Average Soil Loss Research Articles

Assessment of soil loss and nutrient depletion due to cassava harvesting: A case study from low input traditional agriculture

Cassava is a major food crop for farmers and especially small holder farmers and cultivated under low input other than the irrigation. It is cultivated as mono crop or intercrop at early stage and cultivating throughout the year. It is harvested carefully because of cyanogenic glucosides and consumed with in day. Easy and un-damageable uprooting of the tuber mainly depends on soil moisture, texture and agronomic practices. The study was focused with the objectives of the assessment of soil loss due to the harvesting of cassava roots tubers under low input agriculture, and to estimate the amount of plant nutrients loss due to crop harvest for cassava. Also the observation was made the correlation between the soil loss and physical characters of the tuber, soil texture and agronomic practices. Average plant specific soil loss due to crop harvesting was 80. 7 g root−1 and crop specific soil loss due to crop harvesting was 7. 64 kg ha−1 harvest−1 loss in Valliagmam area in Jaffna, Sri Lanka. Soil moisture content at harvesting time was a significant factor that explained the variations in the soil lost at cassava harvesting. Soil moisture has linear positive relationship with average plant specific soil loss due to crop harvesting. Soil nutrient loss during cassava harvesting by removal of adhering soil with root tuber was 1. 15 kg of N, 1. 99 kg of P and 2. 91 kg of K ha−1 harvest−1. Application of fertilizer is important since considerable amount nutrient loss was observed due to soil loss due to crop harvest.

The history and assessment of effectiveness of soil erosion control measures deployed in Russia

Research activities aimed at design and application of soil conservation measures for reduction of soil losses from cultivated fields started in Russia in the last quarter of the 19th century. A network of "zonal agrofor-estry melioration experimental stations" was organized in the different landscape zones of Russia in the first half of the 20th century. The main task of the experiments was to develop effective soil conservation measures for Russian climatic,soil and land use conditions. The most widespread and large-scale introduction of coun-termeasures to cope with soil erosion by water and wind into agricultural practice supported by serious governmental investments took place during the Soviet Union period after the Second World War. After the Soviet Union collapse in 1991 ,general deterioration of the agricultural economy sector and the absence of investments resulted in cessation of organized soil conservation measures application at the nation-wide level. However, some of the long-term erosion control measures such as forest shelter belts, artificial slope terracing, water diversion dams above formerly active gully heads survived until the present. In the case study of sediment redistribution within the small cultivated catchment presented in this paper an attempt was made to evaluate average annual erosion rates on arable slopes with and without soil conservation measures for two time intervals. It has been found that application of conservation measures on cultivated slopes within the experimental part of the case study catchment has led to a decrease of average soil loss rates by at least 2. 5 2. 8 times. The figures obtained are in good agreement with previously published results of direct monitoring of snowmelt erosion rates, reporting approximately a 3 -fold decrease of average snowmelt erosion rates in the experimental sub-catchment compared to a traditionally cultivated control sub-catchment. A substantial decrease of soil erosion rates on arable slopes has been equally reflected in a corresponding decrease of aggradation rates in the main valley bottom and tributaries.

Dynamic monitoring of soil erosion for upper stream of Miyun Reservoir in the last 30 years

The Revised Universal Soil Loss Equation (RUSLE) was applied to assess the spatial distribution and dynamic properties of soil loss with geographic information system (GIS) and remote sensing (RS) technologies. To improve the accuracy of soil-erosion estimates, a new C-factor estimation model was developed based on land cover and time series normalized difference vegetation index (NDVI) datasets. The new C-factor was then applied in the RUSLE to integrate rainfall, soil, vegetation, and topography data of different periods, and thus monitor the distribution of soil erosion patterns and their dynamics during a 30-year period of the upstream watershed of Miyun Reservoir (UWMR), China. The results showed that the new C-factor estimation method, which considers land cover status and dynamics, and explicitly incorporates within-land cover variability, was more rational, quantitative, and reliable. An average annual soil loss in UWMR of 25.68, 21.04, and 16.80 t ha−1 a−1 was estimated for 1990, 2000 and 2010, respectively, corroborated by comparing spatial and temporal variation in sediment yield. Between 2000 and 2010, a 1.38% average annual increase was observed in the area of lands that lost less than 5 t ha−1 a−1, while during 1990–2000 such lands only increased on average by 0.46%. Areas that classified as severe, very severe and extremely severe accounted for 5.68% of the total UWMR in 2010, and primarily occurred in dry areas or grasslands of sloping fields. The reason for the change in rate of soil loss is explained by an increased appreciation of soil conservation by developers and planners. Moreover, we recommend that UWMR watershed adopt further conservation measures such as terraced plowing of dry land, afforestation, or grassland enclosures as part of a concerted effort to reduce on-going soil erosion.

Application of the Water Erosion Prediction Project (WEPP) in Olive Orchards on Vertic Soil with Different Management Conditions

<abstract><title><italic>Abstract.</italic></title> Vertic soils are common in Mediterranean areas, such as in some olive-growing areas in Andalusia in southern Spain. Model calibration can be especially complex in orchards due to the higher spatial variability induced by the tree/lane distribution and the impact of management, and even more in Vertic soils because of the complexity introduced by the cracking/swelling cycles of the soil, whose impact can remain for many months. The WEPP model was evaluated using monthly runoff and erosion data collected from an experiment in an olive orchard on a Vertic soil during four hydrological years, comparing three different soil management systems: no tillage with bare soil (NT), conventional tillage (CT), and cover crop (CC). These three systems differed greatly in average annual runoff and soil losses. Satisfactory calibration of the model required characterization of the main hydrological features of the study period (distinguishing “dry” and “wet” years) due to their large impact on the infiltration properties of the soil. The best predictions were obtained for the wet years and NT management. High values of r² and Nash-Sutcliffe model efficiency (NSE) were obtained at a monthly scale under wet conditions. Annual erosion rates were not well predicted, probably due to the difficulties in simulating the spatial complexity of olive orchards and the limitations of WEPP for modeling soil moisture dynamics at different depths derived from the cracking/swelling processes of Vertic soils as well as their impact on erodibility. The presented parameterization constitutes a basic guideline for the application of the WEPP model in olive-growing areas and on Vertic soils.

Assessing the significance of soil erosion for arable weed seedbank diversity in agro-ecosystems

Accelerated soil erosion threatens sustainable food production by degrading the physical and biogeochemical functioning of arable field soils and lowering crop yields. Much less recognized is the potential for soil erosion to impinge on wider ecosystem services including the weed seedbank that underpins much of the biodiversity in temperate agro-ecosystems of northern Europe. This paper assesses the likely impact of soil erosion on the composition and abundance of the arable weed seedbank, and presents an overview of erosion mechanisms affecting arable land coupled with an outline of the main factors influencing arable weed seedbank abundance and composition. The information presented on both these sets of processes enables assessment of the likely impact of soil erosion on arable seedbank biodiversity at the field and landscape scales. Combining mean annual net erosion rates of c. 7 t ha−1 yr−1 and seedbank densities c. 2000 seeds m−2, both figures broadly representative of UK conditions, produces an average annual loss of the field seed inventory of c. 0.5% yr−1. Where seedbank abundance is otherwise relatively stable (i.e. losses through death, germination and weed control are largely balanced by gain through seed rain), average soil loss rates could export c. 10% of the arable weed seedbank in 20 years. Net erosion data conceal within-field sediment deposition within swales, foot slopes, buffer strips and hedgerows which provides a further dimension of spatial restructuring of weed assemblages. Seed size and shape also influence hydrodynamic behaviour through selective entrainment and preferential deposition. It is concluded that earth surface processes play an under-recognized role in structuring field-scale weed-based biodiversity in agro-ecosystems over decadal timescales.

Costs of Nutrient Losses in Priceless Soils Eroded From the Highlands of Northwestern Ethiopia

A study was conducted in 2011 to estimate soil and nutrient losses caused by water erosion and predict nutrient replacement costs on different land use types and slope classes at Harfetay watershed, Northwestern Ethiopia. The revised soil loss equation (RUSLE) was used to estimate the soil loss from the different land uses and slope classes in watershed. Moreover, nutrient loss from similar units was calculated by multiplying the in situ nutrient concentration of soil samples by the estimated soil loss using RUSLE. The replacement costs of nutrient losses were calculated by multiplying the nutrient loss with the price of available nutrients in urea and diammonium phosphate. The estimate of the RUSLE indicated that the average soil losses in the study watershed were 119 tons ha-1 year-1 for non-conserved crop land, 23 tons for conserved farmlands, 23 tons for forest and shrub lands, 19 tons for grazing lands, and 6 tons for plantation forest. The mean soil loss for lower slope classes (<15%), middle slope classes (15-30%) and upper slope classes (>30%) were 30.11, 48.09 and 57.22 tons ha-1 year-1, respectively. The highest losses of total nitrogen (154.7 kg ha-1 year-1), available phosphorus (1.84 kg ha-1 year-1), and organic matter (1677.9 kg ha-1 year-1) were obtained from non-conserved cropland. Conversely, the lowest values of the same parameters were registered from the land covered with plantation forest. Comparing slope classes for non conserved cropland, organic matter and nutrient losses were higher in upper slope classes followed by middle and lower ones. The replacement cost of available N and available P for non-conserved cropland, conserved cropland, forest/shrub lands, grazing lands and plantations were 121.22, 36.41, 27.09, 32.22 and 13.10 Birr ha-1 year-1, respectively (1USD = 19 Birr); and the weighted mean replacement cost in the watershed was estimated to be 98.1 Birr ha-1 year-1 which is about 20% of the cost of fertilizer applied per individual farmers in the watershed. From the study it was possible to conclude that conversion of forest lands and plantation forests to cropland causes serious soil and nutrient losses. Construction of conservation structures on cropland, however, will reduce soil and nutrient losses. To halt soil and nutrient loss and ensure sustainable land management and agricultural development in the Harfetay watershed and similar watersheds, policy and development interventions including increasing awareness of farmers on of soil and nutrient losses, enforcing land use policies and expanding bio-physical soil conservation practices are required.

Critical Season for Soil Erosion in the Moldavian Plateau

Abstract Experiments conducted at Agricultural Research and Development Station of Podu-Iloaiei, Iaşi County, Romania, during 2002 - 2011, followed study runoff and soil erosion in different cultures, and establish critical season of soil erosion in this area. Establish critical season of soil erosion is necessary to satisfy the critical level of ground cover, which is required to maintain a low risk of soil erosion. Average annual soil loss by erosion, recorded in maize and sunflower were (mean on 10 years) of 6.753 and 7.385 t/ha/year, respectively. In sunflower and corn of the total soil loss recorded in the Moldavian Plateau, 19.7- 20.4% occurred in spring, 68.7 to 69.2% in summer and 6.1- 6.6% in the autumn. Differences of 4.5 to 4.9% of the total annual soil losses by erosion were recorded in winter, with snow melt. Season critic of soil erosion in the Moldavian Plateau, when recording the most aggressive rain event occurs in June and July. Mean soil loss due to erosion, recorded in June and July were 0.424 t/ha for winter rape, winter wheat 0.291 and 0.093 t/ha the perennial grasses in the second year of vegetation.

Use of Satellite Data, GIS and RUSLE for Estimation of Average Annual Soil Loss in Daltonganj Watershed of Jharkhand (India)

The present study demonstrated the utility of high resolution LISS IV satellite data for accurate mapping of landuse landcover which forms an important component while computing the land cover and management factor and erosion control practice factor for soil loss estimation using RUSLE model. The Cartosat-I DEM was used for computing the flow accumulation and the slope length (LS) factor with adequate precision. The results showed that the Daltonganj watershed has an average annual soil loss upto 69 tons ha -1 yr -1 . The maximum area contributing to soil erosion was from agricultural lands where the slope is less than 5˚ and having soil loss upto 10 tons ha -1 yr -1 however the maximum rate of soil erosion was observed near the upper catchment near the 6 th order river channel and over the hilly region with annual average soil erosion between 26 and 30 tons ha -1 yr -1 .

Erosivity, surface runoff, and soil erosion estimation using GIS-coupled runoff–erosion model in the Mamuaba catchment, Brazil

This study evaluates erosivity, surface runoff generation, and soil erosion rates for Mamuaba catchment, sub-catchment of Gramame River basin (Brazil) by using the ArcView Soil and Water Assessment Tool (AvSWAT) model. Calibration and validation of the model was performed on monthly basis, and it could simulate surface runoff and soil erosion to a good level of accuracy. Daily rainfall data between 1969 and 1989 from six rain gauges were used, and the monthly rainfall erosivity of each station was computed for all the studied years. In order to evaluate the calibration and validation of the model, monthly runoff data between January 1978 and April 1982 from one runoff gauge were used as well. The estimated soil loss rates were also realistic when compared to what can be observed in the field and to results from previous studies around of catchment. The long-term average soil loss was estimated at 9.4 t ha(-1) year(-1); most of the area of the catchment (60%) was predicted to suffer from a low- to moderate-erosion risk (<6 t ha(-1) year(-1)) and, in 20% of the catchment, the soil erosion was estimated to exceed > 12 t ha(-1) year(-1). Expectedly, estimated soil loss was significantly correlated with measured rainfall and simulated surface runoff. Based on the estimated soil loss rates, the catchment was divided into four priority categories (low, moderate, high and very high) for conservation intervention. The study demonstrates that the AvSWAT model provides a useful tool for soil erosion assessment from catchments and facilitates the planning for a sustainable land management in northeastern Brazil.

Advanced modelling of runoff and soil redistribution for agricultural systems: The SERT model

Hydrological and soil erosion models allow mapping and quantifying rates of runoff depths and soil redistribution for different land uses and climatic scenarios. Mediterranean soils are threatened by marked seasonal changes in the climatic, thus soil and vegetation parameters and modelling predictions at monthly scale are required. The semi-physically-based Soil Erosion and Redistribution Tool (SERT) model is presented together with the results of its application in a Mediterranean agro-ecosystem (NE Spain) with a detailed database. The hydrological module is based on the recently published DR2 (Distributed Rainfall-Runoff) water balance model and the effects of man-made infrastructures on the natural dynamics of runoff connectivity are added. The erosion module is built using, as the basis, the Revised Morgan, Morgan and Finney model, and the new Remaining runoff Transport Capacity (TCr) factor used to estimate the rates of soil loss and deposition. Predicted runoff depth varied in time and space, presenting areas without runoff production mainly in Rendzic Leptosols and Haplic Calcisols between November and April. Average soil erosion was high in cultivated and bare soils, ca. 20 and 10Mgha−1yr−1, whereas rangeland soils were affected by moderate and, in some areas, by limited erosion processes. Soil erosion was minimal in February (0.08Mgha−1month−1 on average) and 23 times higher in October. The SERT model allowed mapping the significant changes in the monthly values of soil redistribution quantifying the variability in the magnitude of the processes involved. Predicted values of average soil loss and deposition were validated against quantified values with 137Cs obtaining an average Nash–Sutcliffe efficiency of 0.48 (Pearson's r=0.709) and a sediment balance of −1.15Mgyr−1 for the whole catchment that is consistent with the karst processes of the study area. The new model is an easy-to-run, reliable, low-input-demanding management tool with valuable outputs for hydrological and soil erosion studies in small agricultural catchments.

Modelling soil erosion risk based on RUSLE-3D using GIS in a Shivalik sub-watershed

The RUSLE-3D (Revised Universal Soil Loss Equation-3D) model was implemented in geographic information system (GIS) for predicting the soil loss and the spatial patterns of soil erosion risk required for soil conservation planning. High resolution remote sensing data (IKONOS and IRS LISS-IV) were used to prepare land use/land cover and soil maps to derive the vegetation cover and the soil erodibility factor whereas Digital Elevation Model (DEM) was used to generate spatial topographic factor. Soil erodibility (K) factor in the sub-watershed ranged from 0.30 to 0.48. The sub-watershed is dominated by natural forest in the hilly landform and agricultural land in the piedmont and alluvial plains. Average soil loss was predicted to be lowest in very dense forest and highest in the open forest in the hilly landform. Agricultural land-1 and agriculture land-2 to have moderately high and low soil erosion risk, respectively. The study predicted that 15% area has ‘moderate’ to ‘moderately high’ and 26% area has high to very high risk of soil erosion in the sub-watershed.

Assessment Erosion 3D Hazard with USLE and Surfer Tool: A Case Study of Sumani Watershed in West Sumatra Indonesia

Quantitative evaluation of soil erosion rate is an important basic to investigate and improve land use system, which has not been sufficiently conducted in Indonesia. The Universal Soil Loss Equation (USLE) and Erosion Three Dimension (E3D) in Surfer were used to identify characteristic of dominant erosion factors in Sumani Watershed in West Sumatra, Indonesia using data soil survey and monitoring sediment yield in outlet watershed. Climatology data from three stations were used to calculate Rainfall erosivity (R) factor. As many as101 sampling sites were used to investigate soil erodibility (K-factor) with physico-chemical laboratory analysis. Digital elevation model (DEM) of Sumani Watershed was used to calculate slope length and Steepness (LS-factor). Landsat TM imagery and field survey were used to determine crop management (C-factor) and conservation practices (P-factor). Calculating soil loss and map of USLE factor were determined by Kriging method in Surfer 9. Sumani Watershed had erosion hazard in criteria as: severe to extreme severe (26.23%), moderate (24.59%) and very low to low (49.18%). Annual average soil loss for Sumani watershed was 76.70 Mg ha-1 y-1 in 2011. Upland area was designated as having a severe to extreme severe erosion hazard compared to lowland which was designated as having very less to moderate. On the other land, soil eroded from upland were deposited in lowland. These results were verified by comparing one year’s sediment yield observation on the outlet of the watershed. Land use (C-factor), rainfall erosivity (R- factor), soil erodibility (K-factor), slope length and steepness (LS-factor) were dominant factors that affected soil erosion. Traditional soil conservation practices were applied by farmer for a long time such as terrace in Sawah. The USLE model in Surfer was used to identify specific regions susceptible to soil erosion by water and was also applied to identify suitable sites to conduct soil conservation planning in Sumani Watershed.[How to Cite : Aflizar, R Afrizal, T Masunaga. 2013. Assessment Erosion 3D Hazard with USLE and Surfer Tool: A Case Study of Sumani Watershed in West Sumatra Indonesia. J Trop Soils, 18 (1): 81-92. doi: 10.5400/jts.2013.18.1.81][Permalink/DOI: www.dx.doi.org/10.5400/jts.2013.18.1.81]

Spatial Estimation of Soil Erosion Risk Using RUSLE Approach, RS, and GIS Techniques: A Case Study of Kufranja Watershed, Northern Jordan

Wadi Kufranja catchment (126.3 km2), northern Jordan, was selected to estimate annual soil loss using the Revised Universal Soil Loss Equation (RUSLE), remote sensing (RS), and geographic information system (GIS). RUSLE factors (R, K, LS, C and P) were computed and presented by raster layers in a GIS environment, then multiplied together to predict soil erosion rates, and to generate soil erosion risk categories and soil erosion severity maps. The estimated potential average annual soil loss is 10 ton·ha-1·year-1 for the catchment, and the potential erosion rates from recognized erosion classes ranged from 0.0 to 1850 ton·ha-1·year-1. About 42.1% (5317.23 ha) of the catchment area was predicted to have moderate risk of erosion, with soil loss between 5 - 25 ton·ha-1·year-1. Risk of erosion is severe to extreme over 31.2% (3940.56 ha) of the catchment, where calculated soil loss is 25 - 50 and >50 ton·ha-1·year-1. Apart from the gentle slopes of the alluvial fan (Krayma town and surroundings), the lower and the middle reaches of the watershed suffer from severe to extreme erosion risk. High terrain, slope steepness, removal of vegetation, and poor conservation practices are the most prominent causes of soil erosion.

Assessment of Soil Loss of the Dhalai River Basin, Tripura, India Using USLE

Soil erosion is one of the most important environmental problems, and it remains as a major threat to the land use of hilly regions of Tripura. The present study aims at estimating potential and actual soil loss (t·h-1·y-1) as well as to indentify the major erosion prone sub-watersheds in the study area. Average annual soil loss has been estimated by multiplying five parameters, i.e.: R (the rainfall erosivity factor), K (the soil erodibility factor), LS (the topographic factor), C (the crop management factor) and P (the conservation support practice). Such estimation is based on the principles de- fined in the Universal Soil Loss Equation (USLE) with some modifications. This intensity of soil erosion has been divided into different priority classes. The whole study area has been subdivided into 23 sub watersheds in order to identify the priority areas in terms of the intensity of soil erosion. Each sub-watershed has further been studied intensively in terms of rainfall, soil type, slope, land use/land cover and soil erosion to determine the dominant factor leading to higher erosion. The average annual predicted soil loss ranges between 11 and 836 t·h-1·y-1. Low soil loss areas (·h-1·y-1) have mostly been recorded under densely forested areas.

토양 특성 및 토지이용에 따른 낙동강 상류지역 토양침식위험성 평가

This study was conducted to evaluate soil erosion risk with a standard unit watershed in the upper Upper Nakdong River Basin according to soil characteristics and landuse using the spatial soil erosion map. The study area is , which consists of 2 subbasins, 35 standard unit watersheds (Andong basin 18, Imha basin 17). As a evaluation of soil erosion potential using the spatial soil erosion map, total annual soil loss and soil loss per area estimated (Andong basin 979, Imha basin 1,034) and (Andong basin 6.0, Imha basin 5.2), respectively. 54.2% of soil loss was originated from Arable land (Andong basin 49.0%, Imha basin 59.0%), and the area of regions, graded as higher Moderate for annual soil loss, was (Andong basin 84.9, Imha basin 116.8). Average soil loss per area of unit watersheds by classification according to soil dominant parent material types ranked Sedimentary rock group > Mixed group > Metamorphic rock group > Igneous rock group. In conclusion, the results of this study inform that the classification of soil parent material type would be effective for soil erosion analysis and interpretation in the Upper Nakdong River Basin.

English

Contour ridging is a widely used soil and water conservation practice in Southern Africa. However, in recent years, a number of investigators questioned the effectiveness of contour ridges in controlling surface runoff and soil erosion from smallholder farmers&rsquo; fields. To be an effective conservation practice, contour ridges must store infiltration excess surface runoff as surface depression storage in furrows between the ridges. In this study, three experimental runoff plots were established in Chilindamaji and six in Kamundi watershed in Malawi. Of the six plots in Kamundi, three had agroforestry contour hedgerows (AF1, AF2, and AF3) and the other three (K1, K2, and K3) had no contour hedgerows. None of the Chilindamaji plots (C1, C2, and C3) had agroforestry contour hedgerows. Hydrologic response analysis of data obtained from the nine runoff plots revealed that plots that retained more water as infiltration and surface depression storage had less runoff and soil erosion. For both sites, the average soil loss rates for the bare, 50% residue cover, and the contour ridge plots were 115, 66, and 5 ton/ha/year. The average soil loss rates for the three agroforestry plots were 4.2 ton/ha/year. Our results show that 50% residue cover reduced soil loss as compared to a bare soil, but are not as effective as the contour ridge and the agroforestry contour hedgerow treatments in reducing surface runoff and soil loss. &nbsp; Key words: Contour ridges, infiltration, runoff, soil loss, agroforestry, residue cover.

Magnetic susceptibility and Cs-137 inventory variability as influenced by land use change and slope positions in a hilly, semiarid region of west-central Iran

The objective of this study was to explore the slope position and land use change effects on the variability in magnetic susceptibility and 137Cs inventory as the soil redistribution indicators in a hilly semiarid calcareous area in Iran. The selected study area is located in a hilly region with pasture and cultivation land use of Fereydunshahr, Isfahan Province in west-central Iran. In the two mentioned dominant ecosystems, four slope positions including summit, shoulder, backslope and footslope were identified and in each land use and slope position, three cores were selected to collect 72 soil samples from three depths (0–10, 10–20, 20–30 cm) in an area of 15 × 15 cm. Additional 28 soil samples were collected from the reference site for soil loss and deposition calculations by using the Cs-137 measurement. The results of the study with the use of the Cs-137 technique showed that the average soil loss in the pasture land (46.4 t ha− 1 yr− 1) was significantly (p < 0.05) lower than the average soil loss in the cultivated land (80.4 t ha− 1 yr− 1). The highest soil loss in both land uses was obtained in the shoulder position, 60.1 and 84.4 t ha− 1 yr− 1, respectively, for the pasture and cultivated lands. Moreover, the highest rates of soil deposition was observed in a footslope position in both land uses and they were 34 and 32.4 t ha− 1 yr− 1 for the pasture and cultivated lands, respectively. Magnetic susceptibility was significantly (p < 0.05) greater in pasture (χlf = 41.51 × 10− 8 m3/kg) than in the cultivated land (χlf = 34.90 × 10− 8 m3/kg). The pasture land with a lower soil loss rate, indicated significantly higher magnetic susceptibility in all landform positions as compared to that in the cultivated land. The results of the correlation analysis showed that among the studied soil physico-chemical properties, χlf (r = 0.83, p < 0.01) in the pasture land had the highest correlation with the Cs-137 inventory. Throughout the non-linear regression analysis, χlf was introduced for relating soil parameters and the cesium inventory explained 68% and 79% of the total variability of 137Cs in the pasture and cultivated lands, respectively. The results implied that the variability in the magnetic susceptibility within the hillslope is consistent with the variation of the Cs-inventory; and the results thus demonstrate the slope and land use effects on soil redistribution.

Applying the QREI30index within the USLE modelling environment

The USLE/RUSLE model was designed to predict long-term (~20 years) average annual soil loss by accounting for the effects of climate, soil, topography and crops. The USLE/RUSLE model operates mathematically in two steps. The first step involves the prediction of soil loss from the ‘unit’ plot, a bare fallow area 22.1 m long on a 9% slope gradient with cultivation up and down the slope. Appropriate values of the factors accounting for slope length, gradient, crops and crop management and soil conservation practice are then used to adjust that soil loss to predict soil loss from areas that have conditions that are different from the unit plot. Replacing EI30, the USLE/RUSLE event erosivity index, by the product of the runoff ratio (QR) and EI30, can enhance the capacity of the model to predict short-term soil loss from the unit plot if appropriate data on runoff is available. Replacing the EI30 index by another index has consequences on other factors in the model. The USLE/RUSLE soil erodibility factor cannot be used when the erosivity factor is based on QREI30. Also, the USLE/RUSLE factors for slope length, slope gradient crops and crop management, and soil conservation practice cannot be used when runoff from other than the unit plot is used to calculate QR. Here, equations are provided to convert the USLE/RUSLE factors to values suitable for use when the erosivity factor is based on the QREI30 index under these circumstances. At some geographic locations, non linear relationships exist between soil loss from bare fallow areas and the QREI30 index. The effect of this on the slope length factor associated with the QREI30 index is demonstrated using data from runoff and soil loss plots located at the Sparacia site, Sicily. Copyright © 2012 John Wiley & Sons, Ltd.

Estimation of soil losses by USLE model using GIS at Mashhad plain, Northeast of Iran

The Universal Soil Loss Equation (USLE) is an erosion estimation model to assess the soil losses that would generally result from splash, sheet, and rill erosion. At the present study, spatial distribution of different erosion prone areas were identified by USLE model to determine the average annual soil losses at Mashhad plain, northeast of Iran. Soil losses were estimated on a 100 × 100 m cell basis resolution by overlaying the five digital parameter layers (R, K, LS, C, P). To determine the critical soil loss regions at the plain, cell-based USLE parameters were multiplied by Arc-GIS ver.9.3. The estimated annual soil losses values were subsequently grouped into five classes ranging from 0 to 0.25 t/h/year around the trough line of the plain at Kashaf-rud River to 2–10 t/ha/year at the hills and pediment plains. Our results indicated a good correlation between land units of hills and pediment plains with the values of soil losses at the study area (R2 = 0.72), also the statistical analysis exhibited a high correlation between land use/cover of dry farming and soil losses (R2 = 0.78).

Effect of tillage methods on soil erosion in Norway

Soil erosion is considered a serious environmental problem in parts of Norway. The effect on water quality is the most important concern, and the improvement of water quality is the major aim for mitigation techniques and regulations on tillage. Documentation of effects of tillage practices therefore has a high priority. In this paper, results from five plot experiments are presented. They are all located in the grain-growing district in southeastern Norway on clay and loam soils. Tillage treatments for spring cereals and winter cereals are compared. The effect of tillage is pronounced on erodible soils. The results showed that annual average soil losses in surface runoff for autumn-tilled and spring-tilled plots were 7 and 0.8 t ha−1yr−1 at Bjørnebekk; 4.3 and 0.4 t ha−1yr−1 at Askim; 2.6 and 0.2 t ha−1yr−1 at Hellerud; 1.1 and 0.2 t ha−1yr−1 at Øsaker; and 0.18 and 0.1 t ha−1yr−1 at Syverud, respectively. The corresponding total phosphorus losses were 8.4 and 1.5 kg ha−1yr−1 at Bjørnebekk; 4.5 and 0.8 kg ha−1yr−1 at Askim; 3.0 and 0.8 kg ha−1yr−1 at Hellerud; 1.30 and 0.44 kg ha−1yr−1 at Øsaker; and 0.43 and 0.45 kg ha−1yr−1 at Syverud for autumn and spring tillage, respectively. The effects were less pronounced on soils with a lower erodibility, but reduced autumn tillage is the most effective way to mitigate soil erosion as well as total phosphorus losses. The study also showed that the total phosphorus losses are closely correlated with soil losses. The results show the importance of soil tillage for soil and phosphorus losses and suggest that farmers avoid autumn tillage on areas with high erosion risk.