Cumulative Soil Loss Research Articles

Influence of Sedum Plant on Sediment Yield from an Acid Soil under Simulated Rainfall

Managing soil erosion by water from marginal acidic soil employing traditional methods is difficult, if not impossible. The ability of Sedum sediforme (Rupestria group) to germinate, grow, and establish good ground cover under harsh environmental conditions induced us to assess its effectiveness as surface cover on an acid soil taken from mountain cuts (non-agricultural field) in Yamaguchi prefecture, Japan. This soil is widely used for road embankments in this prefecture. Two rainfall intensities, 30 and 60 mm h-1, were tested for 2 h and 1 h, respectively, on sedum grown in soil plots measuring 50 30 5 cm at three levels of vegetation cover: bare soil, 25% cover, and 75% cover. Under both simulated rainfall intensities, the sediment concentration, total soil loss, and total splashed soil decreased significantly with increasing vegetation cover. The dissipation of the raindrop impact energy by sedum cover was among the main factors contributing to the improvement of aggregate size distribution of the sediment and the total splashed soil and consequently a decrease in the seal formation on the soil surface. Compared with the bare soil, cumulative soil loss decreased by 77% and 73% under 30 and 60 mm h-1 rainfall intensities, respectively. The total splashed soil under sedum cover decreased by 30% as compared to that from the bare soil. The mean weight diameter of the surface soil aggregate increased significantly with increasing sedum cover. This is attributed to its ability to effectively protect the soil surface, thereby reducing soil aggregate breakdown and detachment, and consequently soil erosion.

Modification of a rainfall simulation procedure at runoff plots for soil erosion investigation

A modification of a rainfall simulation procedure at runoff plots for the study of erosion is suggested. It is based on the (1) physically substantiated erosion parameter of simulated rainfall A, (2) the new erosion index for natural rains AI derived from the erosion parameter A, and (3) USLE and RUSLE equations. To simplify the testing procedure and interpretation of the measured data, we use rainfall of permanent intensity I, drop size, and rainfall velocity V. To study the influence of any factor (or their combination) on the soil loss, the experiment was performed at several runoff plots, one of which was a control (fallow soil, and soil tillage performed along the slope). According to the measurement results, a graph of the dependence between the cumulative soil loss and the AI index was compiled that fits the linear regression equation. Thus, the derived equations are also valid for natural rains. The critical values of AI cr upon which the runoff and soil loss start are determined from these equations. The soil erodibility factor is calculated from the equation obtained for the control plot using the relief factor of the RUSLE equation. The influence of the studied factors on soil erosion is assessed from the comparison of equations obtained for the appropriate sites and the control. Upon the infiltration study, the water discharge is measured until its stabilization, when the steady infiltration velocity is reached. The following investigation results are cited as examples: (1) the influence of the initial soil moisture, the soil mulching with straw, and the plant cover on the soil loss; (2) application of the obtained experimental data for assessing the average annual soil loss from natural rains; and (3) the relationship between the infiltration and the rainfall erosivity index AI.

Effectiveness of hydrated lime and artificial zeolite amendments and sedum (Sedum sediforme) plant cover in controlling soil erosion from an acid soil

There are over 350 different species of sedum (Sedum spp.) and most of them can tolerate harsh conditions including very cold to hot temperatures, drought, and poor and stony soil. Sedum plants are used in rock gardens and edging flower beds, and for greening the tops of buildings, cottages, and thatched roofs. However, little is known about the effectiveness of sedum as vegetation cover in protecting soil erosion from a road embankment made of acid soil. Acid soil is believed to be vulnerable to soil erosion and is not suitable for plant growth. Liming treatment is required first before revegetation to alleviate the soil acidity; however, lime incorporation may affect the soil physical properties and, consequently, runoff and sediment generation. A rainfall simulation study was conducted to test the effectiveness of hydrated lime and artificial zeolite as amendments and Sedum sediforme (Rupestria group) as vegetation cover in controlling soil erosion from an acid soil taken from mountain cuts in Yamaguchi prefecture, Japan, where it is used for road embankment. The soil was treated with 0.5% lime and 10% zeolite. Two rainfall intensities of 30 and 60 mm/h were tested for 2 and 1 h, respectively, on sedum-growing soil plots measuring 0.50 by 0.30 by 0.05 m. Three levels of vegetation cover (bare soil, 25%, 75%) of sedum plant of 5-month growth under 2-day irrigation intervals were tested. The incorporation of hydrated lime and artificial zeolite amendments improved wet aggregate stability, which contributed to significant decrease in surface runoff, sediment concentration, and total soil loss by rain splash from the bare soil. Zeolite was more effective in promoting plant growth than the lime treatment; as a result the decrease in sediment generation and soil loss by rain splash, compared with the control, was larger with zeolite than with lime. Under both intensities of simulated rain, the sediment concentration and total soil loss by rain splash decreased significantly (P < 0.05) with increasing surface cover. The correlation between cumulative soil loss (CSL) and cumulative surface runoff was linear and significant (P < 0.001) and the slope coefficient decreased with increasing surface cover. This suggests that the sediment carrying capacity or the erosivity of the surface runoff was constant and it decreased with increasing surface cover. The sedum cover reduced the CSL up to 72 and 79% under 30 and 60 mm/h rainfall intensities, respectively. The mean weight diameter of the soil sediment transported by runoff and soil loss by rain splash were significantly increased, and therefore, the silt and clay proportion of the crust material formed on the soil surface decreased up to 6 and 16% under 25 and 75% vegetation cover, respectively. These results demonstrate that hydrated lime and artificial zeolite could be used as amendments and sedum plant as vegetation covers in controlling soil erosion from an acid soil.

A comparison of mineral-magnetic and distributed RUSLE modeling in the assessment of soil loss on a southeastern U.S. cropland

As geospatial technologies increasingly figure into resource management activities, there is a corresponding need to provide commensurately detailed high resolution spatial data. This study addresses the capacity of rapidly and cheaply acquired mineral-magnetic data to provide detailed spatially distributed assessments of long-term cumulative soil loss from agricultural fields. Model output from a simple distributed implementation of the Revised Universal Soil Loss Equation (RUSLE) and from a field-data-oriented soil magnetism-based erosion model are compared for a small Alabama (USA) farm lot. An undisturbed reference soil toposequence is used as input to the magnetism model, in contrast with earlier studies that relied on a single reference soil profile. Results from this procedure, while likely to be more dependable, proved primarily to further emphasize spatial patterns noted in prior studies. In addition, the use of a toposequence decreased the area over which RUSLE and magnetism models were in agreement. RUSLE underpredicted denudation relative to magnetism-model results over upper slopes, and overpredicted it on lower slopes. The locations of former access roads may explain underprediction on the upper slopes. The differences between the two method outcomes are discussed with regard to the potential for spatial variability in parent materials, the efficacies of non-fluvial soil redistribution processes, and the availability of detailed land use records for the 100+ years of agricultural activities at the site.

Runoff and soil loss under individual plants of a semi‐arid Mediterranean shrubland: influence of plant morphology and rainfall intensity

AbstractThe influence of plant morphology and rainfall intensity on soil loss and runoff was determined at the plant scale for three representative species of a semi‐arid patchy shrubland vegetation of east Spain, representing contrasting canopy structures and plant phenologies (Rosmarinus officinalis, Anthyllis cytisoides and Stipa tenacissima).Twenty‐seven microplots of less than 1 m2, each containing one single plant, were built to quantify runoff volume and sediment yield under the canopies of the three species. Runoff and rates of soil loss measured in these plots under natural rainfall conditions were compared with control microplots built in the bare inter‐plant areas. Precipitation was automatic‐ally recorded and rainfall intensity calculated over a two‐year period.Results indicated that individual plants played a relevant role in interrill erosion control at the microscale. Compared with a bare soil surface, rates of soil loss and runoff reduction varied strongly depending on the species. Cumulative soil loss was reduced by 94·3, 88·0 and 30·2 per cent, and cumulative runoff volume was reduced by 66·4, 50·8 and 18·4 per cent under the Rosmarinus, Stipa and Anthyllis canopies, respectively, compared with a bare surface. Anthyllis was significantly less efficient than the two other species in reducing runoff volume under its canopy. Differences between species could only be identified above a rainfall intensity threshold of 20 mm h−1. The different plant morphologies and plant compon‐ents explained the different erosive responses of the three species. Canopy cover played a major role in runoff and soil loss reduction. The presence of a second layer of protection at the soil surface (litter cover) was fundamental for erosion control during intense rainfall. Rainfall intensity and soil water status prior to rainfall strongly influenced runoff and soil loss rates. The possible use of these species in restoration programmes of degraded areas is discussed. Copyright © 2006 John Wiley & Sons, Ltd.

Management of a previously eroded tropical Alfisol with herbaceous legumes: Soil loss and physical properties under mound tillage

A study was carried out on a previously eroded Oxic Paleustalf in Ibadan, southwestern Nigeria to determine the extent of soil degradation under mound tillage with some herbaceous legumes and residue management methods. A series of factorial experiments was carried out on 12 existing runoff plots. The study commenced in 1996 after a 5-year natural fallow. Mound tillage was introduced in 1997 till 1999. The legumes – Vigna unguiculata (cowpea), Mucuna pruriens and Pueraria phaseoloides – were intercropped with maize in 1996 and 1998 while yam was planted alone in 1997 and 1999. This paper covers 1997–1999. At the end of each year, residues were either burned or mulched on respective plots. Soil loss, runoff, variations in mound height, bulk density, soil water retention and sorptivity were measured. Cumulative runoff was similar among interactions of legume and residue management in 1997 (57–151 mm) and 1999 (206–397 mm). However, in 1998, cumulative runoff of 95 mm observed for Mucuna-burned residue was significantly greater than the 46 mm observed for cowpea-burned residue and the 39–51 mm observed for mulched residues of cowpea, Mucuna and Pueraria. Cumulative soil loss of 7.6 Mg ha −1 observed for Mucuna-burned residue in 1997 was significantly greater than those for Pueraria-mulched (0.9 Mg ha −1) and Mucuna-mulched (1.4 Mg ha −1) residues whereas in 1999 it was similar to soil loss from cowpea treatments and Pueraria-burned residue (2.3–5.3 Mg ha −1). There were no significant differences in soil loss in 1998 (1–3.2 Mg ha −1) whereas Mucuna-burned residue had a greater soil loss (28.6 Mg ha −1) than mulched cowpea (6.9 Mg ha −1) and Pueraria (5.4 Mg ha −1). Mound heights (23 cm average) decreased non-linearly with cumulative rainfall. A cumulative rainfall of 500 mm removed 0.3–2.3 cm of soil from mounds in 1997, 3.5–6.9 cm in 1998 and 2.3–4.6 cm in 1999, indicating that (detached but less transported) soil from mounds was far higher than observed soil loss in each year. Soil water retention was improved at potentials ranging from −1 to −1500 kPa by Mucuna-mulched residue compared to the various burned-residue treatments. Also, mound sorptivity at −1 cm water head (14.3 cm h −1/2) was higher than furrow sorptivity (8.5 cm h −1/2), indicating differences in hydraulic characteristics between mound and furrow. Pueraria-mulched residues for mounds had the highest sorptivity of 17.24 cm h −1/2, whereas the least value of 6.96 cm h −1/2 was observed in furrow of Mucuna-burned residue. Pueraria phas eoloides was considered the best option for soil conservation on the previously eroded soil, cultivated with mound tillage.

Effect of land management on runoff and soil losses from two small watersheds in St Lucia

AbstractThe influence of land use on runoff and soil loss was assessed on two small watersheds in the Eastern Caribbean island of St Lucia, under contrasting land management regimes. The data generated from these watersheds revealed that the soil losses from an intensively cultivated agricultural watershed were 20‐times higher in magnitude than that of a forested watershed both for peak rainfall event and for total duration of analysis. This was due to higher surface runoff rates and exposure of soil to direct raindrop impact within cultivated areas. Whereas the forest canopy cover in combination with higher infiltration capacities of the forested land reduced the erosive runoff from the forest watershed and thus the soil loss. Moreover, the energy intensities of large storms in excess of 40 mm were estimated and found to range between 400 MJ mm ha−1 h−1 and 1834 MJ mm ha−1 h−1.1Megajoules‐millimeters per hectare‐hour. Soil loss from the agricultural watershed was strongly correlated (R2 = 0·85) to storm energy‐intensity (EI30). However, the correlation of soil loss with the EI30 (R2 = 0·71) was poor for the forest watershed due to the effect of canopy vegetation, which significantly reduced the energy of raindrop impact. Over the study period, cumulative soil losses were 10·0 t ha−1 for the agricultural site and 0·5 t ha−1 for the forest site.2Metric tons per hectare. The largest storm observed during the study period resulted in erosion losses of 3·78 t ha−1 and 0·2 t ha−1 from the agricultural and forest sites respectively. The regression models were developed using the measured data for prediction of runoff and soil loss over the watersheds of St Lucia under similar conditions. This study contributed towards efficient watershed management planning and implementation of suitable water conservation measures in St Lucia. Copyright © 2005 John Wiley & Sons, Ltd.

Particle-size and analytical considerations in the mineral-magnetic interpretation of soil loss from cultivated landscapes

Prior research has highlighted the potential for using soil magnetism as a rapid estimator of total cumulative soil loss on cultivated land. In this study, the influences of particle size, choice of magnetic measurement and initial conditions on a proposed model linking surface soil magnetism and soil loss are described and evaluated. Output model curves are generated for several parameter sets corresponding to different model assumptions and physical scenarios. Output is also compared to a new high-resolution surfacial magnetism data set from a cultivated site, Gilbert Farm in northwestern Alabama (USA), to further evaluate the model. Magnetic susceptibility values at Gilbert Farm range from 150 to 220 (×10−8) m3 kg−1 in a control soil profile. The original model output ranges from 180 to 192 (×10−8) m3 kg−1 and many magnetism values in the cultivated area fall outside this range. Introduction of a particle-size sorting correction factor decreases the range of output values and results in even greater numbers of out-of-range observations. However, there is evidence suggesting that particle-size distributions in the upper soil at this site are not strongly affected by differences in water erosion mechanism. Lower tillage depths cause magnetic susceptibility values to come in range, but may be unrealistic and create a twin-value problem for complex magnetic profiles. Use of the remanence (SIRM)/volume susceptibility (κlf) ratio profile, with values ranging from 35 to 120 mA m−1/10−5 SI, instead of magnetic susceptibility as used in the original model, was found to eliminate out-of-range and twin value. Anomalous magnetism values were identifiable and treatable on the high resolution magnetism maps, but other types of natural spatial variation remain at issue.

Particle-size and analytical considerations in the mineral-magnetic interpretation of soil loss from cultivated landscapes

Prior research has highlighted the potential for using soil magnetism as a rapid estimator of total cumulative soil loss on cultivated land. In this study, the influences of particle size, choice of magnetic measurement and initial conditions on a proposed model linking surface soil magnetism and soil loss are described and evaluated. Output model curves are generated for several parameter sets corresponding to different model assumptions and physical scenarios. Output is also compared to a new high-resolution surfacial magnetism data set from a cultivated site, Gilbert Farm in northwestern Alabama (USA), to further evaluate the model. Magnetic susceptibility values at Gilbert Farm range from 150 to 220 (×10 −8) m 3 kg −1 in a control soil profile. The original model output ranges from 180 to 192 (×10 −8) m 3 kg −1 and many magnetism values in the cultivated area fall outside this range. Introduction of a particle-size sorting correction factor decreases the range of output values and results in even greater numbers of out-of-range observations. However, there is evidence suggesting that particle-size distributions in the upper soil at this site are not strongly affected by differences in water erosion mechanism. Lower tillage depths cause magnetic susceptibility values to come in range, but may be unrealistic and create a twin-value problem for complex magnetic profiles. Use of the remanence (SIRM)/volume susceptibility ( κ lf) ratio profile, with values ranging from 35 to 120 mA m −1/10 −5 SI, instead of magnetic susceptibility as used in the original model, was found to eliminate out-of-range and twin value. Anomalous magnetism values were identifiable and treatable on the high resolution magnetism maps, but other types of natural spatial variation remain at issue.

Perdas de solo e água em um Argissolo Vermelho Amarelo, submetido a diferentes intensidades de chuva simulada

Este trabalho foi desenvolvido com o objetivo de se estimar as perdas de solo e água em um Argissolo Vermelho Amarelo, utilizando-se um simulador de chuvas pendular. Para testes com 35 min de duração, o simulador foi regulado adequadamente, a fim de aplicar chuvas com cinco diferentes valores de energia cinética (138, 184, 229, 275 e 321 J m-2) correspondendo às intensidades de 30, 40, 50, 60 e 70 mm h-1, respectivamente. Com os resultados obtidos, pôde-se ajustar equações de regressão entre as perdas de solo e de água, e o tempo de precipitação. Utilizando-se as equações ajustadas, obtiveram-se valores de perda que variaram de 2,83 a 26,82 g m-2 (solo) e de 0,00209 a 0,01370 m³ m-2 (água) quando a energia cinética da chuva variou de 138 para 321 J m-2, respectivamente. Comparando-se os valores simulados com os dados de campo, verificaram-se variações máximas de 3,4 e 5,7%, para as perdas de solo e água, respectivamente.

A pedological investigation of soil erosion severity on undulating land in Lithuania

It is essential that we can rapidly characterize soil erosion severity. This paper describes a field methodology to classify soil erosion severity on Dystric Albeluvisols in Lithuania. The goal was to assess cumulative soil loss due to the combined action of accelerated and natural soil erosion. Evaluation of soil erosion severity helps us understand which segments of the landscape are susceptible to erosion and therefore require soil conservation. Factors considered in evaluating soil erosion severity included the existing genetic soil horizons remaining after soil erosion processes, the estimated thickness of lost soil, and slope inclination. The estimated depth of soil loss due to the combined action of natural (geological) and accelerated soil erosion was 0.1–0.8 m on the undulating hilly topography of the Zemaiciai Uplands of Western Lithuania. Erosion rates increased with slope steepness. Soil erosion changed soil physical and chemical properties. Therefore, natural soil fertility, as indicated by spring barley yields, decreased 22, 40 and 62% on slopes of 2–5° (3.5–8.3%), 5-10° (8.3–17.7%) and 10–15° (17.7–26.3%), respectively, compared with flat land. Crop yield was strongly negatively correlated (R2 = 0.79, P < 0.001, n = 138) with erosion severity. Due to pedological translocation, non-eroded Dystric Albeluvisols had relatively little clay and silt in eluvial (E) soil horizons, with their relative accumulation in illuvial (Bt) horizons . Thus, severely eroded soils had argillaceous top soils, due to exhumation of Bt horizons. The suggested classification system enables rapid assessment of past soil erosion severity and may have broader applicability in areas of Podzolic soils. Key words: Dystric Albeluvisols, soil erosion severity, slope steepness, soil properties, pedology

PRE–WETTING EFFECT ON FURROW IRRIGATION EROSION: A FIELD STUDY</

Flowing water quickly saturates dry surface soil as water advances in irrigation furrows. Conversely, rain wets surface soil before runoff occurs. Rapid wetting destroys soil aggregates as water quickly displaces trapped air. Slowly increasing soil water content prior to saturation increases aggregate stability. We hypothesized that instantaneous wetting of dry surface soil during furrow irrigation results in greater soil erosion than if furrow soil was pre–wet immediately before irrigation. We conducted ten irrigation trials on 27–m long furrows in three different fields. Soil was pre–wet by surface drip irrigation (12 to 14 mm) or by lightly spraying with water (1.3 mm). Pre–wetting with drip irrigation significantly (P < 0.05) reduced soil loss for 5 of the first 7 irrigations compared to dry soil. The pre–wetting effect on soil loss was not always dramatic, but cumulative soil loss for the first seven irrigations was significantly different among the three treatments: 16, 30, and 56 Mg ha –1 for drip, spray, and dry treatments, respectively. The dry treatment never had less soil loss than either pre–wetting treatment. Pre–wetting furrow soil by spraying apparently did not add enough water to stabilize soil aggregates and decrease soil erosion for most irrigations. This study demonstrated that erosion was greater when water flowed over initially dry soil, which is typical with furrow irrigation, compared to water flowing over initially wet soil, which occurs during rain.

Field Assessment of the Effect of Cumulative Soil Loss on Soil Productivity

(2001). Field Assessment of the Effect of Cumulative Soil Loss on Soil Productivity. East African Agricultural and Forestry Journal: Vol. 67, No. 1-2, pp. 129-145.

Flow Interruption Effects on Intake Rate and Rill Erosion in Two Soils

Efficiency of surface irrigation is often low because of poor infiltration uniformity, resulting from relatively long periods of infiltration at the upstream end and short periods of infiltration at the downstream end of the field. Surge irrigation, the intermittent supply of water to furrows, generally reduces soil intake rate (IR) and improves moisture uniformity over the entire field. However, IR reduction varies from one irrigation scheme to another, depends on soil and water properties, and is difficult to predict. A laboratory study using miniflumes was designed to investigate the effect of interrupted flow on IR and soil loss from short rills. Two soils differing in their textures, a silt loam (Calcic Haploxeralf) derived from loess and a clay soil (Typic Haploxerert), were studied. Intake rate in the clay soil was greater than that in the silt loam. Therefore, different inflow rates were applied to the two soils to achieve similar runoff flow rates from the two soils. Cumulative infiltration decreased from 646 mL in continuous flow to 539 mL in interrupted flow for the silt loam and from 1142 to 1068 mL in the clay soil. Interrupted flow also reduced cumulative soil loss by 84% in the clay soil but had only a small effect on soil loss from the silt loam. However, when flow rate was increased from 80 to 320 mL min−1, interrupted flow reduced soil loss in the silt loam as much as in the clay soil. Consolidation of the soil surface and formation of cohesive forces between soil particles of the silt loam with unstable structure during flow interruption was suggested as the explanation for the effect of flow interruption on intake rate and soil detachment. These results need to be verified in field experiments.

A probabilistic approach for predicting rainfall soil erosion losses in semiarid areas

The implementation of soil and water conservation structures in semiarid areas, usually poses a difficult design problem. This is, in large part, due to the high variability of rainfall and the huge potential impact of extreme hydrologic events on structures and on the landscape in general. Magnitudes of runoff and soil loss or sedimentation rates in those environments are better not assessed by conventional modelling techniques, which tend to average out event magnitude and recurrence variability in time and space. A probability-based approach is proposed here to analyse and predict rainfall erosion losses. The maximum annual storm and its associated erosivity is used as a core element in the assessment of annual interrill and rill erosion rates. Frequency and cumulative soil loss distributions are obtained by combining verified annual and maximum daily rainfall frequency distributions with a proposed erosion algorithm. This stochastic representation of erosion permits to evaluate soil losses for the maximum annual storm, as well as annual erosion rates as a function of recurrence interval. The proposed method was verified with a short series of measured soil loss data in Cape Verde. The physical basis underlying the prediction algorithm and method in general, could be sustained by experimental data and field survey evidence. The method seems applicable to arid and semiarid ecosystems with a high seasonal concentration of precipitation and with rainfall limited to only a few major storm events.

Seeding and Mulching Treatments as Conservation Measures of Two Burned Soils in the Central Ebro Valley, NE Spain

The effectiveness of seeding introduced species, with or without straw mulching, was tested as a measure of post-fire erosion control in gypsiferous (Xeric Haplogypsid) and calcareous soils (Xeric Torriorthent) in Central Ebro Valley (NE-Spain). Paired control, seeding, and combined seeding and mulching plots were established in four replicated plots for each soil tested. Seeding rate was 30 g m -2 and straw mulch was applied at 100 g m -2 in each plot. Plant projective cover (total and specific), plant biomass, bare soil cover and sediment yield were determined over a 2-year period. During the first year of sampling, species introduced by seeding increased plant cover (about 30%) without significant differences observed between soils. Plant cover was similar in seeding-only and seeding-mulching treatments, although the latter treatment significantly enhanced plant weight. During the second year these differences disappeared because species introduced by seeding practically did not survive. So, the introduced herbs did not interfere with native plants. Bare soil cover remained significantly lower in treated plots than on the control plots for both soils during both years of sampling. In the second year, the reduction of bare soil was attributed to both the straw mulch and litter from the seeding species. Soil protection was significantly higher in calcareous soils than in gypsiferous soils which is related to their physical and chemical properties. Cumulative sediment yield decreased significantly over time with both treatments on both soils. Soil losses from control plots were three times higher than seeding plots and 3.3 times higher than from seeding and mulching plots in gypsiferous soils. Soil losses from control plots were two times higher than from seeding plots and 2.7 times higher than the combined seeding and mulching plots in the calcareous soils. Cumulative soil loss was higher from the gypsiferous soils than from the calcareous soils due to the lower plant cover.

Statistical Distributions of Soil Loss from Runoff Plots and WEPP Model Simulations

AbstractSoil conservation measures may be better designed with the knowledge of daily distributions of erosion. Collecting reliable data to determine daily erosion distributions is costly; however, new process‐based soil erosion models have the potential to simulate extended records. The objectives of this study were to analyze frequency distributions of measured daily soil loss values and to determine if the Water Erosion Prediction Project (WEPP) model accurately reproduced statistical distributions of the measured daily erosion series. A Log‐Pearson Type III (LP III) distribution was fitted to measured and WEPP‐predicted soil loss values from six sites for periods ranging from 6 to 10 yr. Cumulative soil loss as a function of storm recurrence interval was used to show the relative contributions of large and small storms to total soil loss at each site. Results showed that both measured and predicted frequency curves fell within the 95% confidence range of the LP III distributions. This was true both using weather data from the site for the period of monitoring as well as when using synthetic weather series generated with the CLIGEN model. Thus the results were encouraging in terms of using WEPP in conjunction with CLIGEN to generate long‐term daily soil loss frequency distributions, which can contribute toward alleviating the problem of having only a short monitoring period for measured erosion. Cumulative soil loss results indicated that large storms contributed a major portion of the erosion under conditions where cover was high, but not necessarily under conditions of low cover.

The impact of erosion on soil productivity—an experimental design applied in são paulo state, brazil

Soil erosion is the principal threat to agricultural sustainability, affecting both the characteristics of the in situ soil and its productive potential. However, soils vary in their resilience and there are very few empirical data upon which to appreciate the degree and type of impact on the soil caused by erosion. This paper describes an experiment designed to generate such data based on soil loss and runoff plots, and it reports on nearly nine years of experience with the design at the Instituto Agronômico, Campinas, Brazil on a Latosol (Oxisol). After seven years of erosion induced by four levels of artificial cover, the effective rainfall on the most eroded soil was 20 percent less than on the control full cover. Crop yields were also found to be significantly affected: in 1995 by nearly 700 kg/ha and in 1996 by over 1000 kg/ha—a 50% decline in yield, amounting to a loss of 4 kg/ha of maize per tonne of cumulative soil loss. Losses of nutrients (organic C, P, K, Ca and Mg) in the runoff and eroded soil were also significant with far higher levels of loss associated with the eroded sediment. Changes in the in situ soil were less clear, but a test of trends showed that the decreases in organic matter and increases in acidity could unambiguously be attributed to soil erosion. Average enrichment ratios of the eroded sediment were 1.3 for organic C, 2.6 for P, 0.7 for K, 1.3 for Ca and 1.2 for Mg. Erosion has also affected the maize quality—mainly N, Ca and B nutrient content. Through these various measures, we conclude that seven years of induced erosion has had a marked effect on soil productivity, and for the first time we are now in a position to begin calculating the financial impact of the erosion process on future yields and farmer livelihoods.

Soil Erosion Effects on Soil Properties in a Highland Area of Central Kenya

AbstractOne of the most important features that is neglected in many soil erosion studies in Africa is the monitoring of changes to the soil during the progress of the experiment. Objectives of this study were therefore to monitor runoff, soil loss, and enrichments of eroded soil material and to assess the effect of cumulative soil loss on soil chemical properties of an Alfisol in one of the high‐potential areas of Central Kenya highlands.Runoff, soil loss, and enrichments of eroded sediments were measured on newly opened ground from 1991 to 1992. Annual rainfall was 948 and 1125 mm for 1991 and 1992, respectively. Soil loss ranged from 0.8 to 247.3 t ha−1, and runoff ranged from 1 to 89 mm. No significant correlations were observed between enrichment ratios (ER) and soil loss. The ER were ≥ 1 and sediments were mostly enriched with P and Na. The P and Na concentrations were 4 to 10 and 2 to 3 times the source material, respectively. Sediment from the plots was 247 to 936% richer in P than the soil from which it originated. Changes in soil pH, percentage organic C, and percentage total N following erosion were significantly correlated with cumulative soil loss (r values of 0.77, 0.59, and 0.71, respectively, n = 20). The data indicated that nutrient loss due to erosion is one of the major causes of soil fertility depletion of Kenyan soils.

Erosion Response of a Disturbed Sagebrush Steppe Hillslope

AbstractLand management activities that disrupt surface vegetation cover pose a serious threat to the long‐term stability of buried‐waste sites located within the semiarid sagebrush (Artemisia tridentata Nutt.) steppe region of the northwestern USA. In this study, we evaluated the erosion response of a sagebrush hillslope subjected to three vegetation cover treatments: natural (undisturbed), bare (plant canopy and litter cover removed), and clipped (canopy removed). A rotating boom rainfall simulator was used to apply rain at 60 or 120 mm/h intensities to runoff plots (3.0 m by 10.7 m) with dry, wet, and very wet antecedent moisture conditions, and during two late and one early summer seasons. Supplemental overland flow was added at the upper end of each plot to simulate increased slope length during very wet runs. Maximum soil loss rates on the natural, clipped, and bare treatments were, respectively, 1, 5, and 216 mg/m2 per s during the 60 mm/h rainfall intensity, and 13, 79, and 1473 mg/m2 per s during the 120 mm/h rainfall intensity. Cumulative soil loss was typically 100 to 1000 times greater on the bare treatment than on the natural or clipped treatments. Increases in simulated slope length produced a near linear increase in soil loss from the bare treatment plots (about 0.02 g/m2 per s soil loss per m of slope length) until 30 m, after which the effect of slope length declined. Surface crust development and mound‐intermound microtopography played important roles in governing soil detachment and transport on the hillslope. Despite high rainfall intensity and surface runoff rates, rill erosion was negligible on both the undisturbed and disturbed portions of the hillslope.