Interrill Soil Loss Research Articles

Rill and Interrill Soil Loss Estimations Using the USLE-MB Equation at the Sparacia Experimental Site (South Italy)

A reliable prediction of event soil loss at the plot scale can be obtained by Universal Soil Loss Equation (USLE)-type models. For the Sparacia site (South Italy), the USLE-MB model was recently developed, in which the effect of the erosive agent is modeled using the rainfall erosivity index of the USLE by a power b1 > 1 of the runoff coefficient QR. In this investigation, the model is parameterized separately using plot data collected for rill and interrill events that occurred in the Sparacia experimental area. The values b1 = 1.406 and b1 = 1.012 were obtained for the interrill and rill databases, respectively, which revealed a different effect of the runoff coefficient on soil loss due to the two erosive processes. Different relationships expressive of topographic factors were also deduced. The USLE-MB estimation performance significantly improved when operating the distinction between the two databases compared with the model parameterized on the complete database. The model was particularly reliable in estimating the highest event soil loss values, which were associated with the occurrence of rills. Finally, the proposed parameterization procedure lends itself to being tested in the framework of empirical soil loss modeling.

Rare earth elements tracing interrill erosion processes as affected by near-surface hydraulic gradients

Understanding interrill erosion processes is important for the development of process-based interrill erosion models. The objectives of this study were to identify dominant interrill erosion processes and to improve interrill erosion predictive equations. Six rare earth elements (REEs) were applied in different slope segments and soil layers to track sediment movement and deposition in order to gain insights into the near-surface hydraulic gradient-affected (drainage, saturation, and seepage conditions) interrill erosion processes under three rainfall intensities of 30, 60, and 90 mm h−1. The results showed that the contributions of interrill soil losses from each tracer segment to the total soil loss first increased and then decreased along the slope under drainage/saturation conditions, while they continuously increased under seepage conditions. Transport by raindrop-induced and sheet flow-driven rolling, creeping, or sliding was the dominant transport mode. The dominant process of interrill erosion was transport-limited under drainage/saturation conditions and detachment-limited under seepage conditions. Under transport-limited conditions, raindrop-induced transport was more relevant than raindrop-impacted sheet flow-driven transport. However, the raindrop-impacted sheet flow-driven transport was more important than raindrop-induced transport under detachment-limited conditions. The response relationships of sediment transport capacity and soil detachment rate to the near-surface hydraulic gradient, rainfall intensity, slope gradient, and slope length could be described well via power equations (R2 ≥ 0.81). The R2 values of the power equations were 2.5 %–1840.0 % higher than those calculated with existing interrill erosion empirical equations, and the average absolute relative error (RME) derived in this study decreased by 38.0 %–87.2 %. In addition, interrill erodibility should be further divided into interrill sediment transportability under transport-limited conditions and interrill detachability under detachment-limited conditions.

Relationship between remote sensing data and field-observed interril erosion

Abstract: The objective of this work was to evaluate the relationship between different remote sensing data, derived from satellite images, and interrill soil losses obtained in the field by using a portable rainfall simulator. The study was carried out in an area of a hydrographic basin, located in Médio Paraíba do Sul, in the state of Rio de Janeiro - one of the regions most affected by water erosion in Brazil. Evaluations were performed for different vegetation indices (NDVI, Savi, EVI, and EVI2) and fraction images (FI), derived from linear spectral mixture analysis (LSMA), obtained from RapidEye, Sentinel2A, and Landsat 8 OLI images. Vegetation indices are more adequate to predict soil loss than FI, highlighting EVI2, whose exponential model showed R2 of 0.74. The best prediction models are generated from the RapidEye image, which shows the highest spatial resolution among the sensors evaluated.

Impact of subsurface rock fragments on runoff and interrill soil loss from cultivated soils

ABSTRACTField and laboratory studies have indicated that rock fragments in the topsoil may have a large impact on soil properties, soil quality, hydraulic, hydrological and erosion processes. In most studies, the rock fragments investigated still remain visible at the soil surface and only properties of these visible rock fragments are used for predicting runoff and soil loss. However, there are indications that rock fragments completely incorporated in the topsoil could also significantly influence the percolation and water distribution in stony soils and therefore, also infiltration, runoff and soil loss rates. Therefore, in this study interrill laboratory experiments with simulated rainfall for 60 min were conducted to assess the influence of subsurface rock fragments incorporated in a disturbed silt loam soil at different depths below the soil surface (i.e. 0.001, 0.01, 0.05 and 0.10 m), on infiltration, surface runoff and interrill erosion processes for small and large rock fragment sizes (i.e. mean diameter 0.04 and 0.20 m, respectively). Although only small differences in infiltration rate and runoff volume are observed between the soil without rock fragments (control) and the one with subsurface rock fragments, considerable differences in total interrill soil loss are observed between the control treatment and both contrasting rock fragments sizes. This is explained by a rapid increase in soil moisture in the areas above the rock fragments and therefore a decrease in topsoil cohesion compared with the control soil profile. The observed differences in runoff volume and interrill soil loss between the control plots and those with subsurface rock fragments is largest after a cumulative rainfall (Pcum) of 11 mm and progressively decreases with increasing Pcum. The results highlight the impacts and complexity of subsurface rock fragments on the production of runoff volume and soil loss and requires their inclusion in process‐based runoff and erosion models. Copyright © 2011 John Wiley & Sons, Ltd.

Effectiveness of wood waste material for improving infiltration and reducing interrill soil loss in clay-rich volcanic soil

<h3>Objective</h3> Gastric sensorimotor function, abuse history, ‘trait’ and ‘state’ psychological factors and ‘somatisation’ all play a role in functional dyspepsia (FD) and its associated impaired quality of life (QoL), but their interplay remains poorly understood. We aimed to test a comprehensive, a priori hypothesised model of interactions between these dimensions in FD. <h3>Design</h3> In 259 FD patients, we studied gastric sensitivity with a barostat. We measured abuse history (sexual/physical, childhood/adulthood), ‘trait’ (alexithymia, trait anxiety) and ‘state’ (positive/negative affect, depression, panic disorder) psychological factors, somatic symptom reporting (somatic symptom count, dyspepsia, irritable bowel syndrome and fatigue symptoms) and QoL (physical, mental) using validated questionnaires. Confirmatory factor analysis (CFA) was used to assess whether four a priori hypothesised latent variables (‘abuse’, ‘trait affectivity’, ‘state affect’ and ‘somatic symptom reporting’) were adequately supported by the data. Structural equation modelling (SEM) was used to test the a priori hypothesised relationships between these latent variables and the observed variables gastric sensitivity and QoL. <h3>Results</h3> Both the CFA and SEM models fitted the data adequately. Abuse exerted its effect directly on ‘somatic symptom reporting’, rather than indirectly through psychological factors. A reciprocal relationship between ‘somatic symptom reporting’ and ‘state affect’ was found. Gastric sensitivity influences ‘somatic symptom reporting’ but not vice versa. ‘Somatic symptom reporting’ and ‘trait affectivity’ are the main determinants of physical and mental QoL, respectively. <h3>Conclusions</h3> We present the first comprehensive model elucidating the complex interactions between multiple dimensions (gastric sensitivity, abuse history, ‘state’ and ‘trait’ psychological factors, somatic symptom reporting and QoL) in FD.

Interrill erosion from disturbed and undisturbed samples in relation to topsoil aggregate stability in red soils from subtropical China

Abstract The assessment of soil erodibility to water erosion in the field is often expensive and time-consuming. This study was designed to reveal the effects of aggregate breakdown mechanisms on interrill erosion dynamics and develop an improved model for assessing interrill soil loss, which incorporated the soil aggregate stability tests as a substitute for the interrill erodibility parameter, from both disturbed and undisturbed samples for red soils in subtropical China. Six cultivated areas of sloping land with red soils were selected, and topsoil aggregate stability was analyzed using the Le Bissonnais method to determine the different disaggregation forces. Laboratory rainfall simulations were designed to distinguish the effects of slaking (at different wetting rates) and mechanical breakdown (with and without screening) on soil erosion characteristics. Field rainstorm simulations with medium and high rainfall intensities were conducted on runoff plots (2 m 1 m) with slope gradients varying from 10% to 20% for each soil type. A new instability index, Ka , which considers aggregate breakdown mechanisms in interrill erosion processes, was proposed based on the disturbed sample results. Ka showed a close relationship with erosion rates in both disturbed and undisturbed samples. Following from the results of undisturbed sample experiments, Ka was used as a substitute for the erodibility factor, and introduced into the WEPP model, establishing a new erosion predication formula for red soils which had a good correlation coefficient ( R 2 = 0.89**). This research made a good attempt at estimating the interrill erosion rate on the basis of aggregate stability from simple laboratory determinations. These results extend the validity of soil aggregation characterization as an appropriate indicator of soil susceptibility to interrill erosion in red soils from subtropical China. The formula based on the instability index, Ka , has the potential to improve the methodology used for assessing interrill erosion rates.

Temporal changes on the effect of rock fragments in interrill soil loss: a simulation experiment and a simple descriptive model

Soils with rock fragments have been studied under several aspects in the last years. Research shows that a single pattern in the erosional response of these soils to rainfalls is not always found. In order to contribute to the understanding of this topic, an experiment was carried out, simulating interrill areas covered by rock fragments. This paper specifically aims at presenting and discussing temporal changes on sediment exported from such areas, also introducing a simple descriptive model to represent soil loss temporal evolution. Small bottom perforated boxes, 612 cm2 area, were filled with a silt-loam fine earth, very poor in organic matter, covered with simulated rock fragments and leaned at 10% slope gradient. The experiment comprised the exposure to 240 mm natural rainfall of 48 boxes corresponding to selected combinations, 4 replicates each, of rock fragments cover (0, 17, 30 and 66%), size (2, 4 and 10 cm), form (rectangular and circular) and position (resting on top and embedded). During the experiment boxes were kept under near saturation soil water conditions. Water and soil exported from the boxes as infiltration, runoff, wash and splash were measured after each period of precipitation. Recorded values of soil loss plotted against precipitation, both expressed in cumulative terms, follow a sigmoid curve. This pattern of response was interpreted as a result of crust formation on soil surface exposed to rainfalls, a hypothesis suggested by observations during the experiment and confirmed at its end. Parameters of this model were related with rock cover and characteristics. The effect of rock fragments on soil loss varies with time, a conclusion that must be taken into account when interpreting either results from experiments with different durations or the evolution of stoniness on eroding surfaces.

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

AbstractIt 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.

Soil mineralogy effects on seal formation, runoff and soil loss

Interaction between clay particles is one of the main factors responsible for soil aggregation. Therefore, soil mineralogy, which has substantial effects on clay dispersion, may also influence aggregate stability, seal formation, runoff and soil loss. In spite of this, the effects of soil mineralogy on these phenomena have received much less attention in the literature than those of other soil properties. This paper reviews the effects of soil mineralogy on aggregate stability, seal formation and micromorphology, and on the associated infiltration rate (IR), runoff and soil loss. The paper is focused mainly on the authors' previous studies. In order to determine these effects, various soils with different mineralogy were collected from Israel, South Africa and Kenya. In these soils, the aggregate stability was determined under fast wetting conditions, and the IR and the interrill soil loss were determined using rainfall simulator of a rotating disk type. The micromorphology of the crust, which was developed at the soil surface by the rainstorm, was determined by scanning electron microscope. Clay mineralogy was found to be a dominant factor in controlling aggregate stability, seal formation, soil IR and interrill soil loss. The phyllosilicate soils, which were review in this paper, were divided into two main groups: (i) stable soils with final IR>8.0 mm h −1 and (ii) unstable soils with final IR<4.5 mm h −1. These two soil groups differ in their mineralogy. Kaolinitic and illitic soils that do not contain smectite were stable soils and less susceptible to seal formation. In contrast, kaolinitic and illitic soils that contain some smectite and smectitic soils were unstable. Examination of the susceptibility of 21 phyllosilicate soils to interrill erosion indicated that these soils could be divided into three groups. Soil loss was higher for unstable soils than for stable soils, but the soil loss of the smectitic soils was significantly higher than that of the unstable soils, which contained kaolinite or illite as the dominant clay.

Ecological erosion control on coal-spoil banks: an evaluation

The relative merits of slope protection by forestation and by mechanical protection with contour wattles are evaluated for a steep, 17–18°, embankment of coal-briquette spoils, where drought and spoil properties prevent the establishment of ground vegetation. Ground loss, monitored for 6 years by erosion pins, shows that both treatments reduce the development of surface flow pathways. However, inter-rill soil losses are not significantly smaller on the wattle-protected than on the unprotected control slope. By contrast, ground losses under forest (1.9 mm year −1) are significantly smaller than on either the unprotected slope (7.0 mm year −1) or that protected by wattles (6.2 mm year −1). Ground losses from sites with >20% leaf litter cover average 0.54 mm year −1 and never exceed 3.5 mm year −1.

An improved rainfall erosivity index obtained from experimental interrill soil losses in soils with a Mediterranean climate

The most common index to predict rainfall erosivity is based on the kinetic energy (KE) and the maximum intensity in a 30-min period. However, rainfalls recorded in the Mediterranean climate are, in most cases, the short duration (<30 min) and the high intensity. The goal of this work was to improve rainfall erosivity indices for the Mediterranean conditions from experimental interrill soil losses measured in natural conditions in 1-m 2 plots. The plots were located in three vineyard fields, whose soils are classified as Typic Calcixerept, Typic Xerofluvent and Typic Xerorthent, and ploughed at the same time as the vineyards. Soil losses and runoff were collected after each rainfall event during 1 year and rainfall data were obtained from bucket gauges installed at the same places. Mean intensity of the storms was less than 10 mm h −1, but maximum intensities in short periods were as high as 103 mm h −1. Kinetic energy was calculated using different expressions proposed in the literature and improved with our data obtained with a disdrometer type Joss Waldvogel. Soil losses were related to kinetic energy and to different combinations of kinetic energy and maximum intensity for different time intervals. The best correlation was that obtained between soil losses and the product of kinetic energy by Sempere Torres and the maximum intensity in 5-min intervals ( I 5), which explained more than 80% of the variability. When a surface crust was formed quickly there was no significant relation between soil loss and rainfall parameters.

Relações da erosão em entressulcos com o tipo e com a quantidade de resíduo vegetal na superfície do solo

Os resíduos vegetais na superfície do solo são muito efetivos em dissipar a energia de impacto das gotas de chuva, além de constituírem barreira física ao livre escoamento superficial da água. A presença desses resíduos em contato direto com a superfície do solo pode influenciar, decisivamente, a erosão em entressulcos. Este estudo objetivou avaliar as relações da erosão em entressulcos com a quantidade de resíduo vegetal em cobertura e verificar as diferenças nessas relações para palha de milho e palha de trigo. Um experimento de campo foi instalado no Centro de Pesquisa de Florestas e Conservação do Solo da FEPAGRO, em Santa Maria, RS, em Podzólico Vermelho-Escuro franco-arenoso. As parcelas experimentais mediam 0,50 x 0,75 m, com a maior dimensão no sentido do declive do terreno, que era de 0,17 m m-1, arranjadas em quatro blocos completos ao acaso. Palhas de milho e de trigo, picadas em fragmentos de 7,5 cm, foram distribuídas, nas parcelas, sobre solo recentemente preparado, em quantidades de 0,00, 0,05, 0,10, 0,20, 0,40 e 0,80 kg m-2. Em seguida, foi aplicada uma chuva simulada de intensidade média de 67 mm h-1 e duração de 90 min. As taxas de perdas de solo e água por erosão em entressulcos variaram ao longo da chuva, dependendo da quantidade de resíduo vegetal existente na superfície do solo, porém não foram observadas variações significativas em relação ao tipo de palha. A relação da erosão em entressulcos com a fração do solo coberto (dada em função da quantidade de palha) pode ser expressa por meio de uma equação exponencial. Por ser um modelo simples, com medidas de fácil obtenção, sugere-se esse modelo para estimar o subfator cobertura do solo em entressulcos por resíduos em contato direto com a superfície.

Soil loss by splash and wash during rainfall from two loess soils

Physical processes occurring during surface seal formation through a rainstorm are well understood, but limited information is available regarding the quantity and particle size distribution of splash and runoff at certain time intervals. In this study, we evaluated the quantity and particle size distribution of suspensions of both splash and interrill runoff in two loess soils with different mineralogy and aggregate stability, and somewhat different particle size distribution, but similar organic matter content. The soils were subjected to simulated rainstorms of ∼ 40 turn h − 1 and 100 mm h −1 intensities. The amount of splash was about four times higher for the Saskatchewan soil (Typic Haploboroll) with high smectite than for the Grenada soil (Typic Fragiudalf) which is rich in Fe-oxyhydroxides. The amount of splashed material and sediment load increased with increased rainfall intensity for both soils. Splash was decreased after wetting of the soil surface. The decrease in splash rate was more rapid with high rainfall intensity. The amount of clay size particles of the splash was similar to the original soil material. Micromorphological observations confirmed the fluctuations in clay content with time, at the very surface. Soil materials splashed were much higher (10 to 20 times) than the interrill runoff losses. The latter was controlled by the rainfall intensity. The soil material from Saskatchewan, produced more than 11 Mg ha − 1 of interrill runoff with low rainfall intensity. High rainfall intensity produced 10 times more soil loss than low rainfall intensity. High amount of soil loss clearly shows that the Saskatchewan soil would benefit from erosion control measures. Both rainfall intensities removed preferentially more clay from the Saskatchewan B horizon material. This has important agronomic and environmental implications for this soil. Interrill soil losses from the Granada A horizon material were much less, with no clear evidence of preferential removal of clay size particles.

Prewetting Rate and Aging Effects on Seal Formation and Interrill Soil Erosion1

Seal formation and interrill soil erosion are affected by antecedent soil water content. We hypothesized that other time-dependent variables, such as prewetting rate and aging duration, would also affect seal formation and interrill soil loss. Aggregates (4-9.5 mm) from a Calcic Haploxeralf and a Typic Chromoxerert were packed in 400 × 200 mm pans, placed under a rainfall simulator, and prewetted by either (i) a matrix potential of -0.2 kPa, or (ii) 5 mm of rain at rates of 1, 6, or 30 mm h-1. After prewetting, the aggregates were left to age for 15 min or 18 h, then subjected to 60 mm of distilled water simulated rainfall of moderate (12.4 kJ m-3) kinetic energy. Final infiltration rate increased from 5.0 to 26.6 mm h-1, percent runoff decreased from 59.1 to 2.5, and soil loss decreased from 302 to 5.4 g m-2 as prewetting rate decreased from 30 to 1 mm h-1 in the Typic Chromoxerert; similar results were observed in the Calcic Haploxeralf. For aggregates from both soils, aging increased the final infiltration rate and decreased runoff, only when partial slaking was achieved by slow and moderate prewetting rates. Conversely, 18 h of aging also effectively decreased soil loss in the fast prewetting rate in the aggregates of both soils. Surface sealing was enhanced by aggregate slaking and breakdown. Slaking was reduced by slow prewetting and cohesive forces. Aging increased the cohesion forces between soil particles and reduced the latter's susceptibility to sealing and erosion.

Laboratory Determination of Interrill Soil Erodibility

AbstractLaboratory soil pans and rainfall simulators have been used to study fundamental erosion processes affecting interrill soil loss. Problems exist when laboratory results are extended to those determined under field conditions. Experimental methodology influences a soil's interrill erodibility and interrill erodibility ranking among soils. We compared interrill soil loss and erodibility data from two erosion pans with field data from identical soils. Three plot size‐rainfall simulator methodologies were used: (1) 0.14‐m2 lab pan under a constant drop size (4.6 mm) rainfall simulator, (2) 0.32‐m2 lab pan with soil border areas under an oscillating nozzle (2.3 mm median drop diameter) rainfall simulator, and (3) 1‐m2 field plots under the same rainfall simulator as used in Method 2. Soil loss was measured at 5‐min intervals. Interrill erodibility (Ki) was calculated from two equations (E = KiiI2 and E = KiqIq) using measured soil loss (E), rainfall intensity (I), and flow discharge (q) values. The interrill erosion equation, methodology, time, and initial water content influenced calculated Ki values. Soil loss and Ki values from Method 1 did not correlate with and were greater than corresponding values from Methods 2 and 3. Soil loss and Ki values from Method 2 were correlated (r = 0.56 to 0.79) with corresponding values from Method 3. The Kiq values decreased with time and were a function of soil properties related to soil detachment and sediment transport. The Kii values (i) increased with time, (ii) were primarily a function of soil properties related to soil detachment only, and (iii) did not account for infiltration and runoff differences among soils.

Evaluation of the CREAMS model. 4. Derivation of interrill erodibility parameters from laboratory rainfall simulator data and prediction of soil loss under a field rainulator using the derived parameters

This study investigated the use of laboratory rainfall simulator data for the derivation of CREAMS (chemicals runoff, and Erosion from Agricultural Management Systems) interrill erodibility parameters K and nbov. The laboratory rainfall simulator method of collecting erosion data was validated using the surface of an Irving clay (black earth). Reliable CREAMS K and nbov values for this Irving clay had previously been determined from field rainulator data. In this study, CREAMS erodibility parameters were derived for the same soil type using laboratory rainfall simulator data. The values of these parameters fell within the 90% confidence region for parameters derived from non-rilled field rainulator plots. Both nbov and K, determined from laboratory data, varied with slope, indicating that the slope gradient response predicted by CREAMS may not be applicable for interrill erosion on short, steep slopes. For slopes &lt; 8%, a default value of nbov = 0.01 with K = 0.37 (English units) gave good predictions of observed soil losses. However, for slopes &gt; 8%, there was an over-prediction of observed soil loss up to 60% when these parameter values were used. The data indicate that for predictions of interrill soil loss from steeper slopes, nbov and K values should be adjusted to achieve greater accuracy. When values of K = 0.37 and nbov = 0.01 were used with field data obtained from a site with a slope of 4%, predicted interrill soil losses correlated well with both the estimated interrill component of measured field soil losses and observed soil losses from interrill field plots. It is concluded that the laboratory rainfall simulator used in this study produces hydrology and erosion data that can be used to derive realistic CREAMS parameters for interrill erosion.

Interrill Erodibility Affected by Cropping Systems and Initial Soil Water Content

The effects of continuous soybean and continuous corn cropping systems and initial water content (IWC) of the soil on runoff, soil loss, and interrill erodibility were studied in the laboratory. Samples of a Mexico silt loam (Udollic Ochraqualf) were packed in 0.3-m-wide 1.0-m-long soil beds and subjected to a series of simulated rainfall events. Differences in measured runoff and soil loss between the cropping systems were less than 1.0%. The IWC did not affect soil loss during the initial event, but it had a significant effect (p < 0.05) during the following event where an increase in mean IWC from 4 to 15% decreased mean soil loss from 12.9 to 10.7 g min1 m2. Cropping did not influence interrill erodibility (Ki) calculated from a power relationship with rainfall intensity. There was a negative linear relationship between Ki and IWC. Calculating Ki from rainfall intensity and runoff rate improved the relationship between Ki and IWC. Our results indicate that interrill soil losses and erodibility are sensitive to IWC and need to be considered in interrill erosion research and modeling, particularly for silt loam soils. Our results also indicate that including a runoff rate term in the equation used to predict interrill erosion will improve its prediction accuracy.

Seal Formation and Interrill Soil Erosion

AbstractInterrill soil erosion depends primarily on soil detachment by raindrop impact (splash) and the transport capacity of thin sheet flow. Both splash and sheet flow erosion depend on soil surface properties. The purpose of this study was to investigate the effect of seal formation on interrill soil loss. Samples of three soil types — a Typic Chromoxerert, a Calcic Haploxeralf and a Typic Rhodoxeralf — with various naturally occurring exchangeable sodium percentage (ESP) levels were used. The soils were exposed to simulated rain using three different waters: distilled (DW), tap (TW), and saline (SW). The electrical conductivity (EC) of the TW and SW was 0.8 and 5.0 dS m−1, respectively. Seal formation was characterized by the final infiltration rate (FIR) and amount of runoff. Seal formation was enhanced with an increase in soil sodicity and a decrease in water salinity for each soil type. Nearly 70% of the variation in FIR (and seal formation) was explained by water salinity and soil ESP. Most of the variation in soil loss was explained by clay content, soil ESP, and water salinity. With the exception of samples with ESP &lt;5 rained on with DW, soil loss increased linearly with an increase in soil clay content. Seal strength, as inferred from surface pitting by impacting raindrops, decreased with an increase in clay content, and was inversely related to soil erosion.

RELATIONSHIPS BETWEEN RAINFALL INTENSITY AND THE INTERRILL SOIL LOSS-SLOPE STEEPNESS RATIO AS AFFECTED BY ANTECEDENT WATER CONTENT

Rainfall intensity (I), antecedent water content, and slope steepness affect soil loss from interrill areas. Objectives of this field study were to (i) test the validity of the assumption that interrill soil loss is a function of I 2 , (ii) determine effect of antecedent water content on interrill erodibilities (K i ) for two slope steepnesses, (iii) evaluate the slope factor used in the water erosion prediction project (WEPP), and (iv) evaluate the product of I, flow discharge, and slope steepness as a possible interrill erosion model. Four soils, ranging in texture from sandy loam to clay, were exposed to sequences of simulated rainfall at three intensities (50, 70, and 100 mm h −1 ). Soil loss and runoff were measured from airdried and prewetted flat plots and from air-dried and prewetted ridged plots [...]

Comparison of interrill soil loss for laboratory and field procedures

This paper focuses on the way that experimental methodology can affect erosion research results. Soil erosion rates obtained from two laboratory soil pan (or plot box) designs were compared with reported field soil loss values. Two types of simulated rainfall, from a constant drop size (4.6 mm) simulator and an oscillating nozzle (mean drop size of 2.3 mm) simulator, were used and both splash and wash (soil losses) were measured from each soil pan. Ranking of soil loss values between a 0.14 m 2 soil pan for the constant drop size simulator and the field experiments were directly opposite. Splash and wash for the nozzle type simulator were much less than for the constant drop simulator for the 0.14 m 2 box. Wash values for a 0.32 m 2 soil pan with a 0.30 m wide surrounding soil border were within the range of reported field soil loss values. Design of the 0.32 m 2 pan allows for a separation of erosion sub-processes controlling interrill soil loss. Design of the 0.14 m 2 pan limits its use primarily to splash detachment studies.