Assessing soil quality indicator under different land use and soil erosion using multivariate statistical techniques

Soil degradation associated with soil erosion and land use is a critical problem in Iran and there is little or insufficient scientific information in assessing soil quality indicator. In this study, factor analysis (FA) and discriminant analysis (DA) were used to identify the most sensitive indicators of soil quality for evaluating land use and soil erosion within the Hiv catchment in Iran and subsequently compare soil quality assessment using expert opinion based on soil surface factors (SSF) form of Bureau of Land Management (BLM) method. Therefore, 19 soil physical, chemical, and biochemical properties were measured from 56 different sampling sites covering three land use/soil erosion categories (rangeland/surface erosion, orchard/surface erosion, and rangeland/stream bank erosion). FA identified four factors that explained for 82 % of the variation in soil properties. Three factors showed significant differences among the three land use/soil erosion categories. The results indicated that based upon backward-mode DA, dehydrogenase, silt, and manganese allowed more than 80 % of the samples to be correctly assigned to their land use and erosional status. Canonical scores of discriminant functions were significantly correlated to the six soil surface indices derived of BLM method. Stepwise linear regression revealed that soil surface indices: soil movement, surface litter, pedestalling, and sum of SSF were also positively related to the dehydrogenase and silt. This suggests that dehydrogenase and silt are most sensitive to land use and soil erosion.     

Land degradation due to erosion in public perception. Case study: Secaşul Mare river basin settlements (Transylvanian Depression,Romania)

According to the International Decade for Natural Disaster Reduction (IDNDR 1990–1999), the risk indicates potential losses due to particular natural phenomenon, and these could be reduced by improving of prevention and education. People perceive these losses differently depending on phenomenon occurrence, severity, and impact in time. Starting from this idea, this research presents public perception on land degradation through erosion in a small area from the central part of Romania (south-west of Transylvanian Depression). The research was based on a questionnaire consisting of 16 questions. The items were structured by issues: awareness assessment regarding hazard and risk phenomena, assessment of type of property and land use, assessment of knowledge and information on the possible production of negative effects by natural phenomena, and evaluation of land owners’ attitudes towards the occurrence of erosion on their land. Results reveal that the public perception on erosion is weak. This process is perceived as insignificant due to lack of phenomenon knowledge and especially because of scarcity preoccupation in land’s quality monitoring. Even though the owned lands are affected by erosion forms, the owners are not aware of the phenomenon that generates them. Material damages caused by erosion, loss of soil quality, and land fertility decrease are less perceived because the economic losses fill only at long term. This perception leads to underestimating erosion risk compared to other natural phenomena and to a passive attitude towards this particular phenomenon.     

Use of USLE/GIS Methodology for Predicting Soil Loss in a Semiarid Agricultural Watershed

The Universal Soil Loss Equation (USLE) is an erosion model to estimate average soil loss that would generally result from splash, sheet, and rill erosion from agricultural plots. Recently, use of USLE has been extended as a useful tool predicting soil losses and planning control practices in agricultural watersheds by the effective integration of the GIS-based procedures to estimate the factor values in a grid cell basis. This study was performed in the Kazan Watershed located in the central Anatolia, Turkey, to predict soil erosion risk by the USLE/GIS methodology for planning conservation measures in the site. Rain erosivity (R), soil erodibility (K), and cover management factor (C) values of the model were calculated from erosivity map, soil map, and land use map of Turkey, respectively. R values were site-specifically corrected using DEM and climatic data. The topographical and hydrological effects on the soil loss were characterized by LS factor evaluated by the flow accumulation tool using DEM and watershed delineation techniques. From resulting soil loss map of the watershed, the magnitude of the soil erosion was estimated in terms of the different soil units and land uses and the most erosion-prone areas where irreversible soil losses occurred were reasonably located in the Kazan watershed. This could be very useful for deciding restoration practices to control the soil erosion of the sites to be severely influenced.     

Phosphorus losses from arable fields in Sweden—effects of field-specific factors and long-term trends

Accelerated eutrophication of surface water is often caused by high phosphorus (P) losses from agricultural fields. Long-term measurements of P concentrations from arable fields are therefore important for understanding of processes and key factors behind losses. Unfortunately, long-time series are difficult to compare due to high variablity, non-normal distribution, precipitation variability and flow relatedness. The objective was to use locally weighted scatterplot smoothing (LOWESS) and Seasonal Kendall Test to account for discharge effects on concentrations of P forms and suspended soil material, and to identify trends for seven agricultural fields included in a Swedish water quality monitoring program. Soil P content and sorption capacity governed concentrations and losses of dissolved reactive phosphorus (DRP). Other factors, such as preferential flow may influence the importance of these factors. Suspended soil material and unreactive phosphorus (UP) concentrations in water discharge depended on soil texture, slope of the field and total soil P content. Statistically significant trends in concentrations of different P forms were found for two fields. These trends are probably a consequence of changes in P additions and soils P saturation levels.     

A method to assess soil erosion from smallholder farmers’ fields

Soil erosion by water is a major threat to sustainable food production systems in Africa. This study presents a qualitative soil erosion assessment method that links the number of broken ridges (NBRS) observed on a smallholder farmer’s field after a rain event to factors of soil erosion (e.g., rainfall intensity, slope steepness, crop canopy height, and conservation practice) and to soil loss data measured from a runoff plot and receiving small streams. The assessment method consists of a rapid survey of smallholder farmers combined with field monitoring. Results show an indirect relationship between NBRS and factors of soil erosion. Results also show a direct relationship between NBRS and suspended sediment concentrations measured from an experimental runoff plot and receiving streams that drain the sub-watersheds where farmers’ fields are located. Given the limited human and financial resources available to soil erosion research in developing countries, monitoring NBRS is a simple, cost-effective, and reliable erosion assessment method for regions where smallholder farmers practice contour ridging.     

Adapting the RUSLE and GIS to model soil erosion risk in a mountains karst watershed, Guizhou Province, China

Soil erosion is a serious environmental problem in Guizhou Province, which is located in the centre of the karst areas of southwestern China. Unfortunately, Guizhou Province suffers from a lack of financial resources to research, monitor and model soil erosion at large watershed. In order to assess the soil erosion risk, soil erosion modeling at the watershed scale are urgently needed to be undertaken. This study integrated the Revised Universal Soil Loss Equation (RUSLE) with a Geographic Information System (GIS) to estimate soil loss and identify the risk erosion areas in the Maotiao River watershed, which is a typical rural watershed in Guizhou Province. All factors used in the RUSLE were calculated for the watershed using local data. It was classified into five categories ranging from minimal risk to extreme erosion risk depending on the calculated soil erosion amount. The soil erosion map was linked to land use, elevation and slope maps to explore the relationship between soil erosion and environmental factors and identify the areas of soil erosion risk. The results can be used to advice the local government in prioritizing the areas of immediate erosion mitigation. The integrated approach allows for relatively easy, fast, and cost-effective estimation of spatially distributed soil erosion. It thus indicates that RUSLE-GIS model is a useful and efficient tool for evaluating and mapping soil erosion risk at a large watershed scale in Guizhou Province.     

Properties and erosional response of soils in a degraded ecosystem in Crete (Greece)

To study desertification processes relating to soil erosion, a climatological and altitudinal gradient from south to north was selected in Crete (Greece) and four locations were selected along the gradient. At the locations precipitation ranged from 1400 mm/year at the highest location to 400 mm/year at the lowest. All locations are affected by the actual land use: intensive grazing, small controlled fires, and abandoned agricultural terraces. Representative soil profiles were described in the field and analyzed in the laboratory, and rainfall simulation experiments in the field measured soil erosion over different soil surfaces and land uses. Data on physical and chemical properties were obtained from the soil profiles and soil hydrology, and erosion data were obtained from the rainfall simulation experiments. Soil aggregation was studied with samples taken from the soil in the rainfall simulation plots and special attention being paid to the aggregate size distribution and the water-stable microaggregation. The interaction between climatological conditions and land use seems to be the main factor controlling soil erosion. This paper describes how the expected erosion along the gradient (from the most humid to the driest site) can be affected and disturbed by specific processes derived from land use.     

Monitoring fugitive dust emissions from off-highway vehicles traveling on unpaved roads and trails using passive samplers

Vehicles traveling on dry, unpaved roads generate copious quantities fugitive dust that contributes to soil erosion, and potentially threatens human health and ecosystems. The purpose of this study was to develop a low-cost technique for monitoring road dust that would enable land managers to estimate soil loss. The "sticky-trap" collectors developed were evaluated at the Turkey Bay off-highway vehicle (OHV) riding area on the Land Between the Lakes National Recreation Area, in western Kentucky. The results showed that the dust plume created by vehicle traffic was heterogeneous: larger particles were in the lower part of the plume and deposited closer to the source, smaller particles were carried higher in the plume and traveled at least 100 m away from the source. Collection of particles parallel to the source was also heterogeneous, suggesting that measurements taken at a single point may not be appropriate for estimating erosion losses. Measurements taken along two trails indicate that when large numbers of riders are present, dust concentrations may reach unhealthful conditions for riders, but that it is unlikely that fugitive dust is harming native vegetation, given frequent rainfall. The study demonstrated that OHV traffic contributes to substantial erosion of roadbeds because of aeolian transport.     

Effects of land use on phosphorus loss in the hilly area of the Loess Plateau, China

The hilly area of Loess Plateau has some of the highest soil erosion rates in the world, and serious soil erosion causes great losses of plant nutrients. As the most common land use in Loess Plateau, slope farmland contributed most of the erosion soils. This study was designed to examine the effects of land use and slope angle of farmland on phosphorus (P) loss in the hilly area of loess plateau. Farmland (FR), barrenland (BR), and four forest treantment (seabuckthorn+ poplar (SP), immature seabuckthorn (IS), mature seabuckthorn (MS), immature Chinese pine (ICP)) were the types of land use; 10, 15, 20, 25, 30 degrees were the slope angles of FR that were compared. The results showed a larger proportion of P loss occurred in erosion soil fraction of FR, ICP, ICP, and the five slope treatments of FR; in SP, IS, and MS, P loss was primarily through runoff. FR produced more P loss than SP, IS, ICP, BR, and MS. 20∼30 degrees may be the slope ranges for P loss of FR; FR in this ranges would loss more P with soil erosion. SP, IS, and MS were reasonable land uses for their less runoff, soil loss, and P loss. Farmlands over 15 degrees should be abandoned or reforested for it would produce more runoff, soil loss, and P loss.     

Check dam sediments: an important indicator of the effects of environmental changes on soil erosion in the Loess Plateau in China

Check dam sediments document the process of soil erosion for a watershed. The main objectives of this research are as follows: first, to determine whether the sediments trapped in check dams can provide useful information about local erosion and the environment, and second, to obtain the extent to which they can be stratigraphically interpreted and correlated to the land use history of an area controlled by check dams. Particle size and the concentration of ¹³⁷Cs in sediments are the indicators used to study the effects of environmental changes on soil erosion in the Loess Plateau, China. A total of 216 soil samples were collected from four sediment profile cores at the Yangjuangou watershed check dam constructed in 1955 and fully silted with sediments by 1965. The results indicated that ¹³⁷Cs dating and sediment particle size can characterize the sediment deposition process. Silt makes up more than 50 % of the sediment; both the clay and silt sediment fractions decrease gradually in the upstream direction. The sediment profiles are characterized by three depositional layers. These layers suggest changes in the land use. The top layer showed tillage disturbance, with moderate sediments and new soil mixed from 0 to 20 cm. A transition stage from wetlands (characterized by vegetation such as bulrush) to cropland is inferred from sediments at depths of 20–85 cm. Below 85 cm, sedimentary layering is obvious and there is no tillage disturbance. At the downstream site, A0, the average rate of sediment deposition from 1958 to 1963 was approximately 6,125.4 t year^?1 km^?2. Because of their high time resolution, check dam sediments indicate the effects of environmental changes on soil erosion, and they can provide a multiyear record of the soil erosion evolution at the local scale in the middle reaches of the Yellow River.     

Visualising the equilibrium distribution and mobility of organic contaminants in soil using the chemical partitioning space

Assessing the behaviour of organic chemicals in soil is a complex task as it is governed by the physical chemical properties of the chemicals, the characteristics of the soil as well as the ambient conditions of the environment. The chemical partitioning space, defined by the air-water partition coefficient (K(AW)) and the soil organic carbon-water partition coefficient (K(OC)), was employed to visualize the equilibrium distribution of organic contaminants between the air-filled pores, the pore water and the solid phases of the bulk soil and the relative importance of the three transport processes removing contaminants from soil (evaporation, leaching and particle erosion). The partitioning properties of twenty neutral organic chemicals (i.e. herbicides, pharmaceuticals, polychlorinated biphenyls and volatile chemicals) were estimated using poly-parameter linear free energy relationships and superimposed onto these maps. This allows instantaneous estimation of the equilibrium phase distribution and mobility of neutral organic chemicals in soil. Although there is a link between the major phase and the dominant transport process, such that chemicals found in air-filled pore space are subject to evaporation, those in water-filled pore space undergo leaching and those in the sorbed phase are associated with particle erosion, the partitioning coefficient thresholds for distribution and mobility can often deviate by many orders of magnitude. In particular, even a small fraction of chemical in pore water or pore air allows for evaporation and leaching to dominate over solid phase transport. Multiple maps that represent soils that differ in the amount and type of soil organic matter, water saturation, temperature, depth of surface soil horizon, and mineral matters were evaluated.     

The use of spatial empirical models to estimate soil erosion in arid ecosystems

The central objective of this project was to utilize geographical information systems and remote sensing to compare soil erosion models, including Modified Pacific South-west Inter Agency Committee (MPSIAC), Erosion Potential Method (EPM), and Revised Universal Soil Loss Equation (RUSLE), and to determine their applicability for arid regions such as Kuwait. The northern portion of Umm Nigga, containing both coastal and desert ecosystems, falls within the boundaries of the de-militarized zone (DMZ) adjacent to Iraq and has been fenced off to restrict public access since 1994. Results showed that the MPSIAC and EPM models were similar in spatial distribution of erosion, though the MPSIAC had a more realistic spatial distribution of erosion and presented finer level details. The RUSLE presented unrealistic results. We then predicted the amount of soil loss between coastal and desert areas and fenced and unfenced sites for each model. In the MPSIAC and EPM models, soil loss was different between fenced and unfenced sites at the desert areas, which was higher at the unfenced due to the low vegetation cover. The overall results implied that vegetation cover played an important role in reducing soil erosion and that fencing is much more important in the desert ecosystems to protect against human activities such as overgrazing. We conclude that the MPSIAC model is best for predicting soil erosion for arid regions such as Kuwait. We also recommend the integration of field-based experiments with lab-based spatial analysis and modeling in future research.     

The role of forest stand density in controlling soil erosion: implications to sediment-related disasters in Japan

The role of forest stand density in controlling soil erosion was investigated in Ehime Prefecture, Japan. The main objective was to compare soil erosion under different forest conditions including forest type, species composition, and stand density as influenced by thinning operations. Relative yield index (Ry) was used as an indicator of stand density to reflect the degree of management operations in the watershed. Eleven treatments were established based on the above forest conditions. Soil loss was collected in each of the 11 treatments after each rainfall event for a period of 1 year. The paper presents summary data on soil loss as affected by forest conditions and rainfall patterns. Findings showed that an appropriate forest management operation, which can be insured by stand density control, is needed to reduce soil loss. The present study plays an important role in clarifying technical processes related to soil erosion, while it helps linking these elements to current Japanese forestry issues and bringing new inputs to reducing sediment-related disasters in Japan.     

A field study of the influence of land management and soil properties on runoff and soil loss in central Spain

Since the 1950s afforestation of degraded land has been the principal means of combatting erosion in a seasonally arid area of central Spain. In the 1970s tree planting of steep hillsides and gully sides was preceded by bench terracing. Experimental sites have been established to monitor runoff and soil losses under mature Pinus forest, 12-year-old Pinus forest, and Cistus matorral. The experiment is being conducted at three scales: large gully or small watershed (c. 3.5 ha), runoff erosion plot (10–21.5 m²), and rainfall simulation plot (1 m²). Monitoring began in October 1992. Discharge was recorded continuously, while sediment loss and soil moisture content were measured on a storm basis. The paper presents summary data on runoff and soil erosion for the three scales and comments on relationships between land management, site characteristics, and these losses. We stress the crucial role of vegetation and its interrelationship with soil properties such as structure and aggregate stability. Matorral was effective in combatting water and soil loss, but we question the practice of afforesting seasonally arid, steeply sided areas that have highly erodible soils.     

Morphometry and land cover based multi-criteria analysis for assessing the soil erosion susceptibility of the western Himalayan watershed

Complex mountainous environments such as Himalayas are highly susceptibility to natural hazards particular those that are triggered by the action of water such as floods, soil erosion, mass movements and siltation of the hydro-electric power dams. Among all the natural hazards, soil erosion is the most implicit and the devastating hazard affecting the life and property of the millions of people living in these regions. Hence to review and devise strategies to reduce the adverse impacts of soil erosion is of utmost importance to the planners of watershed management programs in these regions. This paper demonstrates the use of satellite based remote sensing data coupled with the observational field data in a multi-criteria analytical (MCA) framework to estimate the soil erosion susceptibility of the sub-watersheds of the Rembiara basin falling in the western Himalaya, using geographical information system (GIS). In this paper, watershed morphometry and land cover are used as an inputs to the MCA framework to prioritize the sub-watersheds of this basin on the basis of their different susceptibilities to soil erosion. Methodology included the derivation of a set of drainage and land cover parameters that act as the indicators of erosion susceptibility. Further the output from the MCA resulted in the categorization of the sub-watersheds into low, medium, high and very high erosion susceptibility classes. A detailed prioritization map for the susceptible sub-watersheds based on the combined role of land cover and morphometry is finally presented. Besides, maps identifying the susceptible sub-watersheds based on morphometry and land cover only are also presented. The results of this study are part of the watershed management program in the study area and are directed to instigate appropriate measures to alleviate the soil erosion in the study area.     

Estimates of soil erosion using cesium-137 tracer models

The soil erosion was studied by ¹³⁷Cs technique in Yatagan basin in Western Turkey, where there exist intensive agricultural activities. This region is subject to serious soil loss problems and yet there is not any erosion data towards soil management and control guidelines. During the soil survey studies, the soil profiles were examined carefully to select the reference points. The soil samples were collected from the slope facets in three different study areas (Kırtas, Peynirli and Kayısalan Hills). Three different models were applied for erosion rate calculations in undisturbed and cultivated sites. The profile distribution model (PDM) was used for undisturbed soils, while proportional model (PM) and simplified mass balance model (SMBM) were used for cultivated soils. The mean annual erosion rates found using PDM in undisturbed soils were 15 t ha⁻¹ year⁻¹ at the Peynirli Hill and 27 t ha⁻¹ year⁻¹ at the Kırtas Hill. With the PM and SMBM in cultivated soils at Kayışalan, the mean annual erosion rates were obtained to be 65 and 116 t ha⁻¹ year⁻¹, respectively. The results of ¹³⁷Cs technique were compared with the results of the Universal Soil Loss Equation (USLE).     

10-Daily soil erosion modelling over sub-Saharan Africa

Soil erosion is considered to be one of the greatest environmental problems of sub-Saharan Africa. This paper investigates the advantages and disadvantages of modelling soil erosion at the continental scale and suggests an operational methodology for mapping and quantifying 10-daily water runoff and soil erosion over this scale using remote sensing data in a geographical information system framework. An attempt is made to compare the estimates of this study with general data on the severity of soil erosion over Africa and with measured rates of soil loss at different locations over the continent. The results show that the measured and estimated rates of erosion are in some areas very similar and in general within the same order of magnitude. The importance and the potential of using the soil erosion estimates with simple models and easily accessible free data for various continental-scale environmental applications are also demonstrated.     

Effect of dehydrogenase,phosphatase and urease activity in cotton soil after applying thiamethoxam as seed treatment

Soil enzymes are indicators of microbial activities in soil and are often considered as an indicator of soil health and fertility. They are very sensitive to the agricultural practices, pH of the soil, nutrients, inhibitors and weather conditions. To understand the effect of an insecticide, thiamethoxam, on different soil enzyme activities, the experiments were conducted at cotton experimental fields of Punjab Agricultural University, Ludhiana. The results here were presented to understand the impact of thiamethoxam on soil enzyme activities. Thiamethoxam was applied as seed treatment to control the pest. Soil from three localities, i.e. soil in which seed was treated with recommended dose at 2.1 g a.i. kg^?1, soil in which seed was treated with four times recommended dose at 8.4 g a.i. kg^?1 and from the control field, were tested for different enzyme activities. Phosphatase and dehydrogenase activities were high in control soil in comparison to control soil while no effect of this insecticide on urease activity. Thiamethoxam had inhibitory effects on dehydrogenase and phosphatase activities. Therefore, it can be attributed that agricultural practices, weather conditions and use of thiamethoxam might be responsible for the different level of enzyme activities in soil.     

Comparison of tracer techniques for monitoring sewer losses

Two different experimental techniques employing conservative tracers to determine exfiltration losses in a sewer system are reported. Both techniques compare the in-sewer responses measured along designated indicator and reference sections to assess the level of exfiltration although with different degrees of reliability. The experimental and interpretation errors associated with a pulse dosing technique, in which Rhodamine WT is used as the single tracer, are described. The estimation of exfiltration requires the comparison of indicator and reference peaks which need to be well resolved and reproducible in order to provide realistic results. A more consistent technique involves the continuous dosing of two different tracers with the objective of producing simultaneous downstream peak tracer concentrations. Any errors due to flow variations are eliminated and the longer measurement period allows both peak and background concentrations to be more accurately determined. Rhodamine WT, Li and Br were used in different combinations over the approximately 20 min duration of each continuous dosing experiment and were found to demonstrate conservative behaviours with measured recoveries of 97.6-100.6%, 97.3-101.4% and 108.4-109.2%, respectively. The analytical problems associated with the determination of the different tracers in sewage are described and are shown to be responsible for the reduced accuracy of the results associated with the use of Br. The preferred combination of tracers is Rhodamine WT as the indicator and Li as the reference and these are shown to be capable of estimating sewer losses to an accuracy of +/-1.0% using the continuous dosing approach.     

Effect of land use land cover change on soil erosion potential in an agricultural watershed

Universal soil loss equation (USLE) was used in conjunction with a geographic information system to determine the influence of land use and land cover change (LUCC) on soil erosion potential of a reservoir catchment during the period 1989 to 2004. Results showed that the mean soil erosion potential of the watershed was increased slightly from 12.11 t ha^???1 year^???1 in the year 1989 to 13.21 t ha^???1 year^???1 in the year 2004. Spatial analysis revealed that the disappearance of forest patches from relatively flat areas, increased in wasteland in steep slope, and intensification of cultivation practice in relatively more erosion-prone soil were the main factors contributing toward the increased soil erosion potential of the watershed during the study period. Results indicated that transition of other land use land cover (LUC) categories to cropland was the most detrimental to watershed in terms of soil loss while forest acted as the most effective barrier to soil loss. A p value of 0.5503 obtained for two-tailed paired t test between the mean erosion potential of microwatersheds in 1989 and 2004 also indicated towards a moderate change in soil erosion potential of the watershed over the studied period. This study revealed that the spatial location of LUC parcels with respect to terrain and associated soil properties should be an important consideration in soil erosion assessment process.