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Tillage and water erosion induce spatially dependent changes in soil properties that influence productivity. Soil–landscape rehabilitation (returning translocated topsoil to landscape positions of soil loss by erosion) is one method to improve the productivity of severely eroded land. The objective of this study was to investigate relationships among key soil chemical, biological, and physical factors and crop growth and grain yield in eroded and rehabilitated landform positions. Soil–landscape rehabilitation was performed by moving 15–20 cm of topsoil from the lower slope to the upper slope positions of replicate plots; adjacent plots were left in their eroded condition. Crop response was monitored for 6 years. Rehabilitation resulted in large changes in the upper slope, especially in the most eroded landscape positions, where rehabilitated plots had lower inorganic carbon (IC) and higher organic carbon, available macronutrients, water infiltration rates, fungal and bacterial populations, and other measures of soil quality compared with control plots. Differences in surface soil IC that result from extensive erosion exposing calcareous subsoils, explained 70% of the yield variability in the upper slope. In the lower slope, the soil removal treatment was the main predictor of crop yield. Areas of soil removal had relatively high early‐season water content and low fungal and bacterial populations. Improving soil properties in areas of high soil loss by erosion increased both grain yield and yield stability across climatic conditions. Soil properties were highly variable in eroded landscapes.Soil properties were drastically changed by replacing translocated topsoil.Soil properties were highly correlated with each other.Differences in surface soil IC explained 70% of the upper slope yield variability.Toeslopes with soil removed had low yields, high water content, and low microbial populations.

Delineating the relative solubility of soil phosphorus (P) in agricultural landscapes is essential to predicting potential P mobilization in the landscape and can improve nutrient management strategies. This study describes spatial patterns of soil extractable P (easily, moderately, and poorly soluble P) in agricultural landscapes of the Red River basin and the southern Great Lakes region. Surface soils (0–30 cm) and select deeper cores (0–90 cm) were collected from 10 cropped fields ranging in terrain (near‐level to hummocky), soil texture (clay to loam), composition (calcareous to noncalcareous), and climate across these differing glacial landscapes. Poorly soluble P dominated (up to 91%) total extractable P in the surface soils at eight sites. No differences in the relative solubilities of soil extractable P with microtopography were apparent in landscapes without defined surface depressions. In contrast, in landscapes with pronounced surface depressions, increased easily soluble P (Sol‐P), and decreased soil P sorption capacity were found in soil in wetter, low‐slope zones relative to drier upslope locations. The Sol‐P pool was most important to soil P retention (up to 28%) within the surface depressions of the Red River basin and at sites with low‐carbonate soils in the southern Lake Erie watershed (up to 28%), representing areas at elevated risk of soil P remobilization. This study demonstrates interrelationships among soil extractable P pools, soil development, and soil moisture regimes in agricultural glacial landscapes and provides insight into identifying potential areas for soil P remobilization and associated P availability to crops and runoff. We examined soil extractable phosphorus (P) across 10 agricultural fields.There are distinct patterns in the relative solubility of soil P with landform position.Surface depressions showed elevated concentrations of easily soluble P.Lower‐slope soils showed a reduced capacity to sorb added P relative to upper‐slope

Approaches to restore productivity to eroded soils are urgently needed to sustain food security. We evaluated plant response to soil‐landscape rehabilitation, in which approximately 15 cm of topsoil was moved from depositional landscape positions to the eroded upper slope. Crop response was monitored for 6 yr of a corn (Zea maysL.)–soybean [Glycine max(L.) Merr.] rotation at a severely eroded site and for 4 yr of a wheat (Triticum aestivumL.)–soybean rotation at a moderately eroded site. Experiments were conducted in years with relatively wet springs and droughty summers. In the severely eroded landscape, addition of 15 cm of soil increased crop biomass by 25–95% on a kg ha–1basis and increased grain yields by 20–49% (corn) and 12–59% (soybean), with the largest yield increases recorded in the most eroded landscape positions. Soil addition increased corn grain protein and test weight. No significant differences were observed in crop emergence rate or stand establishment. In the moderately eroded landscape, soil addition significantly increased crop biomass, but not grain yield. In both landscapes, yields were lower in areas of soil removal than in adjacent areas from which no soil was removed, which is likely at least partially an artifact of the plot design. While more research is needed to evaluate long‐term impacts, the results of these studies show that soil‐landscape rehabilitation may help alleviate the effects of past erosion and provide immediate benefits to the productivity of severely eroded soils. Replacing translocated topsoil can restore productivity to severely eroded land.Adding 15 cm of topsoil increased corn and soybean grain yields by 12–59%.Adding topsoil increased crop biomass but not emergence rates or stand establishment.Adding topsoil did not significantly increase grain yield on moderately eroded land.Areas of soil removal had lower crop yields, partially due to excessive moisture.

Meteoric beryllium‐10 (10Bem, t1/2= 1.4 Myr) is a cosmogenic radionuclide that remains largely underutilized for deriving hillslope‐scale estimates of erosion on uplands under conditions of land use change. We applied two different models for estimating erosion rates from observed 10Bemconcentrations (a one‐dimensional model predicting vertical profiles of 10Bemwithin hillslope soils [loss only, diffusion only, LODO] and a two‐dimensional model predicting the concurrent evolution of hillslope topography and 10Bemdistributions via bioturbation, chemical mobility, and surface erosion [Be2D]). Both models were used to derive pre‐European and post‐European settlement erosion rates (Enatand Epost, respectively) across paired cultivated and uncultivated hillslopes in west‐central Minnesota, USA. Epostestimates from 10Bemwere compared to Epostestimates derived from 137Cs inventories and the process‐based Water and Tillage Erosion Model (WaTEM). The results from these models suggest that erosion rates from upper positions on the cultivated hillslope have increased from an average of 0.047 mm/year under natural conditions to Epostvalues of 3.09 mm/year. The Be2D and LODO models, on average, produced Epostestimates that were similar in magnitude to WaTEM and 137Cs conversion models. This numerical convergence does not imply absolute 10Bemmodel accuracy, particularly when considering the uncertainties inherent in each approach, but it does suggest that the orders of magnitude increase in estimated erosion rates from Enatto Epostis robust. Additionally, the pattern of Epostestimates produced using 10Bemconversion models is supported by the distribution of soil inorganic carbon at the study site. Our results demonstrate that 10Bemcan provide reasonable estimates of both predisturbance and postdisturbance erosion rates in landscapes that have undergone extensive human modification. Agricultural practices have substantially changed soil erosion rates in the Midwestern United States. Although much work has been devoted to understanding the changes in soil erosion rates with land cover change, the ability to quantify those changes at discrete locations on the landscape over long periods of time has been limited. We use a set of tracers and models to estimate presettlement and postsettlement erosion rates on a hillslope in west‐central Minnesota, USA, and show that soil erosion has increased by approximately 1 to 2 orders of magnitude over a period of approximately 110 years. This has implications for how we view our current agricultural landscapes and how we think about soil sustainability in the future. Meteoric beryllium‐10 is used to generate point‐based estimates of long‐term erosion on paired hillslopesThese estimates suggest that erosion rates have increased by 2 orders of magnitude under agricultural managementModel choice influences erosion rate magnitude, but average rates are similar to estimates from process‐based models and cesium‐137

The continued phosphorus (P) impairment of freshwaters and the associated risk of eutrophication raise questions regarding the efficiency of current beneficial management practices (BMPs) for improving water quality. Vegetated buffer strips (VBSs) are widely encouraged BMPs for reducing P export from agricultural land. However, there is a lack of evidence regarding the long‐term efficiency of VBSs for reducing legacy P losses. This research used soil analyses to investigate the P removal efficiency of an unmanaged VBS for controlling P loss from agricultural land in Manitoba, Canada, between 1954 and 2011. The results showed statistically significant retention of total P, Olsen extractable P, and 0.01 M CaCl2extractable P by a 5‐m wide VBS compared with field soils. We found that surface soils at 5‐m into the VBS had a significantly greater P sorption capacity and a smaller degree of P saturation (DPS) than adjacent field soils. The elevated DPS in field soils is likely associated with gradual P enrichment as a result of manure or fertilizer application over time and the strong affinity of P compounds for soil. Although P stratification in the VBS over 57 yr resulted in a significant increase (∼11%) in DPS of VBS topsoil compared with VBS subsoil, our findings do not support the saturation of VBS soils with P. However, cutting and removal of vegetation from VBS could be a useful strategy to remove P from VBS and minimize possible P remobilization associated with vegetation senescence, especially where the climate is cold and runoff is dominated by snowmelt. Vegetated buffer strips (VBSs) reduced legacy P losses from adjacent land.VBS soils had a significantly greater P sorption capacity than field soils.VBS soils had a significantly smaller degree of P saturation than field soils.VBS soils did not get saturated with P exports from adjacent land even after 57 yr.

The use of sediment color as a fingerprint property to determine sediment sources is an emerging technique that can provide a rapid and inexpensive means of investigating sediment sources. The present study aims to test the feasibility of color fingerprint properties to apportion sediment sources within the South Tobacco Creek Watershed (74 km2) in Manitoba, Canada. Suspended sediment from 2009 to 2011 at six monitoring stations and potential source samples along the main stem of the creek were collected. Reflectance spectra of sediments and source materials were quantified using a diffuse reflectance spectrometry, and 16 color coefficients were derived from several color space models. Canonical discriminant analysis was used to reclassify and downsize sediment source groups. After the linear additive test and stepwise discriminant function analysis, four color coefficients were chosen to fit the Stable Isotope Analysis in R model. Consistent with the conventional fingerprinting approach, the color fingerprint results demonstrated a switch in the dominant sediment source between the headwaters and the outlet of the watershed, with the main sources being topsoil in the upper reaches, whereas outcrop shale and stream bank materials dominated in the lower reaches. The color fingerprinting approach can be integrated with conventional fingerprints (e.g., geochemical and fallout radionuclide properties) to improve source discrimination, which is a key component for source ascription modeling. We concluded that the use of color fingerprints is a promising, cost‐effective technique for sediment source fingerprinting. Defining sources and testing the behavior of tracers are critical for sediment source apportionment.The predominant sources of river sediment varied at different reaches of the study creek.Integrating color and conventional fingerprinting techniques likely improves source apportionment.Color fingerprinting is a promising, cost‐effective technique for sediment source ascription.

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In a preceding study, converting conventional tillage (ConvT) to conservation tillage (ConsT) was reported to decrease nitrogen (N) but to increase phosphorus (P) losses during snowmelt runoff. A field‐scale study was conducted from 2004 to 2012 to determine if conversion of ConsT to rotational tillage (RotaT), where conservation tillage was interrupted by a fall tillage pass every other year, could effectively reduce P losses compared with ConsT. The RotaT study was conducted on long‐term paired watersheds established in 1993. The ConvT field in the pair has remained under ConvT practice since 1993, whereas tillage was minimized on the ConsT field from 1997 until 2007. In fall 2007, RotaT was introduced to the ConsT field, and heavy‐duty cultivator passes were conducted in the late fall of years 2007, 2009, and 2011. Runoff volume and nutrient content were monitored at the edge of the two fields, and soil and crop residue samples were taken in each field. Greater soil Olsen P and more P released from crop residue are likely the reasons for the increased P losses in the ConsT treatment (2004–2007) relative to the ConvT treatment (2004–2007). Analysis of covariance indicated that, compared with ConsT (2004–2007), RotaT (2008–2012) increased the concentrations of dissolved organic carbon (DOC) by 62%, total dissolved N (TDN) by 190%, and total N (TN) by 272% and increased the loads of DOC by 34%, TDN by 34%, and TN by 60%. However, RotaT (2008–2012) decreased soil test P in surface soil, P released from crop residue, and duration of runoff compared with ConsT (2004–2007) and thus decreased the concentrations of total dissolved P (TDP) by 46% and total P (TP) by 38% and decreased the loads of TDP by 56% and TP by 42%. In the Canadian Prairies, where P is a major environmental concern compared with N, RotaT was demonstrated to be an effective practice to reduce P losses compared with ConsT.

An 8‐yr field‐scale study, 2005 to 2012, investigated effects of agricultural land use on nutrient and sediment losses during snowmelt runoff from four treatment fields in southern Manitoba. In 2005, two fields with a long‐term history of annual crop (AC) production were planted to perennial forage (PF), while two other fields were left in AC production. In 2009, the AC fields were converted to PF, while the PF fields were returned to AC. Runoff flow rates were monitored at the lower edge of the fields, and nutrient concentrations of runoff water were determined. The effects of AC and PF on selected variables were similar for the spatial (between‐fields) and temporal (within‐field) comparisons. The flow‐weighted mean concentrations (FWMCs) and loads of particulate N, P, and sediment were not affected by treatment. Soil test N and the FWMC and load of NOx(NO3−+ NO2−) were significantly greater in the AC treatment, but the FWMC and load of NH3were greater in the PF treatment. Loads of total dissolved N (TDN) and total N (TN) were not affected by treatment, although the concentrations of TDN and TN were greater in the AC treatment. The PF treatment significantly increased FWMCs and loads of total dissolved P (TDP) and total P (TP). On an annual snowmelt runoff basis, the PF treatment increased the FWMC of TDP by 53% and TP by 52% and increased the load of TDP by 221% and TP by 160% compared with the AC treatment. The greater P and NH3losses in the PF treatment were attributed mainly to nutrient release from forage residue due to freezing.

A long‐term, field‐scale study in southern Manitoba, Canada, was used to identify the critical factors controlling yearly transport of nitrogen (N) and phosphorus (P) by snowmelt runoff. Flow monitoring and water sampling for total and dissolved N and P were performed at the edge of field. The flow‐weighted mean concentrations and loads of N and P for the early (the first half of yearly total volume of snowmelt runoff), late (the second half of yearly total volume of snowmelt runoff), and yearly snowmelt runoff were calculated as response variables. A data set of management practices, weather variables, and hydrologic variables was generated and used as predictor variables. Partial least squares regression analysis indicated that critical factors affecting the water chemistry of snowmelt runoff depended on the water quality variable and stage of runoff. Management practices within each year, such as nitrogen application rate, number of tillage passes, and residue burial ratio, were critical factors for flow‐weighted mean concentration of N, but not for P concentration or nutrient loads. However, the most important factors controlling nutrient concentrations and loads were those related to the volume of runoff, including snow water equivalent, flow rate, and runoff duration. The critical factors identified for field‐scale yearly snowmelt losses provide the basis for modeling of nutrient losses in southern Manitoba and potentially throughout areas with similar climate in the northern Great Plains region, and will aid in the design of effective practices to reduce agricultural nonpoint nutrient pollution in downstream waters.

Most beneficial management practices (BMPs) recommended for reducing nutrient losses from agricultural land have been established and tested in temperate and humid regions. Previous studies on the effects of these BMPs in cold‐climate regions, especially at the small watershed scale, are rare. In this study, runoff and water quality were monitored from 1999 to 2008 at the outlets of two subwatersheds in the South Tobacco Creek watershed in Manitoba, Canada. Five BMPs—a holding pond below a beef cattle overwintering feedlot, riparian zone and grassed waterway management, grazing restriction, perennial forage conversion, and nutrient management—were implemented in one of these two subwatersheds beginning in 2005. We determined that >80% of the N and P in runoff at the outlets of the two subwatersheds were lost in dissolved forms, ≈ 50% during snowmelt events and ≈ 33% during rainfall events. When all snowmelt‐ and rainfall‐induced runoff events were considered, the five BMPs collectively decreased total N (TN) and total P (TP) exports in runoff at the treatment subwatershed outlet by 41 and 38%, respectively. The corresponding reductions in flow‐weighted mean concentrations (FWMCs) were 43% for TN and 32% for TP. In most cases, similar reductions in exports and FWMCs were measured for both dissolved and particulate forms of N and P, and during both rainfall and snowmelt‐induced runoff events. Indirect assessment suggests that retention of nutrients in the holding pond could account for as much as 63 and 57%, respectively, of the BMP‐induced reductions in TN and TP exports at the treatment subwatershed outlet. The nutrient management BMP was estimated to have reduced N and P inputs on land by 36 and 59%, respectively, in part due to the lower rates of nutrient application to fields converted from annual crop to perennial forage. Overall, even though the proportional contributions of individual BMPs were not directly measured in this study, the collective reduction of nutrient losses from the five BMPs was substantial.

The fallout radionuclide cesium‐137 (137Cs) has been successfully used in soil erosion studies worldwide. However, discrepancies often exist between the erosion rates estimated using various conversion models. As a result, there is often confusion in the use of the various models and in the interpretation of the data. Therefore, the objective of this study was to test the structural and parametrical uncertainties associated with four conversion models typically used in cultivated agricultural landscapes. For the structural uncertainties, the Soil Constituent Redistribution by Erosion Model (SCREM) was developed and used to simulate the redistribution of fallout 137Cs due to tillage and water erosion along a simple two‐dimensional (horizontal and vertical) transect. The SCREM‐predicted 137Cs inventories were then imported into the conversion models to estimate the erosion rates. The structural uncertainties of the conversion models were assessed based on the comparisons between the conversion‐model‐estimated erosion rates and the erosion rates determined or used in the SCREM. For the parametrical uncertainties, test runs were conducted by varying the values of the parameters used in the model, and the parametrical uncertainties were assessed based on the responsive changes of the estimated erosion rates. Our results suggest that: (i) the performance/accuracy of the conversion models was largely dependent on the relative contributions of water vs. tillage erosion; and (ii) the estimated erosion rates were highly sensitive to the input values of the reference 137Cs level, particle size correction factors and tillage depth. Guidelines were proposed to aid researchers in selecting and applying the conversion models under various situations common to agricultural landscapes.

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 dispersivity of translocation. In this study, we used a convoluting procedure and developed a Tillage Translocation Model (TillTM) 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.

Delivery of a hydrogel providing sustained release of recombinant TIMP-3 attenuated adverse ventricular remodeling after myocardial infarction in pigs.