High Rates Of Soil Loss Research Articles

Effects of soil redistribution on soil properties in a cultivated Solonetzic-Chernozemic landscape of southwestern Saskatchewan

Although approximately 1.3 million ha of mixed Solonetzic – Chernozemic landscapes are cultivated in Saskatchewan, little information is available on the effects that agriculture has had on the quality of these soils. At our research site in southwestern Saskatchewan a clear landscape-scale pattern of soil distribution occurred. Regosolic and thin Chernozemic soils were associated with the long, gentle (2–5%) slopes and Solonetzic-influenced soils were associated with higher catchment area footslope and depressional positions. High rates of soil loss occurred throughout the landscape – overall a net soil loss of 31 Mg ha yr−1 was calculated using 137Cs redistribution techniques. No net depositional sites were observed in the 45 sampling points in the landscape, suggesting that the site was dominated by wind erosion. The high rates of loss were consistent with very low levels of soil organic carbon storage (37 to 46 Mg ha−1 to 45 cm) at all slope positions in the landscape and with the occurrence of sub-soil features in the plough layer. The Solonetzic-influenced soils occupy 38% of the site and have high sodium adsorption ratios (from 18 to 38 in the B horizon) and high soil resistance values as determined with a penetrometer. For the Solonetz and Solodized Solonetz soils these growth-limiting properties occur immediately below the 10-cm plough layer and may constitute a largely irreversible decrease in their productive capacity. Key words: Cesium-137, soil erosion, soil quality, landscape-scale, organic carbon

Economic incentives for farmers in the Philippine uplands to adopt hedgerow intercropping

Land degradation in the Philippine uplands is severe and widespread. Most upland areas are steep, and intense rainfall on soils disturbed by intensive agriculture can produce high rates of soil loss. This has serious implications for the economic welfare of a growing upland population with few feasible livelihood alternatives. Hedgerow intercropping can greatly reduce soil loss from annual cropping systems and has been considered an appropriate technology for soil conservation research and extension in the Philippine uplands. However, adoption of hedgerow intercropping has been sporadic and transient, rarely continuing once external support has been withdrawn. The objective of this paper is to investigate the economic incentives for farmers in the Philippine uplands to adopt hedgerow intercropping relative to traditional open-field maize farming. Cost-benefit analysis is used to compare the economic viability of hedgerow intercropping, as it has been promoted to upland farmers, with the viability of traditional methods of open-field farming. The APSIM and SCUAF models were used to predict the effect of soil erosion on maize yields from open-field farming and hedgerow intercropping. The results indicate that there have been strong economic incentives for farmers with limited planning horizons to reject hedgerow intercropping because the benefits of sustained yields are not realized rapidly enough to compensate for high establishment costs. Alternative forms of hedgerow intercropping such as natural vegetation and grass strips reduce establishment and maintenance costs and are therefore more economically attractive to farmers than hedgerow intercropping with shrub legumes. The long-term economic viability of hedgerow intercropping depends on the economic setting and the potential for hedgerow intercropping to sustain maize production relative to traditional open-field farming.

5707488 Screen/vortex apparatus for cleaning recycled pulp related process

Surface runoff and sediment production on unpaved forest roads in a humid Mediterranean mountainous area has been studied using a simple portable rainfall simulator at an intensity of 90 mm h− 1. Thirty six rainfall simulations were carried out on road plots: on the roadbank (12), on the sidecast fill (12), and on the roadbed (12). On the roadbanks, the steady-state runoff coefficient was 85.9% and runoff flow appeared after 63 s on average. On the sidecast fills, the steady-state runoff coefficient was 58.6% and mean time to runoff was 48 s. Finally, on the roadbeds, the steady-state runoff coefficient was 21.5% and mean time to runoff was 41 s. The highest soil loss rate was found on the roadbanks (486.7 g m− 2), mainly due to low plant cover, soil texture and rock fragments. The total soil erosion on the roadbanks was 3 and 18 times higher than those from the roadbeds and the sidecast fills, respectively. As a consequence, roadbanks can be considered the main source of sediments on the studied sites, but the function of unpaved forest roads as source points for runoff generation is more important.

Evaluation of WEPP Runoff And Soil Loss Predictions Using Natural Runoff Plot Data

Model testing and evaluation are critical to the acceptance of any new prediction tool. This study was conducted to evaluate the overall performance of the Water Erosion Prediction Project (WEPP) hillslope model in predicting runoff and soil loss under cropped conditions. Natural runoff plot data, including 4,124 selected events, 556 plot years, and 34 cropping scenarios, from eight locations were selected. The average length of record for the cropping scenarios was about nine years. Several common crops and tillage systems were included. The WEPP input files for soil, slope, climate, and crop management were compiled based on measured data. The coefficient of determination (r2) between model-predicted and measured-runoff volumes for optimized Green and Ampt hydraulic conductivity (Kb) was 0.77 for selected events, 0.76 for annual values, and 0.87 for average annual values; the r2 between predicted and measured soil losses (excluding fallow and corn plots at Bethany, Mo.) was 0.36, 0.60, and 0.85, respectively. Similar predictions of runoff and soil loss were also obtained with WEPP internally estimated Kb values. Runoff and soil loss were slightly overpredicted for small storms and for years with low runoff and soil loss rates, and were underpredicted for large storms and for years with high runoff and soil loss rates. However, average runoff and soil loss rates for different cropping and management systems were adequately predicted. The accuracy and reliability of the predictions were shown to improve from an event to annual to average annual basis. Results of this study show that the WEPP model is a useful tool for predicting runoff and soil loss rates under cropped conditions.

Cesium-137-measured erosion rates for soils of five parent-material groups in southwestern Saskatchewan

Despite the wide-spread perception that the soils of southwestern Saskatchewan are particularly erosion prone, few observations have been made on soil loss in this area. We used 137Cs redistribution to examine rates of soil loss associated with five parent-material groups in this area. Five sites were sampled in each parent-material group: one uncultivated site and four cultivated sites. Ten samples were taken at each site from landscape positions that have been shown in previous studies to have the highest rates of soil loss. The highest rates (median soil loss of −30 t ha−1 yr−1) were associated with glacial till landscapes; medium (−21 t ha−1 yr−1) but highly variable rates of loss, with coarse sandy glaciofluvial–lacustrine landscapes; and lower and consistent losses of around −12 t ha−1 yr−1, with silty glaciolacustrine and aeolian landscapes and with fine sandy glaciofluvial–lacustrine landscapes. The observed rates of loss can be used to calibrate models of geomorphic instability for this area. Key words: Soil erosion, soil quality, landscape-scale analysis, soil organic matter

Landscape-scale changes in indicators of soil quality due to cultivation in Saskatchewan, Canada

Quantitative assessments of the impact of agricultural practises on soil quality have been hindered by the lack of basic spatial units for designing landscape-scale research projects. This paper builds on the relationship which has been demonstrated to exist between small (5 m by 5 m) slope segments and soil distribution in order to define larger landform element complexes in till landscapes of southern Saskatchewan, Canada. Distinctive pedogenic regimes are associated with these complexes. These complexes were then used to stratify the landscape at four conterminous sites with different cultivation histories and to assess changes in indicators of soil quality. Soil redistribution (as assessed by 137Cs redistribution) has had a major impact on these landscapes. The shoulder and level summit complexes have experienced continued high rates of soil loss. The shoulder complexes have lost 55% of their original soil organic carbon (a loss of 64 mg ha −1) over 80 years and 70% of this loss is attributable to net soil export from these positions. The portions of the footslope complexes dominated by Orthic Black Chernozemic soils initially act as sediment deposition sites in the first 22 years of cultivation, but ultimately this soil is removed from these positions and a moderate decline in soil quality occurs. The Gleysolic-dominated portions of the footslopes and the level depressional complexes occupy 15% of the landscape and are the major long-term sediment depositional sites; the biochemical indicators of soil quality (soil organic carbon and total soil nitrogen) show a major and beneficial increase in these positions.

On-site economic evaluation of soil conservation practices in Honduras

Abstract Factors affecting the cost to the farmer of employing soil erosion reduction strategies are examined for the steep hillsides near Tegucigalpa, Honduras. Linear programming and MOTAD are used to examine these factors. Results indicate that some modest reductions in erosion can be achieved at little cost to the farmer by reorganizing production, switching rotations, and using contour plowing. These modest reductions still lead to extremely high rates of erosion. Sharper reductions may be achieved at progressively higher costs as erosion control structures are constructed and acreage is left fallow. There is a high cost to the farmer of reducing erosion to ‘sustainable’ levels. A consistent tradeoff emerges between levels of soil conservation, income, and risk; erosion reduction efforts lead to lower incomes and higher risk. The analysis of likely benefits to farmers for erosion reduction shows that even under assumptions of very high yield losses from soil erosion, optimal farm plans still lead to high rates of soil loss, implying a need for policies that internalize externalities if off-farm damages are to be minimized.

On‐site economic evaluation of soil conservation practices in Honduras

AbstractFactors affecting the cost to the farmer of employing soil erosion reduction strategics are examined for the steep hillsides near Tegucigalpa, Honduras. Linear programming and MOTAD are used to examine these factors. Results indicate that some modest reductions in erosion can be achieved at little cost to the farmer by reorganizing production, switching rotations, and using contour plowing. These modest reductions still lead to extremely high rates of erosion. Sharper reductions may be achieved at progressively higher costs as erosion control structures are constructed and acreage is left fallow. There is a high cost to the farmer of reducing erosion to ‘sustainable’ levels. A consistent tradeoff emerges between levels of soil conservation, income, and risk; erosion reduction efforts lead to lower incomes and higher risk. The analysis of likely benefits to farmers for erosion reduction shows that even under assumptions of very high yield losses from soil erosion, optimal farm plans still lead to high rates of soil loss, implying a need for policies that internalize externalities if off‐farm damages are to be minimized.

Remote sensing and gis based mapping and modeling of water erosion and sediment yield in a semi‐arid watershed of Morocco

Abstract Water erosion, considered as a natural process accelerated by man, is the main cause of the degradation of our agro‐pedological heritage as well as the deterioration of water quality that it entails. Topographical and climatological factors associated with high population growth make Morocco a favorable area for erosion phenomena (water erosion, wind erosion, etc). The present study calls upon the use of remote sensing and a geographical information system (GIS) for quantifying annual soil losses in conjunction with the use of the universal soil loss equation (USLE), the quanity of sediments that will be delivered to the drainage network as well as the erosional potential of the Oued Aricha watershed (Province of Settat, Morocco). As expected, the highest soil loss rates were recorded in regions of bare soils. We also noted that important soil losses (more than 20 t/ha/yr) can be related to only one third of the study area (34.94%); the soil loss map also shows that these areas are mostly located...

SPATIAL PATTERN OF SOIL REDISTRIBUTION IN BOROLL LANDSCAPES, SOUTHERN SASKATCHEWAN, CANADA1

The spatial distribution of soil loss and gain in agricultural fields was examined at twenty-one sites in the Boroll soil zone of southern Saskatchewan. The rates of soil loss and gain are assessed using cesium-137 redistribution techniques. The correlations between the rates of soil redistribution and individual slope variables (e.g., gradient and length) are very low. Statistically distinct rates of soil redistribution are, however, associated with three-dimensional landform elements of the slope systems examined. In the aridic and ustic Boroll soil regions the highest rates of soil loss are associated with divergent back-slopes and shoulders; in the udic Boroll zone the highest losses occur on the convergent backslope sites. In all three zones soil gain is concentrated in the convergent footslope elements. The differences in the observed spatial pattern of soil redistribution between the udic Boroll region and the aridic and ustic Boroll regions is attributed to differences in the dominant detachment and transport process in the landscape.

RATES OF SOIL REDISTRIBUTION ASSOCIATED WITH SOIL ZONES AND SLOPE CLASSES IN SOUTHERN SASKATCHEWAN

The usefulness of the average slope measurements available from soil surveys in the development of regional erosional inventories depends on the relationship between the average slope measurements of the mapped area and the mean rates of soil redistribution within the areas. Using 137Cs redistribution techniques we examined the relationship between mean rates of soil redistribution and average slope characteristics at 21 areas in the Brown, Dark Brown, and Black Chernozem soil zones of southern Saskatchewan. Net soil losses averaged 5.8 t ha−1 yr−1 for areas with mean gradients between 0 and 1.5°, 7.8 t ha−1 yr−1 for areas with mean gradients between 1.0 and 3°, and 11.3 t ha−1 yr−1 for areas with mean gradients between 3.5 and 8.5°. For all three slope classes, the highest rates of soil loss were found in the Dark Brown soil zone and the lowest rates in the Black soil zone. Net soil loss alone was, however, an inadequate indicator of the rate of loss within the areas because a considerable proportion of eroded soil was deposited within the confines of the study areas. Our results indicate that a distinct rate of soil loss was associated with the average slope characteriestics of the study area, but that both net soil loss from the field and mean soil loss within the field need to be considered together if a complete erosional assessment is to be made of an area. Key words: Soil erosion, soil deposition, 137Cs redistribution, slope gradient, Saskatchewan

Severe erosion on agricultural land in east Sussex, UK October 1987

Severe erosion occurred as a result of heavy rainfall on 7 October 1987 and subsequent storms. Rates of erosion were highest on land drilled with winter cereals in the previous three weeks but erosion also occurred on ploughed land. In an area of c36 km 2 some erosion was recorded on all cereal fields. Several fields suffered losses >50 m 3 ha −1 and rates reached>200 m 3 ha −1 on one field. This is the most serious erosion on agricultural land recorded in Britain. In autumn months heavy rain on erodible, silt-rich soils prone to crusting inevitably leads to runoff and high rates of soil loss but a number of factors contributed to the severity of this event: the amount of bare, recently drilled land; the timing of drilling; the size of fields, steepness and length of slopes; the rolling of drilled fields, and the prevalence of wheelings.

Soil and erosion features of the central plateau region of Tigrai, Ethiopia

The results of reconnaissance soil surveys covering 6,000 km 2 are used to describe the Central Plateau region, which lies at elevations of 2,000 to 2,800 m in northern Ethiopia. Landform and soil sequences on calcareous shales, dolerites and sandstones are described, in which the principal soil units are Lithosols, Luvisols, Cambisols, Arenosols and Vertisols. Detailed morphological and analytical data are presented for a profile representative of arable soils in each sequence. Small-scale subsistence cultivation of cereals is the dominant land use; all land which is physically cultivable is at present cultivated. Settlement patterns are closely related to soil type, nucleated settlement occurring on fine textured soils but dispersed settlement on coarser textured and more freely draining soils. Erosion and soil moisture features of the three landforms described were investigated and compared. Empirical methods and suspended sediment measurements indicate high rates of regional soil loss (17–33 t ha −1 yr −1), accounted for by seasonally high rates of rainfall erosivity, steep terrain and poor land use. The recent development of gully erosion is seen to be linked to the disintegration of waterfall tufas. Application of the universal soil loss equation to arable lands indicates potential annual soil losses in the range of 400 t ha −1 on Vertisols to 200 t ha −1 on Cambisols: differences in rates are ascribed principally to differences in crop planting dates, which affect the degree of vegetative protection during periods of high rainfall erosivity. Soil moisture is shown to be in the available range for less than three months in the year. The time at which moisture in the profile enters the available range differed between the three soils monitored and was found to be closely related to the crop planting date, thus indirectly affecting the erosion hazard.