“十四五”全国农业机械化发展规划

由于人口的高速增长和饮食结构改变所带来的粮食需求增加正引发日益严峻的全球粮食安全问题。在世界各地,随着农业机械化程度的提高,面临土壤压实和土壤肥力持续恶化的问题。虽然集约化的耕作模式和规模化种植制度提升了粮食产量,在一定程度上缓解全球粮食安全,但这种相对单一的耕作模式显著增加了土壤的压力。土壤压实通过增加土壤容重和土壤强度降低土壤孔隙度和土壤水分入渗及持水能力等,对土壤物理特性,特别是水分和养分的存储和供应产生不利影响,严重危害土壤健康。因此土壤压实将逐渐成为限制粮食产量的关键因素之一。本文基于国内外有关土壤压实的研究,综合分析了土壤压实对土壤物理、化学和生物特性的影响和潜在作用机制,并剖析了影响土壤压实的关键因素以及有效解决土壤压实的潜在应对措施。由于影响因素众多且相互制约,致使人们对土壤压实的发生机制尚不清楚。未来对土壤压实的研究仍需不断深入,包括压实对微生物群落结构的影响以及田间试验和室内培养试验方法的优化等,为更积极有效地预防土壤压实、防治土壤退化提供技术支撑。     

水土保持措施及其减水减沙效益分析

水土流失已经和正在蚕食着人们赖以生存的宝贵的水土资源，如何有效地控制水土流失日益受到社会各界和科学家们的广泛关注。中国在水土保持方面创造了许多颇具特色的水土保持措施，如：生物林草措施、耕作措施和水土保持工程措施。该文总结了目前所采用的主要水土保持措施类型。采用坡度、坡长校正公式将数据转化为具有可比性的量值(标准小区)，定量分析了各种水土保持措施对于减少径流和土壤侵蚀产沙的效果，即治理措施的减水减沙效益，为小流域土壤侵蚀预报、水土保持措施的优化及合理配置、优化土地利用结构等提供参考依据。     

土壤结皮对降雨入渗和产流产沙的影响

 依据250场次人工降雨和相应的径流、泥沙资料,采用对比法,分析结皮与无结皮土壤对降雨入渗和产流产沙的影响。结果表明,非结皮土壤的平均入渗率是结皮土壤的1.25倍,平均产沙总量为1.28倍,而结皮土壤的平均产流总量是非结皮土壤的1.15倍。因此,土壤结皮具有减缓降雨入渗、增大地表径流和抑制产沙的作用,且雨强愈小影响作用愈大,雨强愈大,影响作用愈小。     

Effect of ground‐cover type on surface runoff and subsequent soil erosion in Champagne vineyards in France

This study was conducted in Champagne vineyards in France, and the objectives were to compare the main cultivation practices in Champagne vineyards and to specify the conditions required for the optimum effect of inter‐row grass cover on runoff and erosion in experimental plots of 0.25 m² under simulated rainfall. Three types of ground cover were studied. In the bark‐and‐vine‐prunings plots, the runoff coefficient (RC) ranged from 1.3 to 4.0% and soil losses were <1 g/m²/h. In the bare soil (BS) plot, the highest RC of the study was found (80.0%) and soil losses reached 7.4 g/m²/h. In the grass cover plots, the RC and amount of eroded soil were highly variable: the RCs ranged from 0.4 to 77.0%, and soil losses were between less than 1 and 13.4 g/m²/h. Soil type, soil moisture, slope and agricultural practices did not account for the variability. In fact, the density of grass cover in the wheel tracks explained a portion of this variability. The lack of grass in the centre of the inter‐row allowed for a preferential flow and created an erosion line in the wheel tracks where the soil was compacted. This study showed that grass cover in a vineyard was not necessarily sufficient to reduce surface runoff and prevent soil erosion. To be effective, the grass cover must be dense enough in the wheel tracks of agricultural machinery to avoid RCs close to the RC achieved with BS.     

Soil loss and runoff on semiarid land as amended with urban solid refuse

Organic amendment is a proved method of improving soil physical properties thus affecting runoff and soil erosion. Urban wastes are a potential source of organic matter and their use would also be a convenient way of disposing of them. A field experiment was conducted from October 1988 to September 1993 in a semiarid Mediterranean site to determine the effect of applying several rates (65, 130, 195 and 260 Mg ha⁻¹) of organic urban solid refuse (USR) on total runoff and soil loss. At the lowest rate, total runoff decreased by 67 per cent compared to the control plot. The decrease was 98 per cent when the highest rate was used. The lowest rate reduced total sediment loss by 81 per cent and the highest rate of 99 per cent. The decrease in soil erodibility at the different USR rates varied from 76 to 95 per cent depending on the year for the lowest rate and between 90 and 99 per cent for the other rates. Clear differences in the hydrologic and erosion responses were found between the eight initial rainfall events (during the first 10 months of the experiment) and the remainder of the events. The causes of such differences were due to the initial tillage of the soil by rotovation and the growth of natural vegetation in the treated plots. The mechanical effect of tillage reduced runoff and increased soil erodibility, although the effect was short‐lived. The addition of USR reduced runoff but lasted longer. An applied rate of 90–100 Mg ha⁻¹ could be considered suitable for application in semiarid zones. Copyright © 2000 John Wiley & Sons, Ltd.     

The effects of minimal tillage and contour cultivation on surface runoff, soil loss and crop yield in the long-term Woburn Erosion Reference Experiment on sandy soil at Woburn, England

Abstract. Over a 10-year period, runoff and soil erosion on the plots of the Woburn Erosion Reference Experiment were concentrated in periods with sparse vegetation cover: in winter after the late planting of cereals; in spring after the planting of beets; or when soils were bare after harvest. The mean event runoff of 1.32 mm from plots cultivated up-and-downslope was significantly greater ( P <0.05) than that from plots cultivated across-slope (0.82 mm). However, mean event soil loss was not significantly different between the two cultivation directions. No significant differences were found between minimal and standard cultivations. Mean event runoff from the across-slope/minimal tillage treatment combination (0.58 mm) was significantly less ( P <0.01) than from the up-and-downslope/minimal tillage (1.41 mm), up-and-downslope/standard tillage (1.24 mm), and across-slope/standard tillage (1.07 mm) treatment combinations. Runoff from the across-slope/standard treatment combination was significantly ( P <0.05) less than from the up-and-downslope/minimal tillage treatment. The across-slope/minimal tillage treatment combination had a significantly smaller ( P <0.05) event soil loss (67 kg ha⁻¹) than the up-and-downslope/standard tillage (278 kg ha⁻¹) and up-and-downslope/minimal tillage (245 kg ha⁻¹) combinations. Crop yields were significantly ( P <0.05) higher on across-slope plots in 1988, 1996 and 1997 than on up-and-downslope plots, and were also higher (but not significantly) on the across-slope plots in 7 of the 8 remaining years. Minimal cultivation decreased yield compared with standard cultivation in one year only. We recommend that across-slope cultivation combined with minimal tillage be investigated at field scale to assess its suitability for incorporation into UK farming systems.     

Soil erosion and runoff response to plant‐cover strips on semiarid slopes (SE Spain)

Over a four‐year period (1997–2000), soil loss and surface‐runoff patterns were monitored in hillside erosion plots with almond trees under different plant‐cover strips (thyme, barley and lentils) on the south flank of the Sierra Nevada (Lanjaron) in south‐eastern Spain. The erosion plots (580 m a.s.l.), located on a 35 per cent slope, were 144 m² (24 m×6 m) in area. The plant‐cover strips, 3 m wide, ran across the slope. The most effective plant cover proved to be thyme, reducing soil loss by 97 per cent and runoff by 91 per cent, compared to bare soil. Barley reduced soil loss by 87 per cent and runoff by 59 per cent, compared to bare soil, while these percentages were 58 per cent and 18 per cent for lentils. Thyme proved 77 per cent more effective than barley and 93 per cent more effective than lentils in reducing soil loss; thyme was also 79 per cent more effective than barley and 90 per cent more than lentil in blocking runoff. The present study demonstrates the effectiveness of plant‐cover strips in controlling soil erosion and runoff on sloping agricultural land. Copyright © 2005 John Wiley & Sons, Ltd.     

Effects of soil degradation and management practices on the surface water dynamics in the Talgua River Watershed in Honduras

When tropical forests are felled, subsequent land uses affect surface runoff, soil erosion, and soil compaction. In some cases, they can markedly change the hydrology of a region with disastrous effects on human life. The objective of this paper is to investigate the effect of rainfall on stream hydrology due to conversion of primary forests to agriculture. Near surface water dynamics were compared for three land uses on the steep hillsides in the Talgua River Watershed in Honduras: degraded grass‐covered field; traditional coffee plantation; and primary forest. Infiltration and surface runoff rates were measured using several methods. A clear difference was observed in hydraulic conductivity between the degraded and non‐degraded lands. The degraded grass‐covered hillslopes developed a surface restrictive layer with a low saturated hydraulic conductivity of 8 to 11 mm/hr, resulting in more frequent overland flow than traditional coffee plantation and primary forest. Soils under the latter two land‐use types maintained high infiltration capacities and readily conducted water vertically at rates of 109 and 840 mm/hr, respectively. Dye tests confirmed that the coffee plantation and primary forest both maintained well‐connected macropores through which water flowed readily. In contrast, macropores in the degraded soil profile were filled by fine soil particles. Soils in the degraded grass‐covered field also showed more compaction than soils in the coffee plantation. Copyright © 2004 John Wiley & Sons, Ltd.     

高分子聚合物对土壤物理及坡面产流产沙特征的影响

 为研究高分子聚合物对土壤改良和防治水土流失的作用,选择聚丙烯酸、聚乙烯醇、脲醛树脂3种高分子聚合物,通过室内试验和人工模拟降雨试验,以不同浓度施入土壤,观察其对土壤物理及坡面产流产沙特性的影响。结果表明:1)3种高分子聚合物均是较好的土壤结构改良剂,经聚合物处理后的土壤水稳性团粒含量平均增加17.27%,渗透性能提高41.81%,密度减小11.18%,土壤持水能力较对照提高2.8倍。2)坡地喷施上述高分子聚合物能显著推迟产流时间,降低产流速度,与对照相比,施加聚合物的坡地减少径流量42.05%、土壤侵蚀量58%以上。3)根据其对土壤改良、减流减沙、防治土壤侵蚀效果的影响,确定3种高分子聚合物最佳施用浓度范围分别为116～145mL/m2,36～40 g/m2,180.0～240.0mL/m2,其中聚丙烯酸为作用效果最显著的高分子聚合物。上述3种高分子聚合物在改良土壤,防治水土流失方面有广泛的应用前景,今后还需对其效果持续性、最佳施用量等进一步研究。     

Effects of surface‐applied and soil‐incorporated lime on some physical attributes of a Dystrudept soil

It is generally accepted that liming ameliorates soil acidity. However, the method of lime application is thought by many to influence its effectiveness in acid soils. In this study, we wanted to assess the degree of effectiveness of surface‐applied lime and lime incorporated into the soil on soil structural attributes and water retention of a Dystrudept soil in the SE region of the State of Paraná, Brazil. Lime was added at the rate of 15 t/ha to soil through: (i) surface broadcasting, (ii) incorporation via ploughing and harrowing, (iii) incorporation via subsoiling and harrowing. A control treatment with zero lime application was included in the experiment. The addition of lime by surface broadcasting resulted in significant reductions in soil bulk density (BD) and macroporosity (Ma) and increases in total porosity (TP) and microporosity (Mi) of the top soil layer (0–0.10 m). The reverse was the case in the 0.10‐ to 0.20‐m soil layer; where lime was incorporated via ploughing and harrowing, increases in BD and reductions in TP and Ma were observed. Addition of lime also significantly increased soil water retention, with maximum retention recorded from soil amended with surface broadcast lime. Changes in soil chemical attributes (increases in pH, Ca²⁺ and Mg²⁺ contents; reductions in potential acidity and Al³⁺ content) were responsible for the changes observed in structural and physical attributes, and water retention. Bearing in mind the lower application costs, improvement in the soil chemical attributes for plant development and soil physical quality, surface broadcast lime can be considered a promising alternative for no‐till farmers.     

The effects of cover crops and conventional tillage on soil and runoff loss in vineyards and olive groves in several Mediterranean countries

Cover crops (CC) in vineyards and olive groves provide an alternative to conventional tillage (CT) for land management. Runoff, sediment and nutrient loss from six sites in France, Spain and Portugal were compared over 3–4 yr. In general, runoff loss was not significantly reduced by the CC alternatives: average annual runoff coefficients ranged from 4.9 to 22.8% in CT compared with 1.9–25% in the CC alternatives. However, at two sites, reductions in average annual runoff coefficients were greater for CC: 17.2 and 10.4% in CT, 6.1 and 1.9% in CC. Nutrient loss in runoff followed a similar pattern to runoff, as did pesticide loss on the one site; reductions occurred when runoff losses were significantly reduced by CC. The lack of differences at the other sites is thought to be due to a combination of soil conditions at the surface (compaction and capping) and sub‐surface (low‐permeability horizons close to the surface). In contrast, CC always resulted in reductions in soil erosion loss, plus similar reductions in nutrients and organic matter (OM) associated with sediment. Soil erosion loss ranged from 1.4 to 90 t/ha/yr in CT compared with 0.04–42.7 t/ha/yr in CC. Overall, reductions in runoff and associated nutrient and pesticide loss from vineyards and olives occurred with the introduction of CCs only when soil permeability was sufficiently high to reduce runoff. In contrast, reduction in soil erosion and associated nutrients and OM occurred even when the amount of runoff was not reduced. In the most extreme encountered situations (highly erodible soils in vulnerable landscape positions and subject to highly erosive rainfall), additional conservation measures are needed to prevent unsustainable soil loss.     

Soil loss and run‐off characteristics under different soil amendments and cropping systems in the semi‐deciduous forest zone of Ghana

Soil erosion is a major constraint to crop production on smallholder arable lands in Sub‐Saharan Africa (SSA). Although different agronomic and mechanical measures have been proposed to minimize soil loss in the region and elsewhere, soil management practices involving biochar‐inorganic inputs interactions under common cropping systems within the framework of climate‐smart agriculture, have been little studied. This study aimed to assess the effect of different soil and crop management practices on soil loss characteristics under selected cropping systems, typical of the sub‐region. A two‐factor field experiment was conducted on run‐off plots under different soil amendments over three consecutive cropping seasons in the semi‐deciduous forest zone of Ghana. The treatments, consisting of three soil amendments (inorganic fertilizer, biochar, inorganic fertilizer + biochar and control) and four cropping systems (maize, soyabean, cowpea, maize intercropped with soyabean) constituted the sub‐plot and main plot factors, respectively. A bare plot was included as a soil erosion check. Seasonal soil loss was greater on the bare plots, which ranged from 9.75–14.5 Mg ha^?1. For individual crops grown alone, soil loss was 31%–40% less under cowpea than under maize. The soil management options, in addition to their direct role in plant nutrition, contributed to significant (p < 0.05) reductions in soil loss. The least soil loss (1.23–2.66 Mg ha^?1) was observed under NPK fertilizer + biochar treatment (NPK + BC) over the three consecutive cropping seasons. Biochar in combination with NPK fertilizer improved soil moisture content under cowpea crops and produced considerably smaller bulk density values than most other treatments. The NPK + BC consistently outperformed the separate mineral fertilizer and biochar treatments in biomass yield under all cropping systems. Biochar associated with inorganic fertilizers gave economic returns with value–cost ratio (VCR) > 2 under soyabean cropping system but had VCR < 2 under all other cropping systems. The study showed that biochar/NPK interactions could be exploited in minimizing soil loss from arable lands in SSA.     

野外模拟崩岗崩积体坡面产流过程及水分分布

为研究崩岗崩积体坡面产流特征及土体水分分布特征,采用人工模拟降雨方法,在广东五华县莲塘岗崩岗选择7个不同部位的崩积体,进行28场人工模拟降雨,测定降雨过程中坡面产流时间及水分分布。结果表明:1)坡面产流时间与降雨强度呈负指数幂函数关系;2)老崩积体坡面产流时间与10 cm深处土体初始含水率呈负对数函数关系,其他深度土体初始含水率,以及新崩积体各土层初始含水率与坡面产流时间关系不密切;3)根据土体初始含水率和降雨强度,可以应用三维曲面模型预测崩积体坡面产流所需时间;4)当降雨强度≥3.5 mm/min时,崩积体坡面产流时间与坡度呈现出负相关关系,即随着坡度增大,产流时间变短;5)崩积体坡面产流后,新、老崩积体10 cm深处土体含水率差异明显,新崩积体土体含水率在20%以下,老崩积体土体含水率在20%以上;6)无论是降雨结束时还是降雨后24 h的水分再分布,新崩积体的湿润锋深度均大于老崩积体,表明在降雨作用下新崩积体的失稳深度大于老崩积体的失稳深度。该研究为崩岗崩积体侵蚀预测和防治提供参考。     

The impact of tropical rainstorms on sediment and runoff generation from bare and grass-covered surfaces: a plot study from Singapore

The characteristically short, intense rainstorms of Singapore occur throughout the year. The impact of such rainstorms on runoff and sediment generation from bare and grass-covered slopes of urban Singapore is examined through observations made on an experimental plot for a representative sample of natural rainstorms. While the responses of the bare surfaces to the incoming rainfall are instantaneous and significant (runoff: up to 91 per cent of total rainfall), irrespective of the dimension of the rainfall, the grass-covered slopes respond more slowly and gently (runoff: 4·8 per cent–17 per cent of the total rainfall). The sediment generating potential under the two types of landcover is closely linked to the short-term intensities of the incoming rainfall, particularly on bare surfaces where high-intensity rainstorms of less than 10 minute duration are capable of generating measurable sediment and runoff. The sediment discharge from the bare surfaces during the long construction period is not only controlled by the episodic heavy storms, but also to a considerable extent by the more frequent, low-magnitude rainstorms, which contribute to a more sustained sediment movement. With a higher frequency of occurrence, such short-duration, high-intensity rainstorms have a significant impact on the sediment and runoff generation potential of the extensive bare surfaces at the construction sites in urban Singapore. © 1998 John Wiley & Sons, Ltd.     

川北紫色土深丘区径流及土壤侵蚀研究

研究川北紫色土深丘区径流及土壤侵蚀规律可为土壤侵蚀模型提供参数和依据,对试验区长期定位观测获取的11 a的降雨、径流及泥沙数据,年内及年际的分布特征进行分析,并对径流和泥沙进行曲线回归分析。结果表明:试验区径流及土壤流失主要集中在6—8月;相关性分析显示径流与降雨达到了显著水平,土壤流失与径流达到显著或极显著水平,与降雨量未达到显著水平。径流对降雨变化的响应程度更为剧烈,并表现出一定的滞后性。土壤流失量对径流的变化响应则较为复杂,但其总体变化趋势一致。回归分析表明径流月/年回归模型分别以指数/幂函数模型为最佳,且月回归模型优于年回归模型;泥沙月/年回归模型均以幂函数模型最佳,年回归模型估算较月回归模型准确。     

红壤有机碳流失特征及其与泥沙径流流失量的定量关系

通过野外微型径流小区模拟降雨试验,对坡面小区尺度水力侵蚀过程中物理运移土壤有机碳的规律进行研究。结果表明:2 m×5 m径流小区持续降雨30 min后,大雨强(1.64 mm min-1)和小雨强(0.58 mm min-1)降雨条件下泥沙携带流失的有机碳总量分别为56.09 g和3.18 g,溶解于径流流失的有机碳总量分别为13.55 g和2.81 g。降雨强度和持续时间对有机碳流失的过程特征有显著影响。降雨强度越大,泥沙携带及溶解于径流的有机碳流失速率和总量也越大。大雨强泥沙有机碳富集比在产流发生后的18min内大于1,随后降至1以下。小雨强泥沙有机碳富集比始终小于1。大雨强径流有机碳浓度与径流量呈立方关系,小雨强有机碳流失量随径流量增加呈线性递增趋势;大雨强泥沙有机碳含量与泥沙量之间具有明显的立方关系。     

Soil degradation by Erosion of a typic hapludalf in central Ohio and its rehabilitation

Soil erosion and runoff were monitored from 1988 to 1990 on a Miamian soil (Typic Hapludalf) of 5-6 per cent slope using field runoff plots. Four treatments were studied: (i) disk-plough up and down the slope to 0.3 m depth (DP); (ii) disk-plough up and down the slope followed by a protective netting (PN); (iii) uncultivated fallow without any vegetation followed by surface soil removal (R); (iv) uncultivated fallow with natural vegetation followed by ploughing (F). Mean annual runoff losses were 6, 114 and 128 mm, or 4, 20 and 18 per cent of the rainfall, and mean annual soil losses were 1.2, 85.0 and 64.0 Mg ha⁻¹ in 1988, 1989 and 1990, respectively. Mean runoff amounts were 26, 69, 116 and 118mm and mean annual soil losses were 0.4, 23.2, 58.6 and 118 Mg ha⁻¹ for the F, PN, DP and R treatments, respectively. In comparison with DP, PN decreased annual runoff by 40.3 per cent and annual soil loss by 79.5 per cent. The high mean soil loss for the R treatment was due to erosion following soil removal. An additional 2920 Mg ha⁻¹ of surface soil was removed from the R treatment in May 1990. The F treatment reduced runoff by 78, 77 and 62 per cent and reduced soil loss by 99.7, 99.4 and 98.4 per cent compared with the R, DP and PN treatments, respectively. Mean losses of K, Ca, Mg and P were 1.3, 4, 1 and 01 kg ha⁻¹, respectively for F, 3, 16, 5 and 0.3kg ha⁻¹, respectively, for PN, 5, 31, 1 and 0.6kg ha⁻¹, respectively, for DP, and 3, 32, 12 and 0.4 kg ha⁻¹, respectively, for R. Soil and nutrient losses for each treatment were in the order R > DP > PN > F. The soil organic carbon (SOC) content was significantly affected by soil erosion and management treatments, and ranged from 0.98 per cent for the R treatment to 2.3 per cent for the F treatment. Soil surface removal for the R treatment in 1990 reduced water-stable aggregates (WSA) by 9.0 per cent, SOC by 0.6 per cent, and clay content of the uppermost 0-50 mm depth by about 7.0 per cent. Mean total porosity (f_t) ranged from 0.43 for the F to 0.52 for the DP treatment. Cumulative infiltration for 3h ranged from 13 cm for R to 34cm for PN, with corresponding infiltration rates of 4 cm h⁻¹ and 13 cm h⁻¹, respectively. Regardless of the treatment, there were also temporal changes in soil properties. In comparison with 1988, measurements made in 1990 showed a significant decrease in WSA of 21.3 per cent, an increase in clay content of 2.8 per cent, and a decrease in SOC of 0.39 per cent. Runoff and soil losses were significantly correlated with the mean weight diameter (MWD), SOC, bulk density (p_b) and available water capacity (AWC). Plant height measured 8 weeks after planting (WAP) for the R treatment was reduced by 33.3 per cent, 33.0 per cent and 29.0 per cent compared withh DP, PN and F, respectively. Nitrogen uptake by maize plants (Zea mays L.) 10 WAP for the R treatment was lower by 15 per cent, 8 per cent, and 6 per cent compared with the DP, PN and F treatments, respectively, while P uptake was lower by 33 per cent, 32 per cent and 29 per cent, respectively, compared with the same treatments. Grain yield was 9.78 Mg ha⁻¹ for PN, 9.76 Mg ha⁻¹ for DP, 8.64 Mg ha⁻¹ for F and 6.60 Mg ha⁻¹ for R during the 1990 crop season. Grain yield was reduced by about 32.4 per cent in the R treatment compared with the PN treatment, representing a maize grain yield reduction of 158 kg ha⁻¹ for each centimeter of soil lost.     

Effects of soil crust and crop on runoff and erosion in Loess Plateau

Soil crust formed after rainfall has a strong influence on soil erosion, water use, and crop growth on sloping farmland. To study the effect of soil crust on sloping farmland on runoff amount and erosion sediment yield, the soil crust on sloping farmland has been studied in this paper for plantings of corn, soybeans, millet, and winter wheat. Using an outdoor rainfall simulator, the influence of soil crust on runoff rate and sediment yield on sloping farmland covered by crops has been observed. The results revealed that soil crust thickness was increased after rainfall and soil crust coverage showed little change after rainfall. Soil crust had a significant impact on runoff and sediment yield on sloping farmland. Slopes with soil crust showed higher runoff rate and less soil loss than slopes without soil crust. On slopes planted with four crops (corn, soybeans, millet, and winter wheat), runoff rates on slopes with soil crust were respectively 20%, 25%, 25%, and 21% higher than on slopes without soil crust; sediment yield on slopes with soil crust was respectively 15%, 14%, 14%, and 8% lower than on slopes without soil crust. Crops enlarged the runoff difference between the two kinds of slope and decreased the sediment yield difference between them. Crop growth enhanced these differences in runoff and sediment yield between slopes with and without soil crust.