Erosion rates on bare loamy sand soils in east Shropshire, UK

Abstract. Results from over seven years of monitoring of erosion rates on bare arable loamy sand soils at the Hilton experimental site, Shropshire, UK, are reported. On bare plots, rates are very variable; erosion during one summer convectional storm exceeded that recorded during six individual years of plot measurement. Exposure of erodible arable soils to convectional storms puts them at risk of excessive erosion. Plot erosion rates were frequently high, with rates up to 67.4 t/ha occurring during an individual storm. Rates were influenced by rainfall erosivity, slope steepness and soil organic content. Mean soil organic content on the bare plots decreased over five years by 0.08%/yr.     

The effect of simulated runoff on the erosion of gypsiferous soils

The effect of runoff generation on the erosion of gypsiferous soils under different experimental conditions was investigated by applying simulated rainfalls of 48 and 58 mm h⁻¹ to experimental plots exhibiting representative characteristics of these soils. The 45 experiments indicate differing erosive behaviour as test conditions varied. Suspended gypsum yields ranged from 0-3.9 gm⁻² h⁻¹ the higher values occurring with the steeper slopes and dry soil conditions. The differences among the soils tested were mainly due to variations in underlying rock outcrop, whilst within each soil type, slope was the most important variable. Transport of suspended gypsum by runoff is inversely related to rock outcrop, and positively related to slope. The highest erosion rates are registered in Gypsic Calcisols, followed by Gypsic Calcisols (lithic phase), while production of suspended gypsum is not verified for Dystric Leptosols. By transporting gypsum particles down-slope, runoff is probably responsible for the dynamic evolution of gypsiferous hillslopes as well as the genetic evolution of the studied soils.     

Pore-size distribution in loamy soils: A comparison between microtomographic and capillarimetric determination methods

Pore-size distribution in a soddy-podzolic silt loamy soil developing from mantle loesslike loam (Eutric Albic Retisol (Loamic, Cutanic)) was calculated from the water retention curve according to Jurin’s equation and directly determined in microtomographic experiments. Rounded macropores with the diameter of their sections from 75 to 1000 μm predominate in horizontal sections if the studied soil samples. A larger part of the soil pores (>30–35%) belongs to micro- and nanopores, and they cannot be quantitatively determined by the tomographic method, because their sizes are smaller than the detection limit of the applied X-ray microtomography (8.75 μm per pixel). This leads to a significantly larger pore volume determined from the water retention curve in comparison with the “tomographic” pore volume. A comparative analysis of pore-size distribution curves obtained by these methods shows that the major regularities of the pore-size distribution in the range from 30 to 5000 μm are similar in both cases. Fine macropores and, partly, mesopores predominate. Common characteristics of the pore-size distribution curves obtained by these methods, including the coincidence of the peaks, attest to the validity of classical approaches, according to which the hydrology of soil pore space can be perceived as a physical model of cylindrical capillaries of different sizes with capillary-sorbed water.     

Similarities and dissimilarities between the dynamics of sand and dust during wind erosion of loamy sandy soil

Aeolian dynamics were measured during a wind erosion event on an agricultural field in Northern Germany. Because the topsoil was loamy sand, particle flow behaved as a sand–dust mixture and not as pure sand (>63 μm) or pure dust (<63 μm). Although generally similar, the erosion, transportation and deposition patterns were not identical for the two particle fractions. The difference was most pronounced for accumulation (defined as deposition minus erosion). For dust, accumulation was negative all over the field because grains were removed in dust clouds. For sand, spots of negative accumulation (erosion) alternated with spots of positive accumulation (accretion) and the net result for the field as a whole was close to zero. The study shows that accumulation maps cannot be used to reconstruct the areas of high aeolian activity. It also demonstrates that during wind erosion, the wind behaves as a selective medium. In topsoil with a median grain diameter between 40 and 160 μm, fine particles are more easily eroded than coarse. In topsoil with a median grain diameter <40 μm, the coarsest particles are more easily eroded. Topsoil with a median grain diameter around 90 μm is very susceptible to granulometric selectivity. The results show that soil lost through wind erosion in NW Germany can amount to several tons per hectare per erosion event, which suggests that wind erosion of soil is more important than water erosion in this region.     

Aggregate stability in range sandy loam soils Relationships with runoff and erosion

The spatial variability of soil aggregate stability and its relationship to runoff and soil erosion were examined in a catena of soils and vegetation in a semiarid environment at the Rambla Honda field site (Tabernas, Almería, SE Spain) to evaluate the validity of structural stability as a soil erosion indicator in sandy loam range soils. The influence of soil properties and topography on the variability of aggregate stability was also examined. Methods include: 1) aggregate stability assessment at 12 sites (3 repetitions per site) on the hillslope by two methods: a) aggregate size distribution by dry sieving b) water drop test; 2) soil organic carbon content; 3) particle size distribution determination; 4) terrain attributes derived from a digital elevation model (1-m resolution); 5) monitoring runoff and erosion for nearly 3 years in eight (10 × 2 m) plots distributed over the hillslope. Results: 41% of the average soil mass is formed by > 2-mm aggregates. However, wet aggregate stability is poor, with a mean (of a total of 1440 aggregates) of only 26 drop impacts necessary to break up a wet aggregate (pF = 1). Significant relationships were found in the number of water drops required for aggregate breakdown and runoff and erosion rates. However, no significant relationships between the mean weight diameter of aggregates under dry conditions and runoff or erosion rates were observed. The relationships of aggregates with other soil properties, hillslope position and proximity to plants are also analysed. The most significant correlation found was between the number of drop impacts and soil organic matter content. The stability of topsoil aggregates seems to be a valuable indicator of field-assessed runoff and inter-rill erosion of sandy loam range soils under semiarid conditions.     

An experimental study of crust development on chalk downland soils and their impact on runoff and erosion

The sealing of soil surfaces by rainfall, the development of soil crusts and their impact on runoff and erosion was investigated in the laboratory by means of simulated rainfall. The soils investigated were stone-free samples of chalk soils from southeast England, and soils with a 25% cover of stones. Vertical change to the surface and immediate subsurface of the soils was assessed through the examination of thin sections scanned into a computer and analysed with image processing software. Changes in roughness and microtopography of the soil surface were measured by use of a laser micromapper. Crusting occurred both in the presence and absence of stones and was inversely related to the organic matter content and aggregate stability of the soils. Crusting of stone-free soils was accompanied by a reduction in roughness of the soil surface, but roughness of the stone-covered surfaces increased as crusting developed. Increases in the particle density of the crust were related to silt content. Organic-rich soil from under permanent grass and from a soil recently brought into arable cultivation crusted less than soils used for arable cultivation for longer periods with lower organic content. The inwashing of silt into the pores of the soil during crusting reduces infiltration, and increases runoff and erosion. In the presence of a 25% cover of surface stones, the reduction in infiltration was 25% less than for stone-free soils and erosion ∼50% less.     

Organic matter and polyacrylamide amendment of Norfolk loamy sand

Loamy sand soils of the southeastern USA Coastal Plains often have poor physical properties because they contain cemented subsurface hard layers that restrict root development and yield. Their physical properties can be improved by adding amendments. Polyacrylamide (PAM) amendments and/or organic matter (OM) in the form of ground wheat (Triticum aestivum L.) stubble or pecan (Carya illinoensis) branches were mixed into a blend of 90% E horizon and 10% Ap horizon (to assure microbial presence) obtained from a Norfolk soil (Acrisol or fine-loamy, siliceous, thermic Typic Kandiudult). We hypothesized that incorporation of these amendments would improve soil physical properties by reducing strength and improving aggregation. Amended treatments contained 450 g of soil, OM, and 30 or 120 mg kg⁻¹ of PAM (12 mg mol⁻¹, anionic, and 35% charge density); treatments were incubated for 96 days at 10% (w/w) water content. Twice during the incubation period, treatments were leached with 1.3 pore volumes of deionized water. After leaching and equilibrating to stable water contents, treatments were analyzed for bulk densities and probed with a 5-mm diameter flat-tipped bench-top penetrometer to measure penetration resistances. Though penetration resistances increased for the highest level of PAM amendment, they showed no significance when both PAM and OM were added to the soil. When compared to controls, treatments with PAM at 120 mg kg⁻¹ had decreased bulk densities. Treatments with both rates of PAM had decreased requirements for water needed to maintain treatments at 10% water contents. Aggregation increased with increasing amounts of PAM but showed no consistent trend when both PAM and OM were added to the soil. Because PAM increased aggregation and water holding capacities in these coastal soils, it could reduce the need for deep tillage. However, more work needs to be done to determine an effective mix of PAM and OM.     

Effect of rock fragment cover on interrill soil erosion from bare soils in Western Andalusia, Spain

It is known that rock fragments on the surface of soils can enhance infiltration and protect the soil against rainfall erosion. However, the effect of rock fragments in natural forest soils is less well understood. In this article, we studied the influence of rock fragment cover on run‐off, infiltration and interrill soil erosion under simulated rainfall on natural bare soils in a Spanish dehesa (managed holm oak woodland). We studied 60 plots with different rock fragment cover ranging from 3% to 85% under three simulated rainfall intensities (50, 100 and 150 mm/h). Surface run‐off appeared later and sediment yield values were smaller in soils with greater rock fragment cover. Rock fragment cover also increased infiltration rates. The final infiltration rates were 54–98% at a rainfall intensity of 50 mm/h, 31–88% at 100 mm/h and 20–80% at 150 mm/h. The interrill soil loss rates were decreased by rock fragment cover and increased with rainfall intensity. The soil loss rate was always small (0.02–1 Mg ha/h) when rock fragment cover was 75% or more. Rock fragment cover was related to soil loss rate by an exponential function.     

Off‐site impacts of soil erosion and runoff: Why connectivity is more important than erosion rates

Off‐site impacts of soil erosion are of greater social and economic concern in Western Europe than on‐site impacts. They fall into two related categories: muddy flooding of properties and ecological impacts on watercourses because of excessive sedimentation and associated pollutants. Critical to these impacts is the connectedness of the runoff and sediment system between agricultural fields and the river system. We argue that well‐connected systems causing off‐site damage are not necessarily related to areas of high erosion rates; emphasis should therefore be on the way in which connections occur. In temperate, arable systems, important elements of connectivity are anthropogenic in origin: roads, tracks, sunken lanes, field drains, ditches, culverts and permeable field boundaries. Mapping these features allows us to understand how they affect runoff and modify its impacts, to design appropriate mitigation measures and to better validate model predictions. Published maps (digital and paper) do not, by themselves, give sufficient information. Field mapping and observation, aided by remote sensing, are also necessary.     

Effects of N placement,carbon distribution and temperature on N2O emissions in clay loam and loamy sand soils

Changes in the profile distribution of soil C stocks for conventional versus no‐tillage can affect N₂O losses. Uncertainty remains whether deep N placement into a wetter layer in humid areas would affect N₂O losses. This study evaluated the effects of soil carbon profile distribution (inverted, normal), depth of nitrogen placement (5 cm, 15 cm), temperature (10, 20 and 30 °C) and soil texture (clay loam, loamy sand) on N₂O emissions from soil cores in a 216‐h incubation after simulated rainfall. N₂O losses were larger from the clay loam than from the loamy sand, and cumulative N₂O emissions from the inverted profile, with greater C levels at depth, were more than those from the profile with more C near the upper surface. Cumulative N₂O losses from the inverted clay loam profile with deep N placement (1.16 mg N per kg dry soil; 0.71% of applied N) on average were almost double those in the loamy sand (0.62 mg N per kg dry soil; 0.42%). The smallest N₂O losses were measured from the profiles with more C close to the upper surface with a shallow placement of N for the clay loam (0.19 mg N per kg dry soil; 0.12%) and loamy sand (0.33 mg N per kg dry soil; 0.23%). An exponential relationship between N₂O fluxes and temperature was measured. We conclude that large N₂O losses may occur under the combination of greater soil C content at deeper layers (ploughed soils) and moist profiles after N application (humid regions). Deep N placement appears to aggravate rather than ameliorate these concerns.     

Effects of 'Agri-SC' soil conditioner on the erodibility of loamy sand soils in East Shropshire, UK: preliminary results

Abstract. The effect of Agri-SC' soil conditioner on the erodibility of loamy sand soils has been investigated at the Hilton experimental site, Shropshire, since March 1988. Factors measured have included runoff and erosion, soil structure, crust strength, splash susceptibility, aggregate stability, soil micromorphological properties, response to compaction and penetrometer resistance.
Treatment decreased runoff and erosion rates, bulk density, splash erosion, crust strength and penetrometer resistance, and increased pore space and aggregate stability. The effects on crust strength, aggregate stability and bulk density were statistically significant. The results suggest that applications of 'Agri-SC' could have beneficial effects for soil conservation.     

Effects of bentonite on water infiltration in a loamy sand soil

Water loss as deep percolation is considerable in furrow irrigation in light soils due to the high infiltration rate. Application of soil conditioners such as bentonite reduces the infiltration rate and improves irrigation application efficiency (E_a) in these soils. The effects of bentonite application rates (BAR) of 0, 2, 4 and 6 g L^?1 on infiltration of a loamy sand soil were determined in a soil column in the laboratory. The exponent of the Kostiakov infiltration equation was not influenced by BAR. Maximum reduction in infiltration equation coefficient and final infiltration rate (i _f) occurred with 2 g bentonite L^?1 and this reduction was lower on increasing BAR from 2 to 4 and 4 to 6 g L^?1 compared with control. The effect of 2 g L^?1 BAR on infiltration and its effect on the design of furrow irrigation in a field with a loamy sand soil indicated that in the first irrigation after field ploughing and seed planting, longer furrow length, lower deep percolation and higher E_a are obtained.     

Wind-splash erosion of bare peat on UK upland moorlands

Peat is a common land surface material in many countries of the world and is particularly important in upland regions of the UK. Peat landscapes represent an important land use for hill farming, water management, and shooting, and are a globally scarce resource. Wind is a fundamental characteristic of upland environments in the UK and has long been recognised as a significant factor in peat erosion. This paper presents the first results of a project that aims to determine the significance of wind action in the erosion of upland peat. Wind erosion monitoring is being undertaken at Moor House in the North Pennines on a 3-ha area of relatively flat, sparsely vegetated peat. Measurements using arrays of passive horizontal mass flux gauges (fixed orientation vertical slot gauges), together with a vertical array of mass flux samplers (directional), provide estimates of sediment flux. A micrometeorological station records local wind speed (four heights), wind direction, rainfall, soil moisture, and temperature conditions. For 1999 and 2000, the annual horizontal net erosion flux is 0.46 and 0.48 t ha⁻¹, respectively. Results of detailed monitoring over a 10-month period demonstrate that the peat sediment flux collected in windward- and leeward-oriented sediment traps on 10 separate occasions is between 3 and 12 times greater in the windward-facing traps. The concentration of peat with height decays rapidly and the majority of the peat is transported close to the ground surface. Above 0.3 m, very little peat is found. Significant horizontal fluxes of peat occur in both wet and dry periods. This is evaluated using the local micrometeorological data to try and predict sediment yields. Correlations among time-averaged friction velocity measurements, surface conditions, and sediment flux are complex. Event-based measurements, as opposed to cumulative sediment yields, are required to resolve this. These results quantify for the first time the significance of wind action in the erosion of peat in a UK upland environment.     

Effect of compost on erodibility of loamy sand under simulated rainfall

Three types of composts [vegetable, fruit and yard waste compost (VFYW), garden waste compost (GW), and spent mushroom compost (SM)] were applied at a rate of 30 m³ ha⁻¹ for 10 years to loamy sand, to determine its effect on the aggregate stability and susceptibility to water erosion. Aggregate stability was measured using the stability index derived from the wet sieving method while a laboratory rainfall simulator was used to measure runoff, sheet and splash erosion. Only GW recorded a significant increase (45%) in aggregate stability. Runoff, sheet erosion, and splash erosion did not show significant improvement for any of the compost types. SM application resulted in a significant increase (51%) in the shear strength of the soil after rainfall. Long term compost application does not appreciably improve the resistance of loamy sand to water erosion.     

Effects of field reorganisation on the spatial variability of runoff and erosion rates in vineyards of Northeastern Spain

This study analyses the spatial variability of runoff and erosion rates in vineyards due to mechanisation works. Runoff samples were collected at three positions in two plots after 33 erosive events in three years (2001, 2003, 2004) with different rainfall patterns. Three replications were considered at each position. Soil properties were evaluated in order to analyse its relationship with runoff and erosion rates. Runoff and erosion rates were, on average, higher in the levelled plot (HD), ranging between 8·4 and 34·3 per cent, than in the non‐levelled plot (LD) ranging between 8·2 and 24·1 per cent. Mean sediment concentration in runoff ranged between 6 and 8 g L⁻¹ in the HD plot and about 4·6 g L⁻¹ in the LD plot, but with high differences within the plot. In the HD plot, runoff‐rainfall rates were significantly higher (at 95 per cent level) in the upper part of the slope and decreased along the slope, while in the LD plot, differences in runoff rates were not significant and similar to those observed in the less disturbed areas of the HD plot. The higher susceptibility to soil sealing in areas where the original topsoil was removed conditioned runoff rates. In the lower part of the HD plot runoff rates were, on average, 20 per cent lower than in the upper part of the slope. In those positions runoff rates up to 79 per cent were recorded. Organic matter content and water retention capacity at different potentials are the soil characteristics related to the differences on runoff and erosion rates in the resulting soils. Copyright © 2009 John Wiley & Sons, Ltd.     

Earthworm channels in cultivated clayey and loamy Norwegian soils

Studies of earthworm species and their activity, expressed as channels, on cultivated loamy (Humic Cryaquept) and clayey soils (Typic Endoaqualf and Typic Cryaquept) were conducted in southern and central Norway before conversion from conventional to organic cropping systems. At all the three study areas: Landvik (Grimstad), Voll (Ås) and Kvithamar (Stjørdal), the earthworm species Aporrectodea caliginosa, Aporrectodea rosea, Allolobophora chlorotica and Lumbricus rubellus were found. At Landvik, where the deep-burrowing species Aporrectodea longa, A. caliginosa and Lumbricus terrestris dominated, medium (4–6 mm) and coarse (>6 mm) earthworm channels were most numerous below the plough layer. Almost no coarse pores were found at Voll and Kvithamar. The volume of earthworm channels below the plough layer was 0.6–0.8% of total soil volume at Landvik and Voll and 0.3–0.4% at Kvithamar. Earthworm channels >6 mm below the plough layer were useful to identify present and previous activity of deep-burrowing earthworms such as L. terrestris. Below the plough layer, roots were almost entirely restricted to earthworm channels and interaggregate spaces.     

Using the RUSLE to identify factors controlling erosion rates of mine soils

Observable differences in particle size, smoothness and compaction between cap site (slope 2·8 per cent) and batter site (slope 20·7 per cent) surfaces on the waste rock dump at Ranger Uranium Mine were quantified in terms of revised universal soil loss equation (RUSLE) parameter values. Cap site surface material had a K_m (erodibility corrected for sediment density) of 0·030 and batter site surface material had a K_m of 0·0056. Using these K_m values (derived from particle size distributions), slope length and steepness (LS) factors of 0·36 for the cap site and 3·66 for the batter site, and a cover (C) factor of 0·45 for the cap site and 0·16 for the batter site, the RUSLE predicts an erosion rate from the cap site that is 1·9 times greater than erosion from the much steeper batter site. The RUSLE indicates that the finer particle size and blocky soil structure of the cap site (D₅₀ = 0·91 mm) compared with the looser granular structure of the batter site (D₅₀ = 1·74 mm) strongly influence erosion. The predictions are similar to observed soil losses from erosion plots on these sites under rainfall simulation events, for which the measured erosion rate from the cap site was approximately twice that from the batter site. For the RUSLE to predict the observed erosion rates, the support practice (P) factor for the cap site would have to be approximately 30 per cent greater than the P factor for the batter site. The higher cap site P factor probably results from smoothing and compaction caused by vehicle movement across the surface. Compaction is considered to have greatly reduced infiltration capacity, thus increasing the erodibility of the cap site. Vehicles probably also crushed the surface material at the cap site, creating the observed finer particle size distribution and further increasing the erodibility. Compaction, through its effects on erodibility (K_m) and surface roughness (P), is concluded to be the major cause of higher erosion from the cap site, even though the slope steepness is 10 times less. Parameterisation of the RUSLE quantifies the differences between sites and explains the unexpected erosion rates observed. The results highlight the need for careful management of rehabilitated sites to avoid increases in erosion which may arise from compaction by machinery.     

Tillage and surface moisture effects on bare-soil albedo of a tropical loamy sand

Effects of four tillage systems on the albedo of a tropical loamy sand were studied under dry and moist surface conditions. The aim was to determine whether tillage-induced roughness and soil wetness significantly affected soil albedo. Changes in smooth reference surface albedo with respect to four roughness conditions were used to assess tillage effects. Surface albedo (), soil moisture content (θ_m) and soil surface roughness (δ) were measured. Two types of pyranometers used for albedometers are CM 3 and SP LITE. Mean albedo of a reference smooth surface (<2 mm sieved soil) was 0.16 and 0.20 for CM 3 and SP LITE under moist condition, and 0.29 and 0.28 under dry condition, respectively. Bare-soil shortwave albedo generally increased with an increase in solar zenith angle, whereas albedo decreased with an increase in surface roughness and soil wetness. Linear relationships of albedo with surface roughness and soil moisture content indicated that albedo was more sensitive to surface roughness under dry condition. The goodness-of-fit of a multiple linear regression model combining the effects of roughness and wetness on surface albedo was 0.96 with a standard error of 0.01. This simple model could be used to estimate albedo of bare soil similar to the tropical loamy sand reported in this study. This study provides useful information for modelling tillage effects on the energy budget at the soil surface.     

A comparison of measured catchment sediment yields with measured and predicted hillslope erosion rates in Europe

Purpose  

This study aims to understand better the relationship between measured soil loss rates due to sheet and rill erosion (SL), predicted SL rates and measured catchment sediment yields (SY) in Europe.