parent materials with an additional 9 climatic and vegetation indices for mapping soil classes. The soil–environmental relationships were inferred using the random forest (RF) classifier. The fitted models were used to predict 23 soil great groups, 9 soil orders, and 10 parent material classes. Accuracy assessments were performed using n = 14 570 validation points for parent material classes and n = 14 316 validation points for soil classes, acquired from the BC Soil Information System. The accuracy rates for soil great groups, orders, and parent material classes were 55%, 62%, and 69%, respectively, and kappa coefficients were 0.37, 0.41, and 0.59, respectively. This study demonstrated that when RF was trained using CSMs, the accuracy for the resulting DSM was higher than the original CSM. To assess prediction uncertainties, ignorance uncertainty maps were developed using class-probability layers generated by the RF models.

This research was conducted in Jableh city in the Latakia Governorate during 2019–2020 to study the level of pollution of the soils and plants of some greenhouses in Jableh city with the elements cadmium and nickel. Several greenhouses were randomly distributed in different areas in Jableh city based on the period of their investment (5, 10, 20, and 25 years), as the investment period was considered the variable factor between greenhouses. The homogeneity of greenhouse texture was taken into consideration as much as possible. Two-layer soil samples were collected (0–20 and 20–40 cm). Electrical conductivity, pH, the ratio of organic matter and the major basic elements (nitrogen, phosphorus, and potassium), and the total cadmium and nickel in the soil, plants, and cucumber fruits were determined. SPSS was used (completely randomized design). The results showed that there was pollution of greenhouse soils with the elements cadmium and nickel in a manner that is proportional to the increase in the period of investment. They also showed that the content of cadmium and nickel in cucumber fruits in the oldest houses exceeded the permissible limits. A strong positive second-degree significant (1%) correlation was observed between the available phosphorus and the total cadmium and nickel in the soil, and a strong correlation between the soil and plant content of these two elements and an increasing investment period.

Cultivated Organic soils in Montreal's southwest plain are the most productive soils in the province of Quebec. After their initial drainage to enable farming, Organic soils are susceptible to many forms of degradation and soil loss. In this study, we characterized the physical, chemical, and pedological properties of 114 sites from five peatlands to form soil conservation management zones. We attempted to use the maximum peat thickness (MPT) as a soil degradation proxy. The MPT can be defined as the thickness of the layer of peat until coprogenous or mineral materials are reached. The latter are undesired growing media and are not considered in MPT calculation. A series of multivariate analysis of variance indicated that MPT was moderately related to soil degradation (optimal model's Pillai's trace = 0.495). Three soil degradation groups were defined, separated by two MPT thresholds: 60 and 100 cm. When looking at 17 different depth-property combinations, shallower sites (MPT < 60 cm) showed signs of soil degradation significantly higher than sites with an MPT above 60 cm. The second threshold was proposed for practical purposes. Then, these thresholds were used to separate the study area into spatially distinct management zones. Important spatial contrasts were found. This supports the theory that precision agriculture techniques are needed to target fields to optimize soil conservation interventions. The relationship between the MPT and soil degradation should be further explored to account for other degradation factors, and to better identify degraded soils and soils at risk.

Climate change is creating opportunities for agricultural expansion northward into the boreal forest. Converting forested land to agricultural land generally results in significant losses of organic matter (OM), which can impact soil health (SH). The objectives of this study were to assess the effects of land conversion on indicators of SH and to use the Comprehensive Assessment for Soil Health (CASH) framework to integrate measures of these indicators into a score to evaluate land conversion effects. Total carbon and nitrogen were also measured in this study. Soils (0–5 and 5–15 cm) were collected from six dairy farms near Thunder Bay, ON, that included a mature forest, a field converted from forest to agriculture <10 years ago and a field converted from forest to agriculture >50 years ago. Land conversion resulted in significant declines in permanganate oxidizable carbon, wet aggregate stability, soil respiration, and concentrations of OM, autoclave citrate extractable protein, total nitrogen, and total carbon. Lower CASH scores in the soils converted to agriculture are interpreted to represent a decline in SH but the scores, along with soil organic matter (SOM) concentrations, remain high (CASH = 80; OM = 6%). There was no effect of time since conversion, suggesting that any degradation to SH happens quickly and is closely tied to declines in SOM.

The present study is aimed at assessing the impact of different tillage practices and mulch input rates on soil erosion and soil properties in Central Benin. The experiment was carried out at two sites (Dan and Za-zounmè) using a randomized complete block design. The effect of three tillage practices: contour ridging (CR), slope ridging (SR), and no-tillage (NT) and four mulch input rates (0, 3, 5, and 7 t·ha⁻¹) was investigated. The runoff, the soil, and nutrients losses were measured during the major rainy seasons of 2018 and 2019. Bulk density, gravimetric moisture, and water infiltration were collected in 2019. The effect of the interaction between tillage practices and mulch input rates was significant on runoff amount, runoff coefficient, soil loss, N, P, and K losses, and soil moisture. Over the investigated seasons, CR + 7M decreased runoff amount, runoff coefficient, soil loss, and N, P, and K losses by 100% compared to the treatments. NT was found to be effective in runoff and soil erosion controlling when combined with a mulch quantity greater than 3 t·ha⁻¹, and NT + 5M and NT + 7M reduced the soil loss, respectively, by more than 30% compared to the farmer’s practice (SR + 0M) at both sites. Contour ridge treatments yielded more soil moisture than NT and slope ridge treatments. Whatever the tillage practice, the greatest gravimetric moisture was recorded on 5 and 7 t·ha⁻¹ plots (i.e., CR + 7M, NT + 7M, and SR + 7M). This study provides decision makers with requisite information for effective soil erosion management in Benin where mechanization aids are limited.

Urease inhibitor (specifically, N-(n-butyl) thiophosphoric triamide, NBPT) and nitrification inhibitors (NIs) have been used to minimize nitrogen (N) loss from urea. However, their effects on improving crop N use efficiency (NUE) are usually inconsistent. A 2-year study was conducted to determine the best combination of NBPT and different NIs on urea that will maximize NUE while reducing nitrate leaching. Treatments consisted of untreated urea, NBPT-treated urea, and six types of (NBPT + NI)-treated urea that were surface applied at 80 kg N ha⁻¹ on plots seeded to canola (2019) and wheat (2020) at Carman and Portage in Manitoba, Canada. Plots at Carman had lysimeters installed to measure leached water and nitrate. The sites had at least 35% lesser rainfall than climate normal during each growing season. At each site, average grain yields, N removal, and residual nitrate were not significantly different between untreated urea and inhibitor-treated urea. Over the 2 years, there was no significant benefit of NBPT or NBPT + NI on crop NUE at each site. Cumulative leached nitrate (19–40 kg N ha⁻¹) did not differ significantly among urea treated with and without inhibitors. This is because >50% of the precipitation occurred when the effectiveness of NI had elapsed. Although NBPT and NI are known to reduce N losses to the atmosphere, this study suggests that the agronomic benefit and nitrate leaching prevention by NI applied in the spring may be limited in regions where large precipitation occurs later in the growing season or during non-growing season.

Tile drainage and surface runoff are major pathways for pollution of water resources by agricultural nutrients and chemicals. Little is known, however, of the pathways and amounts of carbon entry into water resources from agricultural land. This paper evaluates dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) losses in tile drainage and surface runoff from a Brookston clay loam after more than a half century of monoculture maize (Zea mays L.), continuous bluegrass sod (Poa Pratensis L.), and maize-oat (Avena sativa L.)–alfalfa (Medicago sativa L.)–alfalfa rotation. Water loss in tile drainage and surface runoff accounted for 27%, 32%, and 18% of annual precipitation (876 mm) for rotation, monoculture maize, and continuous sod, respectively. Tile drainage comprised 66%–89% of water loss from rotation and continuous sod, but only 15% from monoculture maize, with the remaining 85% of water loss from monoculture maize due to surface runoff. On an annualized basis, the measured dissolved C loss was 79 and 83 kg C ha^–1 yr^–1) from rotation and continuous sod, respectively, while 49 kg C ha^–1 yr^–1 was lost from monoculture maize. As up to 9% off-gassing loss of CO₂ from water samples was measured, total dissolved carbon losses in tile drainage and runoff water were likely greater. For Brookston clay loam soil, leaching into tile drains was the dominant mechanism for dissolved carbon loss from long-term continuous sod and crop rotation, while surface runoff was the dominant mechanism for dissolved carbon loss from long-term monoculture maize.

Aiming at the problems of serious soil desertification and continuous reduction of effective soil nutrients in the agricultural and animal husbandry interlaced arid area in Inner Mongolia, this study used Aohan alfalfa, old awn wheat, and fodder oats at the Siziwang Banner, Ulanchabu City, Inner Mongolia Autonomous Region. There were a total of five treatments, namely, single seeding alfalfa, single seeding old awn wheat, single seeding fodder oats, alfalfa and old awn wheat mixed sowing, and control. The results showed that the urease activity and microbial biomass nitrogen content of mixed planting were higher than other treatments. With the advancement of the growth period, the bacteria α-diversity index showed an upward trend; β-diversity analysis showed that planting method was the main factor affecting bacteria diversity and sampling time was the main factor affecting fungi diversity. In summary, mixed planting treatment was more helpful to improve soil enzyme activity, microbial biomass, and enrich soil microbial diversity, which was of great significance to maintain the balance of soil ecosystem. It is hoped that this study will contribute to the theoretical basis and practical experiences for efficient utilization of microbial resources in the field of soil improvement.

The accumulation of phosphorus (P) in agricultural soils and subsequent losses to waterways contribute to eutrophication in surface water bodies. In agricultural lands prone to prolonged flooding during spring snowmelt, P may be released to overlying floodwater and transported to lakes downstream. Ferric chloride (FeCl₃) is a potential soil amendment to mitigate P losses, but its effectiveness for flooded soils with snowmelt is not well documented. Thirty-six intact soil monoliths taken from four agricultural fields in Manitoba's Red River Valley region were surface-amended with FeCl₃ at three rates (0, 2.5, and 5 Mg ha^–1) to evaluate the effectiveness of FeCl₃ in minimizing P losses to porewater and floodwater. Over 8 weeks of simulated snowmelt flooding, porewater, and floodwater samples taken weekly were analyzed for concentrations of dissolved reactive P (DRP), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), and pH. Change in the redox potential was also measured weekly. With time of flooding, redox potential decreased in all soil monoliths. At early stages of flooding, the porewater pH values were significantly lower in FeCl₃-amended monoliths but increased with flooding time. Porewater and floodwater DRP concentrations increased in all soils when flooded, but the magnitudes varied. Amendment of FeCl₃ decreased the DRP concentrations from 17% to 97% in porewater and 26% to 99% in floodwater, with the effectiveness varying depending on the soil, FeCl₃ rate, and flooding time. Amendment of FeCl₃ increased porewater concentrations of Ca, Mg, Fe, and Mn. Soil amendment with FeCl₃ at both rates shows promise in mitigating redox-induced P losses from flooded soils.

Feedlot manure is rich in plant nutrients and can immobilize potentially toxic metals. However, pelleted manure compost as an amendment material in mine spoils (chat) is not well studied. This study was conducted to investigate the impact of pelleted cattle manure on improving chat properties facilitating phyto-stabilization and the establishment of grasses. A greenhouse pot experiment was conducted with unamended and amended chat (lime treated) with pelleted manure at three rates (60, 120, and 180 Mg ha⁻¹) with and without bentonite (B), using two native grasses, switchgrass (Panicum virgatum L.) and wheatgrass (Pascopyrum smithii (Rydb.) A. Löve). Leachates from pots were collected periodically until harvest. Nutrients and metal concentrations were measured in chat treatments, and metal concentrations were measured in plant tissues and leachates. Manure-amended chat reduced leachate Cd and Zn on average by >75% and >80%, respectively. Above-ground dry matter yield increased by >2.5-fold and >4-fold, respectively, in switchgrass and wheatgrass with the increase of 3-fold manure rate. The manure rate at 180 Mg ha⁻¹ reduced plant Cd and Zn by 50% and 20%, respectively, in wheatgrass, and 30% and no reduction, respectively, in switchgrass, compared to the 60 Mg ha⁻¹ manure rate. Overall, pelleted manure compost significantly increased available nutrients and decreased available metals in amended chat, with no significant effect of B. This study indicated that pelleted manure, preferably at 180 Mg ha⁻¹ rate with lime, can be used in acidic metal-contaminated chat to facilitate the establishment of perennial native grasses and reduce the potentially toxic metal availability.

Shallow soils occur throughout the world and are recognized as Leptosols at the highest level in the World Reference Base. These soils are notionally characterized as having a lithic contact close to the soil surface. Within the Canadian System of Soil Classification (CSSC), shallow soils are currently handled at the family level according to the depth at which the lithic contact is encountered. At the series level, these soils are usually designated as a shallow phase of a non-shallow soil series, ignoring the hierarchical structure of the CSSC. Shallow soils occur almost anywhere in Canada where the glacial drift is thin. The presence of bedrock close to the surface impacts drainage, the amount of available moisture, depth for rooting, and has a major influence on soil formation. Consequently, it is proposed that the importance of shallow soils be elevated to the order level, to be consistent with the frequency of their occurrence in the Canadian landscape and for consistency with other soil classification systems of the world. This requires integration at the great group and subgroup levels within all orders of the CSSC, as well as changes to the current formal definition of soil. These proposed modifications include nullifying the minimum 10 cm depth requirement as part of the current definition of soil in the CSSC for closer consistency with ecological land classification and other soil classification systems of the world. Proposed modifications to the current key to the soil orders, great groups, and subgroups are presented and discussed.

In the first edition (1974) of Canadian System of Soil Classification (CSSC), the taxonomic criteria for LFH organic horizons allowed application to any soil and land use developed under imperfectly to well-drained conditions. However, in the third edition (1998) of CSSC, the narrower taxonomic criteria for LFH horizons restricted application to only forest soils. A limited survey was conducted of some soil scientists across Canada to ask them if they had observed LFH horizons in nonforest soils. Distinct LFH horizons were observed across Canada under agriculture such as in no-till fields, tame and native pastures, and in reclaimed soils. They have also been observed in urban areas such as golf courses and grass-recreation fields. LFH horizons could also potentially develop under other nonforest land uses across Canada. Since no-till and native and tame pastures are most dominant in the prairies, the potential for LFH horizons is greatest in this region than elsewhere. However, they may occur anywhere in Canada where accumulation exceeds decomposition of organic material and they contain more than 17% organic carbon by weight or 30% organic matter. Therefore, we propose that the taxonomic criteria for applying LFH horizons be revised and broadened to include nonforest soils and be applicable to any soil order (where relevant) within Canada, and be at the discretion of the field pedologist. It is critical to identify and monitor LFH horizons over time because they are important for soil health, climate change, greenhouse gases, carbon sequestration, nutrient cycling, soil erosion, and hydrology.

To investigate the multiscale effects of freeze–thaw cycles on the mechanical properties and structural damage of paleosols, remodeled paleosol specimens at natural moisture content were subjected to multiple freeze–thaw cycles, followed by scanning electron microscopy, nuclear magnetic resonance (NMR) pore testing, and triaxial shear testing, and then the shear strength deterioration mechanism of paleosols was elaborated on from three aspects: fine, mesoscopic, and macroscopic. The main experimental results were as follows: (1) at the fine level, the NMR T₂ spectrum distribution curve showed one primary and two secondary peaks, in which the main spectrum occupied the majority, and the spectrum area showed an exponential function distribution relationship with the number of freeze–thaw cycles. With the accumulation of freeze–thaw cycles, the medium and large pores increased significantly. (2) At the mesoscopic level, when the specimens underwent freeze–thaw cycles, the interparticle contact pattern and particle morphology changed and the particle roundness increased. As the freeze–thaw cycle continued, fissures gradually developed and increased the most after the first freeze–thaw cycle, but the probability entropy of soil particles showed a decreasing trend with the increase of the number of freez–thaw cycles. (3) At the macro level, the number of freeze–thaw cycles gradually accumulated, the specimen stress–strain curve softened significantly, the shear strength deterioration effect was obvious, the deterioration value was the largest after one freeze–thaw cycle and gradually stabilized after 10 cycles, and the deterioration effect of cohesion was greater than that of the internal friction angle.

Appropriate soil management maintains and improves the health of the entire ecosystem. Soil appropriate administration necessitates proper characterization of its properties including soil organic matter (SOM) and soil moisture content (SMC). Image-based soil characterization has shown strong potential in comparison with traditional methods. This study compared the performance of 22 different supervised regression and machine learning algorithms, including support vector machines (SVMs), Gaussian process regression (GPR) models, ensembles of trees, and artificial neural network (ANN), in predicting SOM and SMC from soil images taken with a digital camera in the laboratory setting. A total of 22 image parameters were extracted and used as predictor variables in the models in two steps. First models were developed using all 22 extracted features and then using a subset of six best features for both SOM and SMC. Saturation index (redness index) was the most important variable for SOM prediction, and contrast (median S) for SMC prediction, respectively. The color and textural parameters demonstrated a high correlation with both SOM and SMC. Results revealed a satisfactory agreement between the image parameters and the laboratory-measured SOM (R² and root mean square error (RMSE) of 0.74 and 9.80% using cubist) and SMC (R² and RMSE of 0.86 and 8.79% using random forest) for the validation data set using six predictor variables. Overall, GPR models and tree models (cubist, RF, and boosted trees) best captured and explained the nonlinear relationships between SOM, SMC, and image parameters for this study.

The amounts and arrangements of polysaccharides (cellulose and hemicellulose), proteins, phenolic lignin, and pectin that make up plant tissue, in part, determine its decay rate. Lignin-rich and/or nitrogen-poor tissue has been described as biochemically recalcitrant causing a slow decay rate. Although a controversial mechanism for organic matter storage in soils with mineral particles, biochemical recalcitrance is still poorly understood in organic peat soil (Histosols). To investigate the role of Sphagnum in formation of peat soil, we characterize biochemical components for 10 species and examine persistence of the components in soil to 150 cm depth in three peatland ecosystems. We hypothesize that species from hummock microforms have more biochemical structural components and cohesion than species from hollows. Relative proportions of biochemical components changed markedly between plant material and the top 10 cm of peat soil, suggesting that decomposition occurred at the peat soil surface, but thereafter relative proportions of biochemical components did not vary significantly to 150 cm deep. A few differences in biochemical components that distinguished hummock species from hollow species persisted to the deepest depth sampled. Although persistence of the lignin-like component was expected, persistence of soluble and ionically bound pectin compounds was surprising as these biopolymers are thought to be readily decomposable. Our findings indicate that structural components of Sphagnum, specifically polysaccharides and pectin in addition to oft-cited phenolic lignin-like components, persist in peat soil and should not be overlooked in trying to understand carbon dynamics in Sphagnum-dominated ecosystems.

Sound micronutrient management requires an understanding of nutrient interactions and transformation processes in soil–plant systems which can regulate bioavailability and plant uptake. A series of studies were conducted under controlled environment and field conditions to evaluate wheat response to Cu and Zn fertilization on P-deficient soils from western Canada. The grain and straw yields of wheat were reduced in two (Waskada and Tisdale) of three soils used in the controlled environment study, while yield was not affected at the Echo field site in 2016 when both Cu and Zn sulfate fertilizer were applied at 5 kg·ha^–1 rates. Zinc concentration in soil and plant tissues was increased to apparent toxic levels with fertilizer addition in Waskada soils. An imbalance in tissue P:Zn concentration related to micronutrient fertilization was observed in Waskada and Tisdale soils. The availability of Cu and Zn in post-harvest soils was increased with increasing rate of these fertilizers' addition. Chemical and spectroscopic speciation using sequential extraction and X-ray absorption near edge structure, respectively, revealed that Cu and Zn were mostly speciated as carbonate phases, and complexation of these elements with carbonate and phyllosilicate minerals is likely the process controlling bioavailability in the soils.

Cryosols with thick surface organic horizons consisting of folic material derived from forest litter and feathermosses occur on northerly slope aspects in the Rocky Mountains of northern British Columbia. Designation of a new Folic Organic Cryosol subgroup in the Canadian System of Soil Classification would enable more realistic depiction of soil landscape patterns in future soil inventories.

The Maoniuping rare earth mine in Mianning, Liangshan Prefecture, is the largest rare earth deposit in China and the second largest rare earth deposit in the world. During the mining of rare earths, F and Pb, both types of heavy metal waste can directly or indirectly enter the soil, causing local soil contamination, which in turn poses a threat to the health of local residents. In this study, soil samples were incubated with fertilizer passivation solutions with pH values of 4, 5, 6, 7, 8, and 9, with the soil water content adjusted to 50% of the maximum water holding capacity in the field. The Pb-F contamination of the soil samples was analyzed to determine the existing states of the soil F and Pb and to study the remediation effect of fertilizer passivation solutions on the Pb-F contaminated soil. The results showed that under different passivation conditions, the pH, Pb, and F of the soil substantially changed and the passivation effect was enhanced over time. The pH of the soil significantly increased. The analysis of the effects of F and Pb treatment revealed that when the passivation fertilizer solution of pH 5 was used, the available Pb and F in the soil decreased the most, and the residual state of Pb and F increased to 77.86% and 57.24%, respectively.