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.     

Semi-empirical model of the rill erosion of soils

Semi-empirical equations for describing the erosive and transporting capacities of low-depth flows with account for their interaction with eroded soil were developed and experimentally and theoretically substantiated. These equations can form the basis for a unified model of rill erosion under irrigation, rainfall, and snowmelt runoff conditions.     

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.     

Thermoluminescence dating of soils developed in Late Devensian loess at Pegwell Bay, Kent

Thermoluminescence (TL) measurements on the present organic surface soil and two buried soils in loess and colluvium derived from loess at Pegwell Bay, Kent, suggest that the signal is almost completely zeroed during soil development, mainly by optical bleaching. The technique may therefore be used to date buried soils developed in loess and possibly other terrestrial sediments. Decalcification, gleying and other soil-forming processes may also affect the TL signal of the soil parent material, and seem to be the main reasons why the Btg horizons of the Early Holocene buried soil at Pegwell Bay give more recent TL dates than the parent calcareous loess.     

Wind erosion in agricultural soils: an example of limited supply of particles available for erosion

Soil erosion by wind is a complex process since many interacting factors are involved. In addition, wind erosion can show a considerable spatial and temporal variability associated with changes in soil surface conditions. During a wind erosion experiment conducted in August 1995 within an agricultural field of Central Aragón (NE Spain) [López, M.V., Sabre, M., Gracia, R., Arrúe, J.L., Gomes, L., 1998. Tillage effects on soil surface conditions and dust emission by wind erosion in semiarid Aragón (NE Spain). Soil Tillage Res. (in press)], a decay in dust emission (vertical dust flux) with an increase in wind speed was observed at the end of the experimental period. A further analysis of the evolution of the vertical flux with time in response to changes in soil erodibility is shown in the present study. The analysis is based on the comparison of the measured flux with the potential flux predicted for identical wind conditions assuming that the supply of erodible material at the soil surface was unlimited. The potential flux was estimated by using the dust emission model developed by Marticorena and Bergametti [Maticorena, B., Bergametti, G., 1995. Modeling the atmospheric dust cycle: 1. Design of a soil-derived dust emission scheme. J. Geophys. Res. 100, pp. 16415–16430]. The model is based on the parameterization of the threshold wind shear velocity as a function of the aggregate size distribution and the roughness length of soil surface. The results indicate that the observed reduction in soil erodibility with time was probably due to variations in the aggregate size distribution and, more precisely, to a limited supply of erodible particles at the soil surface. This study underlines the need to consider the temporal variability of the surface conditions in wind erosion research and derived models.     

Compaction,hydrological processes and soil erosion on loamy sands in east Shropshire,England

Field investigations on loamy sands in east Shropshire show that compaction by agricultural machinery increases soil bulk density and soil erodibility, and decreases infiltration rates. Structural and hydrological changes, in combination with runoff concentration in cultivation lines, can contribute to serious erosion of arable soils. Compacted soils are also more responsive to rainfall and evidence is presented that intensities as low as approximately 1 mm h^?1 can be erosive. Evidence suggests that compacted subsoils impede infiltration and so contribute to surface runoff and serious topsoil erosion.     

Loss of yield caused by soil erosion on sandy soils in the UK

Abstract. Soil productivity, the intrinsic ability of land to yield useful products, can be affected by soil erosion. While much research has been carried out on the processes, there is as yet little information on the impact of soil erosion on in situ productivity of agricultural land in the British Isles. This paper reports the results of a de-surfacing experiment on deep sandy soils in East Anglia. Grain yields of fertilized barley planted immediately after de-surfacing were at least 15 and 45% less on 15 and 25 cm de-surfaced plots than on non-desurfaced soils. There was strong evidence pointing to an acceleration of soil erosion itself on the de-surfaced plots. Both the amount of water stored in the topsoil and water use by the crop decreased with increasing severity of simulated erosion. We observed a drop in organic matter and readily available nitrogen with erosion. Nitrogen mineralization and leaching losses were also affected by simulated soil erosion. The experiment showed that sudden severe erosion may induce substantial barley production losses on deep sandy soils. The size and effect of de-surfacing depends on a number of factors such as soil depth, subsoil type, precipitation and crop type.     

Management-induced structural dynamics in paddy soils of south east China simulated in microcosms

The puddling of paddy soils is the most common method of lowland rice cultivation in Asian countries and results in a complete distortion of the soil structure of the puddled layer and the formation of a distinct plough pan. In addition, the soil structure and the interrelated chemical and biological parameters in these soils are influenced by the alternating of flooding and drying stages. Since physical properties are basic features for the availability of water and nutrients characteristics such as soil structure and soil moisture have been recorded at the different stages of rice growth in detail. For a better understanding these results have been compared with micropedological investigations. For these purposes undisturbed microcosms filled with paddy soils of three different sites from south east China were taken and planted with rice in a climate chamber.Management-induced dynamics have been reflected very prominently as far as bulk density, pore size distribution and soil moisture of the puddled layer are concerned. The properties of the undisturbed plough pan did not change during all stages of the experiment. Most significant effects of soil puddling have been found in the soil with a clay content of more than 40%. Comparing the different sampling stages after puddling the soils with high clay contents have shown the greatest variety in pore size distribution.Micropedological investigations demonstrated the different texture-influenced aspects of pore size distribution and the arrangement of soil structure in the topsoil in detail. Micrographs verified the changes of microhabitats caused by soil structure dynamics. The structural alteration consequences different living-conditions of microorganisms and, therefore, population dynamics related to the management of paddy soils which has been reflected in this study.     

坡度与种植方式对紫色土侵蚀与养分流失的影响研究

在涪陵区水土保持监测分站内建立6个径流小区,对紫色土坡耕地水土流失进行试验监测,结果表明:各小区径流量、产沙量总体随降雨量的增大而增大.自然生态修复措施防治水土流失效果显著,3.66 m3的径流量仅有0.41 kg·m3的产沙量,可有效防治紫色土坡耕地的水土流失.采用顺坡耕作措施的小区径流量与降雨量达显著正相关,而产沙量与降雨量未显著相关.径流量和产沙量大小顺序均为25°坡耕地>20°坡耕地>10°坡耕地>15°坡耕地,在15°耕地上径流量与产沙量均为最小,但15°是否是涪陵区最适宜的耕地坡度,仍有待今后收集更多的降雨资料加以分析说明.对一次强降雨进行养分流失观测,养分流失量与径流量及产沙量大小顺序基本一致.开发建设项目弃土弃渣监测点径流量与产沙量均大大高于其他小区,说明开发建设水土保持项目中防治水土流失的重要性.     

Unity of mechanisms of water and wind erosion of soils

An equation for the threshold velocity of the water or wind flow at which erosion of a homogeneous model soil begins was derived on the basis of accepted and explicitly formulated suppositions and limitations and tested using experimental data. The validity of the proposed mechanisms and equations describing the lifting force of the soil-eroding water or wind flow and the interaggregate cohesion in a model homogeneous incoherent soil was confirmed. The limit for the decrease in the threshold flow velocity with decreasing size of the soil particles (aggregates) was theoretically substantiated. The first unified equation of the threshold velocity of the water or wind flow for a homogeneous model soil in dimensionless variables was derived and experimentally justified.     

Wetting rate and sodicity effects on interrill erosion from semi-arid Israeli soils

Interrill erosion depends on soil detachment and sediment transport, which are affected by seal formation and runoff. The objective of this study was to investigate the effect of wetting rate (WR) on runoff and soil erosion in semi-arid Israeli soils varying in clay content and exchangeable sodium percentage (ESP). Six soils, ranging in clay content between 90 and 680 g kg⁻¹ and ESP between 0.9 and 20, were packed in 0.2 m×0.4 m trays, wetted at 3 WRs (2, 8, or 64 mm h⁻¹), and thereafter exposed to 60 mm of distilled water rain in a laboratory rainfall simulator. Under non-sodic conditions (ESP<2), highest runoff and erosion were obtained from loam (220 g kg⁻¹ clay and 350 g kg⁻¹ silt) which was ascribed to its high susceptibility to seal formation, runoff and detachability. Runoff and erosion increased with an increase in ESP and WR. The effect of WR on runoff and erosion was negligible in loamy sand and generally increased with an increase in clay content. In clay soils (>600 g kg⁻¹ clay), WR played a greater role in determining runoff and erosion compared with raindrop impact. A linear type dependence existed between erosion and runoff for soils with ESP<5 or when slow WR was used. For high ESP soils, or when medium or fast WR were used, an exponential type relation described better the dependence of erosion on runoff. It is suggested that for sodic soils or for conditions favoring aggregate slaking, runoff level and its velocity were high enough to initiate rill erosion that supplemented raindrop detachment in markedly increasing erosion.     

Soil alteration due to erosion, ploughing and levelling of vineyards in north east Spain

Since the 1970s and 1980s, the vineyard areas in the Mediterranean region of north east Spain have undergone profound transformation to allow greater mechanization. This has involved land levelling, deep ploughing and the elimination of traditional soil conservation measures. Recently the EU Common Agricultural Policy encourages this through the vineyard restructuring and conversion plans (Commission Regulation EC No 1227/2000 of 31 May 2000) by subsidizing up to 50% of the cost of soil preparation such as soil movement and land levelling. A clear example of the problems that this causes is in the Penedès vineyard region (Catalonia, north east Spain), and the present research analyses the changes in soil properties caused by erosion, deep ploughing and land levelling. The study was carried out in an area of 30 000 ha for which a Soil Information System at a scale of 1:50 000 was developed based on 394 field observations (89 soil profiles and 251 auger hole samples down to 120 cm). The results show that 74% of the described soil profiles are disturbed with evidence of soil mixing and/or profile truncation due to erosion, deep ploughing and/or land levelling. The evidence from the topsoils is mainly the presence of fragments of calcic or petrocalcic horizons, marls and sandstones. Other important properties for crops such as organic matter (OM) content and soil depth show statistically significant differences between disturbed soils and undisturbed soils (22.3–33.3% OM content depletion and 35.1% soil depth reduction). These results confirm that the soils of the region are significantly altered by mechanical operations which also influence soil erosion and contribute to global warming effect through depletion of soil OM.     

Runoff and losses by erosion in soils amended with sewage sludge

In order to promote the transformation of a burnt Mediterranean forest area into a dehesa system, 10 t ha⁻¹ of dry matter of the same sewage sludge in three different forms: fresh, composted and thermally‐dried, were added superficially to field plots of loam and sandy soils located on a 16 per cent slope. This application is equivalent to 13ċ8 t ha⁻¹ of composted sludge, 50 t ha⁻¹ of fresh sludge and 11ċ3 t ha⁻¹ of thermally‐dried sludge. The surface addition of a single application of thermally‐dried sludge resulted in a decrease in runoff and erosion in both kinds of soil. Runoff in thermally‐dried sludge plots was lower than in the control treatment (32 per cent for the loam soil and 26 per cent for the sandy soil). The addition of any type of sludge to both soil types also reduces sediment production. Significant differences between the control and sludge treatments indicate that the rapid development of plant cover and the direct protective effect of sludge on the soil are the main agents that influence soil erosion rates. Results suggest that the surface application of thermally‐dried sludge is the most efficient way to enhance soil infiltration. Copyright © 2003 John Wiley & Sons, Ltd.     

Rainfall erosion of some Alberta soils A laboratory simulation study

This laboratory rainfall simulation study investigates the effects of soil properties, slope steepness, and cover density on rainfall erosion potential of 153 soil samples collected in Southern Alberta, Canada. Simulated rainfall amount was held constant for these tests Of all the factors examined, simulated vegetative cover was found to be most significant. When cover was held constant, soil aggregate stability is the best predictor of variations of soil erodibility. Organic carbon content, texture and runoff amount (infiltration capacity) are other significant variables Slope was found to be significantly related to wash loss but not splash loss Two factors were proposed to explain the lack of relationship between splash loss and slope: (a) the proportion of splashed particles collected outside the sample plan may vary with the size of the pan; (b) soil transportability by splash increases only slightly with slope angle and therefore splash loss is only marginally related to slope steepness     

Distribution of the particle-size fractions in soddy-podzolic soils subjected to sheet erosion

Tendencies in the formation of organomineral profiles of arable agrosoddy-podzolic soils on slopes in different denudation and accumulation zones were characterized on the basis of an integrated study of the humus status of the soils (using the granulodensimetric fractionation method), the content of clay, and the composition of clay minerals. It was shown that the organomineral and mineralogical parameters of the surface-horizon transformation could be used for improving the diagnostic accuracy of soils on the slopes basing on their conventional characteristics.     

Impacts of the ancient Maya on soils and soil erosion in the central Maya Lowlands

Many studies across the central and southern Maya Lowlands of Belize, Guatemala, Honduras, and Mexico have produced records of land degradation, mostly sedimentation and soil erosion, during the ancient Maya period from before 1000 BC to the Maya Collapse of c. AD 900. This paper provides new data from two sites (Blue Creek and Cancuén), synthesizes more than a decade of the authors' research in Guatemala, Belize, and Mexico, and synthesizes other findings from this region. These research projects analyzed more than 100 excavations in upland and depression sites, cored lakes and wetland sediments, and studied sediments in the field and laboratory using radiocarbon dating, a battery of soil chemistry tests, stratigraphic analysis, magnetic susceptibility, elemental analyses, and artifact identification. Our objective was to date when sedimentation and soil erosion occurred, identify stable surfaces, and correlate them with the state of knowledge about past land use. These findings indicate three general epochs of accelerated soil erosion and identified two major paleosols. The three waves of soil erosion occurred in the Preclassic period (c. 1000 BC to AD 250), the Late Classic (AD 550 to 900), and in the last several decades. The major paleosol (‘Eklu'um’) in these sites is a well-developed Mollisol or Vertisol that started forming in the early Holocene and was buried in either the Preclassic or Classic periods (AD 250 to 900). At some sites the Eklu'um paleosol lies beneath sediments with a fainter paleosol, which in turn lies buried below Classic period and later sediments. This picture shows higher than expected soil erosion linked to the region's first pioneer farmers in the Preclassic and less than expected soil erosion in the Late Classic when population peaked and land use was the most intensive. In other regions like Cancuén, Guatemala, however, most soil erosion occurred during the Maya Late Classic (AD 550–830). Erosion here was intense but short-lived: depressions record 1–3 m of aggradation in two centuries. A third epoch of accelerated soil loss and aggradation arose with the rapid land use changes brought by new pioneers during the last several decades.     

Wind tunnel test and Cs tracing study on wind erosion of several soils in Tibet

The soils of alpine meadows and alpine grassland steppes, aeolian soils, coarse-grained soils, and farm soils cultivated from alpine grasslands in Tibet are typical soils that are suffering from different degrees of soil erosion by wind. Based on field investigations, wind tunnel experiments, and a ¹³⁷Cs trace study, this work tested the erodibility of these soils by wind, simulated the protective functions of natural vegetation and the accelerative effects of damage by livestock, woodcutting, and cultivation on erosion, and estimated erosion rates from 1963 to 2001. The results indicated that alpine meadows have the strongest resistance to wind erosion, and that undamaged alpine meadow soils generally sustain only weak or no wind erosion. Alpine grassland steppes with good vegetation cover and little damage by humans exhibit good resistance to wind erosion and suffered from only slight erosion. However, soil erodibility increased remarkably in response to serious disturbance by livestock and woodcutting; wind erosion reached 33.03 t ha⁻¹ year⁻¹. The erodibility of semi-stabilized aeolian soil and mobile aeolian soil was highest, at 52.17 and 56.4 t ha⁻¹ year⁻¹, respectively. The mean erosion rates of coarse-grained soil with various levels of vegetation coverage and of farm soil were intermediate, at 45.85 and 51.33 t ha⁻¹ year⁻¹, respectively. Restricting livestock, woodcutting, and excessive grassland cultivation are the keys to controlling wind erosion in Tibet. In agricultural regions, taking protective cultivation and management to enhance surface roughness is a useful way to control wind erosion.