The assessment of soil loss by water erosion in China

Soil erosion is a major environmental problem in China. Planning for soil erosion control requires accurate soil erosion rate and spatial distribution information. The aim of this article is to present the methods and results of the national soil erosion survey of China completed in 2011. A multi-stage, unequal probability, systematic area sampling method was employed. A total of 32,948 sample units, which were either 0.2–3 km² small catchments or 1 km² grids, were investigated on site. Soil erosion rates were calculated with the Chinese Soil Loss Equation in 10 m by 10 m grids for each sample unit, along with the area of soil loss exceeding the soil loss tolerance and the proportion of area in excess of soil loss tolerance relative to the total land area of the sample units. Maps were created by using a spatial interpolation method at national, river basin, and provincial scales. Results showed that the calculated average soil erosion rate was 5 t ha⁻¹ yr⁻¹ in China, and was 18.2 t ha⁻¹ yr⁻¹ for sloped, cultivated cropland. Intensive soil erosion occurred on cropland, overgrazing grassland, and sparsely forested land. The proportions of soil loss tolerance exceedance areas of sample units were interpolated through the country in 250 m grids. The national average ratio was 13.5%, which represents the area of land in China that requires the implementation of soil conservation practices. These survey results and the maps provide the basic information for national conservation planning and policymaking.     

The effect of land management practices on soil erosion and land desertification in an olive grove

The need for reliable estimates of soil loss under different land management practices (LMPs) is becoming imperative in the Mediterranean basin to inform decisions on more effective strategies for land management. The effect of LMPs on soil erosion and land degradation has been investigated using experiments from November 2008 to November 2011 in an olive grove in central Crete (Greece). The study area was on sloping land with soils formed on marl deposits which are vulnerable to desertification because of surface runoff and tillage. The experimental design included three treatments with two replicates (3 × 5 m experimental plots) corresponding to the following LMPs: (i) no tillage–no herbicide application, (ii) no tillage–herbicide application and (iii) ploughing to 20 cm perpendicular to the contours. The following variables were monitored: surface water runoff, sediment loss, soil temperature at 10 cm, soil moisture content at depths of 20 and 50 cm, as well as selected climatic variables. The results show that the no tillage–no herbicide management practice gave the lowest sediment loss (1.44–4.78 g/m²/yr), the lowest water runoff (1.8–11.5 mm/yr), the greatest amount of water stored in the soil, the lowest soil temperature and the lowest desertification risk compared with the other treatments. Tillage resulted in the greatest sediment loss (13.6–39.2 g/m²/yr) and surface runoff (16.5–65.0 mm/yr), and an intermediate amount of water stored in the soil. In addition, this treatment led to the loss of soil thickness of 3.7 mm/yr because of ploughing. The results demonstrate the high risk of desertification in the investigated region and the methodology can be used in other Mediterranean areas as an assessment framework for evaluating land degradation and the impact of land management on soil erosion.     

Temporal and spatial changes of soil erosion under land use and land cover change based on Chinese soil loss equation in the typical watershed on the Loess Plateau

Land use and land cover change (LULCC) directly affect the temporal and spatial change of soil erosion. As a typical governance watershed in the hilly and gully area of the Loess Plateau, the Jiuyuangou watershed has experienced significant LULCC in the past 10 years due to conversion of farmland to forests, economic construction, and cropland abandonment. However, the evolution process of soil erosion change and LULCC in the watershed is unclear, as is the relationship between the two. This study used satellite images to extract information on LULCC in the watershed and the Chinese soil loss equation (CSLE) model to evaluate the temporal and spatial evolution of soil erosion in the watershed from 2010 to 2020. The main results showed that (1) the continuous vegetation restoration project in the watershed reduced soil erosion from 2010 to 2015; however, the increased frequency of extreme rainfall events after 2015 reduced its impact. The annual average soil erosion modulus decreased from 10.85 t ha⁻¹ year⁻¹ in 2010 to 8.03 t ha⁻¹ year⁻¹ in 2015 but then increased to 10.57 t ha⁻¹ year⁻¹ in 2020; (2) the main land use and land cover (LULC) type in the Jiuyuangou watershed is grassland, accounting for 62% of the total area, followed by forestland, cropland, buildings, and water. Cropland has the largest multi-year average soil erosion modulus, followed by grassland and buildings, with forestland having the smallest; (3) significant spatial correlations occurred between soil erosion change and LULCC for common ‘no change’ and common ‘gain’ in the settlements, roads, and areas near the human influences with good soil and water conservation, but not other regions due to the influence of climatic factors (heavy rain events). Thus, we should repair terraces, control dams in the watershed, and actively conserve water and soil. This study provides a scientific reference for planning and managing water and soil conservation and ecological environment construction in the watershed.     

Assessment of deforestation impact on soil erosion in loess formation using 137Cs method (case study: Golestan Province,Iran)

Golestan, a province in the North-East of Iran, is characterized by high coverage of loess deposits. Since 1963, the area has experienced approximately 200,000 ha deforestation due to land-use changes in agriculture and increasing demand for wood. Approximately, 110,000 ha of the clear-cut lands are under dry-farming, mainly for wheat cropping, and about 86,000 ha have been reforested. This IAEA funded project is the first attempt to use nuclear techniques in the East of Hircanian Forest for determination of on-site impacts of deforestation due to two land-use changes (i.e. dry farming and reforestation). Practicing long-term dry-farming led to 60% soil losses with a mean rate of 2 mm per year. The net erosion rate of croplands on loess deposits in the study area was 32.27 t ha⁻¹ yr⁻¹. Reforestation, cultivation of even-aged Cypress trees since 1993, showed 13 to 60 percent effectiveness in soil conservation. Dry-farming land use resulted in the loss of 95 t ha⁻¹ soil organic carbon (SOC) stock at a mean rate of 1.7 t ha⁻¹ over 54 years. Cultivating Cypress trees successfully restored the SOC content by 100% compared with the SOC in original forests. The conversion of dry-farming lands to orchards of olive trees since 2004, brought more income for farmers but were less effective in soil conservation because of low canopy cover of olive trees. Our data provide key information and guidance for land users and decision-makers about implementing strategic and sustainable conservation practices to restore degraded land.     

Effect of land management on runoff and soil losses from two small watersheds in St Lucia

The influence of land use on runoff and soil loss was assessed on two small watersheds in the Eastern Caribbean island of St Lucia, under contrasting land management regimes. The data generated from these watersheds revealed that the soil losses from an intensively cultivated agricultural watershed were 20‐times higher in magnitude than that of a forested watershed both for peak rainfall event and for total duration of analysis. This was due to higher surface runoff rates and exposure of soil to direct raindrop impact within cultivated areas. Whereas the forest canopy cover in combination with higher infiltration capacities of the forested land reduced the erosive runoff from the forest watershed and thus the soil loss. Moreover, the energy intensities of large storms in excess of 40 mm were estimated and found to range between 400 MJ mm ha⁻¹ h⁻¹ and 1834 MJ mm ha⁻¹ h⁻¹. 1

1 Megajoules‐millimeters per hectare‐hour.

Soil loss from the agricultural watershed was strongly correlated (R² = 0·85) to storm energy‐intensity (EI₃₀). However, the correlation of soil loss with the EI₃₀ (R² = 0·71) was poor for the forest watershed due to the effect of canopy vegetation, which significantly reduced the energy of raindrop impact. Over the study period, cumulative soil losses were 10·0 t ha⁻¹ for the agricultural site and 0·5 t ha⁻¹ for the forest site. 2

2 Metric tons per hectare.

The largest storm observed during the study period resulted in erosion losses of 3·78 t ha⁻¹ and 0·2 t ha⁻¹ from the agricultural and forest sites respectively. The regression models were developed using the measured data for prediction of runoff and soil loss over the watersheds of St Lucia under similar conditions. This study contributed towards efficient watershed management planning and implementation of suitable water conservation measures in St Lucia. Copyright © 2005 John Wiley & Sons, Ltd.     

Surface runoff and soil erosion estimation using the SWAT model in the Keleta Watershed,Ethiopia

This study evaluates surface runoff generation and soil erosion rates for a small watershed (the Keleta Watershed) in the Awash River basin of Ethiopia by using the Soil and Water Assessment Tool (SWAT) 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. The simulated surface runoff closely matched with observed data (derived by hydrograph separation). Surface runoff generation was generally high in parts of the watershed characterized by heavy clay soils with low infiltration capacity, agricultural land use and slope gradients of over 25 per cent. The estimated soil loss rates were also realistic compared to what can be observed in the field and results from previous studies. The long‐term average soil loss was estimated at 4·3 t ha⁻¹ y⁻¹; most of the area of the watershed (∼80 per cent) was predicted to suffer from a low or moderate erosion risk (<8 t ha⁻¹ y⁻¹), and only in ∼1·2 per cent of the watershed was soil erosion estimated to exceed 12 t ha⁻¹ y⁻¹. Expectedly, estimated soil loss was significantly correlated with measured rainfall and simulated surface runoff. Based on the estimated soil loss rates, the watershed was divided into four priority categories for conservation intervention. The study demonstrates that the SWAT model provides a useful tool for soil erosion assessment from watersheds and facilitates planning for a sustainable land management in Ethiopia. Copyright © 2010 John Wiley & Sons, Ltd.     

Carbon sequestration in soils of central Asia

Problems of frequent drought stress, low soil organic carbon (SOC) concentration, low aggregation, susceptibility to compaction, salinization and accelerated soil erosion in dry regions are accentuated by removal of crop residues, mechanical methods of seedbed preparation, summer clean fallowing and overgrazing, and excessive irrigation. The attendant soil degradation and desertification lead to depletion of SOC, decline in biomass production, eutrophication/pollution of waters and emission of greenhouse gases. Adoption of conservation agriculture, based on the use of crop residue mulch and no till farming, can conserve water, reduce soil erosion, improve soil structure, enhance SOC concentration, and reduce the rate of enrichment of atmospheric CO₂. The rate of SOC sequestration with conversion to conservation agriculture, elimination of summer fallowing and growing forages/cover crops may be 100 to 200 kg ha⁻¹ y⁻¹ in coarse‐textured soils of semiarid regions and 150 to 300 kg ha⁻¹ y⁻¹ in heavy‐textured soils of the subhumid regions. The potential of soil C sequestration in central Asia is 10 to 22 Tg C y⁻¹ (16±8 Tg C y⁻¹) for about 50 years, and it represents 20 per cent of the CO₂ emissions by fossil fuel combustion. Copyright © 2004 John Wiley & Sons, Ltd.     

Soil loss estimation using rusle model to prioritize erosion control in KELANI river basin in Sri Lanka

Soil erosion contributes negatively to agricultural production, quality of source water for drinking, ecosystem health in land and aquatic environments, and aesthetic value of landscapes. Approaches to understand the spatial variability of erosion severity are important for improving landuse management. This study uses the Kelani river basin in Sri Lanka as the study area to assess erosion severity using the Revised Universal Soil Loss Equation (RUSLE) model supported by a GIS system. Erosion severity across the river basin was estimated using RUSLE, a Digital Elevation Model (15 × 15 m), twenty years rainfall data at 14 rain gauge stations across the basin, landuse and land cover, and soil maps and cropping factors. The estimated average annual soil loss in Kelani river basin varied from zero to 103.7 t ha-1 yr⁻¹, with a mean annual soil loss estimated at 10.9 t ha⁻¹ yr⁻¹. About 70% of the river basin area was identified with low to moderate erosion severity (<12 t ha−1 yr⁻¹) indicating that erosion control measures are urgently needed to ensure a sustainable ecosystem in the Kelani river basin, which in turn, is connected with the quality of life of over 5 million people. Use of this severity information developed with RUSLE along with its individual parameters can help to design landuse management practices. This effort can be further refined by analyzing RUSLE results along with Kelani river sub-basins level real time erosion estimations as a monitoring measure for conservation practices.     

Soil organic carbon and nitrogen in a Mollisol in central Ohio as affected by tillage and land use

Minimum tillage practices are known for increasing soil organic carbon (SOC). However, not all environmental situations may manifest this potential change. The SOC and N stocks were assessed on a Mollisol in central Ohio in an 8-year-old tillage experiment as well as under two relatively undisturbed land uses; a secondary forest and a pasture on the same soil type. Cropped systems had 51±4 (equiv. mass) Mg ha⁻¹ lower SOC and lower 3.5±0.3 (equiv. mass) Mg ha⁻¹ N in the top 30 cm soil layer than under forest. Being a secondary forest, the loss in SOC and N stocks by cultivation may have been even more than these reported herein. No differences among systems were detected below this depth. The SOC stock in the pasture treatment was 29±3 Mg ha⁻¹ greater in the top 10 cm layer than in cultivated soils, but was similar to those under forest and no-till (NT). Among tillage practices (plow, chisel and NT) only the 0–5 cm soil layer under NT exhibited higher SOC and N concentrations. An analysis of the literature of NT effect on SOC stocks, using meta-analysis, suggested that NT would have an overall positive effect on SOC sequestration rate but with a greater variability of what was previously reported. The average sequestration rate of NT was 330 kg SOC ha⁻¹ year⁻¹ with a 95% confidence interval ranging from 47 to 620 kg SOC ha⁻¹ year⁻¹. There was no effect of soil texture or crop rotation on the SOC sequestration rate that could explain this variability. The conversion factor for SOC stock changes from plow to NT was equal to 1.04. This suggests that the complex mechanisms and pathways of SOC accrual warrant a cautious approach when generalizing the beneficial changes of NT on SOC stocks.     

Residue impacts on runoff and soil erosion for different corn plant populations

The year to year carry-over effects of biomass additions under different plant populations on runoff and erosion are unclear. The objective of this study was to quantify the impact of different plant populations on residue cover to elucidate the effects of residue cover on runoff and erosion. The residue management system involved shredding of corn (maize) biomass after harvest, incorporating the residue in the spring, and leaving the land fallow until it was no-till planted the following spring. Runoff and soil losses were measured on 18 runoff plots with plots arranged in two areas with each having three randomized treatments (0%, 50%, and 100% plant population) with three replications. The two areas were managed as a fallow/no-till corn rotation in two cycles of alternating years. Surface residue cover was highly dynamic with significant changes between cycles and seasons in response to the management practices. The annual soil losses were reduced by 47% and 54% for the 50% and 100% plant populations, respectively compared to the control. However, the annual soil loss even for the 100% plant population was still nearly seven times the tolerable soil loss limit of 7 ton ha⁻¹. The normal erosion protection afforded by no-till practices was lost by the incorporation of residue the previous year.     

Combining Qualitative and Quantitative Methods for Soil Erosion Assessments: An Application in a Sloping Mediterranean Watershed,Cyprus

In arid and semi‐arid regions, water erosion is difficult to model because of highly irregular precipitation regimes and changes in vegetation cover. The application of quantitative, process‐based models at the catchment scale is often problematic because of large data requirements. Qualitative methods require less data and can be more easily performed in a relatively short time, but they are more subjective. The objective of this research is to develop an erosion assessment methodology that combines qualitative field surveys with quantitative model estimates. The qualitative World Overview of Conservation Approaches and Technologies (WOCAT) methodology is based on expert observations per mapping unit, while the Pan‐European Soil Erosion Risk Assessment (PESERA) model simulates hill slope soil loss based on land cover, soil texture, meteorological data and slope profile. This study was conducted in the 106·4‐km² Peristerona watershed in Cyprus with a mean local slope higher than 40% in the mountainous upstream area and less than 8% in the plain. Out of 68 units, PESERA and WOCAT results were in agreement in 40 units, while PESERA results were lower in 25 and higher in 3 units. Both methods identified burnt areas and complex cultivation patterns as the most degraded. The total PESERA‐based sediment yield for the watershed was 1·2 Mg ha⁻¹ y⁻¹, which fell within the range of the sediment yield measured at the check‐dam downstream (0·2–2 Mg ha⁻¹ y⁻¹). This study provides a linkage between qualitative and quantitative soil erosion methods and helps to translate the outcomes of the former into the latter, thus providing a good tool for local erosion assessment. Copyright © 2016 John Wiley & Sons, Ltd.     

Establishing permissible erosion rates for various landforms in Delhi State,India

Permissible erosion rate also known as soil loss tolerance (‘T’ value) is defined as maximum erosion that can take place on a given soil without degrading its long‐term productivity. In India, default ‘T’ value of 11·2 Mg ha⁻¹ y⁻¹ is used for devising land restoration strategies for different types of soils. However, ability of soil to resist degradation varies with soil type, depth and physico‐chemical characteristics. Therefore, the present investigation was undertaken to determine ‘T’ value of different landforms of Delhi State by taking into account the soil saturated hydraulic conductivity (SHC), bulk density (BD), organic carbon, erodibility and soil pH. Soil state was defined by a quantitative model and scaling functions were used to convert soil parameters to a 0–1 scale. The normalised values were multiplied by appropriate weighting factors based on relative importance and sensitivity analysis of each indicator. Categorical rankings of I, II or III were assigned to soil groups based on overall aggregate score. ‘T’ value of different landforms of Delhi State was computed using the guideline of USDA‐Natural Resource Conservation Services. Majority of landforms of Delhi had ‘T’ value of 12·5 Mg ha⁻¹ y⁻¹, except for the soils of hill terrain, dissected hill, pediment and piedmont plain, where ‘T’ value ranged from 5 to 10 Mg ha⁻¹ y⁻¹. These ‘T’ values could be used for conservation planning and will help the planners in devising suitable land restoration strategies. Copyright © 2008 John Wiley & Sons, Ltd.     

Soil Erosion Assessment in Kondoa Eroded Area in Tanzania using Universal Soil Loss Equation,Geographic Information Systems and Socioeconomic Approach

Soil conservation measures including cutoff drains, tree planting, Crops diversifications and destocking were implemented in Kondoa eroded area (KEA) for decades. This study assessed soil erosion changes in KEA and examined drivers of changes using Universal Soil Loss Equation, Geographic Information Systems and socioeconomic survey. Soil erosion was predicted by using data on soil, digital elevation model, rainfall and land use/cover visually interpreted from multitemporal satellite imageries. The predicted average soil erosions were 14·7, 23 and 15.7 Mg ha⁻¹y⁻¹ during 1973, 1986 and 2008, respectively. The area under very high soil erosion severity that was 30% in 1973, 26% in 1986 and 25% in 2008, whereas the area with high erosion severity was 26% in 1973 changed into 49% in 1986 and 2008 indicating recent stabilization. The area with moderate erosion increased from 15%, 16% and 18% during the same period. Field survey confirms a decrease of soil erosion in KEA compared with the past showing better soil conservation. Age of farmers, long‐term adoption of conservation practices and on‐farm tree planting were found to be the major factors contributing toward reduced soil erosion. Major limitations in soil conservation were poor mainstreaming of conservation activities on local production systems and lack of institutions promoting conservation at the community level. The study concluded that long‐term conservation investment for restoration, protection and socioeconomic support contributes significantly in land rehabilitation in KEA. Copyright © 2013 John Wiley & Sons, Ltd.     

Soil erosion assessment of Lake Alemaya catchment,Ethiopia

Land degradation due to soil erosion is the major problem facing Ethiopia today. In the Lake Alemaya catchment soil erosion is caused by the intense rainfall, steep topography, and poor vegetation cover coupled with cultivation of steep lands, and inadequate conservation practices. Sediment from the catchment has affected the storage capacity of Lake Alemaya. This study has integrated the Agricultural Non‐point Source Pollution Model (AGNPS) and the technique of the Gographic Information System (GIS) to quantify soil erosion in the Lake Alemaya catchment. After application of the AGNPS, it appears that 66 per cent of the catchment has a soil erosion rate of 10 to more than 80 t ha⁻¹ y⁻¹. The annual soil loss is estimated at 31 t ha⁻¹, which is more than the permissible value of 1–16 t ha⁻¹ for different agro‐ecological zones of Ethiopia. The sediment yield of the catchment is about 10 148 ton with a delivery ratio of 6·82 per cent. Therefore, an effective management plan is needed for the conservation and rehabilitation of the catchment and to maintain the storage capacity of Lake Alemaya. Copyright © 2006 John Wiley & Sons, Ltd.     

Spatial Estimation of Soil Erosion Risk by Land‐cover Change in the Andes OF Southern Ecuador

Ecuador has the highest deforestation rate in South America, causing large‐scale soil erosion. Inter‐Andean watersheds are especially affected by a rapid increase of the population leading to the conversion of large areas of montane forest into pasture and cropland. In this study, we estimate soil erosion risk in a small mixed land‐use watershed in the southern Andes of Ecuador. Soil loss was estimated at a spatial resolution of 30 m, using the Revised Universal Soil Loss Equation (RUSLE) where the RUSLE factors were estimated on the basis of limited public available data. Land‐cover maps for 1976, 2008 and 2040 were created assuming increasing deforestation rates over the ensuing decades. Greater erosion rates are estimated for succession areas with agricultural cropland and pasture with maximum values of 936 Mg ha⁻¹ y⁻¹, where slopes and precipitation amounts are the greatest. Under natural forest vegetation, the estimated soil erosion rates are negligible (1·5 to 40 Mg ha⁻¹ y⁻¹) even at steep slopes and higher elevations where rainfall amounts and intensities are generally higher. When the entire watershed has undergone substantial deforestation in 2040, erosion values may reach 2,021 Mg ha⁻¹ y⁻¹. Vegetation cover is the most important factor for potential soil erosion. Secondary factors are related to rainfall (R‐factor) and topography (LS factors). Although the spatial predictions of potential soil erosion have only limited meaning for erosion risk, this method provides an important screening tool for land management and assessment of land‐cover change. Copyright © 2013 John Wiley & Sons, Ltd.     

Novel sediment source fingerprinting quantifying erosion-induced total nitrogen and total phosphorus outputs from an intensive agricultural catchment,North China

Intensive farming is a primary cause of increased sediment and associated nitrogen (N) and phosphorus (P) loads in surface water systems. Determining their contributing sources, pathways and loads present major challenges in the high-intensity agricultural catchments. Herein, we quantify the sediment sources and magnitude of sediment total N and total P from different sources using a novel application of compound-specific stable isotope (CSSI) and fallout radionuclides (FRNs) of ¹³⁷Cs and ²¹⁰Pbex in an intensive agricultural catchment in North China. Sediment sources from surface and sub-surface soils were estimated from FRNs fingerprint and accounted for 62 ± 7% and 38 ± 7% respectively, while surface soil from land uses that originated from hillslope were identified by CSSI fingerprint. Using a novel application of FRNs and CSSI sediment fingerprinting techniques, the dominant sediment source was derived from maize farmland (44 ± 0.1%), followed by channel bank (38 ± 7%). The sedimentation rate (13.55 ± 0.30 t ha⁻¹ yr⁻¹) was quantified by the ¹³⁷Cs cores (0–60 cm) at the outlet of this catchment. The total N and total P in sediment were both mostly derived from maize farmland and least from channel banks. The channel banks are significant sediment sources but contribute little to the input of sediment N and P for eutrophication. It implies that chemically-applied farmlands are the main hotspots for catchment erosion control and pollution prevention. The novel application of FRNs and CSSI techniques cost-effectively quantified sediment N and P loads from different sources with a single visit to the catchment, enabling rapid assessment for optimizing soil conservation strategies and land management practices. Keywords: Sediment sources, Land use, N and P loads, Compound-specific stable isotope, Fallout radionuclides.     

Potential of mine land reclamation for soil organic carbon sequestration in Ohio

Soils are an effective sink for carbon storage and immobilization through biomass productivity and enhancement of soil organic carbon (SOC) pool. The SOC sink capacity depends on land use and management. Degraded lands lose large amounts of C through SOC decomposition, erosion, and leaching. Thus, restoration of disturbed and degraded mine lands can lead to increase in biomass productivity, improved soil quality and SOC enhancement and sequestration. Reclamation of mined lands is an aggrading process and offers significant potential to sequester C. A chronosequence study consisting of 0‐, 5‐, 10‐, 15‐, 20‐ and 25‐year‐old reclaimed mine soils in Ohio was initiated to assess the rate of C sequestration by pasture and forest establishment. Undisturbed pasture and forest were used as controls. The SOC pool of reclaimed pasture sites increased from 15·3 Mg ha⁻¹ to 44·4 Mg ha⁻¹ for 0–15 cm depth and from 10·8 Mg ha⁻¹ to 18·3 Mg ha⁻¹ for 15–30 cm depth over the period of 25 years. The SOC pool of reclaimed forest sites increased from 12·7 Mg ha⁻¹ to 45·3 Mg ha⁻¹ for 0–15 cm depth and from 9·1 Mg ha⁻¹ to 13·6 Mg ha⁻¹ for 15–30 cm depth over the same time period. The SOC pool of the pasture site stabilized earlier than that of the forest site which had not yet attained equilibrium. The SOC sequestered in 0–30 cm depth over 25 years was 36·7 Mg ha⁻¹ for pasture and 37·1 Mg ha⁻¹ for forest. Copyright © 2000 John Wiley & Sons, Ltd.     

Land use and soil conservation strategies for potentially highly erodible soils of central-eastern Nigeria

In areas susceptible to erosion, there is the need for a comprehensive soil conservation programme so as to be able to prevent catastrophic soil erosion problems. The absence of such a programme in central eastern Nigeria, that has a total land area of 20 000 km², necessitated the drawing up of a soil conservation strategy for the area. The aim was to provide information for better land-use planning and proper environmental and soil management. To achieve this, topographic, soil and landform maps of the area at the scale of 1:50 000 were used to delineate into slope land units, viz: 0–4 per cent, <4 per cent, drainage basins and headwaters. These slope units and estimated soil erosion hazard units using the revised universal soil loss equation (RUSLE) were employed to form a general purpose land classification based on the USDA land capability classification and FAO framework on land evaluation.The soil loss tolerance of the area falls between 1·16 and 1·30 Mg ha⁻¹ yr⁻¹, while the erosion hazard units are considered generally suitable for the various land utilization types, with a number of limitations the main ones being erosion and waterlogging. The soil conservation measures proposed involved the application of bioenvironmental processes in the area and appropriate watershed management. The techniques proposed are those based on low input technology, affordable by rural farmers. It is concluded that these soil conservation measures will be adequate for sustainable agricultural production in the area. Copyright © 1999 John Wiley & Sons, Ltd.     

Soil Conservation in Europe: Wish or Reality?

Nearly all of Europe is affected by soil erosion. A major policy response is required to reverse the impacts of erosion in degraded areas, particularly in light of the current climate change and water crisis. Soil loss occurs not because of any lack of knowledge on how to protect soils, but a lack in policy governance. The average rate of soil loss by sheet and rill erosion in Europe is 2·46 Mg ha⁻¹ yr⁻¹. To mitigate the impacts of soil erosion, the European Union's Common Agricultural Policy has introduced conservation measures which reduce soil loss by water erosion by 20% in arable lands. Further economic and political action should rebrand the value of soil as part of ecosystem services, increase the income of rural land owners, involve young farmers and organize regional services for licensing land use changes. In a changing World of 9 billion people with the challenge of climate change, water scarcity and depletion of soil fertility, the agriculture economy should evolve taking into account environmental and ecological aspects. © 2016 The Authors Journal of Land Degradation & Development Published by John Wiley & Sons Ltd.     

Runoff Development and Soil Erosion in a Wet Tropical Montane Setting under Coffee Cultivation

The western interior portions of Puerto Rico offer optimal climatic conditions for coffee cultivation. However, land and water degradation result when abrupt topographic relief and high annual rainfall combine with forest conversion for coffee farming. Small‐scale rainfall simulation experiments were conducted to quantify runoff and erosion from four land surface types (i.e., mulched, weed‐covered, and bare soils under active cultivation, and unpaved roads) representative of coffee farms in Puerto Rico. Results show that mulch‐covered soils had runoff coefficients similar to those from undisturbed forested conditions (~4%), and that they eroded at rates about a quarter of those for bare cultivated soils. Weed‐covered soils had surprisingly high runoff coefficients (~70%), yet their erosion rates were only three‐fourths of those for bare soils. Annualized erosion rates from unpaved roads were 65 Mg ha⁻¹ y⁻¹, or ten times greater than bare soils and about a hundred times higher than weed‐ or mulch‐covered surfaces. Farm‐scale sediment production estimates amount to ~11 Mg ha⁻¹ y⁻¹, about two‐orders of magnitude higher than under forested conditions. At the farm‐scale, only 2 – 8% of the total sediment is potentially attributable to cultivated hillslopes. In contrast, unpaved roads may account for over 90% of the sediment budget, even though they comprise only 15% of the farm surface area. Therefore, while providing mulch or a vegetative cover to bare cultivated soils should be part of effective soil management, mitigating the effects of coffee cultivation on downstream water resources must focus on the unpaved road network as the primary sediment source. Copyright © 2016 John Wiley & Sons, Ltd.