Impact of climate change on soil erosion, runoff, and wheat productivity in central Oklahoma

The potential for global climate changes to increase the risk of soil erosion is clear, but the actual damage is not. The objectives of this study were to evaluate the potential impacts of climate change on soil erosion, surface runoff, and wheat productivity in central Oklahoma. Monthly projections were used from the Hadley Centre's general circulation model, HadCM3, using scenarios A2a, B2a, and GGa1 for the periods of 1950–1999 and 2070–2099. Projected changes in monthly precipitation and temperature distributions between the two periods were incorporated into daily weather series by means of a stochastic weather generator (CLIGEN) with its input parameters adjusted to each scenario. The Water Erosion Prediction Project (WEPP) model was run for four climate scenarios including a recent historical climate and three tillage systems (conventional tillage, conservation tillage, and no-till). HadCM3-projected mean annual precipitation during 2070–2099 at El Reno, Oklahoma decreased by 13.6%, 7.2%, and 6.2% for A2a, B2a, and GGa1, respectively; and mean annual temperature increased by 5.7, 4.0, and 4.7 °C, respectively. Predicted average annual soil loss in the tillage systems other than no-till, compared with historical climate (1950–1999), increased by 18–30% for A2a, remained similar for B2a, and increased by 67–82% for GGa1. Predicted soil loss in no-till did not increase in the three scenarios. Predicted mean annual runoff in all three tillage systems increased by 16–25% for A2a, remained similar for B2a, and increased by 6–19% for GGa1. The greater increases in soil loss and runoff in GGa1 were attributed to greater variability in monthly precipitation as projected by HadCM3. The increased variability led to increased frequency of large storms. Small changes in wheat yield, which ranged from a 5% decrease in B2a to a 5% increase in GGa1, were because the adverse effects of the temperature increase on winter wheat growth were largely offset by CO₂ rise as well as the bulky decrease in precipitation occurred outside the growing season. The overall results indicate that no-till and conservation tillage systems will be effective in combating soil erosion under projected climates in central Oklahoma.     

Soil erosion under simulated rainfall in relation to phenological stages of soybeans and tillage methods in Lages, SC, Brazil

Soil tillage may increase vulnerability to water erosion, whereas no tillage and other conservation cultivation techniques are viewed as strategies to control soil erosion. The objective of this research was to quantify runoff and soil losses by water erosion under different soil tillage systems at the Santa Catarina Highlands, southern Brazil. A field study was carried out using a rotating-boom rainfall simulator with 64 mm h⁻¹ rainfall intensity on a Typic Hapludox, between April 2003 and May 2004. Five rainfall tests were applied along successive cropstages. Surface cover was none (fallow) or soybean (Glycine max, L.). Five treatments were investigated, replicated twice. These treatments were conventional tillage on bare soil (BS) as a control treatment and the following treatments under soybean: conventional tillage (CT), no tillage over burnt crop residues on never before cultivated land (NT-B), no tillage over desiccated crop residues, also on never before cultivated land (NT-D) and traditional no tillage over desiccated crop residues on a soil tilled 4 years before this experiment (NT-PT). Water losses by surface runoff seemed to be more influenced by vegetative crop stadium than by tillage system and consequently a wide range of variation in surface runoff was found, following successive cropstages. The most efficient tillage system in reducing surface runoff and soil losses was no tillage, particularly the NT-PT treatment. Sediment losses were more influenced by tillage system than water losses. In the NT-B, NT-D and NT-PT treatments the rate of sediment losses along the crop vegetative cycle showed a tendency to increase from the first to the second cropstages and later to decrease from the third cropstage onwards. In the conventionally tilled treatment (CT) soil losses were greater than in any of the no tillage treatments (NT-D, NT-B and NT-PT) during the initial growth periods, but at the end of the vegetative period differences in sediment rates between tilled and non-tilled treatments tended to be smaller. In the BS control treatment, soil losses progressively increased following the vegetative growth season of soybean.     

Simulating site-specific impacts of climate change on soil erosion and surface hydrology in southern Loess Plateau of China

Proper spatial and temporal treatments of climate change scenarios projected by General Circulation Models (GCMs) are critical to accurate assessment of climatic impacts on natural resources and ecosystems. The objective of this study was to evaluate the site-specific impacts of climate change on soil erosion and surface hydrology at the Changwu station of Shaanxi, China using a new spatiotemporal downscaling method. The Water Erosion Prediction Project (WEPP) model and climate change scenarios projected by the U.K. Hadley Centre's GCM (HadCM3) under the A2, B2, and GGa emissions scenarios were used in this study. The monthly precipitation and temperature projections were downloaded for the periods of 1900–1999 and 2010–2039 for the grid box containing the Changwu station. Univariate transfer functions were derived by matching probability distributions between station-measured and GCM-projected monthly precipitation and temperature for the 1950–1999 period. The derived functions were used to spatially downscale the GCM monthly projections of 2010–2039 in the grid box to the Changwu station. The downscaled monthly data were further disaggregated to daily weather series using a stochastic weather generator (CLIGEN). The HadCM3 projected that average annual precipitation during 2010–2039 would increase by 4 to 18% at Changwu and that frequency and intensity of large storms would also increase. Under the conventional tillage, simulated percent increases during 2010–2039, compared with the present climate, would be 49–112% for runoff and 31–167% for soil loss. However, simulated soil losses under the conservation tillage during 2010–2039 would be reduced by 39–51% compared with those under the conventional tillage in the present climate. The considerable reduction in soil loss in the conservation tillage indicates the importance of adopting conservation tillage in the region to control soil erosion under climate change.     

Simulating site-specific impacts of climate change on soil erosion and surface hydrology in southern Loess Plateau of China

Proper spatial and temporal treatments of climate change scenarios projected by General Circulation Models (GCMs) are critical to accurate assessment of climatic impacts on natural resources and ecosystems. The objective of this study was to evaluate the site-specific impacts of climate change on soil erosion and surface hydrology at the Changwu station of Shaanxi, China using a new spatiotemporal downscaling method. The Water Erosion Prediction Project (WEPP) model and climate change scenarios projected by the U.K. Hadley Centre's GCM (HadCM3) under the A2, B2, and GGa emissions scenarios were used in this study. The monthly precipitation and temperature projections were downloaded for the periods of 1900–1999 and 2010–2039 for the grid box containing the Changwu station. Univariate transfer functions were derived by matching probability distributions between station-measured and GCM-projected monthly precipitation and temperature for the 1950–1999 period. The derived functions were used to spatially downscale the GCM monthly projections of 2010–2039 in the grid box to the Changwu station. The downscaled monthly data were further disaggregated to daily weather series using a stochastic weather generator (CLIGEN). The HadCM3 projected that average annual precipitation during 2010–2039 would increase by 4 to 18% at Changwu and that frequency and intensity of large storms would also increase. Under the conventional tillage, simulated percent increases during 2010–2039, compared with the present climate, would be 49–112% for runoff and 31–167% for soil loss. However, simulated soil losses under the conservation tillage during 2010–2039 would be reduced by 39–51% compared with those under the conventional tillage in the present climate. The considerable reduction in soil loss in the conservation tillage indicates the importance of adopting conservation tillage in the region to control soil erosion under climate change.     

Impact of expected increase in precipitation intensities on soil loss—results of comparative model simulations

The impact of the expected climate change on the frequency and extent of soil erosion processes is hardly assessable so far. This is mainly because available models of climate change reliably produce at best mean daily precipitation data, whereas erosion is the result of extreme but short time rainfall and runoff events, normally lasting no longer than a few hours. The frequency and intensity of these extreme rainfall events are expected to increase in some regions, which could lead to increased erosion rates. Mathematical models are able to describe erosion rates under conditions of these extreme events, however, so far prognostic meteorological data necessary for the application of these models are not available.The use of a new method for the projection of meteorological time series and their extremes using global climate simulations [Enke and Spekat, 1997, Enke, 2000, Enke, 2003, Enke et al., 2005 and Enke et al., in press] permits for the first time an approximation of future soil loss.This research is based on simulated, high resolution data for extreme rainfall events in the period of 2031–2050, which reproduces the mean frequency, intensity and duration of future events with high precipitation intensities relevant to erosion within the investigated seasonal period from June to August. The simulations are performed for two exemplary sites in Saxony, based on the EROSION 2D model (Schmidt, J., 1990. A mathematical model to simulate rainfall erosion, Catena, Suppl. 19), which is a process-based soil erosion model for simulating soil erosion and deposition by water on single slopes. Simulated precipitation for the 2031–2050 time period is used to model soil loss, and results are compared to soil loss based on 20 years of measured precipitation from 1981 to 2000.The simulation results allow the impacts of climate change on erosion rates to be quantified by comparing current climate with predicted, future climate. However, expected changes in land use due to changed economic conditions are not taken into account in this analysis.     

Tillage methods and soil and water conservation in Australia

Tillage in Australia has evolved from ‘imported’ European practices to tillage systems more in tune with ‘older’ fragile soils and more severe climatic conditions. Cereal yields are commonly limited by water supply and the native fertility of many soils is poor. Crop/pasture rotations involving pasture legumes have been the mainstay of cereal production in the winter rainfall areas while production in much of the summer rainfall area has relied more on exploiting native fertility. Soil erosion and structural decline are still considered major issues facing long-term production. The general trend in tillage methods is for less tillage and greater retention of crop residues for soil and water conservation.

Tillage experiments have shown that management strategies involving retention of crop residues (stubble), reduced tillage and crop rotation can reduce erosion and improve yield. Results from experimentation are highly variable, both in magnitude and direction of responses to tillage treatments. Much of this variation is due to variation in seasonal conditions. Simulation models are being used to examine management options and to design experiments based on a knowledge of climate variability and physical and biological processes.     

Assessment of soil erosion in karst regions of Havana,Cuba

Only recently have erosion models begun to be used in research work in Cuba, specifically the USLE and the thematic cartography of factors in a GIS framework without using a specific model. It therefore becomes necessary to include simulation models for karst regions that make possible an integral assessment of the specific types of soil erosion in those environments and take into consideration the effects of climate change in soil management systems. Morphometric analysis of karst doline absorption forms in regions of La Habana Province in 1986, 1997, and 2009 allowed the characterisation and application of the Morgan Morgan Finney (MMF) conceptual empirical erosion model in the Country for the first time. The results showed previously unreported losses of 12·3–13·7 t of soil ha ⁻¹ y⁻¹, which surpasses the permissible erosion threshold. Furthermore, it clearly shows the unsustainable trend of Red Ferralitic and Ferrasol Rhodic (World Reference Base) soils use. The model applied considered the effects of extreme rainfall events associated with climate change in recent years. The results found have led to strategies for coping with future climate change in each scenario and have made it possible to evaluate the consequences. Copyright © 2011 John Wiley & Sons, Ltd.     

Nonlinear responses of soil erosion to climate change: a modelling study on the UK South Downs

A modelling approach is used to estimate some effects of changed climate upon rates of soil erosion on agricultural land on the UK South Downs.Previous studies have concentrated only on estimating shifts in long-term mean erosion rate: these were found to be approximately linear. However such simple shifts mask changes in the underlying distributions of annual erosion. A first series of simulations indicated that, under a wetter climate, erosion rates in wet years will generally increase more than rates in dry years. Under a “best guess” rainfall scenario with a 10% increase in winter rainfall, annual erosion increased by up to 150%. Erosion rates for individual years were shown to change in more complex nonlinear ways however, with decreases as well as increases occurring. These could be explained by the interaction of timing of rainfall with changes in the rate of crop growth.Most earlier work also assumed an equilibrium climate for the simulations, with climatic parameters such as mean monthly rainfall having stabilised at some new value, usually for a 2 × CO₂ atmosphere. This however leads to an “initial conditions” problem: how will soil characteristics have changed by the time of CO₂ doubling? A decrease in erodibility of about 20% by the time of CO₂ doubling was indicated, resulting from changed soil profile properties. However, a second series of runs employed “transient” weather sequences (i.e. with a trend imposed). For these, present-day soil profiles could legitimately be used.     

黑土区垄作方式对坡耕地土壤侵蚀的调控效果

[目的]分析黑土区不同垄作方式对坡耕地土壤侵蚀的调控效果,为该区土壤侵蚀防治提供科学指导。[方法]在5°和10°坡耕地开展人工模拟降雨试验,降雨强度为50,100 mm/h,垄作方式包括：横坡垄作、垄向区田、顺垄+底部横垄和横垄+排水沟,对照处理为传统顺坡垄作。[结果]试验条件下,与顺坡垄作处理相比,横坡垄作、垄向区田、顺垄+底部横垄和横垄+排水沟处理均可有效调节径流、降低土壤侵蚀量,但不同垄作方式对径流和侵蚀的调控效果随着降雨强度和坡度的增加而减小。在5°坡耕地,横坡垄作方式对径流和侵蚀的调控效果最佳,产流率和土壤侵蚀速率分别稳定在15.0 mm/h和0.2 kg/(m~2·h)以下。在50,100 mm/h降雨强度下,与顺坡垄作处理相比,其径流量分别降低92.3%和83.9%,土壤侵蚀量分别降低96.8%和94.6%;而垄向区田方式对径流和侵蚀的调控效果略大于顺垄+底部横垄处理。在10°坡耕地,横坡垄作方式在降雨前期具有较好的蓄水保土作用,但在降雨后期垄体易损坏,造成土壤侵蚀量剧增;横垄+排水沟方式在降雨前期能够蓄水保土,在降雨后期能够较好地进行排水。[结论]在坡度平缓的坡耕地,应...     

Influence of tillage system on denitrification in maize-cropped soils

Denitrification losses show an irregular pattern through the year, often being caused by climatic conditions and management practices. The objectives of the present work were to quantify denitrification losses and to determine the influence of tillage system on the factors that control denitrification in fertilized soils. The modal profile of the soil was an Vertic Argiudoll, clay loam texture, located in Buenos Aires province, Argentina. The treatments were: (a) fertilized, (b) incorporated fertilization and (c) without fertilization for both no tillage and conventional tillage systems. Chambers were placed in the field to measure denitrification. In this clayish soil the estimated mean values of accumulated denitrification during the crop cycle (90 days) were 0.190kgNha^–1 for conventional tillage and 0.350kgNha^–1 for no tillage. In treatments with no tillage, losses by denitrification were approximately twice those of conventional tillage. These differences were also evidenced by the number of microorganisms, which were significantly higher (P<>;5%) for no tillage on all dates, except for at flowering. The increase at flowering coincided with the period of highest rainfall and consequently the highest water contents in the soil. The highest denitrification losses, except for sowing, were measured when soil moisture content was more than 30% (v/v). Denitrification increased in conjunction with an increase in the availability of carbon that is consumed by the heterotrophic microorganisms (including the denitrifiers). Received: 30 July 1996     

垦植方式对山地果园水土流失的影响

应用径流小区法,长期（1996-2006）定位研究福建中部尤溪县垦植方式对山地果园水土流失的影响,结果表明：1）该地区11年平均年降雨量1575.5mm,平均年蒸发量1461.1mm,5月、6月、8月是强降雨高发期,也是水土流失防治的关键期;2）在山地果园开发中,平台开垦的径流系数为0.0688,明显小于顺坡开垦（0.2865）;3）植草能使果园0-30cm土层的土壤含水量提高0.8％-0.9％;4）顺坡清耕区侵蚀模数为2388.2t／（km^2·a）,梯台清耕区土壤侵蚀量达10.3kg/m,土壤侵蚀主要源于台壁受冲刷,顺坡植草区、梯台植草区基本不发生土壤侵蚀。     

Black soil degradation by rainfall erosion in Jilin,China

Black soils, originally characterized by a deep, dark A‐horizon, are widespread in the Northeast Plain of China and have been one of the most fertile agricultural resources in the country. However, more than a half‐century of intensified management degraded its productivity, mainly with the loss of the dark‐coloured A‐horizon by rainfall erosion. Using the Revised Universal Soil Loss Equation (RUSLE), the rainfall erosion losses of black soils in YuShu and DeHui counties of Jilin Province were estimated. The rate of loss of thickness of the A‐horizon of black soils and the time over which the A‐horizons of some black soils in the region might be lost were evaluated. The results showed that about 4–45 t ha⁻¹ topsoil could have been lost each year under corn (Zea mays L.) production. Soybean (Glycine max L. Merr) production would double the losses. Soil losses were directly related to soil type, tillage practices and crop grain yields. The thickness of the A‐horizon of black soils in the region decreased at rates of 0ċ5–4ċ5 mm yr⁻¹, depending on soil type and management practices. Corn production may have resulted in an annual loss of 8ċ3 million tonnes of topsoil from black soils alone in Jilin Province; soybean production could have greatly increased this loss. Traditional intensified farming can accelerate the degradation of black soils; conservation tillage has great potential to prevent rainfall erosion losses for the same soils. Accordingly, to preserve and restore the productivity of black soils, conservation tillage is appropriate and should be adopted in Jilin. Copyright © 2003 John Wiley & Sons, Ltd.     

137Cs tracing of the spatial patterns in soil redistribution,organic carbon and total nitrogen in the southeastern Tibetan Plateau

The southeastern Tibetan Plateau, which profoundly affects East Asia by helping to maintain the stability of climate systems, biological diversity and clean water, is one of the regions most vulnerable to water erosion, wind erosion, tillage erosion, freeze–thaw erosion and overgrazing under global climate changes and intensive human activities. Spatial variations in soil erosion in terraced farmland (TL), sloping farmland (SL) and grassland (GL) were determined by the ¹³⁷Cs tracing method and compared with spatial variations in soil organic carbon (SOC) and total nitrogen (total N). The ¹³⁷Cs concentration in the GL was higher in the 0–0.03 m soil layer than in the other soil layers due to weak migration and diffusion under low precipitation and temperature conditions, while the ¹³⁷Cs concentration in the soil layer of the SL was generally uniform in the 0–0.18 m soil layer due to tillage-induced mixing. Low ¹³⁷Cs inventories appeared at the summit and toe slope positions in the SL due to soil loss by tillage erosion and water erosion, respectively, while the highest ¹³⁷Cs inventories appeared at the middle slope positions due to soil accumulation under relatively flat landform conditions. In the GL, the ¹³⁷Cs data showed that higher soil erosion rates appeared at the summit due to freeze–thaw erosion and steep slope gradients and at the toe slope position due to wind erosion, gully erosion, freeze–thaw erosion and overgrazing. The ¹³⁷Cs inventory generally increased from upper to lower slope positions within each terrace (except the lowest terrace). The ¹³⁷Cs data along the terrace toposequence showed abrupt changes in soil erosion rates between the lower part of the upper terrace and the upper part of the immediate terrace over a short distance and net deposition on the lower and toe terraces. Hence, tillage erosion played an important role in the soil loss at the summit slope positions of each terrace, while water erosion dominantly transported soil from the upper terrace to the lower terrace and resulted in net soil deposition on the flat lower terrace. The SOC inventories showed similar spatial patterns to the ¹³⁷Cs inventories in the SL, TL and GL, and significant correlations were found between the SOC and ¹³⁷Cs inventories in these slope landscapes. The total N inventories showed similar spatial patterns to the inventories of ¹³⁷Cs and SOC, and significant correlations were also found between the total N and ¹³⁷Cs inventories in the SL, TL and GL. Therefore, ¹³⁷Cs can successfully be used for tracing soil, SOC and total N dynamics within slope landscapes in the southeastern Tibetan Plateau.     

不同土壤管理措施下基于水蚀过程的含沙量变异及其驱动

In order to prevent soil erosion in southern China, a study was performed to determine the drivers of sediment concentration variation using simulated rainfall and four soil management systems under field condition. Four soil management systems, i. e., forest and grass coverage (FG), forest coverage with disturbed soil surface (FD), contour tillage (CT) and downslope tillage (DT), were exposed to two rainfall intensities (40 and 54 mm h^-1) using a portable rainfall simulator. The drivers of sediment concentration variation were determined by the variations of runoff rate and sediment concentration as well as their relationships. The effects of the four soil management systems in preventing water and soil losses were compared using runoff rates and sediment concentrations at steady state. At runoff initial stage, sediment concentration variation was mainly driven by rainfall and management. The degree of sediment concentration variation driven by flow varied with different soil management systems. Three best relationships between runoff rate and sediment concentration were identified, i. e., reciprocal (CT), quadratic (FG and FD) and exponential (DT). At steady state, runoff rates of the four soil management systems varied slightly, whereas their sediment concentrations varied greatly. FG and CT were recommended as the best soil management systems for preventing water and soil losses.     

A probabilistic approach for predicting rainfall soil erosion losses in semiarid areas

The implementation of soil and water conservation structures in semiarid areas, usually poses a difficult design problem. This is, in large part, due to the high variability of rainfall and the huge potential impact of extreme hydrologic events on structures and on the landscape in general. Magnitudes of runoff and soil loss or sedimentation rates in those environments are better not assessed by conventional modelling techniques, which tend to average out event magnitude and recurrence variability in time and space. A probability-based approach is proposed here to analyse and predict rainfall erosion losses. The maximum annual storm and its associated erosivity is used as a core element in the assessment of annual interrill and rill erosion rates. Frequency and cumulative soil loss distributions are obtained by combining verified annual and maximum daily rainfall frequency distributions with a proposed erosion algorithm. This stochastic representation of erosion permits to evaluate soil losses for the maximum annual storm, as well as annual erosion rates as a function of recurrence interval. The proposed method was verified with a short series of measured soil loss data in Cape Verde. The physical basis underlying the prediction algorithm and method in general, could be sustained by experimental data and field survey evidence. The method seems applicable to arid and semiarid ecosystems with a high seasonal concentration of precipitation and with rainfall limited to only a few major storm events.     

Relationship between soil erodibility and topsoil aggregate stability or carbon content in a cultivated mediterranean highland (Aveyron,France)

Abstract

In the Rougiers de Camarès area (in the south of France), hillslopes are very susceptible to water erosion. This is the result of physical features (steep slopes, soft bedrocks, thin soils), climatic aggressiveness (frost, storms), as well as farming systems (intensive tillage, short crop cycles, land consolidation). The objective of this work was to study the relationships between soil erodibility, macroaggregate stability, and carbon content of surface samples (0–10 cm), in a Rougiers Entisol (Lithic Udorthent) under various management practices (flat or raised moldboard ploughing, superficial tillage, direct drilling, with inputs in the form of mineral fertilizers or sheep manure). The soil erodibility was assessed by field rainfall simulation (60 mm h^‐1) on manually retilled bare dry soil; water‐stable macroaggregation (>0.2 mm) was assessed by wet‐sieving, after immersion in water. Runoff, turbidity and soil losses were linked to water‐stable macroaggregation and carbon content in the 0–10 cm layer. During the first 30 minutes of rainfall, runoff and soil losses were closely correlated with topsoil initial water‐stable macroaggregation, but not with topsoil carbon content (although there was a correlation between water‐stable macroaggregation and carbon content). At the end of the rain (runoff steady state), turbidity and soil losses were closely correlated with topsoil carbon content, and to a lesser extent, with water‐stable macroaggregation. Water‐stable macroaggregation (which prevents crusting) and carbon content (which has an effect upon liquidity limit, among others) were thus important determining factors of erodibility for the studied soil. The influence of management practices on soil erodibility was therefore dependent upon their effects on these factors.     

黑土坡面垄侧少耕措施的土壤侵蚀特征分析

为探究黑土区坡耕地垄侧少耕措施对土壤侵蚀特征的影响,在5°和7°坡面开展人工模拟降雨试验,降雨强度为75,100 mm/h,横垄处理方式包括全松（土壤容重均为1.00 g/cm³）、上松下实（土壤容重分别为1.00,1.20 g/cm³）、上实下松（土壤容重分别为1.20,1.00 g/cm³）及全实（土壤容重均为1.20 g/cm³）4种。结果表明：垄侧少耕措施有助于延缓横垄溢流时间,具有明显的调控土壤侵蚀作用。土壤侵蚀量大小总体表现为全松>上松下实>全实>上实下松。除75 mm/h降雨强度下的5°坡面外,与全松处理相比,上实下松和全实处理的径流量分别减少16.1%~19.4%和6.6%~11.4%,土壤侵蚀量分别减少25.0%~52.5%和17.9%~31.6%,且上实下松和全实处理的径流率和土壤侵蚀速率随降雨历时的变化相对比较平稳。可见,垄侧少耕措施在调控总径流量和土壤侵蚀量的同时,也具有较好地调控径流侵蚀过程的作用。因此,建议根据黑土区坡耕地具体降雨特征和地形坡度等因素科学选用垄侧少耕措施。     

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.     

Simulation of N<Subscript>2</Subscript>O fluxes from Irish arable soils: effect of climate change and management

Emissions of nitrous oxide (N₂O) from an Irish arable soil were simulated using the DeNitrification–DeComposition (DNDC) model. The soil chosen was a free-draining sandy loam typical of the majority of cereal growing land in Ireland, and one that has been previously used to test and validate DNDC-model. DeNitrification–DeComposition model was considered suitable to estimate N₂O fluxes from Irish arable soils however, underestimated the flux by 24%. The objectives of this study were to estimate future N₂O fluxes from a spring barley field under conventional (moulboard plowing) and reduced (chisel plowing) tillage and different N-fertilzer application rates. Three climate scenarios, a baseline of measured climatic data from the weather station at Kilkenny and a high- and low-temperature-sensitive scenarios predicted by the Hadley Global Climate Model (HadCM₄) based on the AB1 emission scenario of the Intergovernment Panel on Climate Change (IPCC) were investigated. For conventional tillage under all scenarios, three peaks of N₂O emissions were predicted; an early spring peak coinciding mostly with soil plowing, a mid/late spring peak coinciding with fertilizer application and an early autumn peak coinciding with residue incorporation and onset of autumn rainfall. Under reduced tillage, due to the less amount of soil disturbance, the early spring peak was not predicted. In all cases, the total amount of N₂O emitted in the late spring peak due to fertilizer application was less than the sum of the other peaks. Under climate change, using the high-temperature-increase scenario, DNDC predicted an increase in N₂O emissions from both conventional and reduced tillage, ranging from 58% to 88% depending upon N application rate. In contrast, annual fluxes of N₂O either decreased or increased slightly in the low temperature increase scenario relative to N application (−26 to +16%). Outputs from the model indicate that elevated temperature and precipitation increase N mineralization and total denitrification leading to greater fluxes of N₂O. Annual uncertainties due to the use of two different future climate scenarios were significantly high, ranging from 74% to 95% and from 71% to 90% for the conventional and reduced tillage.     

Quantifying soil displacement and tillage erosion rate by different tillage systems in dryland northwestern Iran

Redistribution of soil particles by the force applied by tillage is a major factor in soil degradation of agricultural land. Decreasing tillage intensity can reduce the amount of soil displaced and the distance moved and hence may reduce rates of erosion. To understand the relative importance of erosion, we tabulated machine, soil and landform properties likely to be involved. We compared soil displacement and tillage erosion rates under different systems, including mouldboard ploughing (conventional tillage), chisel ploughing (reduced tillage), stubble cultivator (minimum tillage) and no‐tillage under dryland agriculture in northwestern Iran. The area was undulating and so all tillage took place along contours. Metallic tracers were buried in the soil at known locations and depths and their recovery after tillage provided a measure of soil displacement and tillage erosion. Conventional tillage along a contour line caused significantly greater soil displacement (≃57 cm) in the direction of tillage than reduced and minimum tillage systems (~20 and ~15 cm, respectively). Conventional tillage also caused more lateral soil displacement (downwards in the main direction of slope, the tillage erosion rate) than reduced or minimum tillage systems (48 cm or 152 kg/m vs. 5 and 4 cm or 16 and 7 kg/m, respectively). Although a range of factors contribute to the tillage systems used by farmers, our results suggest that under dryland conditions, similar to those found in our study area, adoption of noninversion, reduced tillage along the contour, for example by chisel ploughing can substantially limit tillage erosion relative to conventional tillage.