The nature, causes and implications of water erosion on arable land in Scotland

Abstract. Erosion was surveyed in Strath Earn, Scotland, following severe weather conditions during the first 18 days of January, 1993. A rapid field mapping system was devised to record the nature of erosion. A total of 208 fields was surveyed and 76 exhibited erosion. Most fields with erosional features were either ploughed or in autumn cereals. The most common form of erosion was ephemeral gullies along topographic hollows. This erosion was primarily associated with ploughed land whereas sheetwash and rill erosion occurred more on autumn sown land. Land use change and climatic variability, especially increasing rainfall over the last 20 years, account for the incidence of erosion. Individual erosion events rarely cause major problems for farmers, but the increasing frequency of erosion events raises important questions for sustainable land use in the arable areas of Scotland.     

A survey to assess the extent of soil water erosion in lowland England and Wales

Abstract. A study of soil water erosion was undertaken between 1982 and 1986 in 17 areas of lowland England and Wales. Air photographs were taken annually, these were checked to identify erosion events and a sample of 392 eroded fields visited between 1983 and 1986. Erosion was most common in fields drilled with winter cereals (39% of cases), which was the crop considered by farmers to be at greatest risk of erosion. Estimated crop losses were greater than 10% for only 5% of fields. 'Clean up' costs were incurred on 15% of the fields studied. Attempts at contour ploughing and planting/drilling appeared to result in more severe erosion, than working up and down the slope. Farmers considered that the main reason for erosion on their farms was arable cropping, and the presence of compacted wheelings/tramlines. Fields where hedges had been removed in the last 20 years suffered from erosion marginally more frequently than other fields. Field slope alone was not found to be a major factor in the occurrence of erosion, with almost 60% of erosion events on slopes of less than 7°. Erosion occurred at least every other year in half the fields studied.     

Soil crusts and deposits as sheet erosion indicators in southern Mali

Rills are indicators of erosion, easily recognized by farmers and extension workers. However, they are rare on fields in Mali with slopes of 0–3%, even though run‐off and sheet erosion may be a problem. The suitability of three other soil surface features as erosion indicators was therefore investigated: (1) structural crusts formed by rainfall impact without lateral soil movement; (2) in situ depositional crusts, formed by sedimentation leaving the finest particles on top; and (3) run‐off deposits of fine and coarse sand, formed after the removal of finer particles. Feature (1) occurred on the elevated parts and ridges, whereas (2) and (3) occurred in lower parts and in furrows. Soil cover with a run‐off deposit of coarse sand proved to be a suitable indicator and this was well explained by erosion risk: a 2% increase in slope related to a 9% increase in deposit cover. The extent of this deposit also related well to cotton yield from the previous season: a 30% increase in deposit cover was reflected in a 23% decrease in cotton yield. Only a few farmers confirmed that the deposits were produced by erosion. It is recommended that soil and water conservation programmes pay more attention to the presence of crusts and deposits.     

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.     

Farmers' knowledge and perceptions of soil erosion and conservation measures in the Central Highlands,Kenya

A lack of appreciation of Kenyan farmers' knowledge and their perceptions of soil erosion and soil conservation measures was the reason for low adoption of recommended technologies. This research was carried out to identify the criteria that farmers used to distinguish farm‐types and to use these types to evaluate different knowledge levels and perceptions of soil erosion and existing soil and water conservation (SWC) measures in the Central Highlands of Kenya. Community meetings and semi‐structured household surveys were carried out in a small catchment, with 120 households. Results partly support the idea of using farmer‐developed criteria to distinguish among land managers with reference to a farm‐type classification. Criteria distinguishing three classes of land managers (good, moderate and poor) were significant with regard to the following land husbandry practices: use of hybrid or recycled seed and use of organic and/or inorganic fertilizers. Farmers were aware of on‐going soil erosion and of several erosion control measures. Whereas a majority of farmers preferred grass‐strips as a SWC measures, they did not recognize agroforestry as a form of SWC measure. Farmers perceived that SWC measures could successfully increase crop yields and soil‐water retention, and increase land value. In general, farmers did not perceive that SWC measures successfully prevented erosion phenomena, given the evidence of on‐site erosion indicators. They attributed the continued erosion to high rainfall, steep slopes, lack of maintenance and poorly designed SWC measures. They did not consider poor soil‐cover, up‐down tillage and tall trees to be the causes of erosion. Farmers faced several constraints in adopting SWC measures: lack of labour, tools, capital and know‐how to construct the measures. Copyright © 2005 John Wiley & Sons, Ltd.     

降雨侵蚀因子和植被类型及覆盖度对坡耕地土壤侵蚀的影响

为探讨降雨和植被对辽西褐土区农耕坡地土壤侵蚀的影响,2006-2010年采用坡面径流小区观测法研究了天然降雨条件下降雨侵蚀因子、植被覆盖度、植被类型对坡耕地地表径流量、土壤侵蚀量的影响。设5°和10°两个坡度水平,以甘薯和谷子为供试作物,2006-2007年对照区为天然荒草地,2008-2010年为裸坡地。结果表明,甘薯地径流量和侵蚀量与降雨量(R)、最大30 min雨强(I_(30))、R×I(平均雨强)、R×I_(30)正相关显著(P0.05);裸坡地径流量与R、R×I_(30)正相关显著(P0.05),侵蚀量与I_(30)、R×I_(30)正相关显著(P0.05),与降雨量相关不显著(P0.05)。甘薯地和裸坡地的径流量和侵蚀量与平均降雨强度正相关均不显著(P0.05)。回归分析表明,降雨量主要影响径流量,最大30 min雨强主要影响侵蚀量。中、高雨强下,侵蚀量与径流量显著正相关(P0.01)。甘薯地径流量和侵蚀量与植被覆盖度呈显著负指数关系(P0.05)。5°坡耕地,不同植被类型侵蚀量为甘薯地荒草地谷子地;10°坡耕地,荒草地侵蚀量总体最少。多元回归分析表明,对土壤侵蚀的影响为地表径流降雨侵蚀力(R×I_(30))植被覆盖度。通过连续5 a坡面径流小区观测,初步探明降雨和植被对辽西褐土区农耕坡地土壤侵蚀的影响,可为该区坡耕地土壤侵蚀的有效防治提供一定的理论依据和技术支撑。     

红壤丘陵区坡长对作物覆盖坡耕地土壤侵蚀的影响

坡长对坡耕地土壤侵蚀的影响随雨强的不同而变化,为解决南方红壤丘陵区坡耕地水土流失问题,该文采用野外人工模拟降雨的方法,研究了南方红壤丘陵区作物覆盖坡耕地上不同雨强下坡长对其土壤侵蚀的影响,并探讨了侵蚀增强的临界雨强和设置水土保持措施的合理坡长,结果表明:产沙量随坡长延长整体呈增大趋势,但存在一定的波动,二者的关系可用幂函数(决定系数0.84)表示。坡长延长相同长度时,产沙量不呈比例增加,但每隔4 m产沙量增量有减少的趋势,且径流侵蚀产生的泥沙中主要为粒径0.002~0.02 mm的粉粒及粒径0.002 mm的黏粒,加剧了耕地土壤粗化,因此,可每隔4 m设置水土保持措施,有效减少坡耕地水土流失。坡面径流侵蚀产沙量随着雨强的增大而增加,坡长越长,产沙量随雨强增加速度越快,二者呈幂函数关系(决定系数0.76),60 mm/h是红壤丘陵区侵蚀增强的临界雨强;雨强、坡长与产沙量均呈正相关关系,且雨强对坡耕地产沙量的影响较坡长大。对不同雨强下坡长对作物覆盖坡耕地土壤侵蚀的影响研究,可以为南方红壤丘陵区坡耕地水土流失的治理提供一定的理论依据。     

Effects of tillage practices combined with mucuna fallow on soil erosion and water dynamics on Ishigaki Island,Japan

Abstract

This study was conducted on a sloping field at the Japan International Research Center for Agricultural Sciences, Okinawa Subtropical Station, Ishigaki Island, Okinawa Prefecture, Japan, to evaluate the effects of zero tillage farming combined with mucuna fallow as a cover crop on soil erosion and water dynamics. Two fallow systems (natural and mucuna) in combination with two soil tillage treatments (zero tillage and conventional tillage) were imposed on three sloping fields (2.0°, 3.5° and 5.0°). A sorghum crop (Sorghum bicolor (L) moench) was planted after the soil tillage treatment. Soil loss for zero tillage farming combined with mucuna fallow was equivalent to only 3% of that for the conventional tillage farming with natural fallow. Runoff water was also reduced by between 74% and 77% when compared with the conventional tillage system with natural fallow. These results indicate that zero tillage with mucuna fallow is a very effective measure for the control of soil erosion and water runoff. Moreover, this farming system improved water infiltration during both the fallow and the sorghum cropping periods. For the zero tillage plot, water loss as deep percolation increased 1.6-fold compared with that for the conventional farming under heavy rainfall conditions. It is expected that under less rainfall areas or seasons, the effects of zero tillage farming combined with the mucuna cover crop may be more pronounced on water runoff control and, therefore, may greatly improve soil water conditions.     

Examples of erosion on brickearth soils in east Kent

Abstract. High rates of erosion are reported from three sites on brickearth (loess) soils in east Kent. Problems are acute where soils are used for intensive production of vegetables and salad crops. Erosion appears to be the result of structural instability, lack of crop cover for much of the year, and certain managment practices, such as ridging the soil for the crop. In the autumn of 1984, about 120 tonnes of soil was lost from rills in a field of onions: an erosion rate of about 15 t ha⁻¹. A large field under winter cereals also eroded and this resulted in damage to property. Conservation techniques are recommended.     

Monitoring of water erosion on arable farms in England and Wales, 1989–90

Abstract. Water erosion was recorded between mid-October and mid-December 1989 in 31 out of 73 erosion-susceptible arable fields being monitored in England and Wales. Most fields were drilled to winter cereals. Tramlines and wheelings were the factors most commonly linked with initiation of erosion, particularly where runoff was concentrated on valley floors or headlands. Lack of crop cover (< 15%) was also an important factor at a number of sites; 25–30% ground cover was generally sufficient to protect the soils from erosion. Erosion was initiated by rainfall events of 15 mm or more in a 24 h period, with a maximum intensity greater than 4 mm/h. A large erosion event in south-west England was associated with 33 mm of rainfall in 4.25 h, with a maximum intensity of 22 mm/h.     

Monitoring of water erosion on arable farms in England and Wales. 1990–94

Abstract. The incidence of soil water erosion was monitored in 12 erosion-susceptible arable catchments ( c . 80 fields) in England and Wales between 1990 and 1994. Factors associated with the initiation of erosion were recorded, and the extent of rills and gullies measured. Approximately 80% of the erosion events were on land cropped to winter cereals. In 30% of cases, the initiation of erosion was linked to valley floor features, which concentrated runoff. Poor crop cover, wheelings and tramlines were also assessed as contributory factors in 22%, 19% and 14% of cases, respectively. In c . 95% of cases rainfall events causing erosion were ≥10 mm day⁻¹ and c . 80% were >15 mm day⁻¹. Erosion was also associated with maximum rainfall intensities of >4 mm h⁻¹ for c . 90% of cases and >10 mm h⁻¹ for c . 20%. Mean net soil erosion rates were approximately 4 t ha⁻¹ per annum (median value 0.41 t ha⁻¹ per annum) and associated mean P losses 3.4 kg ha⁻¹.     

Tillage and crop management effects on soil erosion in central Croatia

Soil erosion continues to be a primary cause for soil degradation and the loss of soil quality throughout the world. Our objectives were to quantify soil erosion (referred to as erosional drift) and to assign erosion risk to six tillage and crop management treatments evaluated from 1995 to 1999 for a 5-year maize (Zea mays L.), soybean (Glycine hyspida L.), winter wheat (Triticum aestivum L.), oil-seed rape (Brassica napus var. oleifera L.), and spring barley (Hordeum vulgare L.) plus double-crop soybean rotation on Stagnic Luvisols in central Croatia. Standard black fallow (tilled, unsown, and without any vegetative cover) Universal Soil Loss Equation (USLE) plots were used to establish the erosion potential associated with the rainfall pattern for each year. Soil loss from the check plots was several times greater than the T value, which is estimated to be 10 t ha⁻¹ per year. During the 2 years when spring seeded maize or soybean were grown (1995 and 1996) erosion risk was extremely high, especially for treatments where tillage and planting (row direction) were up and down the slope. When autumn seeded winter wheat or oil-seed rape were grown (1996/1997 or 1997/1998), soil erosion was insignificant. Also, except when plowing and sowing were up and down slope, erosion loss for the spring barley plus double-crop soybean crops in 1999 was insignificant. With no-tillage, soil erosion from the maize and soybean crops was reduced 40 and 65% compared to plowing up and down slope, even though the planting direction was still up and down the slope. With the exception of maize in 1995, erosion losses were moderate to insignificant when plowing and planting were performed across the slope. We conclude that erosion risk can be used as a reliable indicator of sustainable land management and that using no-tillage or plowing and planting perpendicular to the predominant slope are effective soil conservation practices for this region.     

Interrill soil erosion as affected by tillage and residue cover

No-till cropping systems are effective in reducing soil erosion. The objective of this study was to determine whether high infiltration rates and low runoff and soil loss under long-term, no-till conditions in loessial regions of the Midwest US result from both the well-structured, porous condition of the soil and the protective cover of crop residue or primarily from residue cover. Soil loss, runoff, and infiltration were measured using a rainfall simulator on interrill erosion plots with and without residue cover on a conventional and two no-till systems in central Illinois. For both conventional till and no-till conditions, removing surface residue significantly decreased infiltration rates and increased soil loss. Tilling the no-till surface while maintaining an equal surface cover as with the no-till system slightly increased interrill erosion. Removing residue on a no-till system, however, increased soil loss significantly. A no-till soil condition without adequate residue cover will seal, crust, and erode with extremely high soil losses following surface drying.     

Soil tillage methods to control phosphorus loss and potential side-effects: a Scandinavian review

In Scandinavia high losses of soil and particulate-bound phosphorus (PP) have been shown to occur from tine-cultivated and mouldboard-ploughed soils in clay soil areas, especially in relatively warm, wet winters. The omission in the autumn of primary tillage (not ploughing) and the maintenance of a continuous crop cover are generally used to control soil erosion. In Norway, ploughing and shallow cultivation of sloping fields in spring instead of ploughing in autumn have been shown to reduce particle transport by up to 89% on highly erodible soils. Particle erosion from clay soils can be reduced by 79% by direct drilling in spring compared with autumn ploughing. Field experiments in Scandinavia with ploughless tillage of clay loams and clay soils compared to conventional autumn ploughing usually show reductions in total P losses of 10–80% by both surface and subsurface runoff (lateral movements to drains). However, the effects of not ploughing during the autumn on losses of dissolved reactive P (DRP) are frequently negative, since the DRP losses without ploughing compared to conventional ploughing have increased up to fourfold in field experiments. In addition, a comprehensive Norwegian field experiment at a site with high erosion risk has shown that the proportion of DRP compared to total P was twice as high in runoff water after direct drilling compared to ploughing. Therefore, erosion control measures should be further evaluated for fields with an erosion risk since reduction in PP losses may be low and DRP losses still high. Ploughless tillage systems have potential side-effects, including an increased need for pesticides to control weeds [e.g. Elytrigia repens (L.) Desv. ex Nevski] and plant diseases (e.g. Fusarium spp.) harboured by crop residues on the soil surface. Overall, soil tillage systems should be appraised for their positive and negative environmental effects before they are widely used for all types of soil, management practice, climate and landscape.     

Participatory soil and water conservation planning using an erosion mapping tool in the central highlands of Kenya

Despite several approaches that aimed at mobilising East African farmers to embrace soil and water conservation (SWC) activities, farmers hardly responded since they were seldom involved in the planning of SWC activities. Two tools that employ farmers' participation were developed and applied at Gikuuri catchment in Kenya. The first tool involved farmers to map soil erosion using their own indicators and determine the soil erosion status at catchment scale. This formed the basis upon which they undertook to plan for SWC measures at catchment scale. Farmers also predicted crop yield losses based on the soil erosion status. Farmers widely approved the soil erosion status map since their own indicators and perceptions were used. The second tool provided cash flow trends for a variety of SWC activities and farmer situations. Farmers can use land with a high, moderate or low erosion status and often have rather different socio‐economic settings. The net benefits over 5 yr for bench terraces, fanya juu terraces and grass strips were illustrated to assist farmers in making informed decisions on SWC adoption. The two tools increased awareness on the need for collective actions among farmers and showed fields that cause run‐on on downslope fields. The improved awareness of erosion problems and the related financial consequences increased farmers' willingness to share the investment costs for cut‐off drains. Copyright © 2007 John Wiley & Sons, Ltd.     

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 erosion and participatory remediation strategy for bench terraces in northern Thailand

This study was carried out in Pang Prarachatan village, which is located in Chiang Rai province of northern Thailand. The farmers in this village construct bench terraces to reduce soil erosion and increase plant productivity. However, severe soil erosion occurs frequently on the bare bench terraces. This study investigates the impact of bench terracing on soil erosion. The use of weeds and plant residues to control soil and nutrient losses were also investigated using model slope plots and an artificial rainfall system. Finally, the knowledge gained from this study was transferred to the farmers through a workshop in the village, and their acceptance of the results was evaluated by means of a questionnaire. The severity of soil erosion is thought to vary according to the structure of the bench terrace and the ground cover conditions. Rills are the primary form of erosion on bare bench terraces. In addition, some rills develop into gullies that can run from the upper terrace down to the lower terrace. Nevertheless, rills and gullies are rarely found on weed-covered terraces. Moreover, the results of an erosion experiment using model slope plots and artificial rainfall systems showed that plots covered with weeds and plant residues had much less surface runoff and soil and nutrient losses than bare soil. The amounts of nitrogen and phosphorus absorbed by weeds were 4.7 and 2.3 times smaller than the nitrogen and phosphorus losses due to soil erosion, respectively. The results of the field surveys and model slope experiment were announced to the farmers through participatory workshop in August 2003. The first questionnaire, conducted just after the workshop, clearly showed that around 90% of the farmers agreed to cover their slopes with weeds and plant residues so long as it did not affect soil fertility and plant growth. However, the second questionnaire, conducted in January 2004, showed that only 29% of farmers were covering the bench terraces or non-terraced slopes in their farmlands with weeds and plant residues. Therefore, participatory activities should continue to be held regularly in order to ensure greater acceptance and practice of soil conservation on the part of the farmers.     

Effects of crop-slope interaction on slope runoff and erosion in the Loess Plateau

Crops are the most important ground cover on slope farmland and have a significant impact on the soil erosion. But soil erosion on slope farmland is also affected by many other factors, such as topography and rainfall. In order to explore the effect of crop growth on soil erosion on different slope gradient of slope farmland, and analyze the interaction of crop growth and slope gradient on soil erosion, this study used artificial simulated rainfall to observe the runoff rates and soil loss amounts under different slope gradients for maize, soybeans, and winter wheat in different growth stages. Results showed that crops and slope gradient both significantly affected production and development of slope runoff. Compared with bare land, mean runoff rate on slopes was reduced by 24%, 32%, and 94% respectively, and sediment yield was decreased by 44%, 55%, and 99% respectively on maize, soybean, and winter wheat fields. Inhibitory effects of crops on slope runoff rate and sediment yield were enhanced with crop growth and decreased with increasing slope gradient. Crop growth and coverage could offset the impact of increasing slope gradient on runoff and sediment to some extent and reduced water and soil loss on slopes. Sediment yield was produced largely when the slope gradient was greater than 10 degrees on maize and soybean fields, but soil erosion was effectively inhibited when the slope gradient was less than 15 degrees on winter wheat fields. Crop planting can effectively reduce the impact of slope gradient on soil erosion, especially during the flourishing period of crop growth.     

基于SOTER的海南岛土壤水侵蚀模拟

The actual and potential water erosion rates of soils with different land covers in Hainan Island,China,were estimated based on the universal soil loss equation(USLE) and a 1:200000 Soils and Terrain digital Database(SOTER) Ddatabase,from which soil water erosion factors could be extracted.92.8% of the whole island had a current erosion rate of lowerthan 500t km^-2 a^-1.Soil erosion risk was considered to be high because of its abundant rainfall.Without vegetation tcover,the potential soil erosion ratewould be extremely high and 90.8% ofthe island would have a soil erosion rate higher than 2500t km^-2a^-1.Relative erosion vulnerability of different soil zones,landform types,and lithological regions of the island was compared by introducing a relative erosion hazard parameter α.Cambosols developed from siltstone and mudstone in low hill regions were pinpointed as soils with the highest erosion risk in the island.