Soil erosion and runoff: The need to rethink mitigation strategies for sustainable agricultural landscapes in western Europe

Agricultural landscapes that are intensively farmed, as in western Europe, face the challenge of a transition to more sustainable systems. Although erosion rates are relatively low in western Europe, the agricultural landscape is confronted by the need to mitigate the off-site impacts of erosion. An important challenge is that of disrupting connectivity between runoff and sediment sources, often farmers' fields, and freshwater systems or local communities. Mitigation strategies should include monitoring of erosion rates and off-site impacts and a mix of engineered and alternative measures such as buffer strips and retention ponds. Also needed are supportive government policies and actions including awareness of institutional memory problems and the promotion of farmer education. For the future, the risk of climate change must be appreciated and built into the planning of comprehensive mitigation strategies. Our perspective is that the overall aim should be a ‘sustainable agricultural landscape’ and not simply a reduction of erosion and runoff on farmers' fields.     

On‐site and off‐site effects of wind erosion on European light soils

In intensively cultivated areas with light soils in Europe, wind erosion can have important on‐site and off‐site effects. In the framework of the EU research project Wind Erosion and European Light Soils (WEELS), an assessment has been made of these effects and of the order of magnitude of the damage and costs caused by these effects. An analysis is made of the land use and cropping in four selected sites, and farmers have provided information about the damage of wind erosion. This damage consists mainly of crop losses and additional inputs in the case of resowing. Detailed information from one of these sites shows that depending on the crop the average annual on‐site costs in high‐risk areas amount to about €60 per hectare. However, for sugar beet and oilseed rape the costs can be once in five years as much as €500 per hectare. Farmers are generally well aware of the erosion risk and do apply a variety of control measures. With these measures the average annual costs of wind erosion can be reduced significantly. Copyright © 2001 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.     

Gully erosion: Impacts, factors and control

Gully erosion attracts increasing attention from scientists as reflected by two recent international meetings [Poesen and Valentin (Eds.), Catena 50 (2–4), 87–564; Li et al., 2004. Gully Erosion Under Global Change. Sichuan Science Technology Press, Chengu, China, 354 pp.]. This growing interest is associated with the increasing concern over off-site impacts caused by soil erosion at larger spatial scales than the cultivated plots. The objective of this paper is to review recent studies on impacts, factors and control of gully erosion and update the review on ‘gully erosion and environmental change: importance and research needs’ [Poesen et al., 2003. Catena 50 (2–4), 91–134.]. For the farmers, the development of gullies leads to a loss of crop yields and available land as well as an increase of workload (i.e. labour necessary to cultivate the land). Gullies can also change the mosaic patterns between fallow and cultivated fields, enhancing hillslope erosion in a feedback loop. In addition, gullies tend to enhance drainage and accelerate aridification processes in the semi-arid zones. Fingerprinting the origin of sediments within catchments to determine the relative contributions of potential sediment sources has become essential to identify sources of potential pollution and to develop management strategies to combat soil erosion. In this respect, tracers such as carbon, nitrogen, the nuclear bomb-derived radionuclide 137 Cs, magnetics and the strontium isotopic ratio are increasingly used to fingerprint sediment. Recent studies conducted in Australia, China, Ethiopia and USA showed that the major part of the sediment in reservoirs might have come from gully erosion.Gullies not only occur in marly badlands and mountainous or hilly regions but also more globally in soils subjected to soil crusting such as loess (European belt, Chinese Loess Plateau, North America) and sandy soils (Sahelian zone, north-east Thailand) or in soils prone to piping and tunnelling such as dispersive soils. Most of the time, the gullying processes are triggered by inappropriate cultivation and irrigation systems, overgrazing, log haulage tracks, road building and urbanization. As exemplified by recent examples from all over the world, land use change is expected to have a greater impact on gully erosion than climate change. Yet, reconstructions of historical causes of gully erosion, using high-resolution stratigraphy, archaeological dating of pottery and ¹⁴C dating of wood and charcoal, show that the main gully erosion periods identified in Europe correspond to a combination not only of deforestation and overuse of the land but also to periods with high frequency of extreme rainfall events.Many techniques have proved to be effective for gully prevention and control, including vegetation cover, zero or reduced tillage, stone bunds, exclosures, terracing and check dams. However, these techniques are rarely adopted by farmers in the long run and at a larger spatial scale because their introduction is rarely associated with a rapid benefit for the farmers in terms of an increase in land or labour productivity and is often contingent upon incentives.     

Wind erosion: the perspective of grass-roots communities in the Sahel

Under the harsh conditions prevailing in the West African Sahel, farmers must deal with a range of environmental and socio-economic issues that constrain agriculture. Although scientific evidence indicates that wind erosion is potentially a major land degradation process, little is known about the Sahelian farmer's perception of the relative importance of wind erosion as a constraint to agricultural production. A village-level survey was therefore undertaken to assess farmers' views about the relative importance of perceived constraints to agricultural production in 41 villages across Niger. During the interviews, the communities' views were also recorded regarding the causes and consequences of wind erosion as well as known wind erosion control measures. Wind erosion ranked eighth overall and was listed by male farmers among the top 10 constraints in 54 per cent of the villages. It was perceived by male farmers to be a moderate to high constraint in 39 per cent of the villages but was not considered important by female farmers. Wind erosion ranked third among environmental constraints, behind drought and soil fertility. Wind erosion related health problems were generally of more concern than crop damage or loss of topsoil by wind erosion. Deforestation, removal of crop residue and land-clearing practices were identified by farmers as major contributors to soil losses by wind. To address this issue, at least 10 different low-cost technologies are currently being implemented by farmers, including leaving crop residue in the field, mulching and natural regeneration of vegetation. The survey results indicate that farmers are well aware of the overriding importance of their management practices, as opposed to climatic factors, on the current extent of wind erosion. Copyright © 2001 John Wiley & Sons, Ltd.     

Towards a Pan‐European Assessment of Land Susceptibility to Wind Erosion

Understanding spatial and temporal patterns in land susceptibility to wind erosion is essential to design effective management strategies to control land degradation. The knowledge about the land surface susceptible to wind erosion in European contexts shows significant gaps. The lack of researches, particularly at the landscape to regional scales, prevents national and European institutions from taking actions aimed at an effective mitigating of land degradation. This study provides a preliminary pan‐European assessment that delineates the spatial patterns of land susceptibility to wind erosion and lays the groundwork for future modelling activities. An Index of Land Susceptibility to Wind Erosion (ILSWE) was created by combining spatiotemporal variations of the most influential wind erosion factors (i.e. climatic erosivity, soil erodibility, vegetation cover and landscape roughness). The sensitivity of each input factor was ranked according to fuzzy logic techniques. State‐of‐the‐art findings within the literature on soil erodibility and land susceptibility were used to evaluate the outcomes of the proposed modelling activity. Results show that the approach is suitable for integrating wind erosion information and environmental factors. Within the 34 European countries under investigation, moderate and high levels of land susceptibility to wind erosion were predicted, ranging from 25·8 to 13·0 M ha, respectively (corresponding to 5·3 and 2·9% of total area). New insights into the geography of wind erosion susceptibility in Europe were obtained and provide a solid basis for further investigations into the spatial variability and susceptibility of land to wind erosion across Europe. © 2014 The Authors. Land Degradation and Development published by John Wiley & Sons, Ltd.     

A Note on Soil Erosion and Its Environmental Consequences in the United States

Soil erosion has both on-farm and off-farm impacts. Reduction ofsoil depth can impair the land's productivity, and the transportof sediments can degrade streams, lakes, and estuaries. Since1933, soil conservation policies have existed in the UnitedStates. Originally they focused on the on-farm benefits ofkeeping soil on the land and increasing net farm income.Beginning in the 1980s, however, policy goals increasinglyincluded reductions in off-site impacts of erosion. As aconsequence of conservation efforts associated with explicitU.S. government policies, total soil erosion between 1982 and1992 was reduced by 32% and the sheet and rill erosion ratefell from an average of 4.1 tons per acre per year in 1982 to 3.1 tons per acre in 1992. Wind erosion rate fell from anaverage of 3.3 tons per acre per year to 2.4 tons per acre peryear over the same period. Still, soil erosion is imposingsubstantial social costs. These costs are estimated to be about$37.6 billion annually. To further reduce soil erosion andthereby mitigate its social costs, there are a number of policyoptions available to induce farmers to adopt conservationpractices including education and technical assistance,financial assistance, research and development, land retirement,and regulation and taxes.     

甘肃省武威市风力侵蚀分区治理规划及措施

[目的] 分析甘肃省武威市风力侵蚀空间动态变化特征,确定风力侵蚀可治理区划及其防治对策,为该市风蚀水土保持工作和生态环境建设提供科学参考。[方法] 基于多源地理信息数据,应用遥感、地理信息系统(ArcGIS)等技术手段,使用修正土壤风蚀方程(RWEQ)计算武威市2000-2020年5期风蚀模数,获得区域风蚀的面积分布和变化特征。结合重点建设工程分布等空间要素叠加分析方法,提出该市风力侵蚀可治理区域划分原则,并将该原则应用于划分武威市风力侵蚀可治理区。[结果] 修正土壤风蚀方程(RWEQ)能较好地估算武威市多年风力侵蚀模数,其多年风力侵蚀模数为5 788.98[t/(km²·a)],多年平均土壤风蚀总量1.92×10⁸ t;研究区风力侵蚀在时间上呈现总体下降,偶有上升趋势,且风力侵蚀强度等级明显减弱;在空间上具有明显的空间异质性,主要分布在民勤县、凉州区、古浪县;依据多要素叠加风蚀分区治理方案,武威市可治理风力侵蚀面积共2 872.66 km²,其中民勤县1 468.48 km²,凉州区708.75 km²,古浪县695.43 km²。[结论] 风力侵蚀分区治理是武威市风蚀水土保持的重点工作,根据风蚀分区治理划分结果,针对不同行政区划,民勤县北部坡度较低的平坦戈壁沙漠地区是其重点关注区域,治理措施应以风沙防治和植被恢复为主,并需要注意控制人为工程建设扰动的影响,明确区域管理范围;凉州区应注意采取工程措施和生物措施结合的方式进行治理;古浪县应以封育措施和对天然植被进行保护为主。同时,在戈壁沙漠地区需特别注意大型光伏电站建设等施工扰动的风沙防治和生态恢复。     

The impact of sowing density of small grains on rill and ephemeral gully erosion in concentrated flow zones

Despite the fact that soil erosion by water causes considerable on-site and off-site problems, farmers in Europe are reluctant to adopt prevention and control measures when such measures require additional labour and material inputs. This paper documents the impact of multiple sowing of small grains on concentrated flow erosion rates and grain production for a winter triticale field (X Triticosecale Wittmack ex. A. Camus) in the Belgian loess belt. Multiple sowing refers to drilling more than once in zones of concentrated flow erosion in order to increase the total root mass in this zone. Multiple sowing strongly altered the morphology of erosion channels and reduced soil loss significantly. Statistical analysis confirmed that differences in channel dimensions could be explained by the seedling density. Doubling the root mass in the topsoil by multiple sowing, resulted on average in a reduction of soil loss by 42% for the whole growing season. For the winter period, soil loss reduction, mainly attributed to the triticale roots, amounted even to 53%, showing the tremendous impact of seedling roots on soil erosion by concentrated overland flow in the early stages of vegetation growth. Furthermore, total grain yield in the multiple drilled zones was not significantly smaller compared to the conventionally drilled parts of the field. Grain size of cereals was slightly smaller. The results of this case study indicate that double sowing in concentrated overland flow zones may be a viable soil erosion control technique.     

Dust storm erosion and its impact on soil carbon and nitrogen losses in northern China

There is increased awareness of the environmental impacts of soil carbon (C) and nitrogen (N) losses through wind erosion, especially in areas heavily affected by dust storm erosion. This paper reviews the recent literature concerning dust storm-related soil erosion and its impact on soil C and N losses in northern China. The purpose of our study is to provide an overview of the area of erosion-affected soils and to estimate the magnitude of soil C and N losses from farmland affected by dust storm erosion.According to the second national soil erosion remote-sensing survey in 2000, the area affected by wind erosion was 1.91 million km², accounting for 20% of the total land area in China. This area is expanding quickly as the incidence of heavy dust storms has greatly increased over the last five decades, mainly as a result of the intensification of soil cultivation. The economic and ecological damage caused by wind erosion is considerable. Heavily affected areas show a loss of nutrients and organic carbon in soils and the heavily degraded soils are much less productive. Compared with the non-degraded soil, the C and N contents in degraded soils have declined by 66% and 73%, respectively. The estimated annual losses per cm toplayer of soil C and N by dust storm erosion in northern China range from 53 to 1044 kg ha^− 1 and 5 to 90 kg ha^− 1, respectively. Field studies suggest that soil losses by wind erosion can be reduced by up to 79% when farmers shift from conventional soil tillage methods to no-till. Thus shifting to no-till or reduced tillage systems is an effective practice for protecting soil and soil nutrients. Our study indicates that soil conservation measures along with improved soil fertility management measures should be promoted in dry-land farming areas of northern China. As erosion is a major mechanism of nutrient withdrawal in these areas, we plead for the development of accurate methods for its assessment and for the incorporation of erosion, as a nutrient output term, in nutrient budget studies.     

Dutch policy and practices on erosion control: Then and now

Abstract

Though erosion and its control is not a major issue in The Netherlands, in some regions of the country wind and water erosion have caused severe local damage and nuisance and continue to do so. The earliest farmers settled on the higher parts of The Netherlands but, over time, overexploitation has caused extensive tracts to become drifting sand. From 1500 – 1900 “Erosion Boards” were set up to control the sand drifts. Shifting sand areas were visited twice a year and conservation measures were applied. Despite this promising approach, the area of sand drifts increased because land users were poor and fines were high. Reforestation was important for the battle against drifting sand. Also contributing to the decline of drifting sands were the abolition of communal land use, the introduction of fertilizers and the collapse of the wool industry.

In recent decades, “modern agriculture” has aggravated wind and water erosion problems. Nowadays wind erosion is causing problems in the Peat Reclamation District (PRD) in the north-east of the country. Here, land consolidation is regarded as a possible solution to decrease wind erosion. As a result of water erosion in the hilly part of South Limburg, where loess soils are dominant, towns and villages in the valleys are regularly flooded. It is being attempted to mitigate the problems of flooding by means of legislation and cooperation between stakeholders: Redistribution of land, implementation of measures “on hot spots” in the drainage system and farm management plans. There have been major successes already, but sustainable land use is still a long way off.     

Regional modeling of wind erosion in the North West and South West of Iran

About two-thirds of the Iran’s area is located in the arid and semiarid region. Lack of soil moisture and vegetation is poor in most areas can lead to soil erosion caused by wind. So that the annual suffered severe damage to large areas of rich soils. Modeling studies of wind erosion in Iran is very low and incomplete. Therefore, this study aimed to wind erosion modeling, taking into three factors: wind speed, vegetation and soil types have been done. Wind erosion sensitivity was modeled using the key factors of soil sensitivity, vegetation cover and wind erodibility as proxies. These factors were first estimated separately by factor sensitivity maps and later combined by fuzzy logic into a regional-scale wind erosion sensitivity map. Large areas were evaluated by using publicly available datasets of remotely sensed vegetation information, soil maps and meteorological data on wind speed. The resulting estimates were verified by field studies and examining the economic losses from wind erosion as compensated by the state insurance company. The spatial resolution of the resulting sensitivity map is suitable for regional applications, as identifying sensitive areas is the foundation for diverse land development control measures and implementing management activities.     

Ex-post evaluation of erosion control measures in southern Mali

As part of an impact study of a soil and water conservation (SWC) project in southern Mali, the effect of erosion control measures on soil erosion was evaluated. In one village, a baseline situation from 1988 was compared with the situation in 2003, after farmers had installed stone rows, live fences and grass strips, and had started cultivating across to the slope. This comparison showed a spectacular decrease in gully volume in cultivated fields of 87%, from 58 to 8 m³ ha⁻¹. Estimated annual soil loss decreased with 77% from 42 to 10 t ha⁻¹ year⁻¹. However, baseline data on erosion gullies were not available for other villages. In the absence of baseline data, a simple ‘with–without’ comparison does not allow a correct evaluation because farmers install erosion control measures especially in fields with more erosion. Two alternative methods were used: a reconstructed baseline and a virtual time series. Using the reconstructed baseline, looking not only at active gullies but also at (partly) reclaimed gullies, we concluded that line interventions, gully interventions, and a combination of both, reduced the proportion of active gullies by 48%, 47% and 70%, respectively. Using a virtual time series, comparing erosion in fields with erosion control measures installed in different years, we concluded that erosion gradually decreased by 50% during the 3 years after installation of erosion control measures. In a separate study, we found a positive effect of gully interventions and sowing across to the slope in reducing sheet erosion. A reduction of the slope of the sowing direction by 1% reduced the cover of runoff deposit of coarse sand with 8%. Although a documented baseline is preferred, both a reconstructed baseline and a virtual time series are useful tools and make ex-post evaluations more relevant than a simple with–without comparison.     

东北三省土壤风蚀天数时空变化及分区评述

基于东北三省1981−2017年气候资料,明确不同区域不同耕作阶段（全年、休耕期和播前1个月）不同等级日最大风速发生的变化规律;结合考虑降水影响下的起动风速指标,解析不同区域各阶段风蚀发生天数的时空规律,为各区域提出相适应的土壤保护耕作措施提供科学依据。结果表明：东北三省全年0−3级、4−6级和7级及以上日最大风速年均出现频率分别为48.5%、50.4%和1.1%,研究期内,全年、休耕期和播前1个月0−3级日最大风速出现频率均呈增加趋势,而4级及以上风速出现频率呈减少趋势。研究区域全年风蚀发生天数比例为35.0%,而播前一个月发生风蚀天数占该时期总天数的比例高于全年均值,达57.0%。大部分地区各个时期风蚀发生天数呈减少趋势。辽河平原区和三江平原区休耕期和播前1个月风蚀发生天数均较多,应重视风蚀对土壤的影响。松嫩平原区虽然休耕期土壤风蚀发生频率较低,但播前1个月风蚀发生较多,该区域应倡导免耕技术以降低土壤风蚀。     

Effects of double drilling of small grains on soil erosion by concentrated flow and crop yield

Soil erosion on agricultural land and its detrimental environmental and economical effects has aroused increased interest among both the research and policy-making communities. The call for erosion control measures adapted to local farming practices is high, especially in Europe where farmers are reluctant to adopt soil conservation techniques. This study investigates a new technique for controlling concentrated flow erosion rates in the loess belt of central Belgium: i.e. double drilling of cereals in zones of concentrated flow. Cross-sectional areas of erosion channels as well as crop yield parameters in single- and double-drilled zones were compared. The technique is based on the combined effect of the increased density of plant shoots and roots for reducing soil loss. Results indicate that double drilling can reduce soil loss through concentrated flow by 25% on average and by up to 40% under optimal conditions. No net change in wheat grain yield was observed, and farmers who participated in the experiments were satisfied with the results and the easy application of the technique. Globally, benefits were larger than costs. However, the effectiveness of the technique in reducing soil loss by concentrated flow erosion seems to be topographically restricted. For positions in the landscape with a contributing drainage area larger than ca. 0.75 ha, the effectiveness of double drilling can be doubted. Double drilling should therefore be regarded as one possibility amongst others to reduce concentrated flow erosion rates in farmers’ fields.     

The cost of soil erosion in vineyard fields in the Penedès–Anoia Region (NE Spain)

On-site and off-site environmental impacts of runoff and erosion are usually stressed in order to bring to the public's attention the importance and implications of soil erosion. However, few studies are aimed at calculating the economic implications of erosion, this being the message that farmers and/or policy makers understand best. In this current work we estimated the cost of erosion in vineyards in the Penedès–Anoia region (NE Spain), in which high intensity rain storms (> 80–100 mm h^− 1) are frequent. Modern plantations in the region consist of trained vines, usually planted perpendicular to the maximum slope direction. Broadbase terraces are interspersed between vine rows to intercept surface runoff and convey it out of the field. Part of the sediment generated above these terraces is deposited in them and other parts are either deposited beyond the boundaries of the fields or are exported to the main drainage network. High intensity rainfall produces heavy soil losses (up to 207 Mg ha^− 1 computed in an extreme event in June 2000, which had a maximum intensity in 30-min periods of up to 170 mm h^− 1). To estimate the cost of erosion in vineyard fields of this region, two important aspects were considered. These were a) the cost incurred by the maintenance of the broadbase terraces, drainage channels and filling of ephemeral gullies and b) the cost incurred by the loss of fertilisers (mainly N and P) caused by erosion. According to farmers' records, the former was estimated at 7.5 tractor-hour ha^− 1 year^− 1 (as average), which comprises 5.4% of the income from grape sales. Regarding N and P losses, nutrients exported by runoff were 14.9 kg ha^− 1 N and 11.5 kg ha^− 1 of P, which, if compared to the annual intakes, represent 6% and 26.1% of the N and P respectively. In economic terms, the replacement value of the N and P lost represents 2.4% for N or 1.2% for P of the annual income from the sale of the grapes.     

Comparative measures of effectiveness in farm-level soil conservation

Abstract. Agricultural soil erosion is serious in developed and developing countries alike. Soil runoff can diminish long-term land productivity and accompanying sedimentation of waterways contributes to flooding and substantially reduces both water quality and the useful life of reservoirs and irrigation works. To design effective erosion control policies, planners need to be able to evaluate conservation efforts by fanners. The research reported here develops comparative measures of conservation effectiveness using the management factors of the Universal Soil Loss Equation. These factors measure the effectiveness of farmers' existing conservation practices and can help policymakers identify the regions and types of farms which are not using effective erosion control measures, enabling them to direct scarce personnel and funds to areas where they are most needed.     

国外农田风蚀发生机理与防治技术的研究

土壤风蚀是全球性土地退化的主要原因之一，也是世界上许多国家和地区的主要环境问题之一。该文简要回顾了国外对土壤风蚀发生机理、防治理念和技术的研究，提出林业上植树造林，牧业上防止草原退化，农业上实行保护性耕作是人类可以用来治理和控制土壤风蚀的3个重要原则。我国土壤风蚀和土地退化问题日趋严重，应在全国进行大力宣传，转变土壤风蚀治理的观念，使人们从思想上认识风蚀防治要从植树、种草、农田保护3个方面综合进行。同时，国家要从政策上、资金上为农田保护性耕作的大规模实施提供保证，促进保护性耕作在全国范围内的推广应用。     

水土流失地区精准扶贫政策对农户幸福指数的影响

[目的]研究水土流失地区精准扶贫政策对农户幸福指数的影响,为贫困地区可持续发展提供科学参考。[方法]通过构建农户幸福指数评价指标体系,采取熵值法与加权求和模型对精准扶贫政策影响下的云南省双柏县农户幸福指数进行评价。[结果]在农户幸福指数评价指标的权重中,排在前3位的分别是人均可支配收入、婚姻满意度、生态环境满意度评价指标;双柏县大多数农户对精准扶贫工作认同度较高,总体满意度平均值为67.55分,但是各乡镇农户对政策感知差异较大。收入增减满意度、政策后果满意度、政策宣传满意度是影响双柏县农户对精准扶贫政策总体满意度的关键因素;双柏县农户幸福指数的平均值为65.64分,各乡镇农户幸福指数差异较小,基本维持在59～71分之间。[结论]未来双柏县应以提升农户幸福感和减缓贫困为关键点和突破点,通过精准扶贫政策实现水土流失地区可持续发展。