Erosion Plots Research Articles

Variability of particle size distributions of upward/downward splashed materials in different rainfall intensities and slopes

The particle size distribution (PSD) of the splashed sediment is expected to vary depending on rainfall intensity, slope steepness and slope position. This study therefore discusses the results of analysis of laboratorial experiments to compare PSDs of splashed materials in upward and downward directions of splash cup with original soil PSDs before runoff initiation from different parts of an erosion plot under different rainfall intensities at various slope gradients. To achieve the objectives, a set of laboratorial experiments were conducted using rainfall simulator at erosion plots scale. The rainfall intensities of 30, 60, and 90mmh−1 were applied at 5, 15 and 25% plot slopes for a soil collected from Kojour rangeland watershed in the Alborz Mountains, northern Iran. Besides very oft-reported results of more splashed material in downward direction and positive effects of rainfall intensities (P>0.05) on rate of splashed materials, it was found that there were significant differences between clay, silt and sand contents of original soil and upward and downward splashed materials on slopes of 5 and 15% in all study rainfall intensities. In general, comparison of D10, D50 and D90 of splashed materials in upward and downward splash cups were larger than those of original soil. Furthermore, the sorting of splashed materials in upward and downward of splash cups with respective amounts of 4.84–6.62μm and 5.13–6.54μm under different rainfall intensities and slopes were less than that of the original soil (8.12μm).

Exploring particle size selectivity effects during erosion of purple soils in Chongqing municipality, China

The particle size distributions (PSDs) of soil and associated sediment are of fundamental importance in studying soil erosion dynamics and related environmental issues. However, detailed information on the variation of sediment size distributions within the erosion-delivery continuum and the effects of particle size selectivity on the size distribution of the sediment involved are absent and are urgently needed. A rainfall simulation experiment was performed on an erosion plot constructed on silt loam purple soil, located in Chongqing municipality, China. Three categories of material, namely, mobilized sediment, and exported and deposited sediment, associated with erosion and sediment delivery, were distinguished and sampled. The effective and ultimate PSDs of the sediment were determined and compared with those of the in situ soil. The results show that most of the mobilized and exported sediment was transported as primary particles. However, substantial proportions of aggregates were present in the deposited sediment. The experiment provided evidence of size-selective erosion, transport, and deposition and demonstrated that consideration of both effective and ultimate PSDs can provide an improved understanding of the size selectivity of erosion and sediment delivery processes. Consideration of the former can be important for understanding the erosion and delivery dynamics that control the latter. The results presented in this study demonstrate the potential for using and building on the approach employed, in order to develop a better understanding of the dynamics of sediment transport and deposition, as well as the size-selective nature of sediment mobilization, transport, and deposition.

The impact of standard preparation practice on the runoff and soil erosion rates under laboratory conditions

Abstract. The use of laboratory methods in soil erosion studies, rainfall simulation experiments, Gerlach troughs, and other measurements such as ring infiltrometer has been recently considered more and more because of many advantages in controlling rainfall properties and high accuracy of sampling and measurements. However, different stages of soil removal, transfer, preparation and placement in laboratory plots cause significant changes in soil structure and, subsequently, the results of runoff, sediment concentration and soil loss. Knowing the rate of changes in sediment concentration and soil loss variables with respect to the soil preparation for laboratory studies is therefore inevitable to generalize the laboratory results to field conditions. However, there has been little attention given to evaluate the effects of soil preparation on sediment variables. The present study was therefore conducted to compare sediment concentration and soil loss in natural and prepared soil. To achieve the study purposes, 18 field 1 × 1 m plots were adopted in an 18 % gradient slope with sandy–clay–loam soil in the Kojour watershed, northern Iran. A portable rainfall simulator was then used to simulate rainfall events using one or two nozzles of BEX: 3/8 S24W for various rainfall intensities with a constant height of 3 m above the soil surface. Three rainfall intensities of 40, 60 and 80 mm h−1 were simulated on both prepared and natural soil treatments with three replications. The sediment concentration and soil loss at five 3 min intervals after time to runoff were then measured. The results showed the significant increasing effects of soil preparation (p ≤ 0.01) on the average sediment concentration and soil loss. The increasing rates of runoff coefficient, sediment concentration and soil loss due to the study soil preparation method for laboratory soil erosion plots were 179, 183 and 1050 % (2.79, 2.83 and 11.50 times), respectively.

Platy structure development under no-tillage in the northern humid Pampas of Argentina and its impact on runoff

The no-tillage system (NT) is widespread in the silty soils of the Argentine Humid Pampas. The aims of this study were i) to characterize the evolution of the structure of the A horizon in the northern Humid Pampas due to conversion to NT, particularly the presence of platy structure and its development through time, by taking advantage of a chronosequence since conversion to NT; and ii) to evaluate how platy structure extension in the A horizon relates to characteristics of the crop sequences and runoff in a long-term experiment. Thus, the structure of the A horizon of 25 Argiudolls with different NT history was analyzed using a visual structure evaluation (VSE) method (“le profil cultural”). Fourteen natural-rainfall erosion plots with 3.5% slope were used to analyze the relationship between the soil structural state, the crop sequence and runoff. The VSE method allowed us to understand the structure type organization of silty soils under NT, highlight the regional extent of a platy structure near the soil surface, and study its evolution and impact on runoff. All the sites analyzed exhibited a horizontal platy structure (2–10cm thick), mainly developing on the soil surface or right under the granular structure on the soil surface. Under the platy structure, a cΦ structure was observed in all the sites (30–75% of the A horizon). A relationship was found between the number of consecutive years under NT and the proportion of platy structure. This evolution may result from the combination of an initial development of the platy structure and a late development of a cГ structure from the soil surface. The results obtained during the five-year period analyzed allowed us to prove that platy structure alters the drainage pattern, restricts water entry into the soil and favors surface runoff according to its proportion in the profile of A horizon.

Modification of the USLE K factor for soil erodibility assessment on calcareous soils in Iran

The measurement of soil erodibility (K) in the field is tedious, time-consuming and expensive; therefore, its prediction through pedotransfer functions (PTFs) could be far less costly and time-consuming. The aim of this study was to develop new PTFs to estimate the K factor using multiple linear regression, Mamdani fuzzy inference systems, and artificial neural networks. For this purpose, K was measured in 40 erosion plots with natural rainfall. Various soil properties including the soil particle size distribution, calcium carbonate equivalent, organic matter, permeability, and wet-aggregate stability were measured. The results showed that the mean measured K was 0.014thMJ−1mm−1 and 2.08 times less than the estimated mean K (0.030thMJ−1mm−1) using the USLE model. Permeability, wet-aggregate stability, very fine sand, and calcium carbonate were selected as independent variables by forward stepwise regression in order to assess the ability of multiple linear regression, Mamdani fuzzy inference systems and artificial neural networks to predict K. The calcium carbonate equivalent, which is not accounted for in the USLE model, had a significant impact on K in multiple linear regression due to its strong influence on the stability of aggregates and soil permeability. Statistical indices in validation and calibration datasets determined that the artificial neural networks method with the highest R2, lowest RMSE, and lowest ME was the best model for estimating the K factor. A strong correlation (R2=0.81, n=40, p<0.05) between the estimated K from multiple linear regression and measured K indicates that the use of calcium carbonate equivalent as a predictor variable gives a better estimation of K in areas with calcareous soils.

Long‐Term Impacts of Post‐Fire Mulching on Ground‐Dwelling Arthropod Communities in a Eucalypt Plantation

AbstractIn the past decades, Portugal like several other Mediterranean countries has been affected by frequent wildfires. This has led to various field tests of post‐fire soil conservation measures and, in particular, mulching with forest slash residues. While forest residue mulching was shown to be highly effective in reducing post‐fire erosion, its side effects on soil fauna communities have not been studied and are also difficult to predict from the – scarce – literature on mulch effects in general. Therefore, this study compared the abundance, diversity and taxonomic and functional composition of the ground‐dwelling arthropod communities of three mulched and, as control, three untreated erosion plots of roughly 100 m2 that had been installed in a eucalypt plantation almost immediately after a wildfire in 2010, some five years earlier. This was done using three pitfall traps per plot, placed at the lower, middle and upper part of the study slope. Roughly five years after mulching, its impacts on the ground‐dwelling arthropod were rather limited, especially compared to its effect on overall soil erosion rates. One of the few exceptions was the abundance of the Hymenoptera – one of the most frequently occurring orders – which was significantly lower in the mulched than control plots. This and other near significant mulching impacts found in this study plainly justify a follow‐up study on short‐term effects. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Soil and water losses in eucalyptus plantation and natural forest and determination of the USLE factors at a pilot sub-basin in Rio Grande do Sul, Brazil

ABSTRACT Monitoring water erosion and the factors that control soil and water loss are essential for soil conservation planning. The objective of this study was to evaluate soil and water losses by water erosion under natural rainfall in eucalyptus plantations established in 2001 (EF2), and 2004 (EF1), native forest (NF) and bare soil (BS), during the period of 2007 to 2012; and to determine the USLE factors: rain erosivity (R), erodibility (K) of a Red Argisol and the cover-management factor (C) for EF1, EF2 and NF at a pilot sub-basin, in Eldorado do Sul, RS, Brazil. The R factor was estimated by the EI30 index, using rainfall data from a gauging station located at the sub-basin. The soil and water losses were monitored in erosion plots, providing consistent data for the estimation of the K and C factors. The sub-basin presented an average erosivity of 4,228.52 MJ mm ha-1 h-1 yr-1. The average annual soil losses em EF1 and EF2 (0.81 e 0.12 Mg ha-1 year-1, respectively) were below of the limit of tolerance, 12.9 Mg ha-1 year-1. The percentage values of water loss relating to the total rainfall decreased annually, approaching the values observed at the NF. From the 5th year on after the implantation of the eucalyptus systems, soil losses values were similar to the ones from NF. The erodibility of the Red Argisol was of 0.0026 Mg ha h ha-1 MJ-1mm-1 and the C factor presented values of 0.121, 0.016 and 0.015 for EF1, EF2 and NF, respectively.

Changes in Erosion and Runoff due to Replacement of Pasture Land with Sugarcane Crops

The planting of sugarcane crops has expanded in the last decade in the southeast of Brazil, mainly due to its use for biofuel production, such as ethanol. This expansion in the State of São Paulo has occupied land that was previously used for cattle production. The change in land use affects soil and water through changes in ground cover and disturbance associated with farming practices. The objective of the following study was to determine the impact on runoff and erosion resulting from the conversion of pastureland to sugarcane for biofuel production. Erosion plots measuring 100 m2 were built on a farm in Itirapina-SP, Brazil, on land with a slope gradient of 9% and soil composed of Quartz-sand Neosols (Typic quartzipsaments). The treatments were an 18-year old pasture and a new sugarcane plantation, with three replicates for each. After each rainfall episode, erosion and runoff were monitored during the first and second years after sugarcane was planted. The results show increased runoff and soil loss during the first year, though levels decreased in the second year when the sugarcane residue mulch ground cover increased. In addition, the necessary rainfall characteristics (e.g., intensity, duration) required to produce runoff and soil erosion were identified.

Validating a mass balance accounting approach to using 7Be measurements to estimate event‐based erosion rates over an extended period at the catchment scale

AbstractUse of the fallout radionuclides cesium‐137 and excess lead‐210 offers important advantages over traditional methods of quantifying erosion and soil redistribution rates. However, both radionuclides provide information on longer‐term (i.e., 50–100 years) average rates of soil redistribution. Beryllium‐7, with its half‐life of 53 days, can provide a basis for documenting short‐term soil redistribution and it has been successfully employed in several studies. However, the approach commonly used introduces several important constraints related to the timing and duration of the study period. A new approach proposed by the authors that overcomes these constraints has been successfully validated using an erosion plot experiment undertaken in southern Italy. Here, a further validation exercise undertaken in a small (1.38 ha) catchment is reported. The catchment was instrumented to measure event sediment yields and beryllium‐7 measurements were employed to document the net soil loss for a series of 13 events that occurred between November 2013 and June 2015. In the absence of significant sediment storage within the catchment's ephemeral channel system and of a significant contribution from channel erosion to the measured sediment yield, the estimates of net soil loss for the individual events could be directly compared with the measured sediment yields to validate the former. The close agreement of the two sets of values is seen as successfully validating the use of beryllium‐7 measurements and the new approach to obtain estimates of net soil loss for a sequence of individual events occurring over an extended period at the scale of a small catchment.

Critical Analysis of the van Bemmelen Conversion Factor used to Convert Soil Organic Matter Data to Soil Organic Carbon Data: Comparative Analyses in a UK Loamy Sand Soil

Converting soil organic matter (SOM) data to soil organic carbon (SOC) data usually uses the van Bemmelen factor of 0.58 (or in reverse its reciprocal of 1.724) as a universal conversion factor. The accuracy of this conversion factor has been questioned. Under the Kyoto Protocol (1997) dry combustion is recommended to provide reproducible analyses to measure soil carbon stocks. However, dry combustion equipment is expensive and entails high maintenance. For rapid and inexpensive measurements, loss-on-ignition (LOI) is often used. A total of 278 loamy sand topsoil (0-5 cm depth) samples were taken during three soil sampling sessions (9 January 2007, 22 January 2009 and 10 October 2011) from runoff plots, splash erosion plots and grassed/cultivated plots on the Hilton Experimental Site, Shropshire, UK. A total of 124 soil samples were collected from both runoff and splash plots in both 2007 and 2009 (Bhattacharyya et al., 2011a). Some 22 of the collected samples in 2011 were from grassland (Ah horizon) and eight from cultivated soils (Ap horizon). Homogenized soil samples were split and SOM was determined on oven-dried samples by LOI and total SOC was determined by dry combustion. A conversion factor of 0.845 was used to obtain SOC from total soil C, following Rawlins et al. (2011). Results showed strong associations (R² = 0.70, P 0.001, n = 278) between SOM and SOC data. For all data, SOM to SOC conversion factors varied between 0.36-0.98, with a mean value of 0.66 (SD = 0.105). The mean values of the conversion factor were 0.64, 0.69 and 0.56, respectively, for the samples collected in 2007, 2009 and 2011. Results indicate the van Bemmelen factor (0.58) is a reasonable predictor, but both temporal and spatial variations occur around it within a specific soil type. Thus, caution should be exercised in SOM/SOC data conversions using the van Bemmelen factor.

Effect of laser shock processing on erosive resistance of 6061-T6 aluminum

Application of laser shock processing (LSP) on 6061-T6 aluminum was made in order to evaluate its response to the erosive wear by silica sand. Impact angles of 15°, 30°, 60° and 90° were tested, two particle speeds (37 and 58 m/s) and two LSP irradiation conditions were used. Erosion marks were characterized by 3D profilometry and SEM analysis was conducted to identify the erosion mechanisms for each tested angle. The results showed a maximum erosive wear at low impact angles (ductile type behavior). Erosion strength and the erosion mechanisms were not affected by the application of LSP and they were attributed to the high strain rate of the erosion phenomena. A few differences encountered on the erosion plots were explained on the basis of the surface roughness left by the LSP process. The maximum mass loss and the maximum erosion penetration happened in different impact angles (15° and 30°, respectively). Finally, a well-defined erosion mechanism transition was observed, from cutting action at low impact angle, to crater formation at 90° of incidence.

Trade-off between runoff and sediments from treated erosion plots and polyacrylamide and acrylamide residues

ObjectiveThe present study aimed to evaluate the quantitative effect of polyacrylamide (PAM) on runoff and soil loss, and the amount of PAM polymer and acrylamide (AMD) monomer emissions from experimental plots under laboratory conditions. Materials and methodsThe different levels of treatment of 0, 0.4, 0.6, 1, 2, 3, 4, and 6gm−2 PAM were applied to small plots of 0.05m2 installed in the Rainfall and Soil Erosion Simulation Laboratory of Tarbiat Modares University, Iran, with a simulated rainfall intensity of 72mmh−1, duration of 0.5h, and slope of 20% (i.e., 11.5°) applied to a silty loam, similar to that for real conditions. To determine the optimal level of PAM application for soil and water conservation under laboratory condition, PAM polymer and AMD monomer were measured in outing runoff and sediment. An analytical technique based on a spectrophotometer was developed to quantify the amount of PAM polymer present; the determination of amide groups by the NBM was also formulated for the quantification of PAM polymer. The background AMD concentrations in runoff and sediment were determined using the EPA method 8032A in triplicate. The analysis of AMD was performed on a gas chromatograph system equipped with an electron capture detector and Clarity 4.2 Data Acquisition software. ResultsThe results proved a significant PAM polymer emission in runoff and sediment (P<0.001), a significant AMD monomer emission in output runoff (P<0.02), and no significant AMD residue in the output sediment (P>0.32). The optimal amounts of PAM application that are based on PAM and AMD residues in runoff and sediment and minimum soil loss were at rates of 2 and 0.4, and 2 and 1gm−2, respectively. ConclusionsThe results of this research could be helpful in providing appropriate information to address environmental concerns regarding PAM application for soil erosion control as well as in conservational and engineering planning.

Effect of natural land covers on runoff and soil loss at the hill-slope scale

Erosion plots were selected for characterizing the effects of main natural factors on runoff and soil loss in a semi-arid region. These erosion plots with an area of 40 m2 are located in the Kakhk experimental watershed in Gonabad County of Khorasan-e Razave Province in the north-eastern Iran. Data acquired from 2008 to 2015 include slope, aspect, soil texture and land covers (canopy and litter) factors that were selected as main natural factors and it was tried to determine the effects of these factors on runoff and soil loss amount. In the next stage, it was focused on evaluation of the effects of land covers on runoff generation and soil loss in more details. For this purpose, in each class of the mentioned factors, the relationship between land covers and runoff and soil loss was analysed. The maximum of runoff and soil loss were occurred at E site with the amount of 15.6 mm and 140 g/m2 respectively. Results showed that soil loss and runoff have decreased where the amounts of land covers have increased, and the line gradient is steeper for soil loss reduction than runoff generation. The result especially characterized the role of land covers on soil loss. Based on these results land covers have a significant effect on soil loss but this effect is mostly highlighted in the highest and lowest conditions of erosion potential, rather than the medium erosion potential condition. Furthermore, in each plot and event, a dominant factor determines the quantity of the effect of land cover on runoff and soil loss.

Selective organic carbon losses from soils by sheet erosion and main controls

AbstractAlthough the impact of sheet erosion on the selective transportation of mineral soil particles has been widely investigated, little is yet known about the specific mechanisms of organic carbon (OC) erosion, which constitutes an important link in the global carbon cycle. The present study was conducted to quantify the impact of sheet erosion on OC losses from soils. Erosion plots with the lengths of 1‐ and 5‐m were installed at different topographic positions along a hillslope in a mountainous South African region. A total of 32 rainfall events from a three years period (November 2010 up to February 2013), were studied and evaluated for runoff (R), particulate and dissolved organic carbon (POCL and DOCL). In comparison to the 0–0·05 m bulk soil, the sediments from the 1‐m plots were enriched in OC by a factor 2·6 and those from the 5‐m long plots by a factor of 2·2, respectively. These findings suggest a preferential erosion of OC. In addition, total organic carbon losses (TOCL) were incurred mainly in particulate form (~94%) and the increase in TOCL from 14·09 ± 0·68 g C m−1 yr−1 on 1‐m plots to 50·03 ± 2·89 g C m−1 yr−1 on 5‐m plots illustrated an increase in sheet erosion efficiency with increasing slope length. Both TOCL and sediment enrichment in OC correspondingly increased with a decrease in soil basal grass cover. The characteristics of rainstorms had no significant impact on the selectivity of OC erosion. The results accrued in this study investigating the links between sheet erosion and OC losses, are expected to be of future value in the generation of carbon specific erosion models, which can further help to inform and improve climate change mitigation measures. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Assessing the performance of structure‐from‐motion photogrammetry and terrestrial LiDAR for reconstructing soil surface microtopography of naturally vegetated plots

AbstractSoil microtopography is a property of critical importance in many earth surface processes but is often difficult to quantify. Advances in computer vision technologies have made image‐based three‐dimensional (3D) reconstruction or Structure‐from‐Motion (SfM) available to many scientists as a low cost alternative to laser‐based systems such as terrestrial laser scanning (TLS). While the performance of SfM at acquiring soil surface microtopography has been extensively compared to that of TLS on bare surfaces, little is known about the impact of vegetation on reconstruction performance. This article evaluates the performance of SfM and TLS technologies at reconstructing soil microtopography on 6 m × 2 m erosion plots with vegetation cover ranging from 0% to 77%. Results show that soil surface occlusion by vegetation was more pronounced with TLS compared to SfM, a consequence of the single viewpoint laser scanning strategy adopted in this study. On the bare soil surface, elevation values estimated with SfM were within 5 mm of those from TLS although long distance deformations were observed with the former technology. As vegetation cover increased, agreement between SfM and TLS slightly degraded but was significantly affected beyond 53% of ground cover. Detailed semivariogram analysis on meter‐square‐scale surface patches showed that TLS and SfM surfaces were very similar even on highly vegetated plots but with fine scale details and the dynamic elevation range smoothed out with SfM. Errors in the TLS data were mainly caused by the distance measurement function of the instrument especially at the fringe of occlusion regions where the laser beam intersected foreground and background features simultaneously. From this study, we conclude that a realistic approach to digitizing soil surface microtopography in field conditions can be implemented by combining strengths of the image‐based method (simplicity and effectiveness at reconstructing soil surface under sparse vegetation) with the high accuracy of TLS‐like technologies. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Land use and climate change effects on soil erosion in a semi-arid mountainous watershed (High Atlas, Morocco)

The objective of this study was to simulate the evolution of soil erosion in a semi-arid mountainous watershed (225 km2, High Atlas Mountains, Morocco) under different scenarios of climate and land use change to the end of 21st century. Erosion plots monitored over four years showed spatially contrasted results. Most of the soils produced from 0.015 to 2.5 t ha−1 y−1, whereas badlands produced 350 t ha−1 y−1. The average sediment yield measured at the outlet during the same period was approximately 4 t ha−1 y−1.The STREAM distributed erosion model was parameterized using these field measurements (infiltration rates and runoff sediment concentrations). The results showed an overall agreement between the modelled and measured annual cumulative sediment yields.Simulations of the ARPEGE meteorological model were used for the 1960–1990 and 2070–2100 periods. The changes between these two periods were downscaled using three different methods, decreasing annual precipitations by 10–14%, although with more rainfall in summer and fall. Climate change alone increased sediment yield by 4.7–10.1%. However, simulations showed that land use changes might potentially induce much larger changes in erosion (up to 250%), approximately proportional to the evolution of the extension of badlands.

Growth performance of Sainfoin and its effects on the runoff, soil loss and sediment concentration in a semi-arid region of Turkey

Vegetation is one of the key factors affecting soil erosion in semi-arid environments. The evaluation of the influence of Sainfoin on soil erosion can provide important information about soil and water conservation. In this study, the effects of vegetation destruction and vegetation restoration on soil erosion were quantified using data from field runoff plots established in a semi-arid zone in Northeastern Turkey. This study was performed between 2005 (June) and 2009 (January). The experimental design at the site included a randomized complete block with four replicates (a total of 12 experimental plots: 3 treatments×4 replicates). Each plot was 20-m long×5-m wide, which is wide enough to minimize edge effects and large enough for downslope rills to develop. The control plot (A) was maintained, bare of vegetation by manual removal of the plant cover and, regular herbicide treatments. In the second plot (B), Sainfoin was seeded in 25cm wide and 60cm long rows, at a density of 8.5g of seeds per square meter in October, 2005 after clearing the existing vegetation. The third plot contained natural vegetation shrub (Paliurus spina-christi Mill.) and perennial grass (Cynodon dactylon L., Achillea sp., Astragalus sp.) vegetation (C) that maintained at an approximately 63% coverage (October, 2005) of the soil surface.From 4 randomly selected quadrats (1m×1m) at a vegetation plot, the vegetation cover of all of the plant species was estimated for each cell, and the average vegetation cover for a plot was calculated. The plant height and cover were recorded monthly from March through October in 2006, 2007 and 2008, and the monthly averaged value for each indicator was used in this study.Rainfall was recorded at the same field at 1-min intervals using a tipping-bucket system linked to a data-logger. The erosion plot results presented in this study clearly indicate a decrease in the erosion rates over time. The highest sediment concentration was measured on bare plots (10.4gl−1, 2006), while the lowest sediment concentration was measured on Sainfoin plots (1.76gl−1, 2008). The effective soil conservation ability of Sainfoin differed between seasons and years. In the spring season, when plant cover was 30%, Sainfoin began to exhibit an effective active soil conservation ability. In contrast, when the plant cover was greater than 50%, effective protection was observed in the summer. The results revealed that the plant cover was the main factor reducing surface runoff and sediment production, and that Sainfoin showed a great potential to both reduce erosion and runoff.

Effectiveness Of Soil Conservation To Erosion Control On Several Land Use Types

Abstract The erosion plot method for direct evaluation in agriculture became necessary to (1) quantify soil erosion on cocoa, areca and oil palm, (2) determine the most effective soil conservation, and (3) calculate nutrient content in sediment. The experiment was treated with three conservation practices and the conventional treatment as control in a completely randomised block design. The results showed for the areca land use, that soil conservation with ridges + maize produced the lowest erosion (1.68 t/ha). For cocoa land use, the ridges + groundnut treatment produced the lowest erosion (8.2 t/ha). For oil palm land use, the cover crop of Mucuna bracteata had lowest erosion yield (12.2 t/ha). Soil conservation techniques significantly affected the levels of organic C and available P under the cocoa land use, where ridges + maize have the lowest content of organic C and available P in soil sediment (1.03% and 0.69 ppm). Soil conservation at areca land use also has a significant effect on the levels of organic C and available N, but it did not affect significantly the levels of available P and exchangeable K sediments, where ridges + groundnut have lowest organic C and available N in sediment (1.4% and 0.18%). Furthermore, soil conservation on the land use of oil palm showed a significant effect on the levels of available P, but did not significantly affect the levels of organic C, available N and exchangeable K sediments. Soil conservation with cover crops Mucuna bracteata showed the lowest available P in sediments (0.86 ppm).

Reducing soil erosion by improving community functional diversity in semi‐arid grasslands

Summary Great efforts have been made to control soil erosion by restoring plant communities in degraded ecosystems world‐wide. However, soil erosion has not been substantially reduced mainly because current restoration strategies lead to large areas of mono‐specific vegetation, which are inefficient in reducing soil erosion because of their simple canopy and root structure. Therefore, an advanced understanding of how community functional composition affects soil erosion processes, as well as an improved restoration scheme to reduce soil erosion, is urgently needed. We investigated the effect of community functional composition on soil erosion in restored semi‐arid grasslands on the Loess Plateau of China. Community functional composition of 16 restored grasslands was quantified by community‐weighted mean (CWM) and functional diversity (FD) trait values, which were calculated from nine plant functional traits of thirteen locally dominant plant species. Species richness and evenness were also measured. Soil erosion rates were measured using standard erosion plots. The multimodel inference approach was used to estimate the direction and the relative importance of these biodiversity indices in reducing soil erosion. A robust and strong negative effect of functional divergence (FDiv) on soil erosion was found. The prevalence of particular trait combinations can also decrease soil erosion. The greatest control over soil erosion was exerted when the community mean root diameter was small and the root tensile strength was great. Synthesis and applications: These findings imply that community functional diversity plays an important role in reducing soil erosion in semi‐arid restored grasslands. This means that current restoration strategies can be greatly improved by incorporating community functional diversity into restoration design. We propose a trait‐based restoration framework for reducing soil erosion, termed ‘SSM’ (Screening–Simulating–Maintaining). SSM aims to translate the target of community functional diversity into community assemblages that can be manipulated by practitioners. Based on this framework, a comprehensive procedure, highlighting functional diversity as the primary concern in determining optimal community assemblages, was developed to meet the pressing need for more effective restoration strategies to reduce soil erosion.

No-till surface runoff and soil losses in southern Brazil

No-till is widely used to control soil erosion in agricultural areas in Brazil and is currently practiced on about 30Mha. However, studies have shown that no-till is not as efficient in controlling surface runoff losses as it is in reducing soil loss. The objective of this study is to evaluate soil and surface runoff losses on small and large plots with differing slope lengths, cropping sequences and tillage systems in southern Brazil. Surface runoff and soil losses under natural rainfall erosion plots (3.5×11m, 3.5×22m, 50×100m, and 100×100m) were evaluated in two experiments in a well-drained Oxisol (>60% clay) with 9% and 7% slopes, respectively. The experiment extended over 14 years comparing 4 different soil management systems: (a) bare soil plots with slope length 22m; (b) bare soil plots with slope length 11m; (c) sequence of wheat (Triticum aestivum)/soybean [Glycine max (L.) Merr] with disk plow+lighter off-set disk-harrow (DP+LD); and (d) sequence of wheat/soybean under no-till (NT). In another experiment using large field plots, three soil tillage regimens (DP+LD; heavy off-set disk-harrow+lighter off-set disk-harrow (HD+LD), and NT) were compared over the course of a 5-yr. crop sequence of black oats (Avena estrigosa)/soybean-black oats/corn (Zea mays L.)-wheat/soybean- black oats/soybean -blue lupine (Lupinus angustifolium)/corn. Results for both experiments show that, when compared with conventional soil tillage (DP+LD or HD+LD), soil losses for NT were >70% lower. However, the benefit of reduced surface runoff losses was less evident, suggesting the need to implement additional practices to control surface runoff to avoid transport of pollutants to waterways.