Cumulative Soil Loss Research Articles

Soft intercalated slope stability optimization with a modified polymer curing agent

The demand for high-grade roads is significantly higher in developing countries. However, slopes containing coal gangue weak interlayer pose significant safety risks to highways, railways, and other infrastructures. To address this issue, this study aims to find the best polymer cement ratio scheme of traditional pure acrylic emulsion polymer curing agents. Based on this scheme, a reinforcement method was designed, which combined modified polyvinyl acetate with the coal gangue soft interlayer. The slope test results using a rigid model box showed that the shear strength of the root–soil composite in the PVAC group was higher than that in the pure acrylic emulsion group under different vertical consolidation pressures. Over time, the cumulative soil loss rate of the pure acrylic emulsion group gradually increased, and the soil pH decreased. Conversely, the PVAC group showed minimal changes in these two indicators with time. Under the same conditions, the slope shear strength of the PVAC group remained stronger than that of the pure acrylic emulsion group. The standard deviations of multiple tests for the PVAC group and pure acrylic emulsion group, under a vertical consolidation pressure of 100 kPa, were 7.2 kPa and 9.2 kPa, respectively, indicating greater stability in the PVAC group. With a stability coefficient of 3.39, which surpasses that of the pure acrylic emulsion group, the PVAC group exhibited enhanced slope stability. These results indicate that this method can effectively enhance the stability of coal gangue soft interlayer slopes without causing environmental pollution.

Assessment of the impacts of land-use change and slope position on soil loss by magnetic susceptibility-based models

Soil loss is a global environmental problem resulting from the erosion process caused by many factors, including land use and slope position. Estimation of total soil loss from agricultural fields is useful for understanding the consequences of historical and current erosion. The main purposes of the current study are to explore the application of magnetic measurements in the mapping and measuring soil redistribution in cultivated (MZ13) and forested (MZ17) transects in a Moroccan subcatchment, to develop a methodological approach correlating magnetic susceptibility (MS, denoted χ) variation to soil erosion/aggradation, and to discriminate the effects of land-use change and slope position on the total cumulative soil loss, assessed using three recently established erosion models based on an MS parameter. MS measurements were done on several soil cores collected at different slope positions including the summit (SU), shoulder (SH), back slope (BS), foot slope (FS), toe slope (TS) for Transects MZ13 and MZ17. A tillage homogenization (T-H) model, simple correlation model (SCM), and simple proportional model (SPM) based on χlf (where lf indicates low frequency) were applied to estimate soil loss for each slope position in the two transects. The results show that the correlation between χlf and χfd (which is the frequency-dependent magnetic susceptibility percentage) is positive and high for the two transects (R2 = 0.95; p < 0.01). The results confirm that the χlf enhancement of soils selected in calcareous parent material is related to the pedogenic processes with the formation of superparamagnetic particles distributed along the slope positions. The current study proves that it is possible to trace and monitor soil erosion and deposition using magnetic parameters (χlf and χfd%) for different slope positions along cultivated and forested transects. The results confirm that the soil losses strongly depend on land use and slope position. Higher erosion depth (d) estimated using the three erosion models are comparable and were about d(T-H, BS17L) = −154.9 cm, d(SCM, BS17L) = −142.3 cm, and d(SPM, BS17L) = −143.6 cm for MZ17 Transect, and about d(T-H, FS13M) = −156.3 cm, d(SCM, TS13L) = −143.8 cm, d(SPM, FS13M) = −145.9 cm for MZ13 Transect. The applied models indicate that the strong losses take place in the upper and lower slopes of the cultivated transect, and in the middle and lower slopes of the forested transect.

Effect of mechanical weeding on soil erosion and earthworm abundance in sugar beet (Beta vulgaris L.)

The use of herbicides for weed control in plant production is widely criticized because of their potential aquatic and terrestrial toxicity. However, the environmental risks of mechanical weed control as an alternative control method in row crops have not yet been studied in Europe. Field trials in Southern Lower Saxony were carried out over three years on five sugar beet fields to assess the effect of weeding by hoeing on earthworm abundance, runoff, and soil erosion. Treatments were hoeing (H), herbicide spraying (S) and combined hoeing-spraying (HS), tested in four replicates at each field. The abundance of adult and juvenile earthworms of anecic and endogeic groups was determined in autumn using formalin expulsion 4 months after the final weed control operation. Runoff and soil erosion in mechanically and chemically weeded plots were measured by means of rainfall simulation on 2-m2 subplots after weed control. The experiment was organized in completely randomized block design. The abundance of adult and juvenile earthworms of anecic and endogeic groups was not affected by the weed control treatment. Cumulative runoff and soil loss were significantly reduced by mechanical weed control by a factor of six and eight, respectively, but only if the soil was crusted before weed control. In the absence of a soil crust before weed control there was no difference in runoff and erosion between mechanical and chemical weed control. Measured runoff and soil loss were used to calculate the curve number (CN) and the soil loss ratio (SLR) which are the empirical parameters for the prediction of runoff and soil erosion with the Curve Number SCS method and the Revised Universal Soil Loss Equation, respectively. CN was significantly increased and SLR tended (p =0.08) to be increased if the soil was crusted before weed control. Mechanical weed control reduced CN and SLR in crusted soils but had no effect in non-crusted soils. Therefore, for correct runoff and soil erosion prediction the effect of crusting and mechanical weeding on CN and SLR must be considered. In conclusion, mechanical weeding was revealed to be particularly beneficial for crusted soil by simultaneously reducing toxicological and erosional risks.

Comparison of mechanical vs. chemical weed control in sugar beet – Environmental effects: soil erosion, earthworms, CO2e-emissions

Chemical weed control is widely criticized because of its potential ecotoxicological risks. However, the environmental effects of mechanical weeding have not been studied yet. This study aims to evaluate the effects of hoeing, herbicide spraying and combined hoeing-spraying in sugar beet on soil erosion, earthworm abundance, and greenhouse gas (GHG) emissions. Field trials were carried out in Lower Saxony on five sugar beet fields from 2019 to 2021. Runoff and soil erosion were measured by means of rainfall simulation on 2-m2 subplots after weed control. The earthworm abundance was determined in autumn using formalin expulsion. The resources consumption and GHG emissions of each weeding strategy were estimated using KTBL and Biograce online tools. The earthworm abundance was not affected by weeding strategy in most cases. Cumulative runoff and soil loss were six and eight times lower after hoeing compared to herbicide spraying, but only if the soil was crusted before rainfall simulation; otherwise, weed control did not affect soil erosion. The GHG emissions for mechanical and combined mechanical-chemical weed control were higher by factor 2.5 and 1.7, respectively, as compared to the reference chemical weed control. Hence, hoeing is, though non-toxic and erosion-retarding, the weeding strategy with the highest carbon footprint.

Efficacy of mulch and tillage options to reduce runoff and soil loss from asparagus interrows

In the UK, conventional asparagus cultivation practices on sloping land, erodible soils and increased frequency of extreme rainfall events combine to promote runoff generation and soil loss, particularly from interrows. This instrumented field study investigated the interactive effect of mulch and shallow soil disturbance (working depth of 0.175 m) on reducing runoff and soil loss. Ten treatments were installed in a commercial asparagus field near Ross-on-Wye (England, UK) during May 1st–July 17th, 2012. Straw and compost were applied to the interrows at high and low application rates (straw = 5 t ha−1 and 3 t ha−1 and compost = 18 t ha−1 and 8 t ha−1, respectively), both with or without shallow soil disturbance (SSD and Non-SSD) as compared with a bare soil, unamended Control. Across five sampling periods, Non-SSD straw mulch applied at 5 t ha−1 and 3 t ha−1; Non-SSD compost mulch at 18 t ha−1; and straw mulch applied at 5 t ha−1 with SSD all significantly reduced cumulative total soil loss by 53–72% as compared with the Control. Further, mulch treatments with SSD were in general less effective at reducing total soil loss as compared to non-SSD mulch treatments. Compost application was less effective than straw, due to sub-optimal compost blanket depths as dictated by N restrictions for Nitrate Vulnerable Zones, in which the study took place. Despite an overall reduction in total soil loss of 72% (associated with Non-SSD straw mulch applied at 5 t ha−1), soil erosion rates exceeded 1.4 t ha−1 yr−1, considered to be a tolerable erosion rate in the EU. In addition, measured sediment concentrations in the runoff consistently exceeded the EU water quality guideline value of 25 mg l−1. The results indicate that the efficacy of the treatments tested was not adequate to reduce soil erosion in commercial asparagus fields in the UK to tolerable rates. This may in large part be due to daily foot trafficking events that occur during the asparagus harvesting period (April–June) which disturbs and degrades the treatments applied reduing their efficacy. This study demonstrates that additional research is required in order to identify effective erosion control measures to ensure the sustainability of commercial asparagus production systems in the UK.

A comparative evaluation of random roughness indices by rainfall simulator and photogrammetry

The principal aim of the paper is to determine which index of random roughness is most appropriate for the description of the microtopographic variations within a rainfall series at the interrill scale. The study was conducted with rainfall simulation on interrill-sized plots.The roughness indices were computed from the point cloud or from the Digital Elevation Model (DEM) of the soil surface, obtained from photogrammetric surveys. The indices evaluated can be grouped into five categories: ‘contact method – pin’ and ‘contact method – chain’ where the indices are obtained from the DEM simulating manual techniques (pin meter and chain respectively); ‘fitting plane/surface’, where the indices are the standard deviation of the height differences from a best fitting plane/surface of the DEM or of the cloud; ‘moving window DEM’, where the index is the average standard deviation of the residual topography; and ‘kernel size cloud’, a new index given by the standard deviation of the distances between each point of the cloud and a best fitting plane computed from its nearest neighbors (found in a radius called “kernel size”).The performance of the indices was assessed based on their relationship with the measures of cumulative rainfall and kinetic energy, depression storage, cumulative runoff and soil loss. The best index to represent random roughness variations is that of the ‘moving window DEM’ category with a resolution of 0.0025 m2, RI25, for which the relationships with the cumulative rainfall, the cumulative rainfall kinetic energy and the depression storage, have coefficients of determination of 0.86, 0.85 and 0.80 respectively. For the same relationships, a good but slightly lower performance is provided by the indices of the categories ‘contact method – chain’ and ‘kernel size cloud’. These three categories gave equivalent results regarding the correlation with cumulative runoff and soil loss (mean Pearson correlation coefficient −0.95, CV = 0.025). Instead, the indices of the categories “fitting plane/surface” and “contact method – pin” resulted poorly correlated with all the measured variables.

Wind erosion reduction by water diversion in the lower Heihe River Basin, Northwest China

AbstractThe lower Heihe River Basin, a key ecological function zone in Northwest China, has suffered from serious land degradation by wind erosion for decades, posing a great threat to the national ecological safety. This study explores the dynamics of wind erosion and the soil conservation service (SCS) in this region following water diversion during 2001–2010 with the statistic model of wind erosion on small watershed basis based on remote sensing, climate, and soil data, and impacts of driving factors on the SCS are revealed with scenario analysis. Results suggest that the SCS represented by the soil retention amount was less than 500 t km−2 yr−1 in most parts of the study area and higher than 15,000 t km−2 yr−1 in a few wind erosion hotspots, including the East Juyanhai region, Dingxin Oasis, Ejina Oasis, and its surrounding desert–oasis transitional areas. The cumulative potential soil loss of the study area increased much faster than the cumulative soil retention amount, and fractional vegetation cover influenced by the Ecological Water Diversion Project played a dominant role in improving the SCS, accounting for 82.25% of the change in the SCS of the study area. Climate change played a subordinate role, but there were essential separate and interactive effects of climate factors on the SCS. This study provides a preliminary overview of hotspots of wind erosion and the SCS in the lower Heihe River Basin from a geographical perspective, laying a solid basis for combating land degradation by wind erosion in arid regions of Northwest China.

Evaluation of disruption of sediment connectivity and herbicide transport across a slope by grass strips using a magnetic iron oxide tracer

The use of cover crops has been prescribed as a mitigation measure for offsite contamination, as they reduce sediment and agrochemical loads, thus reducing the hydrological connectivity of the land. However, there is the need to quantify its effectiveness for specific agrochemicals in broader range of conditions, to validate management for its safe environmental use. The objectives of the present study were: (1) to explore the use of simulated rainfall and magnetic iron oxide to understand the impact of vegetation strips on runoff and soil losses at the plot scale and, (2) to evaluate the effectiveness of vegetation strips in buffering sediment and herbicides coming from bare soil areas. The study encompasses six sets of rainfall simulations (three replications each) under four different soil management scenarios: dry vegetation cover sowed that year, dry vegetation cover two years after sowing, freshly-tilled soil, and tilled soil with a compacted surface due to rainfall and trampling. The experiments involved the use of a magnetic iron oxide as a sediment tracer to obtain a better understanding of the trapping efficiency of the vegetation strips. Three runoff plots were established on a hillslope under a Fluvisol alluvial terrace. Each of the plots contained three bare areas tagged with magnetic iron oxide and three strips with Lolium multiflorum L. The results indicate that by using cover crop strips, runoff and sediment losses were approximately 20% and 4%, respectively, of the losses measured in the bare compacted soil, while losses on the freshly-tilled surface were similar to that of the cover crop. Herbicide losses were greatly reduced by the cover crops, with losses ranging from approximately 0.1%–0.6% of the doses applied the day before on the bare area. Nevertheless, on the compacted bare soil, terbuthylazine, oxyfluorfen and diflufenican losses were 1.63%, 4.35% and 9.67%, respectively, of the dose applied the previous day. This can be explained because the tilled and compacted soil showed the highest cumulative runoff and soil losses values (28 mm and 248.9 g m−2). The formation of micro-relief steps after the first simulation reduced the hillslope connectivity and, thus, the soil losses and runoff. Tracer selectivity from soil textures with fine particle size (clay) was observed, as there was an enrichment of these particles in the collected sediment. This study quantified the impact of cover crop strips on mitigating offsite herbicide contamination and improved our understanding of sediment redistribution at the hillslope scale.

Effects of slope gradient on hydro-erosional processes on an aeolian sand-covered loess slope under simulated rainfall

The aeolian sand-covered loess slope of the Wind-Water Erosion Crisscross Region of the Loess Plateau in China may play a key role in contributing excessive sediment to the Yellow River. Understanding its hydro-erosional processes is crucial to assessing, controlling and predicting soil and water losses in this region and maintaining the ecological sustainability of the Yellow River. Simulated rainfall (intensity 90mmh−1) was used to investigate the runoff and soil loss from loess slopes with different slope gradients (18%, 27%, 36%, 47%, and 58%) and overlying sand layer thicknesses (0, 5 and 10cm). As compared with uncovered loess slopes, an overlying sand layer delayed runoff production, reduced cumulative runoff and increased cumulative soil loss, as well as enhancing variations among slope gradients. Cumulative runoff and soil loss from the sand-covered loess slopes increased with increasing slope gradients and then slightly decreased, with a peak at about 47% gradient; they both were greater from the 10-cm sand-covered loess slope than from the 5-cm except for with 18% slope gradient. In general, differences in cumulative runoff between sand layer thicknesses became smaller, while those in cumulative soil loss became larger, with increasing slope gradient. Runoff and soil loss rates on the sand-covered loess slopes exhibited unimodal distributions during the rainstorms. Maximum values tended to occur at the same rain duration, and increased considerably with increasing slope gradient and sand layer thickness on slopes that were less than 47%. Liquefaction process might occur on the lower loess slopes covered with thinner sand layers but failures similar to shallow landslides might occur when the sand layer was thicker on steeper slopes. The presence of an overlying sand layer changed the relationship between runoff and soil loss rates during intense rainstorms and this change varied with different slope gradients. Our results demonstrated that the effects of slope gradient on hydro-erosional processes on the sand-covered loess slopes were important and vary with changing sand thickness. These effects should be considered when assessing and predicting soil losses from such slopes in the study region and from similar slopes elsewhere.

Assessing temporal couplings in social&amp;#8211;ecological island systems: historical deforestation and soil loss on Mauritius (Indian Ocean)

Temporal couplings, such as historical interactions between deforestation and soil loss, are responsible for the current state of a wide range of ecosystem services of the social–ecological system on Mauritius. Islands are suitable study sites for understanding temporal couplings and telecouplings because of their: (1) clearly defined physical boundaries, (2) finite local resources, and (3) relatively short human history. Six well-documented historical deforestation maps, starting from the first colonization of Mauritius in 1638, were used as input parameters to model two scenarios of cumulative soil loss, with and without deforestation, using the revised universal soil loss equation in a geographic information system. The scenarios show that historical deforestation since 1638 has resulted in a cumulative soil loss that drastically exceeds soil loss under a natural baseline scenario without deforestation. The adopted method illustrates to what extent the current state of the soil of a social–ecological system is negatively affected by past human–environment interactions. We suggest that potential negative impacts on insular societies are mitigated by telecouplings such as food, fuel, and fertilizer imports.

Mid-term and scaling effects of forest residue mulching on post-fire runoff and soil erosion

Mulching is an effective post-fire soil erosion mitigation treatment. Experiments with forest residue mulch have demonstrated that it increased ground cover to 70% and reduced runoff and soil loss at small spatial scales and for short post-fire periods. However, no studies have systematically assessed the joint effects of scale, time since burning, and mulching on runoff, soil loss, and organic matter loss. The objective of this study was to evaluate the effects of scale and forest residue mulch using 0.25m2 micro-plots and 100m2 slope-scale plots in a burnt eucalypt plantation in central Portugal. We assessed the underlying processes involved in the post-fire hydrologic and erosive responses, particularly the effects of soil moisture and soil water repellency.Runoff amount in the micro-plots was more than ten-fold the runoff in the larger slope-scale plots in the first year and decreased to eight-fold in the third post-fire year. Soil losses in the micro-plots were initially about twice the values in the slope-scale plots and this ratio increased over time. The mulch greatly reduced the cumulative soil loss measured in the untreated slope-scale plots (616gm−2) by 91% during the five post-fire years. The implications are that applying forest residue mulch immediately after a wildfire can reduce soil losses at spatial scales of interest to land managers throughout the expected post-fire window of disturbance, and that mulching resulted in a substantial relative gain in soil organic matter.

Effects of rainfall and slope on runoff, soil erosion and rill development: an experimental study using two loess soils

AbstractRunoff generation and soil loss from slopes have been studied for decades, but the relationships among runoff, soil loss and rill development are still not well understood. In this paper, rainfall simulation experiments were conducted in two neighbouring plots (scale: 1 m by 5 m) with four varying slopes (17.6%, 26.8%, 36.4% and 46.6%) and two rainfall intensities (90 and 120 mm h−1) using two loess soils. Data on rill development were extracted from the digital elevation models by means of photogrammetry. The effects of rainfall intensity and slope gradient on runoff, soil loss and rill development were different for the two soils. The runoff and soil loss from the Anthrosol surface were generally higher than those from the Calcaric Cambisol surface. Higher rainfall intensity produced less runoff and more sediment for almost each treatment. With increasing slope gradient, the values of cumulative runoff and soil loss peaked, except for the treatments with 90 mm h−1 rainfall on the slopes with Anthrosol. With rainfall duration, runoff discharge decreased for Anthrosol and increased for Calcaric Cambisol for almost all the treatments. For both soils, sediment concentration was very high at the onset of rainfall and decreased quickly. Almost all the sediment concentrations increased on the 17.6% and 26.8% slopes and peaked on the 36.4% and 46.6% slopes. Sediment concentrations were higher on the Anthrosol slopes than on the Calcaric Cambisol slopes. At 90 mm h−1 rainfall intensity, increasingly denser rills appeared on the Anthrosol slope as the slope gradient increased, while only steep slopes (36.4% and 46.6%) developed rills for the Calcaric Cambisol soil. The contributions of rill erosion ranged from 36% to 62% of the cumulative soil losses for Anthrosol, while the maximum contribution of rill erosion to the cumulative soil loss was only 37.9% for Calcaric Cambisol. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Erosion of bulk soil and soil organic carbon after land use change in northwest Vietnam

Soil erosion by water and tillage are major drivers for soil degradation in the mountainous regions of NW Vietnam. Data on cumulative and recent erosion of bulk soil and soil organic carbon (SOC) are needed for carbon budgeting and to evaluate e.g. the impact of erosion on climate change, environmental services and subsequent socioeconomic consequences. Thus, the aims of the present study were (1) to quantify cumulative erosion and recent erosion rates of bulk soil (2) to quantify cumulative eroded SOC and (3) to estimate the proportions of water and tillage induced soil erosion after land use change from primary forest to continuous maize cultivation for up to 21years. Soil erosion rates were determined by 137Cs and ranged from 12 to 89tha−1a−1. A large part of the variation of cumulative bulk soil (R2=0.79) and SOC loss (R2=0.67) between the sites was simply but effectively explained by the ratio of site specific cumulative RUSLE LS factors to clay contents. The newly developed CIDE approach, which attributes SOC changes on steep slopes to either carbon input, decomposition or erosion, delivered 20% higher (up to 0.7kgm−2) and more reliable estimates on cumulative SOC erosion than a traditional approach, because CIDE considered the effects of soil profile truncation, decomposition and humification, which all affected SOC simultaneously to soil erosion. Tillage induced soil flux accounted for 38±3kgm−1 per tillage pass, which was lower than found in similar studies. Soil erosion by water was higher than tillage induced erosion in middle and foot slope positions, accounting for 86 to 89% of total soil erosion. To prevent further soil degradation, erosion protection measures should be implemented.

Pattern of cumulative soil erosion and redistribution pinpointed through magnetic signature of Chernozem soils

An experimental approach for estimation of cumulative soil erosion by using magnetism of Chernozem soils is presented. An agricultural land of 4.5ha, utilized for crop production, has been mapped at 10×10m grid interval by using magnetic methods. Field measurements of magnetic susceptibility show high sensitivity to the present soil surface conditions (crop residue cover, soil compaction, sealing) in addition to the main response to erosional removal of the uppermost soil horizons. Laboratory measurements of magnetic susceptibility (χ), frequency dependent magnetic susceptibility (χfd) and Isothermal Remanent Magnetization on soil samples allow construction of surface maps of these magnetic characteristics. Their systematic depth variations along non-disturbed reference soil profiles have been established, which lead to the construction of empirical predictive curves of cumulative soil loss according to the model, proposed by Royall (2001). Using the predictive curves of χ and χfd, maps of soil magnetic parameters are transformed into the distributed pattern of predicted soil loss. Comparison of the maps with terrain slope reveals that in the upper slope positions (having slopes of 1–5°) tillage redistribution plays the main role. In contrast, at toe slope sites, characterized by higher slopes (11–15°), water erosion caused significant removal of soil material. Mean annual erosion rates of 8–6.8t/ha/y have been calculated, which corresponds to about 50years of agricultural land use.

Collective management on communal grazing lands: Its impact on vegetation attributes and soil erosion in the upper Blue Nile basin, northwestern Ethiopia

Collective action, on communal grazing land, has evolved in the highlands of northwestern Ethiopia to mitigate the problems of feed shortage and land degradation due to overgrazing. The exercise is liked by farmers for improving the availability of natural pasture during the long dry season when other feed sources get depleted. However, large portions of the communal grazing lands are still managed under free grazing throughout the year. This study was undertaken in Maynet village in the upper Blue Nile basin, northwestern Ethiopia, to assess the impacts of three different types of grazing land management (GLM) and two slope gradients (<10%; 15–25%) on aboveground herbaceous biomass yield, ground cover, species richness, runoff, soil loss and soil bulk density of grazing lands. The GLMs include (a) freely open communal GLM, (b) restricted communal GLM – collective management of communal grazing land locally named as ‘yebere sar’ and (c) private holding GLM. Stocking density was more than carrying capacity of grazing lands across all GLMs. However, the extent of overstocking problem was exceptionally severe in freely open communal GLM. The interaction between GLM and slope was significant (P<0.05) for runoff, soil loss and runoff coefficient. The average runoff coefficient was close to 50% in freely open communal GLM on steeper slopes (15–25%). Freely open communal GLM on steeper slopes resulted in consistently highest cumulative runoff and soil loss amounting to 491mm and 32t/ha per year, respectively. Polynomial regression analysis showed that quadratic relationship (r2=0.87) existed between soil loss and runoff. But, soil loss was close to nil when runoff did not exceed 2mm per rainfall event. As expected, restricted communal GLM appeared to reduce surface runoff by more than 40% and curb the rate of soil erosion by more than 50% compared to freely open communal GLM. Its vegetation cover persisted above 70% throughout the year, meeting the threshold level recommended to keep surface runoff and soil loss to minimum. Reducing the problem of overstocking and pasture resting in August–November are important components to improve ground cover and aboveground herbaceous biomass yield, which in turn reduce land degradation on grazing lands.

Assessment of Spatial Variability in Water Erosion Rates in an Olive Orchard at Plot Scale using a Magnetic Iron Oxide Tracer

The combination of runoff plot studies and soil tracking using a silt size magnetic sediment tracer, allowed a better understanding of the relative contribution of different zones in olive (Olea europaea L.) orchard plots to total soil losses. The average erosion rates were different in the tree rows (tr) (0.8 kg m−2 mo−1) and in the inter-tree rows (itr) (1.4 kg m−2 mo−1), inter-tree rills (r) being the most eroded areas (4 kg m−2 mo−1) from October 2008 to April 2010. Since soil under the olive canopies has a high infiltration capacity, splash is a major erosion process in this area, while, in the itr, sheet and rill erosion are the dominant processes. The proposed magnetic tracer technology was an effective tool for determining the cumulative soil losses at the plots for a 17 mo period (average 141 Mg ha−1) with an accuracy of 7.2 Mg ha−1. To achieve this accuracy, determination of bulk density, selectiveness in the transport process, tracer distribution in the soil profile and field calibration of the magnetic susceptibility probe were required. The evolution of tracer distribution provided insight into soil displacement within the runoff plots due to erosion processes. The tracer distribution maps also indicate a high coefficient of variability of the incorporation of tagged soil into the plot, which should be improved in future research to increase the usefulness of this approach in water erosion studies.

Residue and Long-Term Tillage and Crop Rotation Effects on Simulated Rain Infiltration and Sediment Transport

Increased precipitation storage as soil water is crucial to dryland production of wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] on the semiarid southern Great Plains. At the USDA-ARS Conservation and Production Research Laboratory at Bushland, TX, surface runoff from a Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll) is typically greater with no-till (NT) than stubble-mulch (SM) tillage under the 3-yr wheat–sorghum–fallow (WSF) dryland crop rotation. Our objective was to quantify the effects of NT or SM tillage with bare or retained residue on infiltration of simulated rain, sediment transport, and related aggregate stability for continuous wheat (CW) and WSF rotation plots established in 1983. Compared with bare soil, the retained wheat residue cover increased mean 60-min cumulative infiltration across all tillage and rotation combinations by >25 mm and decreased soil loss. Cumulative rain infiltration and total soil loss did not vary significantly (P < 0.05) with tillage, but the mean infiltration rate at 60 min was 15.0 mm h−1 less for NT than SM. The CW rotation typically increased infiltration regardless of residue cover or tillage compared with the WSF rotation, which we attributed to greater aggregate stability. The greater aggregate stability for CW may have decreased soil loss compared with WSF, which was greatest for bare SM tilled sites. We conclude that residue cover significantly increases rain infiltration over bare soil conditions independent of any tillage or rotation treatment effects. Nevertheless, increased rain infiltration due to residue cover was not sustained in the absence of soil disturbance for NT.

Studying the effects of Mahonia aquifolium populations on small‐scale mountain agro‐ecosystems in Hungary with the view to minimise land degradation

AbstractAfter the political changeover in Hungary in 1989, many farm owners faced problems typical of a small sized farm (&lt;1 ha) as well as a lack of various resources. This led to many farms with great horticultural backgrounds being abandoned, especially in mountainous areas where erosion control is essential for soil conservation. Severe changes can occur on soil through property abandonment. The local socio‐economic aspects must be taken into consideration as well as the problem of soil degradation as this will be a motivating factor in preservation initiatives. Under horticultural management, Mahonia aquifolium was tested to determine its efficiency in water erosion control in mountainous conditions in Hungary. Soil loss and water runoff were measured after every rainfall event at six different plots: four cultivated M. aquifolium populations with different ages (4, 12, 20 and 25 years old) and two control plots. A bare soil field and a grass field represented the control plots. The results show that as the age of the M. aquifolium populations increase, the cumulative runoff and sediment values decrease. It also showed that 2 years after setting up a new M. aquifolium plantation, the cumulative runoff decreased by 69 per cent and the cumulative soil loss decreased by 74 per cent. This indicates that a M. aquifolium population could play a significant role in erosion control within a short period of time. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Modeling long-term soil losses on agricultural fields due to ephemeral gully erosion

It is now recognized worldwide that soil erosion on agricultural fields due to ephemeral gullies may be greater than those losses attributed to sheet and rill erosion processes. Yet it is not known whether the common practice of repairing or obliterating these gullies during annual tillage activities exacerbates or mitigates soil losses over long time periods. Here, a numerical model is used to demonstrate the potential effects of annual tillage on cumulative soil losses from four geographic regions plagued by ephemeral gullies as compared to no-till conditions where the gullies are free to grow and evolve over time and space. Historical precipitation data and field measurements were compiled for specific sites in Belgium, Mississippi, Iowa, and Georgia, and the model simulated ephemeral gully development and evolution during the growing seasons over a continuous 10-year period. When agricultural fields are not tilled annually, the simulations suggest that gullies attain their maximum dimensions during the first few years in response to several relatively large runoff events. During subsequent runoff events, the gullies no longer erode their channels significantly, and soil losses due to gully erosion decrease markedly. When agricultural fields are tilled annually, the ephemeral gully channels are reactivated, thus causing significant soil losses each year in response to runoff events. Over the 10-year simulation, the modeling results suggest that erosion rates in these four geographic regions can be 250% to 450% greater when gullies are tilled and reactivated annually as opposed to the no-till condition. These results reveal that routine filling of ephemeral gully channels during tillage practices may result in markedly higher rates of soil loss as compared to allowing these gullies to persist on the landscape, demonstrating a further advantage of adopting no-till management practices.

Historical soil erosion and land-use change during the last two millennia recorded in lake sediments of Frickenhauser See, northern Bavaria, central Germany

Based on palaeolimnological investigations on a 1275 cm long lacustrine sediment record, sediment yields (SY) and denudation rates (DR) for the last 2000 years were reconstructed from Frickenhauser See, a small lake in central Germany. SY and DR generally correspond with the human land-use history derived from pollen analysis and reveal a drastic interruption of natural processes starting in the eleventh century AD. SY increased over 350-fold from 0.9 t/km2 per yr to 328 t/km2 per yr in response to deforestation and subsequent soil erosion. The average denudation rate within the catchment area is 81 mm for the last 2000 years, most of which occurred between AD 1100 and 1870. Taking into account that only one-third of the catchment area is suitable for agriculture, the cumulative soil loss from agricultural fields is around 240 mm (0.31 mm/yr). Historical events such as a widespread abandonment period (AD 1300—1450) and the Thirty Years War (AD 1618—1648) are reflected in the pollen record but cause only minor fluctuations in reconstructed sediment yields. This study demonstrates that by applying a multiproxy approach lacustrine sediments provide an excellent archive to reconstruct the effects of human land use on the geomorphological process system and to identify human—environment interactions.