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.     

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.     

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.     

Modelling Post‐Tree‐Harvesting Soil Erosion and Sediment Deposition Potential in the Turano River Basin (Italian Central Apennine)

The overall aim of the paper is the assessment of human‐induced accelerated soil erosion processes due to forest harvesting in the Upper Turano River Basin. The spatio‐temporal pattern of soil erosion processes was investigated by means of a spatially distributed modelling approach. We used the Unit Stream Power Erosion and Deposition model. During the soil erosion‐modelling phase, the forest cover changes were mapped via remote sensing. According to this operation, the forest sectors exploited for timber production amounted to about 2781 ha or 9·9% of the wooded surface from March 2001 to August 2011. In this period, the average annual net soil erosion rate estimated by means of modelling operations totalled 0·83 Mg ha⁻¹ y⁻¹ for all the forest lands. The net soil erosion rate predicted for the disturbed forest lands is significantly higher than the average value for the entire forest (5·34 Mg ha⁻¹ y⁻¹). Estimates indicate a soil loss equal to 8521 Mg y⁻¹ (net soil erosion 0·34 Mg ha⁻¹ y⁻¹) in the undisturbed forest area (254 km²), whereas the 27·8 km² of disturbed forest area could potentially lose 14 846 Mg y⁻¹. The paper shows that a disturbed forest sector could produce about 74·2% more net erosion than a nine times larger, undisturbed forest sector. Copyright © 2013 John Wiley & Sons, Ltd.     

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.     

Soil Erosion in Steep Road Cut Slopes in Palencia (Spain)

Construction associated to land development, such as roads and railroads, promote severe land degradation. Cutslope sediment yield is one of the major pollutants on waters close to the road and railroad network. To estimate road impact, soil erosion (E), sediment yield (SY) and morphological evolution of a railroad cut in Palencia (Spain), were studied using erosion nails, during the periods 1998–1999, 1999–2000 and 2000–2010. Data from two sample plots were analyzed by an ANOVA for repeated measures. Slope morphological evolution was estimated using a cubic polynomial regression, while E and SY were calculated by integration. The top and the toe of the slope eroded and accumulated 0·5 m respectively, evolving into a concave/convex slope profile. The mean measured E was 220 Mg ha⁻¹ y⁻¹. SY was 31 Mg ha⁻¹ y⁻¹, ranging from 109 Mg ha⁻¹ y⁻¹ to 24 Mg ha⁻¹ y⁻¹. Sediment yield was 4·5 times higher during the first year, than in all subsequent years. Results showed a decreasing trend and a stabilization in E and SY rates. However, both rates remain high and critical over the analyzed time, with regards to soil formation, water protection, land degradation and infrastructure maintenance. Copyright © 2015 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.     

Assessment of soil erosion hazard and prioritization for treatment at the watershed level: Case study in the Chemoga watershed,Blue Nile basin,Ethiopia

Soil erosion by water is the most pressing environmental problem in Ethiopia, particularly in the Highlands where the topography is highly rugged, population pressure is high, steeplands are cultivated and rainfall is erosive. Soil conservation is critically required in these areas. The objective of this study was to assess soil erosion hazard in a typical highland watershed (the Chemoga watershed) and demonstrate that a simple erosion assessment model, the universal soil loss equation (USLE), integrated with satellite remote sensing and geographical information systems can provide useful tools for conservation decision‐making. Monthly precipitation, soil map, a 30‐m digital elevation model derived from topographic map, land‐cover map produced from supervised classification of a Land Sat image, and land use types and slope steepness were used to determine the USLE factor values. The results show that a larger part of the watershed (>58 per cent of total) suffers from a severe or very severe erosion risk (>80 t ha⁻¹ y⁻¹), mainly in the midstream and upstream parts where steeplands are cultivated or overgrazed. In about 25 per cent of the watershed, soil erosion was estimated to exceed 125 t ha⁻¹ y⁻¹. Based on the predicted soil erosion rates, the watershed was divided into six priority categories for conservation intervention and 18 micro‐watersheds were identified that may be used as planning units. Finally, the method used has yielded a fairly reliable estimation of soil loss rates and delineation of erosion‐prone areas. Hence, a similar method can be used in other watersheds to prepare conservation master plans and enable efficient use of limited resources. Copyright © 2009 John Wiley & Sons, Ltd.     

Carbon input, loss and storage in sub-tropical Indian Inceptisol under multi-ratooning sugarcane

Changes in residue management and incorporation of organic manures may help in carbon sequestration, restoring soil organic carbon (SOC) and sustaining the productivity of land under a cropping system. An experiment of multi-ratooning sugarcane (Saccharum officinarum L.) was initiated in 2003 in Inceptisols of Indian subtropics, to assess the effect of different organic manures and chemical fertilizer, on the crop productivity and soil quality. The annual sugarcane shoot biomass production in organic manure treatments was at par with the chemically fertilized treatment. Gross input of carbon (GIC) by the sugarcane crop was estimated to be 11.7–12.4 t ha⁻¹ y⁻¹ in different organic manure treatments compared to 8.4 and 5.0 t ha⁻¹ y⁻¹ in NPK and control treatments, respectively. The respiratory loss of C (RLC) increased linearly with increasing input of C in soil and it ranged from 3.3 to 4.1 t ha⁻¹ y⁻¹ in different treatments with maximum in FYM and minimum in control treatment. The sugarcane biomass added in the soil humified at a rate constant of 0.38 in sub-tropical conditions and an addition of 3.9 t C ha⁻¹ y⁻¹ is required to maintain SOC in equilibrium. After 5 years of sugarcane cropping (one plant + four ratoons) an increase of 2.3–17.1 t ha⁻¹ in SOC over initial content was recorded with different treatments. Results in coming years from this long-term experiment shall add to the present calculated relationships between carbon addition and storage in sugarcane multi-ratooning crop production system under sub-tropical condition of India.     

Application of the caesium‐137 technique to soil degradation studies in the Southwestern Highlands of Ethiopia

Soil degradation is a serious problem in the central and northern Highlands of Ethiopia. It has been so for several decades as a result of over exploitation and mismanagement. Relocation of a portion of the population from these regions to the relatively less populated Southwestern Highlands has taken place for decades to try to address the problem. However, such mass resettlements have caused severe soil degradation problems in many destination areas in the Southwestern Highlands. The aim of this study was to assess the problem of soil degradation using the caesium‐137 isotope and to test its value for erosion study in the region. The adapted USLE was applied to compare results from the caesium‐137 isotope studies. Along a deforestation continuum, fields cultivated for various years were studied for erosion. From a reference grazing land plot, total caesium‐137 fallout of 2026 ± 176 Bq m⁻² with a CV of 24·6 per cent was recorded showing the presence of sufficient fallout to apply the technique. Erosion in cultivated fields was estimated against this reference using conversion models. Results from the Proportional Model |−13·9 ± 2·7|and the adapted USLE |12·3 ± 2·6| were not significantly different (p < 0·05), meaning the technique provides reliable results. A positive relationship was observed between severity of erosion and time of cultivation after forest clearing (R² = 0·78). The mean annual loss of soil from cultivated land, 14·9 ± 2·9 t ha⁻¹ y⁻¹, is already beyond the tolerable threshold and might exacerbate further clearing of forests for cultivation if the land is not properly managed. Copyright © 2011 John Wiley & Sons, Ltd.     

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.     

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 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.     

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.     

Cropping strategies,soil fertility investment and land management practices by smallholder farmers in communal and resettlement areas in Zimbabwe

Three smallholder villages located in typical communal (from 1948), old (1987) and new (2002) resettlement areas, on loamy sand, sandy loam and clay soils, respectively, were selected to explore differences on natural resource management and land productivity. Focus group discussions and surveys were carried out with farmers. Additionally, farmers in three wealth classes per village were chosen for a detailed assessment of their main production systems. Maize grain yields (t ha⁻¹) in the communal (1·5–4·0) and new resettlement areas (1·9–4·3) were similar but significantly higher than in the old resettlement area (0·9–2·7), despite lower soil quality in the communal area. Nutrient input use was the main factor controlling maize productivity in the three areas (R² = 59–83%), while soil quality accounted for up to 12%. Partial N balances (kg ha⁻¹ yr⁻¹) were significantly lower in the new resettlement (−9·1 to +14·3) and old resettlement (+7·4 to +9·6) than in the communal area (+2·1 to +59·6) due to lower nutrient applications. Averaged P balances were usually negative. Consistently, maize yields, nutrient applications and partial N balances were higher in the high wealth class than in poorer classes. This study found that most farmers in the new resettlement area were exploiting the inherent soil nutrient stocks more than farmers in the other two areas. We argue that effective policies supporting an efficient fertilizer distribution and improved soil management practices, with clearer rights to land, are necessary to avoid future land degradation and to improve food security in Zimbabwe, particularly in the resettlement areas. Copyright © 2009 John Wiley & Sons, Ltd.