Measurement and modelling of the effects of initial soil conditions and slope gradient on soil translocation by tillage

Tillage erosion studies have mainly focused on the effect of topography and cultivation practices on soil translocation during tillage. However, the possible effect of initial soil conditions on soil displacement and soil erosion during tillage have not been considered. This study aims at investigating the effect of the initial soil conditions on net soil displacement and the associated erosion rates by a given tillage operation of a stony loam soil. Tillage erosion experiments were carried out with a mouldboard plough on a freshly ploughed (pre-tilled) soil and a soil under grass fallow in the Alentejo region (Southern Portugal).

The experimental results show that both the downslope displacement of soil material and the rate of increase of the downslope displacement with slope gradient are greater when the soil is initially in a loose condition. This was attributed to: (i) a greater tillage depth on the pre-tilled soil and (ii) a reduced internal cohesion of the pre-tilled soil, allowing clods to roll and/or slide down the plough furrow after being overturned by the mouldboard plough.

An analysis of additional available data on soil translocation by mouldboard tillage showed that downslope displacement distances were only significantly related to the slope gradient when tillage is carried out in the downslope direction. When tillage is carried out in the upslope direction, the effect of slope gradient on upslope displacement distances was not significant. This has important implications for the estimation of the tillage transport coefficient, which is a measure for the intensity of tillage erosion, from experimental data. For our experiments, estimated values of the tillage transport coefficient were 70 and 254 kg m⁻¹ per tillage operation for grass fallow and pre-tilled conditions, respectively, corresponding to local maximum erosion rates of ca. 8 and 35 Mg ha⁻¹ per tillage operation and local maximum deposition rates of ca. 33 and 109 Mg ha⁻¹ per tillage operation.     

Soil displacement and tillage erosion during secondary tillage operations: the case of rotary harrow and seeding equipment

This study reports the results of a series of experiments that were set up on agricultural land in central Belgium to investigate soil translocation and erosivity resulting from a secondary tillage operation using an implement sequence of a rotary harrow and seeder. Aluminium cubes were used as tracers of soil movement. Results show that soil displacement resulting from tillage with such an implement sequence is far from insignificant. This is mainly related to the relatively shallow tillage depth as well as to the loose initial soil condition of such secondary tillage operations. The calculated value for the tillage transport coefficient k (123 kg m⁻¹ per tillage operation) is comparable with k-values from implements that are considered to be more erosive, like mouldboard and chisel implements. In conclusion, this study shows that tillage erosion not only results from relatively aggressive tillage operations such as mouldboard and chisel passes, but that secondary operations contribute significantly to soil displacement and tillage erosion.     

Fine-earth translocation by tillage in stony soils in the Guadalentin, south-east Spain: an investigation using caesium-134

Tillage erosion is increasingly recognised as an important soil erosion process on agricultural land. In view of its potential significance, there is a clear need to broaden the experimental database for the magnitude of tillage erosion to include a range of tillage implements and agricultural environments. The study discussed in this paper sought to address the need for such data by examining tillage erosion by a duckfoot chisel plough in stony soils on steep slopes in a semi-arid environment. Results of the investigation of coarse fraction (rock fragment) translocation by tillage in this environment have been presented elsewhere and the paper focuses on tillage translocation and erosion of the fine earth. Tillage translocation was measured at 10 sites, representing both upslope and downslope tillage by a duckfoot chisel plough on five different slopes, with tangents ranging from 0.02 to 0.41. A fine-earth tracer, comprising fine earth labelled with ¹³⁴Cs, was introduced into the plough layer before tillage. After a single pass of the plough, incremental samples of plough soil were excavated and sieved to separate the fine earth from the rock fragments. Translocation of the fine-earth tracer was established by analysing the ¹³⁴Cs content of the samples of fine earth. These data were used to establish translocation distances for each combination of slope and tillage direction. Translocation distances of the fine earth were not significantly different from translocation distances of the coarse fraction. For all sites, except uphill on the 0.41 slope, translocation distances were found to be linearly related to slope tangent. The soil flux due to tillage for each site was calculated using the translocation distance and the mass per unit area of the plough layer. For slopes with tangents <0.25, the relationship between soil flux and tangent was linear and the soil flux coefficient derived was 520–660 kg m⁻¹ per pass. This is much larger than the coefficients found in other studies and this high magnitude is attributed to the non-cohesive nature and high rock fragment content of the soil in this investigation. A second contrast with previous studies was found in non-linearity in the relationship between soil flux and tangent when steeper slopes were included. This was a product of variation in plough depth between the steepest slopes and the remainder of the study area. On the basis of the study it is suggested that an improved understanding of tillage erosion may be obtained by considering the dual processes of tillage detachment (mass per unit area of soil subject to tillage) and tillage displacement (equivalent to translocation distance per pass) in assessing, comparing and modelling tillage translocation. An improved model is proposed that recognises the complexity of soil redistribution by tillage, provides a framework for process-based investigation of the controls on tillage fluxes, and allows identification of potential self-limiting conditions for tillage erosion.     

Soil biochemical response to long-term conservation tillage under semi-arid Mediterranean conditions

We studied the effects of long term conservation tillage (CT) versus traditional tillage (TT) on soil biological status of a semi-arid sandy clay loam soil (Xerofluvent). The study was conducted in a wheat (Triticum aestivum, L.)–sunflower (Helianthus annuus, L.) crop rotation established in 1991 under rainfed conditions in SW Spain. A fodder pea (Pisum arvense, L.) crop was introduced in the rotation in 2005. Soil biological status was evaluated by measuring the microbial biomass carbon (MBC) and some enzyme activities (dehydrogenase, alkaline phosphatase, β-glucosidase and protease) in autumn of 2004 and in summer of 2005, before and after the fodder pea crop, respectively. Soil analyses were performed in samples collected at three depths (0–5, 5–10 and 10–25 cm). In general and in both samplings, increases in the organic matter content, MBC and enzymatic activities were found in the more superficial layers of soil under CT than under TT. Values of MBC were lower in summer, whereas values of enzyme activities were similar in both samplings. Biological properties showed a pronounced decrease with increasing soil depth. Statistical differences in biochemical properties between soils under the different tillage were not found in the deeper layer (10–25 cm). Enzymatic activities, MBC and organic matter (water-soluble carbon (WSC) and soil organic carbon (SOC) contents) were strongly correlated (p < 0.01). Conservation tillage improved the quality of soil in the superficial layer by enhancing its organic matter content and, especially, its biological status, as reflected in the values of stratification ratios for MBC and enzymatic activities.     

Soil quality response to tillage and crop residue removal under subarctic conditions

Little is known about the long-term effects of tillage and crop residue management on soil quality and organic matter conservation in subarctic regions. Therefore, we quantified wet aggregate stability, bulk density, pH, total organic C and N, inorganic N, microbial biomass C and N, microbial biomass C:N ratio, microbial quotient, and potential C and N mineralization for a tillage/crop residue management study in central Alaska. Soil from no-till (NT), disked once each spring (DO), and disked twice (DT, spring and fall) treatments was sampled to 20 cm depth in spring and fall of the 16th and 17th years of the study. Crop residues were either retained or removed after harvest each year. Reducing tillage intensity had greater impact on most soil properties than removing crop residues with the most notable effects in the top 10 cm. Bulk density was the only indicator that showed significant differences for the 10–20 cm depth, with values of 0.74 Mg m⁻³ in the surface 10 cm in NT compared to 0.86 in DT and 1.22 Mg m⁻³ in NT compared to 1.31 in DT for the 10–20 cm depth. Wet aggregate stability ranged from 10% in DT to 20% in NT. Use of NT or DO conserved soil organic matter more than DT. Compared to measurements made in the 3rd and 4th years of the study, the DT treatment lost almost 20% of the soil organic matter. Retaining crop residues on the soil conserved about 650 g m⁻² greater C than removing all residues each year. Soil microbial biomass C and mineralizable C were highest in NT, but the microbial C quotient, which averaged only 0.9%, was not affected by tillage or crop residue treatment. Microbial biomass C:N ratio was 11.3 in DT and 14.4 in the NT, indicating an increasing predominance of fungi with decreasing tillage intensity. Barley grain yield, which averaged 1980 kg ha⁻¹ over the entire 17 years of the study, was highest in DO and not significantly different between NT and DT, but weeds were a serious problem in NT. Reduced tillage can improve important soil quality indicators and conserve organic matter, but long-term NT may not be feasible in the subarctic because of weed problems and build up of surface organic matter.     

Soil organic carbon changes after 12 years of no-tillage and tillage of Grantsburg soils in southern Illinois

Many factors including management history, soil type, climate, and soil landscape processes affect the dynamics of soil organic carbon (SOC). The primary objective of this research was to determine the effects of no-tillage and tillage systems on the SOC content after 12 years of controlled treatments. A tillage experiment with three treatments (no-till (NT), chisel plow (CP) and moldboard plow (MP)) was initiated in the spring of 1989 in southern Illinois. The plot area was previously in a tall fescue hayland for 15 years and had a 6% slope. Maize (Zea mays L.) and soybean (Glycine max L. Merr.) were grown in the plot area on a yearly rotation system starting with maize. Periodically, the SOC content of various soil layers, to a depth of either 30 or 75 cm, was measured and expressed on both a gravimetric and volumetric basis. After 12 years, the 0–15 cm surface soil layer of MP was significantly lower in SOC than the NT and CP plots. For all but 2 values, the significance of findings did not change with the form of expression (gravimetric versus volumetric). The surface layer (0–15 cm), subsoil (15–75 cm), and rooting zone (0–75 cm) of all treatments had reduction in SOC on a volumetric basis when compared to the pre-treatment values for sod. At the end of the 12-year study, the MP system had significantly less SOC in the surface layer, subsurface layer and rooting zone than the NT system at comparable depths. After 12 years of tillage under a maize–soybean rotation, the NT treatment sequestered or maintained more SOC stock (47.0 Mt ha⁻¹) than the CP (43.7 Mt ha⁻¹) and MP (37.7 Mt ha⁻¹) treatments. The annual rate of SOC stock build up in the root zone (0–75 cm), above the MP system base, was 0.71 Mt ha⁻¹ year⁻¹ for the NT system and 0.46 Mt ha⁻¹ year⁻¹ for the CP system. For land coming out of the Conservation Reserve Program and returning to row crop production, NT and CP systems would maintain more SOC stock than MP system and reduce CO₂ emissions to the atmosphere.     

Tillage translocation and tillage erosion in the complex upland landscapes of southwestern Ontario, Canada

Tillage translocation and tillage erosion were measured throughout the topographically complex landscapes of two fields in the upland region of southwestern Ontario. Translocation of soil by tillage was measured by labelling plots of soil with chloride and measuring the tracer's forward displacement in response to single passes by four tillage implements (mouldboard plough, chisel plough, tandem disc and field cultivator). The change in translocation within the landscape was used to measure tillage erosion. All four implements were erosive. A relationship between tillage translocation and slope gradient was observed; however, the variability in translocation could not be explained by slope gradient alone. Slope curvature was responsible for some translocation through the planning action of tillage implements. Tillage depth and speed were subject to considerable discontinuous and inconsistent manipulation by the operator in response to changing topographic and soil conditions. Tillage speed decreased by as much as 60% during upslope tillage and increased by as much as 30% during downslope tillage, relative to that on level ground. Tillage depth decreased by as much as 20% and increased by as much as 30%, relative to that on level ground. This manipulation is typical for tillage in complex landscapes and was presumed largely responsible for the variability in the results. The manipulation of tillage depth and speed are affected by the tractor-implement match and the responsiveness of the tillage operator.     

Assessment of tillage translocation and tillage erosion by hoeing on the steep land in hilly areas of Sichuan, China

Most of the tillage erosion studies have focused on the effect of tractor-plough tillage on soil translocation and soil loss. Only recently, have a few studies contributed to the understanding of tillage erosion by manual tillage. Furthermore, little is known about the impact of tillage erosion in hilly areas of the humid sub-tropics. This study on tillage erosion by hoeing was conducted on a purple soil (Regosols) of the steep land, in Jianyang County, Sichuan Province, southwestern China (30°24′N and 104°35′E) using the physical tracer method.

The effects of hoeing tillage on soil translocation on hillslopes are quite evident. The tillage transport coefficients were 26–38 kg m⁻¹ per tillage pass and 121–175 kg m⁻¹ per tillage pass respectively for k₃- and k₄-values. Given that there was a typical downslope parcel length of 15 m and two times of tillage per year in this area, the tillage erosion rates on the 4–43% hillslopes reached 48–151 Mg ha⁻¹ per year. The downslope soil translocation is closely related to slope gradient. Lateral soil translocation by such tillage is also obvious though it is lower than downslope soil translocation. Strong downslope translocation accounts for thin soil layers and the exposure of parent materials/rocks at the ridge tops and on convexities in the hilly areas. Deterioration in soil quality and therefore reduction in plant productivity due to tillage-induced erosion would be evident at the ridge tops and convex shoulders.     

Influences of tillage operations on soil translocation over sloping land by hoeing tillage

Very few studies have investigated the factors affecting soil displacement and tillage erosion by hoeing tillage. This study adopted a magnetic tracer method to investigate the influences of hoe form and tillage depth on soil translocation over steep hillslopes in Southwest China using a new type of magnetic tracer, i.e., ilmenite powder. Ilmenite powder enhanced the magnetic sensitivity of soil at the end position of tracer distribution, and improved the accuracy and efficiency of tillage translocation measurements. Tillage translocation by wide and perforated hoes was found to be significantly correlated with slope gradient (P < 0.01), however, no significant correlation was found for narrow and bidentate hoe tillage (P > 0.05). Compared with wide hoes, the tillage erosion rates resulting from the use of narrow, perforated and bidentate hoes were reduced by 12.4%, 11.0%, and 16.3%, respectively, indicating that changes in hoe forms resulted in a marked decrease in downslope soil translocation and tillage erosion. Tillage erosion rate decreased by 64% when the tillage depth was reduced from 0.26 to 0.14 m. These results suggest that innovations in hoe form and reductions in tillage depth are important means to manage tillage erosion due to hoeing.     

Long-term tillage system effects under moist cool conditions in Switzerland

How do different soil tillage systems influence soil quality over the years? Under moist cool conditions is it possible in the long term to reduce dramatically soil tillage intensity without experiencing reductions in yield or other problems? In 1987, the Swiss Federal Research Station for Agricultural Economics and Engineering in Tänikon initiated a long-term soil tillage trial to clarify these questions. The trial compared mouldboard plough, chisel, paraplow, shallow tillage and no-tillage systems on a well-drained Orthic Luvisol with 160 g kg⁻¹ clay, 310 g kg⁻¹ silt, and under a climate that has a mean annual precipitation of 1180 mm. The tillage treatment effects were evaluated by measuring several biological, chemical, and physical soil quality indicators. Reduced soil tillage increased earthworm populations, reduced Pseudocercosporella herpotrichoides infection in wheat (Triticum aestivum) and increased plant colonisation by arbuscular mycorrhizal fungi. Yields for no-tillage and other ploughless cultivation techniques were on par with those obtained by ploughing. An exception was direct-drilled maize (Zea mays), where no-tillage decreased yield by more than 10% over the course of 14 years. In the first 7 years of the trial, the level of soil organic carbon in all the tillage regimes was approximately 40% lower than natural grassland (initial situation 1987=75 Mg SOC ha⁻¹). The no-tillage method did not differ from the others in respect of bulk density, but it showed an increased preconsolidation stress and hence better trafficability. Under Switzerland’s moist cool climatic conditions, it is possible to reduce soil tillage intensity without substantial reductions in yield, and at the same time improve soil quality.     

Use of caesium-137 data for validation of spatially distributed erosion models: the implications of tillage erosion

Validation of spatially distributed models using spatially distributed data represents a vital element in the development process; however, it is rarely undertaken. To a large extent, this reflects the problems associated with assembling erosion rate data, at appropriate temporal and spatial scales and with a suitable spatial resolution, for comparison with model results. The caesium-137 (¹³⁷Cs) technique would appear to offer considerable potential for meeting this need for data, at least for longer timescales. Nevertheless, initial attempts to use ¹³⁷Cs for model validation did not prove successful. This lack of success may be explained by the important role of tillage erosion in redistributing soil within agricultural fields and, therefore, contributing to the ¹³⁷Cs-derived soil redistribution rates. This paper examines the implications of tillage erosion for the use of ¹³⁷Cs in erosion model validation and presents an outline methodology for the use of ¹³⁷Cs in model validation. This methodology acknowledges and addresses the constraints imposed by the need to: (1) separate water and tillage erosion contributions to total soil redistribution as represented in ¹³⁷Cs derived rates; (2) account for lateral mixing of ¹³⁷Cs within fields as a result of tillage translocation; (3) simulate long-term water erosion rates using the model under evaluation if ¹³⁷Cs-derived water erosion rates are to be used in model validation. The methodology is dependent on accurate simulation of tillage erosion and tillage translocation. Therefore, as greater understanding of tillage erosion is obtained, the potential for the use of ¹³⁷Cs in water erosion model validation will increase. Caesium-137 measurements remain one of the few sources of spatially distributed erosion information and, therefore, their potential value should be exploited to the full.     

The effect of tillage direction on soil redistribution by mouldboard ploughing on complex slopes

Seven mouldboard ploughing experiments were conducted to systematically investigate the effect of different tillage directions on soil redistribution on hillslopes. The present study included tillage directions other than parallel to the gradient or along the contour, that is, in our experiments the slope gradient changed simultaneously in tillage and in turning direction. Using physical tracers we developed a model of the two-dimensional tracer displacement as a function of topography and tillage variables. The displacements in tillage and in turning direction were separately described as 2nd degree polynomials in both tillage and in turning directions. This model fully accounted for the directionality of tillage. Displacement in turning direction additionally depended on tillage depth, while that in tillage direction was affected by tillage speed and soil bulk density. We found a large effect of tillage directionality on soil redistribution, and tillage at 45° to the gradient turning soil upslope was the least erosive tillage direction. We obtained non-linear relationships between soil redistribution and profile curvature, instead of the linear relationships reported previously. Consequently tillage erosivity varied in tillage direction and a unique tillage transport coefficient could not be obtained for all tillage directions.     

免耕与翻耕条件下农田土壤呼吸的比较

采用开路式土壤碳通量测量系统于2010年3-10月在冬小麦-大豆轮作期对免耕与翻耕田土壤呼吸速率、5cm深土壤温度和湿度进行测定,以研究耕作措施对农田土壤呼吸的影响。结果表明,在冬小麦、大豆生长时段,免耕与翻耕田土壤呼吸速率的季节变化趋势基本一致。冬小麦生长时段免耕与翻耕田土壤呼吸速率的平均值分别为2.50±0.14和2.40±0.29μmol.m-2.s-1,大豆生长时段分别为2.82±0.28和3.50±0.52μmol.m-2.s-1。冬小麦生长时段免耕与翻耕田土壤呼吸无显著差异,但大豆生长时段二者存在显著差异(P<0.05),差异最明显的阶段在大豆开花期(7月下旬-8月中旬)。利用温度影响函数(指数函数)和湿度影响函数(二次函数)耦合的模拟模型进行土壤呼吸与土壤温度和湿度的回归分析,得出免耕条件下土壤温度和湿度可以共同解释25.3%的土壤呼吸变异(R2=0.253,P<0.05),翻耕条件下二者可以共同解释44.0%的土壤呼吸变异(R2=0.440,P<0.01)。可见,一方面,耕作措施对土壤呼吸的影响因种植作物而异,与翻耕相比,免耕显著降低了大豆田土壤呼吸,但对冬小麦田无显著影响;另一方面,免耕下土壤温度和湿度对土壤呼吸的影响比翻耕要小。     

Soil redistribution and organic carbon accumulation under long‐term (29 years) upslope tillage systems

Few studies have demonstrated soil redistribution under upslope tillage (UT) rather than downslope tillage (DT) and its impact on soil organic carbon (SOC) redistribution in long‐term agricultural practices in hillslope landscapes. We selected two neighbouring sites from the Sichuan Basin, China, one under DT and the other under UT, to determine the pattern of soil and SOC redistribution under a long‐term UT practice. DT caused soil loss at upper slope positions and soil accumulation at lower slope positions. However, UT resulted in soil accumulation at upper slope positions and soil loss at lower slope positions. The total erosion rate decreased by 60.5% after 29 years of UT compared with DT. Having the same direction of soil movement by tillage and water exaggerated total soil loss, whereas having the two movements in the contrasting direction of soil for the two reduced it. SOC stocks at positions from summit to downslope were much larger (33.8%) and at toe‐slope positions were only slightly greater (4.5%) in the UT soils than comparable values for the DT site. The accumulation rate of SOC at the UT site increased by 0.26 Mg/ha/year compared with that at the DT site. It is suggested that soil movement by water and tillage erosion occurred in the same direction accelerates the depletion of SOC pools, whereas the opposite direction of soil movement for the two can increase SOC accumulation. Our results suggest that UT has significant impacts on soil redistribution processes and SOC accumulation on steeply sloping land.     

Quantifying tillage translocation and deposition rates due to moldboard plowing in the Palouse region of the Pacific Northwest, USA

Most of the erosion research in the Palouse region of eastern Washington State, USA has focused on quantifying the rates and patterns of water erosion for purposes of conservation planing. Tillage translocation, however, has largely been overlooked as a significant geomorphic process on Palouse hillslopes. Tillage translocation and tillage deposition together have resulted in severe soil degradation in many steep croplands of the Palouse region. Few controlled experiments have heretofore been conducted to model these important geomorphic processes on Palouse hillslopes. The overarching purpose of this investigation, therefore, was to model tillage translocation and deposition due to moldboard plowing in the Palouse region. Soil movement by moldboard plowing was measured using 480-steel flat washers. Washers were buried in silt loam soils on convex–convex shoulder, linear-convex backslope, and linear-concave footslope landform components, and then displaced from their original burial locations by a moldboard plow pulled by a wheel tractor traveling parallel to the contour at ca. 1.0 m s⁻¹. Displaced washers were located using a metal detector, and the distance and azimuth of the resultant displacement of each washer from its original burial location was measured using compass and tape. Resultant displacement distances were then resolved into their component vectors of displacement parallel and perpendicular to the contour. A linear regression equation was developed expressing mean soil displacement distance as a function of slope gradient. Tillage translocation and deposition were modeled as diffusion-type geomorphic processes, and their rates were described in terms of the diffusion constant (k). A multivariate statistical model was developed expressing mean soil displacement distance as a function of gravimetric moisture content, soil bulk density, slope gradient, and direction of furrow slice displacement. Analysis of variance (ANOVA) revealed a weak correlation between soil displacement and both bulk density and moisture content. Soil displacement was, however, significantly correlated with direction of furrow slice displacement. Tillage translocation rates were expressed in terms of the diffusion constant (k) and ranged from 105 to 113 kg m⁻¹ per tillage operation. Tillage deposition rates ranged from 54 to 148 kg m⁻¹ per tillage operation. With respect to tillage deposition, the diffusion constant calculated from volumetric measurements of tillage deposits equals ca. 150 kg/m. The rates of tillage translocation and deposition are not completely in balance; however, these rates do suggest that soil tillage is a significant geomorphic process on Palouse hillslopes and could account for the some of the variations in soil physical properties and crop yield potential at the hillslope and farm-field scale in the Palouse region.     

Straw management and tillage effects on soil water storage under field conditions

Abstract. A two year field study was conducted to evaluate the effects of straw management and tillage on the soil profile (1.5m) water storage, nature of the moisture profile, infiltration and sorptivity as influenced by rainfall, evaporativity (E₀) and soil texture. The straw mulch treatment stored more moisture under low E₀ rainy conditions in three coarse to medium textured soils. Straw incorporation treatment was better under low E₀ rain free conditions, as well as under high E₀ rainy conditions in the two coarser textured soils. In the coarsest textured soil, tillage and straw mulching were not effective in maintaining greater soil water storage under high E₀ because of the very open nature of the soil. The soil moisture profiles showed a sharper increase in water content below the tilled layer in the tillage and straw- incorporation treatments than the untreated and straw mulch treatments. Tillage and straw incorporation treatments increased the sorptivity of the soil compared with untreated and straw mulch treatments respectively. The results of this study suggest that when selecting a suitable soil water conservation practice to increase water storage in the soil profile, information on soil texture and weather (rain and evaporativity) must be considered.     

Characterization of soil profiles in a landscape affected by long-term tillage

Soil movement by tillage redistributes soil within the profile and throughout the landscape, resulting in soil removal from convex slope positions and soil accumulation in concave slope positions. Previous investigations of the spatial variability in surface soil properties and crop yield in a glacial till landscape in west central Minnesota indicated that wheat (Triticum aestivum) yields were decreased in upper hillslope positions affected by high soil erosion loss. In the present study, soil cores were collected and characterized to indicate the effects of long-term intensive tillage on soil properties as a function of depth and tillage erosion. This study provides quantitative measures of the chemical and physical properties of soil profiles in a landscape subject to prolonged tillage erosion, and compares the properties of soil profiles in areas of differing rates of tillage erosion and an uncultivated hillslope. These comparisons emphasize the influence of soil translocation within the landscape by tillage on soil profile characteristics. Soil profiles in areas subject to soil loss by tillage erosion >20 Mg ha⁻¹ year⁻¹ were characterized by truncated profiles, a shallow depth to the C horizon (mean upper boundary 75 cm from the soil surface), a calcic subsoil and a tilled layer containing 19 g kg⁻¹ of inorganic carbon. In contrast, profiles in areas of soil accumulation by tillage >10 Mg ha⁻¹ year⁻¹ exhibited thick sola with low inorganic carbon content (mean 3 g kg⁻¹) and a large depth to the C horizon (usually >1.5 m below the soil surface). When compared to areas of soil accumulation, organic carbon, total nitrogen and Olsen-extractable phosphorus contents measured lower, whereas inorganic carbon content, pH and soil strength measured higher throughout the profile in eroded landscape positions because of the reduced soil organic matter content and the influence of calcic subsoil material. The mean surface soil organic carbon and total nitrogen contents in cultivated areas (regardless of erosion status) were less than half that measured in an uncultivated area, indicating that intensive tillage and cropping has significantly depleted the surface soil organic matter in this landscape. Prolonged intensive tillage and cropping at this site has effectively removed at least 20 cm of soil from the upper hillslope positions.     

浙江省低丘红壤区土壤侵蚀评价研究

本文以浙江省低丘红壤区为研究对象,利用卫星遥感影像构造削弱阴影等干扰的FCD模型,和混合像元法计算植被覆盖度的方法,进行水土流失研究。根据水利部颁布的《土壤侵蚀分类分级标准》,结合植被覆盖度、坡度、利用现状等因子进行土壤侵蚀强度评价。研究结果表明目前红壤区内植被覆盖情况良好,覆盖度基本在30%以上;整体水土流失程度较轻,但是耕地等农用地的侵蚀情况较为严重,特别是红壤区内耕地的强度侵蚀的面积占其总面积的17.65%。另外,耕作侵蚀也是土壤侵蚀非常重要的因素,在估算土壤侵蚀强度的时候也应重视。目前浙江省需要补充大量耕地以满足社会发展的需要,鉴于红壤水土流失易发的特点,在低丘红壤开发时要重视水土流失的预防和控制。     

Ergebnisse zur bodenverlagerung durch bearbeitungserosion in der jungmoränenlandschaft Nordostdeutschlands: Investigations of soil movement by tillage as a type of soil erosion in the young moraine soil landscape of Northeast Germany

Soil translocation by soil tillage can have a considerable importance on arable land. These results were published in the international literature. The aim of the experiments is to quantify the translocation of soil due to tillage with different typical tools. A mouldboard plough and a disc harrow were tested in field experiments on a slope (4° inclination) with sandy soil. The average movement of soil particles of the top soil was determined about the changed tracer concentration. The tracer coloured gravels were most suitable of all tested tracer. The comparison of the tools showed more soil translocation caused by mouldboard plough (145?kg) than by disc harrow (12?kg). The transport was also different: plough 0.50?m and disc harrow 0.11?m average distance.     

Reassessment of tillage erosion rates by manual tillage on steep slopes in northern Thailand

Changing land-use practices in northern Thailand have increased tillage intensity. This study re-assesses the rate of tillage erosion by manual hoeing on steep slopes (17–82%) in northern Thailand. Previously collected soil translocation data during an on-farm tillage erosion experiment and additionally collected data during an on-farm tillage erosion survey have been analysed whereby a new calculation method (i.e. trapezoid tillage step) has been used. A comparison with previously collected data indicates that the trapezoid tillage step method and the tracer method are the most reliable methods to assess downslope translocation by manual tillage. Based on newly acquired understanding of the processes involved, soil fluxes by tillage erosion are quantified by linear functions for different slope gradient classes rather than one single diffusion-type equation for the whole slope range. For slope gradients smaller than 3%, soil fluxes are close to zero as farmers do not have a preferred tillage direction. For slope gradients between 3% and 70%, soil is tilled only in the downslope direction and soil fluxes range between 16 and 67 kg m⁻¹ tillage pass⁻¹. On slopes with gradients in excess of 70%, the angle of repose for soil clods is often exceeded resulting in a sliding down of the complete tilled top layer. These data are used to assess the soil flux for complete cropping cycles for the most dominant cropping systems in the highlands of northern Thailand: i.e. upland rice, maize, (soy) beans, cabbage and ginger. The on-site effects of tillage erosion will be very pronounced if parcels are short with respect to their slope length, cultivated for upland rice or cabbage, or when weed pressure is high. Tillage erosion results in a tillage step with low soil fertility and low infiltration capacity. Solutions to reduce tillage erosion intensity depend on the degree that tillage intensity can be reduced. This might happen by an improved weed management or by changing landuse to perrenial cropping. Other strategies are concentrating nutrients on the truncated hillslope sections and retaining soil on the field by vegetative buffers.