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Healthy soils contribute to a wide range of ecosystem services and virtually all of the UN Sustainable Development Goals, but most of the world's soil resources are in only fair, poor, or very poor condition, and conditions are getting worse in more cases than they are improving. A total of 33% of all soils are moderately to highly degraded as a result of erosion, loss of organic matter, poor nutrient balance, salinization and alkalinization, contamination, acidification, loss of biodiversity, sealing, compaction, and poor water status. Best management practices are available to limit or mitigate threats to soil health, and many of them mitigate multiple soil threats. In many regions of the world, policies or initiatives to protect or enhance the status of soils are in place, and they need to be strengthened and enforced. The Food and Agriculture Organisation will publish its second comprehensive assessment of the status of the world's soils in 2025, and this review provides an interim update on world soil status and offers an accessible overview of the topic. [ABSTRACT FROM AUTHOR]

• Model-predicted soil erosion was compared to soil erosion rates estimated using 137Cs. • Tillage erosion dominated the pattern of soil erosion on upper-slope positions. • Tillage and water erosion contributed to the variation of primary particles. • Colour coefficients are useful in identifying spatial heterogeneity of soil/sediment. Soil erosion and sediment delivery models have been increasingly employed in studies of catchment sediment dynamics in current years. These models are also used to represent the spatial interaction of soil erosion and sediment transport processes, thereby providing spatially-distributed predictions of soil redistribution rates for agricultural landscapes. It has been widely recognized that individual soil erosion processes and their interactions contribute towards total soil erosion; however, quantifying the rates and patterns of soil erosion processes and their interactions within topographically complex landscapes is challenging. Therefore, the objective of this research was to estimate and model the relative contributions of tillage, water and wind erosion towards total soil erosion in the Canadian Prairie provinces of Manitoba and Alberta using 137Cs, a fallout radionuclide tracer, and three well-established models: (i) Tillage Erosion Model (TillEM); (ii) Revised Universal Soil Loss Equation, version 2 (RUSLE2); and (iii) Single-event Wind Erosion Evaluation Program (SWEEP). The findings indicate that the patterns of 137Cs-estimated soil erosion were closely matched with the erosion pattern predicted by TillEM and suggests that tillage erosion dominates the pattern of total soil erosion on the knolls of hummocky landscapes. Additionally, soil particle size variation within the wetland catchments reflected the modeled patterns of water and tillage erosion. Furthermore, our findings confirmed that colour coefficients are useful in identifying spatial heterogeneity of soil within wetland catchments and reflect the patterns of soil loss and gains. These results indicate that water and tillage erosion, and also their interactions, are main erosion processes in the Canadian Prairie Pothole Region (PPR), but that soil movement by tillage practices has been the predominant redistribution process. [ABSTRACT FROM AUTHOR]

• 137Cs revealed the complex patterns of soil redistribution within wetland catchments. • Landform position was a significant factor affecting the spatial variation of 137Cs. • The highest soil loss rates were observed on the upper and middle slope positions. • Sediment budgets were used to quantify sediment fluxes from fields into wetlands. Wetlandscapes are vulnerable to land conversion and sediment infilling from upland agriculture, causing them to act as sinks for sediment deposition and putting at risk their ecosystem services. Wetlandscapes in the Canadian Prairies agroecosystems are particularly susceptible to sediment infilling because of the intensification of human activities and agricultural practices. The rising risk of soil erosion in cultivated landscapes has generated a need to estimate soil redistribution rates and soil loss monitoring tools and techniques. This research examines the effects of agricultural activities on soil loss and sedimentation rates within agricultural landscapes in the Canadian Prairies. Land and atmospheric fluxes of sediment into wetlands are quantified over the past 60 years using catchment-scale tracing (137Cs) and budgeting techniques. Findings indicate that the pattern of 137Cs erosion/deposition varies along catchment toposequences, with erosion near the top of the toposequences (the average annual soil erosion rates were found to be 1.1 kg m−2 yr−1 for Manitoba and 0.3 kg m−2 yr−1 for Alberta) and deposition within the wetland ecosystem (total deposition rates were estimated at about −3.6 kg m−2 yr-1for Manitoba and −0.9 kg m−2 yr−1 for Alberta). The sediment delivery ratios were approximately 57% and 35% in Manitoba and Alberta, respectively, indicating that a noticeable amount of the mobilized sediment exits the field. These transfers from cultivated fields into wetlands reveal that wetlandscapes in Canadian Prairies are vulnerable to sediment infilling, and soil erosion control practices are needed to achieve sustainable management of agricultural landscapes. [ABSTRACT FROM AUTHOR]

A critical time for both water and tillage erosion is the period between growing seasons when the field is tilled and thus bare or nearly bare. During this period, there is a high risk for water erosion, leading to water eroded channels. The existing channels, tillage operations and the combination of these two may strongly affect runoff and sediment generations in the following water erosion events. However, knowledge on this is limited. In this study, plot experiments were conducted to quantify the short-term effects of an existing channel, a single pass of tillage and their interaction on the generation of runoff and sediment. Four treatments: no channel, no tillage (NN, as the control); with a channel, no tillage (CN); no channel, with tillage (NT); and with a channel, with tillage (CT) were examined. Plots under the four treatments were placed under simulated rainfall for at least one hour. Runoff and sediment samples were collected every 5-minutes after runoff initiation. The effects of treatments on the amounts of runoff and sediment were analyzed with ANOVA and ANCOVA. We found that with an existing channel, runoff initiation has accelerated and runoff discharge and sediment export have increased whereas with a single pass of tillage, runoff initiation was delayed and runoff discharge and sediment export have decreased. When an existing channel was tilled, the effects of tillage dominated while the existing channel only demonstrated some minor impacts. Applying this knowledge to a cereal-potato crop rotation common in Atlantic Canada, we recommend spring primary tillage after cereal harvesting and late fall primary tillage after potato harvesting to reduce the overall soil erosion. • Channel accelerated runoff initiation and increased runoff and sediment. • Tillage delayed runoff initiation and decreased runoff and sediment. • When an existing channel is tilled, the effects of tillage dominate. • Spring primary tillage after cereal harvesting is recommended to reduce erosion. • Late fall primary tillage after potato harvesting is recommended to reduce erosion. [ABSTRACT FROM AUTHOR]

Land rolling has become a popular practice in soybean and pulse production in the Northern Great Plains. The practice of land rolling is simply pulling a large-scale cylindrical roller over a cultivated field to push down stones and improve seed-to-soil contact. Many soybean farms in Manitoba are routinely rolled either immediately after seeding or at the very early stages of crop development. There has been considerable concern regarding the potential effects of land rolling on wind-induced soil loss, soil properties, and plant growth in soybean production. To address this concern, an on-farm research project was conducted at eight different field sites in the Red River Valley of southern Manitoba, Canada, in 2018 and 2019. Trials were established with rolled and non-rolled treatments arranged using a randomized complete block design. To examine the environmental and agronomic impacts of land rolling, data was collected to characterize wind-transported sediment (passive uni-directional samplers), soil properties (e.g., surface roughness and moisture content), yield, and plant growth parameters. Despite the land rolling reducing surface roughness the results showed no significant difference in the amount of collected wind-transported sediment between the two treatments. In addition, the particle size of the wind-transported sediment ranged between 0.002 and 0.1 mm suggesting that this size fraction is the most susceptible to wind erosion. Furthermore, there was a small, but significant, increase in soybean yield in the non-rolled treatment, despite having significantly lower volumetric soil moisture content. Overall, while land rolling reduced soil surface roughness and increased the wind erosion risk, it did not result in an increase in the amount of wind-transported soil loss. Lastly, within the Red River Valley the practice of land rolling to support higher soybean yield was not supported; however, the exact reasons for the small yield reduction is not fully understood. • The practice of land rolling significantly increased the volumetric soil moisture content at 0–10 cm soil depth. • Soil surface roughness was significantly decreased by the practice of land rolling. • The practice of land rolling did not significantly increase the amount of soil movement by wind. • The practice of land rolling resulted in a small but significant decrease in soybean yield. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms pose a significant threat to water security, with anthropogenic forcing being implicated as a key driver behind the recent upsurge and global expansion of cyanobacteria in modern times. The potential effects of land‐use alterations and climate change can lead to complicated, less‐predictable scenarios in cyanobacterial management, especially when forecasting cyanobacterial toxin risks. There is a growing need for further investigations into the specific stressors that stimulate cyanobacterial toxins, as well as resolving the uncertainty surrounding the historical or contemporary nature of cyanobacterial‐associated risks. To address this gap, we employed a paleolimnological approach to reconstruct cyanobacterial abundance and microcystin‐producing potential in temperate lakes situated along a human impact gradient. We identified breakpoints (i.e., points of abrupt change) in these time series and examined the impact of landscape and climatic properties on their occurrence. Our findings indicate that lakes subject to greater human influence exhibited an earlier onset of cyanobacterial biomass by 40 years compared to less‐impacted lakes, with land‐use change emerging as the dominant predictor. Moreover, microcystin‐producing potential increased in both high‐ and low‐impact lakes around the 1980s, with climate warming being the primary driver. Our findings chronicle the importance of climate change in increasing the risk of toxigenic cyanobacteria in freshwater resources. [ABSTRACT FROM AUTHOR]

Inhibitors of matrix metalloproteinases (MMPs) have been extensively explored to treat pathologies where excessive MMP activity contributes to adverse tissue remodelling. Although MMP inhibition remains a relevant therapeutic target, MMP inhibitors have not translated to clinical application owing to the dose-limiting side effects following systemic administration of the drugs. Here, we describe the synthesis of a polysaccharide-based hydrogel that can be locally injected into tissues and releases a recombinant tissue inhibitor of MMPs (rTIMP-3) in response to MMP activity. Specifically, rTIMP-3 is sequestered in the hydrogels through electrostatic interactions and is released as crosslinks are degraded by active MMPs. Targeted delivery of the hydrogel/rTIMP-3 construct to regions of MMP overexpression following a myocardial infarction significantly reduced MMP activity and attenuated adverse left ventricular remodelling in a porcine model of myocardial infarction. Our findings demonstrate that local, on-demand MMP inhibition is achievable through the use of an injectable and bioresponsive hydrogel. [ABSTRACT FROM AUTHOR]

The article discusses soil erosion as a cause of soil landscape variability and to the potential to affect crop variability. It presents various studies which demonstrate that soil landscape restoration is a feasible land management practice for restoring crop productivity on eroded hilly land. It also adds that the practice may be considered as the most effective means of managing soil landscape variability and a component of an effective precision conservation tactics.

Abstract: Two approaches have been used in the literature to estimate soil erosion using 137Cs measurements. The traditional-approach requires only one set of samples and uses a single reference 137Cs level, determined off-site, for the whole site. The repeated-sampling-approach requires two sets of samples and uses point-specific values, the 137Cs inventories of the first set of samples, as the reference 137Cs levels. No study has been carried out to investigate the advantages and limitations of these two approaches. In this study, a hay-pasture site, located in Ontario, Canada, with a short period of corn (Zea mays L.) production was examined. Total erosion was estimated using both the traditional- and repeated-sampling-approach. Water and tillage erosion were assessed using established models. The sum of water and tillage erosion served as the model-predicted total soil erosion, assuming negligible wind erosion. The site was classified into five landform elements and the 137Cs-estimated and model-predicted erosion rates were grouped into the landform elements. It was determined that when the reference 137Cs level is accurate, the traditional-approach can produce accurate soil erosion rates, providing that errors due to the conversion models are negligible. However, when there is a large error in the reference 137Cs level, the estimated erosion rates are biased. The repeated-sampling-approach eliminates the bias of reference 137Cs level but has higher random errors. However, the random errors can be reduced by taking multiple samples and using the spatially averaged erosion rate for data interpretation. Landscape segmentation based on topography provides a useful landform division for describing erosion processes and, therefore, practical units for grouping the sampling points. In addition, repeated-sampling-approach also has many advantages due to a shortened time period. In particular, the uncertainties of simple conversion models can be greatly reduced. [Copyright &y& Elsevier]

Abstract: Previous tillage erosion models have generally assumed that tillage operations (over time) are conducted equally in opposite directions across the field. In reality, actual tillage patterns used by farmers are often much more complicated than this. However, to date, no research has been conducted to examine the impact of complex tillage patterns on tillage erosion. In this study, a Directional Tillage Erosion Model (DirTillEM) was developed to better account for the effect of complex tillage patterns and field boundaries on tillage erosion across an agricultural landscape. The DirTillEM was used on a hypothetical, completely level landscape (to negate the influence of topography) using tillage patterns typical of those used in the North American Prairies. The DirTillEM predictions agreed well with Light Detection and Ranging (LiDAR) topographic data collected from the near-level landscapes of the Red River Valley in Manitoba, Canada. Overall, the model predicted that tillage direction (especially when conducted repeatedly in specific patterns over many years) and field boundaries play a very important role in the creation and destruction of morphological features across the landscape – even in near-level landscapes which were previously thought to be less susceptible to the negative effects of tillage erosion. With the increased knowledge of processes involved in tillage translocation and tillage erosion, it is possible to avoid the undesired formation of morphological features within a field. [Copyright &y& Elsevier]

Abstract: This research demonstrated the use of a laser profiling system (LPS) and digital imagery as useful tools in measuring soil micro-topography and crop residue cover following a soil disturbance event. The soil micro-topography was characterized in terms of surface roughness using two geostatistical approaches; semivariance analysis and the mean absolute-elevation-difference method. Univariate statistical analysis was also used. All three procedures used to describe surface roughness were successful in detecting changes in surface roughness due to soil disturbance and the addition of corn residue. There was a definite advantage in using the geostatistical approaches to characterize surface roughness as the indices they provide give insight into the characteristics of the surface roughness. Crop residue cover was measured using digital images and image analysis software to contrast the soil and the crop residues. The series of field experiments examined the roles of both soil disturbance and corn residue and their interactions on surface roughness, crop residue cover, exposed surface area, and near-surface porosity. Soil disturbance and the addition of corn residue were both found to be significant factors affecting the surface roughness, crop residue cover, exposed surface area, and near-surface porosity. Due to the interaction and added effects of crop residue, it was also demonstrated that the calculated surface area may not be a measure of exposed soil area, but rather it is a combination of soil and residue surface areas. Similarly, the roughness of a surface does not only reflect the soil clods produced during tillage but that of the residue itself. Furthermore, it was demonstrated that the information gathered by the LPS and digital imagery can be used to evaluate surface characteristics arising from different tillage practices. [Copyright &y& Elsevier]

Tillage is a driving force of soil movement in cultivated fields. Soil constituents, together with the mass of soil, are redistributed across landscapes by tillage. The pattern of tillage-induced soil constituent redistribution is determined by the pattern of tillage erosion (tillage-induced soil mass loss or gain) and the dispersiviry of translocation. In this study, we used a convoluting procedure and developed a Tillage Translocation Model (TiIITM) to simulate the tillage translocation process and to demonstrate tillage-induced soil mass and soil organic carbon (OC) (as an example of soil constituents) redistributions across four hypothetical landscapes subjected to different tillage patterns (directions) and over different lengths of tillage period. We determined that the local tillage-erosion rate is mainly dependent on topography and that the effects of tillage pattern and the length of tillage period are relatively minor. The redistribution of OC content in the till layer is mainly determined by the number, location, and size of soil loss positions in the landscape, as well as the soil loss rates at these positions. Net loss of OC content occurs in the till layer and this loss increases with time. In contrast, an increase of OC content in the sublayer occurs at soil accumulation positions. The model was validated against field data collected at a site near Cyrus, MN. The patterns of OC and inorganic C redistribution can be adequately estimated by TillTM. There are discrepancies, however, between the model-estimated values and the field measurements due to the limitations and uncertainties associated with the model. The results clearly showed that tillage translocation causes the vertical redistribution of soil constituents across the landscape, which implies that tillage translocation is one of the driving forces behind the spatial variability of soil properties and properties that impact biophysical processes. [ABSTRACT FROM AUTHOR]

Abstract: Total soil erosion is the integrated result of all forms of soil erosion — wind, water and tillage. It has been recognized that in topographically complex landscapes, individual soil erosion processes and their interactions all contribute towards total soil erosion. In this study, two field sites, representing different landscapes in the northern region of the North American Great Plains, were examined. Water and tillage erosions were estimated using the established water and tillage erosion models and total soil erosion was estimated using the 137Cs technique. We determined that the patterns of water and tillage erosion across the landscapes are mainly dependent on topographic features and they are fundamentally different within topographically complex landscapes. On the slope of undulating landscapes, tillage and water erosion both contribute considerably to total soil erosion. On the knoll of hummocky landscapes, tillage erosion dominates the pattern of total soil erosion. Tested against the Cs measurements, the patterns of total soil erosion cannot be well estimated by water or tillage erosion model alone unless one of the two erosion processes predominate over the other erosion processes. Combining water and tillage erosion models generally provides better estimations of total soil erosion than the component models on their own. Most soil properties and crop yield were found to be closely correlated with total soil erosion. For a given erosion process, the soil erosion patterns estimated using different models with reasonable parameter settings were similar to each other. However, it is necessary to choose an optimal model and to obtain accurate parameters for the purpose of accurate assessments of the erosion rates. [Copyright &y& Elsevier]

Abstract: Tillage erosion is a potential contributor to the total soil erosion occurring within cultivated fields. No study has been carried out on tillage erosion associated with cereal-based production systems, which are the predominant form of crop production in the Canadian Prairies. Previous tillage translocation studies have focused on primary tillage implements (i.e. mouldboard and chisel ploughs), with slope gradient normally assumed to be the only factor that affects tillage translocation. Currently, there is a lack of information available with regards to the effect of secondary tillage and seeding implements and of slope curvature toward total tillage translocation and erosion. In this study, 77 plots were established within a field site in southern Manitoba, Canada to examine tillage translocation caused by four tillage implements: air-seeder, spring-tooth-harrow, light-cultivator and deep-tiller. Together, these four implements create a typical conventional tillage sequence for cereal-based production in Canadian Prairies. We determined that secondary tillage implements could be as erosive as primary tillage implements. In addition, the erosivity of the air-seeder was comparable to that of the deep-tiller, the primary tillage implement, when seeding was conducted shortly after the light-cultivator. In the majority of cases, tillage translocation could be explained by slope gradient alone, confirming that slope gradient is the main factor driving tillage translocation. However, slope curvature also significantly affected tillage translocation and should be used for future modeling. [Copyright &y& Elsevier]

Objective: To explore the decline in expertise of the consultant psychiatrist and its replacement by a range of professional colleagues. Conclusion: Averting a devaluing of expertise in Australasia requires thoughtfulness, willingness to quietly and confidently contribute, and professional behaviour. There are early promising developments. [ABSTRACT FROM AUTHOR]

Abstract: Tillage has been and will always be integral to crop production. Tillage can result in the degradation of soil, water, and air quality. Of all farm management practices, tillage may have the greatest impact on the environment. A wide variety of tillage equipment, practices and systems are available to farmers, providing opportunities to enhance environmental performance. These opportunities have made tillage a popular focus of environmental policies and programs such as environmental indicators for agriculture. This paper provides a very brief examination of the role of tillage in crop production, its effect on biophysical processes and, therefore, its impact on the environment. Models of biophysical processes are briefly examined to demonstrate the importance of tillage relative to other farm management practices and to demonstrate the detail of tillage data that these models can demand. The focus of this paper is an examination of the use of information on tillage in Canada''s agri-environmental indicators initiative, National Agri-environmental Health Analysis and Reporting Program (NAHARP). Information on tillage is required for several of the indicators in NAHARP. The type of data used, its source, and its quality are discussed. Recommendations regarding the collection of tillage data and use of tillage information are presented. [Copyright &y& Elsevier]

• Channel decreases total soil translocation during downslope tillage. • Channel increases total soil translocation during upslope and contour tillage. • Channel changes the shape and extent of the tillage tool's zone of influence. • Zone of influence determines the trapping versus energy-intensity-increase effect. • Contour tillage is more efficient than up-down slope tillage in filling channels. A major feature of water erosion is the formation of channels such as rills and gullies. The creation of these channels changes the local topography and, therefore, may affect soil movement during tillage operations. To quantify such interaction between water and tillage erosion, a plot experiment was conducted and point tracers were used to measure tillage translocation under three tillage treatments: downslope (DT), upslope (UT), and contour tillage (CT) with three channel treatments: no channel (C0), 10 cm by 10 cm channel (C10), and 20 cm by 20 cm channel (C20). Forward and lateral translocation, and their resultant total translocation, were calculated by comparing the tracer locations before and after tillage. The results indicate that for DT, the presence of a channel reduced total translocation, whereas for UT, it increased total translocation. This trend was attributed to a decrease in forward translocation under DT and an increase in forward translocation under UT with the presence of channels, while lateral translocation was not significantly affected by the presence of channels. For CT, the presence of a channel increased both forward and lateral soil translocation, and therefore total translocation. These observed patterns of tillage translocation can be well explained by the relative importance of the trapping effect (channel functions like a trap for moving soil) versus the energy-intensity-increase effect (greater energy intensity due to less soil being moved with the presence of a channel). Soil movement decreases when the trapping effect dominates, and it increases when the energy-intensity-increase effect dominates. At the process level, the relative importance of the trapping effect and the energy-intensity-increase effect is determined by the shape and size of the tillage tool's zone of influence (ZoI), which is affected by the location and orientation of the channel, and the direction of tillage. Overall, our results suggest that if channels are formed by water erosion, CT would be better than DT and UT in reducing tillage translocation and filling the channel. The knowledge gained from this study can be used to improve water and tillage erosion modelling. [ABSTRACT FROM AUTHOR]

The sources and distribution of sediment and particulate organic carbon (OC) to Lake Melville, Labrador, were characterized to better understand impacts from climate and hydrological changes to the system. Mass accumulation rates (MARs) across the Lake Melville System (LMS) were established from 15 sediment cores collected in 2013 and 2014 by fitting excess 210Pb (210Pbex) profiles to a two-layer advection-diffusion model. MARs, validated using 137Cs, varied between 0.04 and 0.41 g cm−2 a−1, and overall decreased with increasing distance from the Churchill River, which drains into Goose Bay, a western extension of Lake Melville. The Churchill River is the greatest source of sediment to the system, but surprisingly, MARs were greatest in western Lake Melville rather than Goose Bay, reflecting the contribution of fine material carried eastward in the Churchill River plume and inputs from nearby tributaries. A comparison of 137Cs and 210Pbex inventories to expected atmospheric fallout (1.5 and 23.6 disintegrations per minute (dpm) cm−2, respectively) in sediment across the LMS suggests particles are largely sourced from the watershed. In eastern Lake Melville, elevated 210Pbex inventories and marine OC point to particle scavenging of dissolved 210Pb from inflowing marine water. A transient tracer mixing model was used to determine the depth in each core where >90% of sediment was deposited before and after hydroelectric development at Churchill Falls (1970) and applied to down-core profiles of OC and organic carbon isotopes (δ13Corg). We observed a significant increase of terrestrial OC to Lake Melville post 1970, which we interpret as change from climate or hydrology of the Churchill River. [ABSTRACT FROM AUTHOR]

Feeding cattle on cropland through the winter months using pre-placed fodder bales (bale grazing or in-field bale feeding) has demonstrated economic benefits when compared to confined winter feeding, but very little research has been done to quantify the impacts of recurring cycles of in-field feeding on runoff water quality. In this study, two small watersheds (with and without winter bale grazing; WBG) located in the same annual cropped field in southern Manitoba, Canada were monitored from 2008 to 2016. Winter feeding in the WBG treatment occurred in the winters of 2008/09, 2010/11, 2012/13, and 2014/15. Export of N and P with the WBG treatment was also contrasted with the alternative practice of higher density confined feeding (CF). For WBG, soil fertility was improved, with higher soil test phosphorus (Olsen-P) and soil nitrate (NO 3 − -N) following WBG. Exports of N and P with surface runoff were also higher in snowmelt following WBG when compared to the control watershed, primarily due to higher concentrations of particulate N and P, NH 4 + -N, and dissolved organic N. Higher P loss from the WBG watershed than from the control watershed persisted in the non-grazing years following each bale grazing. In contrast, concentrations of all forms of nitrogen in runoff consistently returned to levels observed prior to bale grazing following a winter without treatment. Annual runoff export of N and P per animal unit day (AUD) following WBG was comparable to that for two CF sites. Higher annual volumes of runoff were observed from the larger area and lower density bale feeding treatment, but with lower concentrations of N and P in comparison to feedlot sites. If WBG continues to be utilized to improve soil fertility and reduce manure transportation costs, the potential negative impacts on runoff water quality must be considered. Higher volumes of snowmelt runoff per AUD from WBG in comparison to CF sites will make runoff capture options more expensive to implement. WBG timing or siting changes that reduce runoff volume and make retention feasible or that decrease accumulation of P at the soil surface will reduce negative water quality impacts associated with WBG. [ABSTRACT FROM AUTHOR]

Abstract: Topographic depressions are abundant in topographically complex landscapes. A common practice with earlier, low resolution Digital Elevation Models (DEMs) was to remove all depressions to ensure that water flowed continuously to the edge of the DEM domain. The assumption was that most depressions were created due to errors in the DEMs. This practice is no longer justified with the increasing availability of high accuracy DEMs. However, very few studies have addressed how DEM processing options such as smoothing and coarsening and setting area and depth thresholds can affect depression identification. In this study, a site located in the Prairie Region of Canada was examined. The site is a hummocky glaciated landscape with many in-field wetlands. Lidar topographic data were collected and were used to generate a 1m by 1m square-grid DEM. Detailed error analyses of the lidar DEM were conducted. A set of DEMs were generated after different degrees of smoothing and coarsening. FlowMapR, an established terrain analysis tool, was used to identify depressions in each DEM with various user-defined area and depth thresholds. The results were validated against a field wetland survey. We determined that the problems associated with depression identification using a lidar DEM are two-fold. On one hand, artefactual depressions created due to DEM errors need to be eliminated, for which the raw lidar DEM need to be smoothed. On the other hand, it is also desirable to remove those topographic depressions that do not function as closed basins at the spatial or temporal scale of the processes of interest. Setting area and depth thresholds appeared to be the preferred choice for this. We suggested using the un-autocorrelated lidar DEM error as the criterion for DEM smoothing and considering depression connections in the selection of area and depth thresholds. Using lidar data on a hummocky landscape with loamy soils in the Prairie Region of Canada, 10 to 20 times smoothing operations with an area threshold of 200m2 and a depth threshold of 0.1m were recommended as guidelines for depression identification. [Copyright &y& Elsevier]

One of the major threats to the sustainability of agriculture within the Americas is that posed by soil erosion due to the actions of rain, wind, and tillage. Soil degradation by tillage erosion is of greatest concern in regions where intensively tilled crops are grown on highly erodible landscapes. To date, very little research has been conducted on the potential for tillage erosion within intensively cultivated vegetable and potato (Solarium tuberosum L.) production, especially within steep mountainous agroecosystems. Therefore, the objective of this study was to iñeasure tillage translocation and tillage erosion by the arado de disco (disk plow), an implement used across Latin America and the most common mechanized primary tillage implement used in the potato- growing volcanic highlands of Costa Rica. Our results suggest that tillage erosion is a major problem in this region. Soil movement down slope by the arado de disco was approximately twice that moved upslope, and a highly significant relationship was observed between both the mean displacement distance of the tilled layer and the mass of translocated soil and slope gradient when all up and downslope cultivated tillage translocation plots were included in the regression analysis. When the data were separated and only those plots cultivated downslope were analyzed, the potential for tillage erosion more than doubled. If tillage operations are only conducted downslope, the rate of tillage erosion is equivalent to ∼250 Mg ha-1 pasc-1(∼112 tn ac-1 pass-1) from the top 5 m (16.4 ft) below a field boundary. These results show that not only is the arado de disco an erosive implement but that downslope-only cultivation is a highly erosive tillage practice-as the measured erosivity values are larger than those typically reported for implements in Europe and North America (where tillage operations are normally conducted in alternating up and downslope directions). Our results also suggest that the variability in both speed of tillage and depth of tillage across the landscape were important factors controlling tillage translocation by the arado de disco. However, since tillage operations on the steep slopes of Volcán Irazú are typically conducted downhill, depth of tillage had a much greater effect on tillage translocation under these conditions than did speed of tillage. It is clear that a reduction in tillage erosion is necessary to reduce soil losses in this intensively cropped region of Costa Rica and for similar steepland agricultural regions in the Americas. [ABSTRACT FROM AUTHOR]

Knowledge of soil movement is important for the design and selection of injection tool to minimise agronomic and environmental concerns associated with liquid manure injection. Laboratory studies were conducted in an indoor soil bin to investigate soil movement in three directions resulting from sweep type injection tools. The first study was carried out to select point tracers. Three tracer sizes (10, 15 and 20mm) and four tracer materials [wood, polyvinyl chloride (PVC), aluminium and steel] were tested for measurements of soil movement resulting from a sweep at constant injection depth and tool forward speed. The test results led to the selection of the 10mm PVC tracers for the subsequent soil movement study. In the soil movement study, three sweeps (small, medium and large) were tested at three injection depths (50, 100 and 150mm), two tool forward speeds (0·6 and 1·4ms−1), and two soil moisture contents (14 and 18%). The selected tracers were used to measure soil movement in forward, upward and lateral directions. Increasing injection depth from 50 to 150 resulted in a 39% increase in the soil forward movement and a 37% increase in the upward movement. The higher tool forward speed produced a 31% higher forward movement and a 56% higher lateral movement. The higher soil moisture content increased the soil upward movement by 17%. The large sweep resulted in a 27 and 48% greater forward movement than the medium and small sweeps, respectively. [Copyright &y& Elsevier]

The Northern Great Plains is a key region to global food production. It is also a region of water stress that includes poor water quality associated with high concentrations of nutrients. Agricultural nitrogen and phosphorus loads to surface waters need to be reduced, yet the unique characteristics of this environment create challenges. The biophysical reality of the Northern Great Plains is one where snowmelt is the major period of nutrient transport, and where nutrients are exported predominantly in dissolved form. This limits the efficacy of many beneficial management practices (BMPs) commonly used in other regions and necessitates place-based solutions. We discuss soil and water management BMPs through a regional lens—first understanding key aspects of hydrology and hydrochemistry affecting BMP efficacy, then discussing the merits of different BMPs for nutrient control. We recommend continued efforts to "keep water on the land" via wetlands and reservoirs. Adoption and expansion of reduced tillage and perennial forage may have contributed to current nutrient problems, but both practices have other environmental and agronomic benefits. The expansion of tile and surface drainage in the Northern Great Plains raises urgent questions about effects on nutrient export and options to mitigate drainage effects. Riparian vegetation is unlikely to significantly aid in nutrient retention, but when viewed against an alternative of extending cultivation and fertilization to the waters' edge, the continued support of buffer strip management and refinement of best practices (e.g., harvesting vegetation) is merited. While the hydrology of the Northern Great Plains creates many challenges for mitigating nutrient losses, it also creates unique opportunities. For example, relocating winter bale-grazing to areas with low hydrologic connectivity should reduce loadings. Managing nutrient applications must be at the center of efforts to mitigate eutrophication. In this region, ensuring nutrients are not applied during hydrologically sensitive periods such as late autumn, on snow, or when soils are frozen will yield benefits. Working to ensure nutrient inputs are balanced with crop demands is crucial in all landscapes. Ultimately, a targeted approach to BMP implementation is required, and this must consider the agronomic and economic context but also the biophysical reality. [ABSTRACT FROM AUTHOR]

The global rise of cyanobacterial blooms emphasizes the need to develop tools to manage water bodies prone to cyanobacterial dominance. Reconstructing cyanobacterial baselines and identifying environmental drivers that favour cyanobacterial dominance are important to guide management decisions. Conventional techniques for estimating cyanobacteria in lake sediments require considerable resources, creating a barrier to routine reconstructions of cyanobacterial time-series. Here, we compare a relatively simple technique based on spectral inferences of cyanobacteria using visible near-infrared reflectance spectroscopy (VNIRS) with a molecular technique based on real-time PCR quantification (qPCR) of the 16S rRNA gene conserved in cyanobacteria in 30 lakes across a broad geographic gradient. We examined the sedimentary record from two perspectives: 1) relationships throughout the entire core (without radiometric dating); 2) relationships post-1900s with the aid of radiometric dating (i.e., 210Pb). Our findings suggest that the VNIRS-based cyanobacteria technique is best suited for reconstructing cyanobacterial abundance in recent decades (i.e., circa 1990 onwards). The VNIRS-based cyanobacteria technique showed agreement with those generated using qPCR, with 23 (76%) lakes showing a strong or very strong positive relationship between the results of the two techniques. However, five (17%) lakes showed negligible relationships, suggesting cyanobacteria VNIRS requires further refinement to understand where VNIRS is unsuitable. This knowledge will help scientists and lake managers select alternative cyanobacterial diagnostics where appropriate. These findings demonstrate the utility of VNIRS, in most instances, as a valuable tool for reconstructing past cyanobacterial prevalence. • Paleolimnology expands monitoring windows, helping establish cyanobacteria baselines. • Limited access to cyano-paleolimnological tools represents a management challenge. • Cyanobacteria VNIRS represents an inexpensive and rapid cyanobacteria diagnostic tool. • Cyanobacteria VNIRS yields similar results to traditional paleolimnological proxies. [ABSTRACT FROM AUTHOR]

Abstract While wetlands are known as long-term storages or sinks for contaminants, not all are equally effective at trapping phosphorus (P). The prevalence of P-sink behavior in prairie pothole wetlands remains unclear, especially across gradients of human disturbance. The objectives of the current study were three-fold: (1) characterize the spatiotemporal variability of wetland hydrology and wetland water P concentration across a range of prairie potholes; (2) establish the propensity of different pothole wetlands to act as sources or sinks of P; and (3) assess the potential controls of climatic conditions, landscape characteristics, wetland soil physiochemical properties and local hydrology on source versus sink dynamics. Ten intact and three consolidated (i.e., drained) wetlands located in southwestern Manitoba, Canada, were monitored for water level fluctuations and water soluble reactive P (SRP) concentration over two years with contrasting antecedent wetness conditions. Soil cores were also collected to measure soil physiochemical properties such as the equilibrium phosphorus concentration (EPC). Water column SRP concentrations were compared to EPC values to infer the time-variable source versus sink behavior of each of wetland. Statistical analyses were then performed to assess whether the source versus sink behavior of individual wetlands could be linked to their physiographic or hydrologic characteristics. Results show that some wetlands persistently acted as P sinks while others switched between source and sink behavior. Persistent P-sink behavior was more common with intact wetlands, as opposed to consolidated wetlands. Wetland soil texture, storage volume and short-term water level fluctuations appeared to control the source versus sink behavior of individual wetlands. The dominant controls on P-sink behavior identified under dry conditions were, however, different from those identified under wetter conditions. This study therefore highlights the importance of considering the non-stationary nature of P-sorption dynamics and their controls, even at sub-annual timescales, in the prairie pothole region. Graphical abstract Unlabelled Image Highlights • Studies on phosphorus (P) dynamics in prairie pothole wetlands (PWs) are scarce. • 13 prairie PWs with differing soil, hydrology and human disturbance were surveyed. • Intact wetlands appear to be more effective at storing P than drained wetlands. • Wetland volume, soil texture and short-term stage fluctuations control P dynamics. • The relative importance of controls on P dynamics changes with wetness conditions. [ABSTRACT FROM AUTHOR]

The movement of excess phosphorus (P) into streams, rivers, and lakes poses a significant threat to water quality and the health of aquatic ecosystems and thus, P has been targeted for reduction. In landscapes dominated by agriculture, P is primarily transported through non-point sources, which a number of best management practices aim to target. One such practice is vegetated buffer strips (VBS), which are designed to use dense vegetation above the surface and extensive root systems below the surface to reduce runoff velocity, trap sediments, increase infiltration, and increase plant uptake of nutrients. The effectiveness of VBS in reducing P concentrations has been studied and reviewed, but most studies have been undertaken in warm or temperate climates, where runoff is primarily driven through summer rainfall events and when vegetation is actively growing. In cold climates, the majority of runoff occurs during the snowmelt period, when soils are frozen and vegetation has been flattened by snow and ice over the winter period and is not actively taking up nutrients. These conditions hinder the ability of VBS to work as designed. Additionally, frozen vegetation can release P after undergoing freeze–thaw cycles (FTCs). Thus, this review aimed to (i) summarize research designed to determine the effectiveness of VBS in reducing P transport in cold climates, (ii) collate research on the potential for vegetation to release P after undergoing FTCs, and (iii) identify research gaps to be addressed in determining VBS effectiveness in cold climates. Cold-climate VBS implemented in Canada, the northern United States, and northern Europe have shown P removal efficiencies ranging from −36% to +89%, a range that identifies the uncertainty surrounding the use of VBS in these landscapes. However, there is consensus among researchers globally that vegetation does release P after undergoing FTCs, though P concentrations from different species vary across studies. The design and management of VBS in cold climates requires careful consideration, and VBS may not always be the best management strategy to reduce P transport. Future research should be undertaken at a larger scale in natural systems and focus on VBS design and management strategies. [ABSTRACT FROM AUTHOR]

The selective nature of interrill erosion – the preferential mobilization and transport of soil particles – can lead to the enrichment of fine-grained soil particles (< 63 μm) and organic carbon (OC) within the mobilized soil. This study investigated the effects of slope gradient, vegetative cover, soil moisture content, texture and organic matter content, as well as their interactions on soil loss, particle size distribution and organic carbon content of soil mobilized under simulated rainfall within two contrasting agricultural regions in Canada. Overall, it was found that the eroded material was enriched in both fine-grained and carbon-rich particles relative to the source soil. It was demonstrated that dispersing and sieving both the source soil and the mobilized soil to < 63 μm (i.e., removal of sand and large particulate organic matter) reduced the relative enrichment of both fine-grained soil particles and OC, which would allow for a more direct comparison of physical and biogeochemical properties between the source and mobilized soil. Furthermore, it was demonstrated that while the soil loss and the degree of enrichment were negatively correlated, there were differences in which soil surface properties had a significant effect in determining soil loss and the selectivity of both fine-grained and organic-rich soil particles and how these surface properties interacted. This suggests that while soil loss may be a good predictor of the degree of enrichment, the factors that control these two processes are different, which is important in understanding the process of selectivity. It was also shown that the OC content of both the source and mobilized soil was positively correlated to the degree of soil aggregation in addition to the silt and clay content. [ABSTRACT FROM AUTHOR]

Erosion influences the lateral and vertical distribution of soil in agricultural landscapes. A better understanding of the effects of erosion and redistribution on soil organic carbon ( C) within croplands would improve our knowledge of how management practices may affect global C dynamics. In this study, the vertical and lateral distribution of soil organic C was characterized to evaluate the amounts and timescales of soil organic C movement, deposition and burial over the last 50 years in different agroecosystems across Canada. There was strong evidence that a substantial portion of eroded sediment and soil organic C was deposited as colluvium close to its source area, thereby burying the original topsoil. The deepest aggraded profile was in a potato field and contained over 70 cm of deposited soil indicating an accumulation rate of 152 Mg ha yr−1; aggraded profiles in other sites had soil deposition rates of 40-90 Mg ha−1 yr−1. The largest stock of soil organic C was 463 Mg ha−1 (to 60 cm depth) and soil C deposition ranged from about 2 to 4 Mg ha−1 yr−1 across all sites. A distinct feature observed in the aggraded profiles at every site was the presence of a large increase in soil organic C concentration near the bottom of the A horizon; the concentration of this C was greater than that at the soil surface. Compared to aggraded profiles, the SOC concentration in eroded profiles did not differ with depth, suggesting that dynamic replacement of soil organic C had occurred in eroded soils. A large amount of soil organic C is buried in depositional areas of Canadian croplands; mineralization of this stock of C appears to have been constrained since burial, but it may be vulnerable to future loss by management practices, land use change and a warming climate. [ABSTRACT FROM AUTHOR]

Algal blooms fueled by phosphorus (P) enrichment are threatening surface water quality around the world. Although P loss from arable land is a critical contributor to P loads in many agricultural watersheds, there has been a lack of understanding of P loss patterns and drivers across regions. Here, we synthesized edge-of-field P and sediment runoff data for 30 arable fields in the Canadian provinces of Saskatchewan, Manitoba and Ontario (a total of 216 site-years) to elucidate spatial and temporal differences in runoff and P mobilization in snowmelt and rainfall runoff, and discuss climatic, soil and management drivers for these patterns. Across all regions, precipitation inputs were positively correlated with runoff amounts and consequently P loads. Runoff and P losses were dominated by snowmelt across all sites, however, regional differences in runoff amounts, and P concentrations, loads and speciation were apparent. Proportions of total P in the dissolved form were greater in the prairie region (55–94% in Manitoba) than in the Great Lakes region (26–35% in Ontario). In Manitoba, dissolved P concentrations in both snowmelt and rainfall runoff were strongly positively correlated to soil Olsen P concentrations in the 0–5 cm soil depth; however, this relationship was not found for Ontario fields, where tile drainage dominated hydrologic losses. Although precipitation amounts and runoff volumes were greater in Ontario than Manitoba, some of the greatest P loads were observed from Manitoba fields, driven by management practices. This synthesis highlights the differences across the Canadian agricultural regions in P runoff patterns and drivers, and suggests the need of co-ordinated and standardized monitoring programs to better understand regional differences and inform management. Phosphorus runoff patterns vary with climatic regions across Canada. †The dissolved P was measured as total dissolved P in MB and dissolved reactive P in SK and ON. ‡Total P was not measured in SK. [Display omitted] • Phosphorus runoff patterns and drivers vary with climatic regions across Canada. • Co-ordinated and standardized monitoring programs are key to clarify regional differences. • Snowmelt dominates runoff volume and phosphorus loss across Canada. • The predominant form of P in runoff differs between the Prairie region and the Great Lakes region. • Reducing phosphorus sources is important for mitigating phosphorus runoff. [ABSTRACT FROM AUTHOR]

Water-induced channel is one of the main forms of soil erosion in cultivated fields. Channelized erosion is often measured by the volume of the channels. Traditionally, the measurements were conducted with rulers or measuring tapes. However, these traditional methods are generally time- and labor-consuming and can cause soil surface disturbance. Close-range photogrammetry with a Consumer-Grade Camera (CGC-CRP) provides an alternative way of measuring channel volume and can overcome limitations of traditional methods and provides much higher spatial resolution. However, quantitative information on the accuracy of this technique is rare. In this study, the accuracy of the CGC-CRP method under different settings were examined with an in-house experiment and validated with a field experiment. In the in-house experiment, a wood board surface with Artificial Channels (AC) of different shapes, orientations, and sizes were built. These ACs were surveyed using the CGC-CRP method with a series of settings of shooting angles and image overlapping rates. Selected cross-sectional areas were extracted to compare against manual measurements to assess the absolute and relative errors of the CGC-CRP method. The applicability of the CGC-CRP method with different settings was evaluated by comparing time consumption and the size of detection areas. The results indicated that in order to maintain an acceptable accuracy level, the image overlapping rate should be ≥70%, and the shooting angle should be in the range of 60° to 80°. For the channel shape, the accuracy for V-channel was ~15% higher than that for U-channel. For the U-channel, the impact of the channel orientation on the accuracy was not significant when the shooting angle was relatively high, whereas for the V-channel, the vertically oriented channel had higher accuracy than horizontal or angle channels. Last, channel size did not strongly affect accuracy when the channel was vertically orientated, and the shooting angle and image overlapping rate were set in the optimum ranges. However, when the shooting angle or image overlapping rate was low, or when the channel was angled or horizontally orientated, the accuracy was lower with larger channel size. In the field experiment, under the optimum camera setting, the error for the ten cross-sectional areas was about 1.6%. This result suggests that the CGC-CRP method is promising in volumetric assessment of rill and gully erosion. The quantitative information on the accuracy provided in this study can help researchers to select the setting of CGC-CRP methods to achieve their required accuracy level. [ABSTRACT FROM AUTHOR]