Marl Soils Research Articles

Survival ofDiaprepes abbreviatus(Coleoptera: Curculionidae) Larvae on Green Buttonwood Trees in Flooded Marl Soil and Potting Medium

ABSTRACT Survival of Diaprepes root weevil Diaprepes abbreviatus (L.) (Coleoptera: Curculionidae) larvae was assessed in flooded marl soil and a flooded nursery potting medium with green buttonwood (Conocarpus erectus L., Combretaceae) as a food source for the larvae. Root-zone flooding may be a viable control option for flood-tolerant ornamental plants including buttonwood. Significantly more larvae survived after 38 d in non-flooded than in flooded marl soil. Similarly, more larvae survived in non-flooded than in flooded potting medium; no larvae were recovered from flooded potting medium. Larval survival rates were significantly higher in flooded marl soil than in flooded potting medium, but there was no difference in survival between non-flooded marl soil and non-flooded potting medium. Larvae recovered from flooded marl soil had significantly smaller head capsule widths and probably were at least 1 instar younger than larvae recovered from non-flooded marl soil or non-flooded potting medium. In summa...

Stabilization of a Saudi calcareous marl soil

Due to the inferior characteristics of indigenous soils in eastern Saudi Arabia, marl is being utilized to improve their properties. Marl is calcareous in nature and it is well known for its heterogeneous nature in terms of composition and properties. Moreover, it is sensitive to changes in water content and it often requires prior treatment without which a significant strength loss will occur upon water flooding. This paper presents the results of a laboratory investigation focused on the improvement of indigenous marl for its use as a road base material. Various tests were conducted to both characterize and quantify the strength and durability of the studied marl under different field-simulated conditions with and without chemical treatment (lime and cement). The improvement in strength was assessed using California Bearing Ratio (CBR), Clegg Impact Hammer (CIH) and unconfined compressive strength tests and the durability was evaluated using standard and modified durability tests. The results indicated that cement is superior to lime both in terms of strength improvement and durability requirements.

Pesticide adsorption and degradation in fine earth and rock fragments of two soils of different origin

The soil skeleton (larger than 2 mm fraction) can provide a source of organic carbon which may represent an unexplored possibility of adsorbing and degrading pesticides. The present paper reports a laboratory experiment on the adsorption of metobromuron and terbuthylazine on the skeleton and fine earth of two Italian soils derived from two parent rocks, a calcareous marl and a sandstone. K F values of 1.30 and 2.22 for metobromuron and 1.24 and 2.21 for terbuthylazine were found in the fine earth of sandstone and calcareous marl, respectively. Surprisingly, the soil skeleton, intended as the 2–10 mm fraction, showed a good adsorption capacity of about 40% and 20% with respect to the fine earth fraction for sandstone and calcareous marl soils, respectively. The derived K oc values for the skeleton turned out to be much higher than those of the fine earth indicating an adsorption activity of organic carbon in the skeleton higher than that of the fine earth. Pesticide degradation followed first order kinetics in all samples and half-life values in the skeleton were in the same range as those in the fine earth demonstrating a biodegradation activity of this substrate. A degradation trial in sterilized skeleton of the two soils supports the previous statement, since degradation was almost absent. The experiment performed indicated a possible contribution of the soil coarse fraction to pesticide adsorption and degradation, helping in their disappearance from the environment.

Influence of Soil Type and Rainfall on Pupal Survival and Adult Emergence of the Fall Armyworm (Lepidoptera: Noctuidae) in Southern Florida

Soil and rainfall influences on pupal survival and adult emergence of the fall armyworm, Spodoptera frugiperda (J. E. Smith), were studied in subtropical Florida. Increasing amounts of simulated rainfall, from 0–8 cm, significantly reduced adult emergence, whereas the effect of soil type (limestone and marl) was not significant in a greenhouse test. A field study evaluated the influence of soil type under natural conditions of temperature and rainfall over a 14-month period. Experiment date, soil type, and the date x soil interaction significantly affected adult emergence. Adult emergence was significantly greater in marl soil than limestone soil on 5 of 8 dates. These data indicate that soil type and environmental factors, such as precipitation and temperature, are likely involved in affecting pupal survival and adult emergence of the fall armyworm in southern Florida.

Water availability in almond orchards on marl soils in southeast Spain: The role of evaporation and runoff

Clean sweeping (i.e., frequent and shallow tillage in orchards) is a common practice in semi-arid areas. A potential drawback in dry areas is that the tree roots cannot access the water in the plough layer. Our objective was to quantify the loss of water by evaporation and the loss or gain by overland flow in almond ( Prunus dulcis Mill.) orchards on loamy soils in southeast Spain. The evaporation from a 15 cm plough layer equals 70–104% of annual precipitation, taking into account losses or gains by overland flow. The large evaporation explains the low canopy cover observed, which averaged 3.2%. The runoff coefficient of the test sites is 1–6%. There is no drainage below 15 cm during dry years, except for an area that receives a net influx of overland flow. The trunk basal area in this depression is 12% larger compared to the rest of the field. The options for increasing the water intake of the trees are to reduce the tillage depth or to switch from clean sweeping to no-tillage combined with chemical weeding.

Temperature Quotients of Ammonia Emission of Different Nitrogen Sources Applied to Four Agricultural Soils

Emission of N as NH3 is the primary gaseous loss of N from N sources applied to soils. Knowledge of NH3 volatilization, however, in relation to temperature is incomplete. Soils used in this study were a Biscayne marl soil (BMS) and Krome gravelly loam (KGL) from Florida, and Quincy fine sand (QFS) and Warden silt loam (WSL) soils from Washington. These soils were amended with either KNO3, NH4NO3, (NH4)2SO4, or urea, and incubated at 11, 20, or 29°C under 20 or 80% field capacity (FC) soil water regimes. A change in the rate of NH3 emission corresponding to a 9°C change in temperature is expressed as the temperature quotient (Q9), which describes the temperature effect on rates of NH3 volatilization. At 20°C, the cumulative NH3 emission at 20% FC was up to 8.1‐fold greater than that at 80% FC. The Q9 values of NH3 emission from the WSL soil were up to 10‐fold greater than those from the other three soils amended with either (NH4)2SO4 or NH4NO3 The Arrhenius activation energy (Ea) was about 188 J mol−1 for the WSL soil but ≤42 J mol−1 for the other soils. Volatilization from the WSL soil was highly temperature dependent. These results indicate that Q9 and Ea could be used as indices for N management for crop production to minimize NH3 emissions. Further research is needed, however, to verify the above relationships across a wide range of soils and agroclimatic regions.

High Water Regime Can Reduce Ammonia Volatilization from Soils under Potato Production

This research was conducted with Biscayne marl soil and Krome gravelly loam from Florida and Quincy fine sand and Warden silt loam from Washington to determine ammonia (NH3) volatilization at various temperature and soil water regimes. Potassium nitrate (KNO3), ammonium nitrate (NH4NO3), ammonium sulfate [(NH4)2SO4], or urea were applied to the soil at a rate of 75 kg N ha−1. Soil water regime was maintained at either 20% or 80% of field capacity (FC) and incubated at 11, 20, or 29°C, which represented the minimum, average, and maximum temperatures, respectively, during the potato growing season in Washington. Results indicated that the ammonia volatilization rate at 20% FC soil water regime was two‐ to three‐fold greater than that at 80% FC. The cumulative volatilization loss over 28 days was up to 25.7%. Results of this study demonstrated that ammonia volatilization was accelerated at low soil water regimes.

Moisture Quotients for Ammonia Volatilization from Four Soils in Potato Production Regions

Ammonia (NH3) emission from nitrogen (N) fertilizers used in agriculture decreases N uptake by the crop and negatively impacts air quality. In order to better understand the factors influencing NH3 emission from agriculture, this research was conducted with four major soils used for potato production: Biscayne Marl Soil (BMS, pH 7.27), and Krome Gravelly Loam (KGL, pH 7.69) from Florida; and Quincy Fine Sand (QFS, pH 6.65), and Warden Silt Loam (WSL, pH 6.46) from Washington. Potassium nitrate (KNO3), ammonium nitrate (NH4NO3), ammonium sulfate ((NH4)2SO4) or urea ((NH)2CO) sources were evaluated for ammonia volatilization at 75 kg N ha−1 rate. The soil water regime was maintained at either 20 or 80% of field capacity (FC), and incubated at 11, 20 or 29°C. Results indicated that NH3 volatilization rate at 20% FC was 2 to 3-fold greater than that at 80% FC. The cumulative volatilization loss over 28 days ranged from 0.21% of N applied as NH4NO3 to 25.7% as (NH4)2SO4. Results of this study demonstrate that NH3 volatilization was accelerated at the low soil water regime. Moisture quotient (Q) is defined as a ratio of NH3 emission rate at 20% FC to that at 80% FC both at the same temperature. The peak Q values of NH3 volatilization were up to 20.8 for the BMS soil at 20°C, 112.9 for the KGL soil at 29°C, 19.0 for the QFS soil at 20°C, and 74.1 for the WSL soil at 29°C, respectively. Thus, maintaining a suitable soil water regime is important to minimize N-loss via NH3 volatilization and to improve N uptake efficiency and air quality.

Human disturbance and environmental factors as drivers of long-term post-fire regeneration patterns in Mediterranean forests

Question: What are the main forces driving natural regeneration in burned mature Mediterranean forests in the medium-long term and what are the likely successional trajectories of unmanaged vegetation? Location: Valencia Region, eastern Spain. Methods: A wildfire burned 33 000 ha of Pinus halepensis and P. pinaster forest in 1979, and subsequent smaller wildfires took place between 1984 and 1996. The study was designed to sample the range of environmental and disturbance (fire recurrence and land use) conditions. The territory was classified into 17 different geomorphological and fire-recurrence units. Vegetation cover and floristic composition were measured on a total of 113 plots (1000 m2 each) randomly selected within these units. Results: The results show that 23 years after the fire the regenerated vegetation consists of successional shrublands, and that forest ecosystem resilience can be very low. The vegetation presents a strong correlation with most of the environmental variables, but fire (one or two fires), soil type and land use (in that order) are the main drivers of vegetation composition. Quercus coccifera shrublands persist on limestone soils while diverse types of other shrublands (dominated by seeder species) are found on marl soils. Conclusions: The results of this study indicate that disturbance factors strongly coupled to human activities, such as land use and fire, play a critical role in the current state of vegetation. Fire creates vegetation patches in different successional states while land use and soil type define the different types of shrubland in terms of their specific composition.

Experimental study on instability of bases on natural and lime/cement-stabilized clayey soils

In many sub-tropical and tropical arid regions of the world, marly soils (marls) and lime or cement stabilization of marl soils are used as a convenient and expedient means of developing foundation base courses and inexpensive wearing courses for transport purposes. The failure of many of these natural and stabilized marls to perform their function has been reported. Mechanical factors, commonly used to explain the causes of the foundation failures, are unsatisfactory and have not been accepted. This study uses physicochemical (reaction) factors to explain the general basic causes of the deterioration of support capability for these types of soils. The presence of palygorskite and sepiolite in marl soil provides it with some very unique features in its natural state, particularly when it is stabilized with lime or cement. The formation of an expansive mineral, ettringite, as a transformation product of palygorskite increases the swelling potential of the stabilized soil. A set of physico-chemical and mechanical experiments, which include slake durability, specific surface area measurement (SSA), California bearing ratio (CBR), atterberg limits testing, and X-ray diffraction (XRD), were performed. In addition, the impact of curing on the stabilized soil behaviour was investigated. The results show that the immersion of the natural marl reduces the dry CBR value to at least one-fourth the dry value. Furthermore, the XRD results indicate that with increasing time and availability of dissolved aluminum and sulfate, ettringite forms in stabilized soil and then the rate of ettringite growth increases. Based on the findings of these experiments, the various interactions, reactions and factors contributing to the stability and instability of marl soils, and lime/cement stabilized marls are discussed. It is concluded that the general traditional soil stabilization evaluation methods are not capable of accounting for the failures that occur in stabilized marl. It is shown that soil mineralogy and pore fluid analysis, in conjunction with X-ray diffraction testing, can be combined to provide a set of practical ways to monitor the possibilities of these failures.

Comparaison des capteurs ASTER et ETM+ pour la cartographie de la dégradation des sols à l'aide de l'indice LDI

This study investigates the utility of the land degradation index (LDI) approach to express land degradation in a small Mediterranean watershed with enhanced thematic mapper plus (ETM+) data. The LDI is based on the concept of the soil line, and was elaborated from advanced spaceborne thermal emission and reflection radiometer (ASTER) sensor data and field spectra measurements. The implementation of the LDI index uses all the bands of the spectral domain in the visible, near infrared (NIR), and short wave infrared (SWIR). Field measurements were carried out in the Saboun experimental basin located in a marl soil region of the Moroccan western Rif for which soil, hydrological, and erosion databases were readily available. The present study provided the opportunity for studying and characterizing the state of soil degradation using the LDI. Our results show the interest of the use of the LDI with ASTER data to study or to map land degradation. It provides more accurate results (Kappa = 0,79) when compared with results obtained with ETM+ data (Kappa = 0,57). Globally, the results represent ground reality with sufficient accuracy to help decision makers in their soil conservation planning process.

Sorption Kinetics and Equilibria of Organic Pesticides in Carbonatic Soils from South Florida

A batch reactor was used to determine sorption kinetic parameters (k2, F, and K*) and the equilibrium sorption coefficient (K). The two-site nonequilibrium (TSNE) batch sorption kinetics model was used to calculate the kinetic parameters. Two probe organic pesticides, atrazine [2-chloro-4-ethylamino-6-isopropylamino-s-triazine] and diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] were studied using three carbonatic soils from South Florida (Chekika, Perrine, and Krome), one noncarbonatic soil from Iowa (Webster), and one organic soil (Lauderhill) from South Florida. Carbonatic soils contained more than 600 g kg(-1) CaCO3. Sorption is initially very fast up to 3 h and then slowly reaches equilibrium. All soil-chemical combinations reached sorption equilibrium after about 24 h and all sorption isotherms were linear. The sorption kinetics data were well described by the TSNE model for all soil-chemical combinations except for the marl soil data (Perrine-Atrazine), which were better described by the one-site nonequilibrium (OSNE) model. Diuron, with higher K, undergoes slower sorption kinetics than atrazine. The Lauderhill soil containing organic carbon (OC) of 450 g kg(-1) exhibited slowest sorption kinetics for both pesticides. An inverse relationship between k3 and K was observed for atrazine and diuron separately in Chekika, Webster, and Lauderhill soils but not in Perrine and Krome soils. The sorption kinetic parameters were used to distinguish the sorption behavior between atrazine and diuron and to identify differences between soils. Normalizing the sorption coefficient (K) to OC showed that atrazine and diuron had K oc values in carbonatic soils that were a third of reported literature values for noncarbonatic soils. Using existing literature K oc values in solute transport models will most likely underestimate the mobility of atrazine, diuron, and other neutral organic chemicals in carbonatic soils.

A spectral index for land degradation mapping using ASTER data: Application to a semi-arid Mediterranean catchment

Flagrant soil erosion in Morocco is an alarming sign of soil degradation. Due to the considerable costs of detailed ground surveys of this phenomenon, remote sensing is an appropriate alternative for analyzing and evaluating the risks of the expansion of soil degradation. In this paper, we characterize the state of land degradation in a small Mediterranean watershed using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and ground-based spectroradiometric measurements. The two visible, the near-infrared and six shortwave infrared bands of the above sensor were calibrated using ground measurements of the spectral reflectance. Field measurements were carried out in the Saboun experimental basin located in the marl soil region of the Moroccan western Rif. The study leads to the development and evaluation of a new spectral approach to express land degradation. This index called Land degradation index (LDI) is based on the concept of the soil line derived from spectroradiometric ground measurements. In this study, we compare LDI and the spectral angle mapping (SAM) approaches to assess and map land degradation. Results show that LDI provides more accurate results for mapping land degradation (Kappa=0.79) when compared to the SAM method (Kappa=0.61). Validation and evaluation of the results are based on the thematic maps derived from the ground data (organic matter, clay, silt and sand) by kriging, DEM, slope gradient and photointerpretation.

Plant colonization after complete and partial removal of disturbed soils for wetland restoration of former agricultural fields in Everglades National Park

The Hole-in-the-Donut is a 4000-ha region of former farmlands within Everglades National Park that is dominated by a monoculture of the non-indigenous pest plant Schinus terebinthifolius (Brazilian pepper). Prior to extensive farming in the region, the area consisted of short hydroperiod graminoid wetlands and mesic pine savannah. Rock plowing in preparation of these lands for farming created an artificial soil layer that broke up the limestone substrate, mixed and aerated the native marl soil layer with the broken limestone, and elevated the surface slightly. Farming practices also included the use of chemical fertilizers and pesticides. The modified soil substrate quickly became dominated by S. terebinthifolius when farming ceased in 1975, despite efforts to control its establishment, such as prescribed fire, herbicide treatment, and mowing. Preliminary evidence indicated that soil removal would prevent re-invasion by S. terebinthifolius and could lead to colonization by native wetlands plants. Two trials, a partial soil removal (PSR) and a compete soil removal (CSR), were performed on a pilot test site beginning in 1989 to determine whether all or only a portion of this modified soil substrate needed to be removed to attain desired results. Removal of rock-plowed surface material lowered elevation in both treatments. While the PSR treatment did show an increase in the number and coverage of hydrophytes for a few years, it did not prohibit re-colonization and re-establishment of a canopy of S. terebinthifolius, and by 1996, the site was again dominated by a monoculture of S. terebinthifolius. By contrast, the CSR treatment showed rapid colonization by hydrophytes and no successful re-colonization by S. terebinthifolius. Lowering elevations by 15 to 45 cm allowed for longer periods of flooding and rapid colonization by hydrophytes on both sites. After the sites were cleared, the average difference in elevation between the two treatment areas was less than a tenth of a meter, but this resulted in a slightly shorter hydroperiod on the PSR site. The small amount of residual rock-plowed soil with high levels of nutrients, along with its slightly shorter hydroperiod on the PSR site, appear to have contributed significantly to the success of S. terebinthifolius in re-colonizing this treatment area.

Endosulfan Losses through Runoff and Leaching from Calcareous Gravelly or Marl Soils

The non‐point loss of a pesticide through runoff and leaching from agricultural fields depends not only on its chemical properties but also on environmental factors such as soil type, rainfall intensity, and water table level. Two major agricultural calcareous soils in South Florida, Krome (loamy‐skeletal, carbonatic, hyperthermic Lithic Udorthents) very gravelly loam (Krome) and Biscayne (loamy, carbonatic, hyperthermic, shallow Typic Fluvaquents) marl (marl), were packed in tilted stainless‐steel runoff–leaching chambers for measuring the transport of endosulfan (6,7,8,9,10,10‐hexachloro‐1,5,5a,6,9,9a‐hexahydro‐6,9‐methano‐2,4,3‐benzadioxathiepin 3‐oxide) isomers in leachates and surface runoff. Endosulfan loss was the greatest in runoff sediment, followed by loss in runoff water, and finally in the leachate. At a rainfall intensity of 75 mm h−1, the infiltration rate in the Krome soil was higher than in the marl soil. Endosulfan movement with infiltration water in Krome soil is a nonequilibrium process. Increasing rainfall intensity to 150 mm h−1 significantly decreased endosulfan leaching and increased runoff. High rainfall intensity and/or water table dramatically increased the endosulfan loss through the sediments in runoff. Marl soil has a higher endosulfan runoff potential than Krome soil. Endosulfan α had a lower average experimental distribution coefficient, KD, than endosulfan β (265 vs. 472). Loss of endosulfan α dissolved in runoff water and through leaching was higher than that of endosulfan β, while loss of endosulfan α from runoff sediments was lower than that of endosulfan β. Endosulfan concentrations in runoff water decreased exponentially with cumulative rainfall and runoff sediment.

Endosulfan Losses through Runoff and Leaching from Calcareous Gravelly or Marl Soils

Endosulfan Losses through Runoff and Leaching from Calcareous Gravelly or Marl Soils

Endosulfan Losses through Runoff and Leaching from Calcareous Gravelly or Marl Soils

Endosulfan Losses through Runoff and Leaching from Calcareous Gravelly or Marl Soils

The impact of soil properties and topography on drought vulnerability of rainfed cropping systems in southern Spain

The acreage of rainfed almond plantations ( Prunus dulcis (Miller)) in Spain has rapidly increased during the last 30 years, reflecting a tendency towards specialisation in perennial, rainfed crops in many Mediterranean regions. Seminatural vegetation and diverse cropping systems have been converted into monocultures with low tree densities leaving the soil unprotected. This paper illustrates the contrast in water conservation strategies between traditional and modern almond plantations in the Murcia region (Spain), and highlights the impacts of intensification on soil degradation. The role of lateral and vertical redistribution of soil moisture in water conservation will be discussed based on the analysis of soil moisture retention characteristics, temporal variation in soil moisture content and soil moisture patterns. A traditional cereal/almond cropping system typical for marl areas with a subdued relief will be compared to a modern almond monoculture in a highly dissected landscape on slate bedrock. The low water holding capacity of the stony soil in the slate area caused rainfall to penetrate deep in the profile and thus soil moisture fluxes were mainly vertical. Semivariograms of topsoil moisture content after an isolated rain day (19 and 27 mm for the nearest raingauges) demonstrated the differences in lateral redistribution of soil moisture between the cropping systems. A spatial pattern in the marl soil with a range of 69 m was observed, whereas soil moisture in the slate area showed no spatial pattern except for higher values in the narrow valley bottom. The scarcity of rainfall producing lateral redistribution of soil moisture explained the lack of reliable moisture supply in the marl area. This led to very low overall plant densities at 16 trees ha −1, restricted to wetter zones upstream of retention dams. The redistribution of soil moisture by vertical fluxes in the stony soils of the slate area explained the uniform, widely spaced trees at densities of 204 trees ha −1. This study has highlighted the need for rainfall to penetrate deep into the soil to sustain almond monocultures in semiarid climates. However, this requires a loose, bare topsoil between the trees and thus large areas of bare soil are exposed on hillslopes resulting in high erosion risks.

The effect of season and parent material on water erosion on highly eroded soils in eastern Spain

On highly eroded soils, where vegetation is absent or negligible, the nature of the parent material can greatly affect hydrological and erosion processes. Moreover, under Mediterranean climatic conditions, season determines soil surface morphologies via the soil water content and thus exerts a major control on runoff and erosion rates. Rainfall simulation experiments and cylinder infiltrometer measurements were carried out on degraded surfaces developed on three different parent materials (marl, clay and sand) during autumn (wet) and summer (dry conditions) in order to determine the influence of season and parent material on infiltration, runoff and erosion. For marl soils, ponding and runoff initiation were rapid, infiltration rates low, and runoff coefficient (81%) and erosion rates high. On the clay and sand soils, ponding and runoff initiation were delayed, infiltration rates greater, and runoff coefficient and erosion rates lower than on marl soils. Seasonally, infiltration rates decrease in autumn and thus runoff increases. Seasonal differences in erosion are less clear due to the increase of the runoff sediment concentration during summer, although the greatest erosion rates were found under autumn conditions. Clay soils show the greatest seasonal differences ( Rc moves from 27% to 51%), which is due to crack development during summer.

Relations between interrill erosion processes and sediment particle size distribution in a semiarid Mediterranean area of SE of Spain

Erosion and sediment characteristics were measured using simulated rainfall on two cultivated soils of contrasting lithology (Quaternary calcareous colluvium and Tertiary marls) in a semiarid Mediterranean area of SE Spain. Two rainfall intensities, high (56.0±2.4 mm h −1) and medium (31.4±1.4 mm h −1), were used in order to know the mechanisms involved in each selected condition. For each simulated event, runoff and sediment were sampled at 1-min intervals on a 1-m wide by 2-m long erosion plot. The erosion rate was calculated as the total amount of soil lost divided by the time period of the test. The duration of the test was that needed to reach steady state runoff, an average time of 24.5 min for Quaternary calcareous colluvium and 17.7 min for Tertiary marls. The size distribution of the transported sediment in the field (effective size distribution) was compared with equivalent measurements of the same samples after chemical and mechanical dispersion (ultimate size distribution) to investigate the detachment and transport mechanisms involved in sediment mobilisation. The results showed that the soil type determined the hydrological response, regardless of the rainfall intensity. The erosional response was, however, determined by the rainfall and soil surface characteristics. In Quaternary calcareous colluvial soils, the predominant erosion process depended on the rainfall intensity, with a prevailing detachment-limited condition in high-intensity events and prevailing transport-limited conditions in those events of medium intensity. These differences in the main erosion processes were reflected in the size of the transported material and in the change in sediment size within the storm. Thus, a time-dependent size distribution of the eroded material (decreasing coarse fractions and increasing fine fractions with runoff time) was observed for high-intensity events. In medium-intensity events, on the other hand, the time-independent size distribution of the eroded material indicated transport-limited erosion. Due to the rapid surface crusting on the Tertiary marl soil, no differences in the main erosion processes or in the sediment size distribution occurred for the different rainfall intensities tested. The erosion of marl soils was determined mainly by the limited quantity of available sediment. The effective size of material was a more sensitive parameter than the ultimate size of the sediment to study the way in which the sediment was transported.