城市功能区、植被类型和利用年限对土壤压实的影响

土地利用会对土壤压实产生影响。本文通过对南京市不同功能区、植被类型和利用年限的土壤进行调查研究,了解这些利用情况对土壤压实的影响程度。结果表明:城郊菜地土壤没有被压实,而城区土壤存在不同程度的压实退化现象;城区内部只有公园土壤与道路绿化带土壤之间的通气孔隙度指标差异显著,其他功能区土壤之间压实指标差异不显著。所以,就压实状况而言,城区内并不存在所谓的功能区之间的差异。植被类型和利用年限对城市土壤的压实都有显著的影响。蔬菜地土壤与自然土壤体积质量和孔隙度相近,为无压实土壤,城区除了树下灌木土壤无压实外,其他植被类型下的土壤均有不同程度的压实退化现象,草坪和裸地土壤压实最为严重。从利用年限看,利用时间少于5年的新土压实程度远远大于利用时间在20年以上老土的压实程度。土壤压实严重与城市建设时的机械压实和草坪建成后的人为践踏密切相关,利用较久的老土壤压实较轻,主要是在无进一步人为践踏情况下,植被生长后根系和土壤生物活动有一定的修复作用。乔木和灌木搭配的修复效果最好。     

城市土壤压实对入渗率的影响

市区土壤经过大规模压实降低了入渗率,从而导致雨水径流增加。在弗罗里达州北部城市建筑工地上采用双环法研究了不同压实程度下土壤的入渗特征。结果表明:弗罗里达州中北部不同压实程度土壤的入渗能力差异较大;土壤压实越严重,其土壤密度越大、孔隙度越小,土壤入渗率越小;严重压实的土壤中存在水分入渗的限制层,致使稳定入渗率明显降低;土壤初始入渗率与稳定入渗率的差异较大,两者之间存在显著的线性相关关系。尽管压实和没有压实的入渗率有较大的变化,但建筑活动或压实处理后减少了入渗率的70%～99%。城市土壤入渗率的减小导致地表径流系数以及发生洪涝的几率和强度增大。     

固定道保护性耕作的试验研究

通过压实试验,分析了无压实以及小型拖拉机、中型拖拉机和联合收获机压实等处理方式的土壤容重、入渗率和耕作阻力。在此基础上,进行了两年的固定道耕作试验,结果表明,机具随机进地行走会造成对土壤的严重压实,降低土壤水分入渗,增加作业能耗,而固定道能够改善土壤结构,提高土壤蓄水能力,减轻地表径流,提高土壤作业适时性和准确性,在目前固定道占地20%的情况下,总产量没有减少     

机械压实对农田土壤性质及土壤侵蚀的影响研究进展

土壤是耕地的重要组成部分,也是农田生态系统的基础,健康的农田土壤对抵抗自然营力如风力、水力、风力等导致的土壤侵蚀至关重要。但随着近些年来农业机械的普及发展,农田土壤也遭受更严重的机械压实。机械作业过程中农田土壤遭受的压实对农田土壤理化性质及土壤生物产生不良影响,机械压实也使农田土壤抵抗侵蚀的能力受到影响,这种影响主要通过机械压实对土壤物理性质的影响间接实现。为明确农田机械压实的研究现状及压实对土壤侵蚀的影响机理,该研究概述了农田土壤机械压实的起因,阐述了机械压实对土壤性质的影响及其作用机理,讨论了机械压实间接影响土壤侵蚀的因素。总结发现,目前研究主要集中在机械压实对土壤性质的影响、土壤性质对土壤侵蚀的影响方面,鲜有研究机械压实对土壤侵蚀的影响机制。最后针对目前机械压实研究的不足提出了未来研究的方向,并探讨了农田土壤机械压实与土壤侵蚀之间的联系,以期将现有机械压实研究理论更好应用到实践,趋利避害,为国内农田土壤侵蚀防治提供参考。     

一种改进的土壤压实模型及试验研究

土壤压实现象普遍存在于农业生态系统中。土壤的压实效应不但会给农业生产带来不良的影响,还可能增加地表径流的产生,从而加快地表水的污染。 为了更好地研究压实土壤中的水分、溶质运移以及压实效应对农业生产及生态与环境的影响,该文在原有土壤压实模型的基础上提出了一种两参数改进模型,并以4种原状土壤为例,用离心机法对改进模型进行验证。研究结果表明：改进模型能够较好地模拟土壤的压实过程,且拟合效果好于L模型;虽然改进模型的物理意义和模型精度与Assouline的三参数模型相当,但是参数少、形式简单是改进模型的优势。同时,改进模型的提出对研究土壤水分特征曲线测定过程中的容重变化特性具有重要的参考价值。     

城市土壤压实对土壤水分特征的影响——以南京市为例

通过对南京市不同土地利用下的土壤容重、孔隙度和土壤水分特征曲线的测定，研究了压实对土壤水分特征参数的影响。结果表明城市土壤存在严重的压实退化现象，土壤容重和孔隙度能够很好地反映土壤的压实程度。随着压实程度的增加，土壤的田间持水量增加，萎蔫点含水量增加，而土壤的最大有效水含量却明显减少。所以，压实土壤对水分的调节能力下降，使其上生长的植物更不容易获得水分供应。     

用人工模拟降雨研究保护性耕作下的地表径流与水分入渗

采用人工模拟降雨试验研究了保护性耕作控制农田地表径流的效果,重点探讨了表土耕作、秸秆覆盖及土壤压实３种因素对地表径流和水分入渗的影响。试验表明,保护性耕作具有明显的处缓径流,增加水分入渗的效果。在土壤干燥,模拟降雨强度为７２ｍｍ／ｈ的条件下,传统翻耕比保护性耕作早１２－１６ｍｉｎ产生径流,入渗率降低６０．９％,总径流量高１１倍。３种试验因素中,秸秆覆盖对径流和入渗的影响最大,压实次之。在本试验中,     

“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。     

矿区机械压实对土壤孔隙特性影响的研究进展

在矿区开采和复垦过程中大型机械的使用产生了土壤压实,并严重扰动了土壤内部结构,导致土壤孔隙数量减少,连通性和渗水能力下降,土壤孔隙作为土壤水气交换的重要场所决定着土壤水分和空气状况,进而影响复垦土壤质量与肥力。为探究矿区机械压实作用对土壤孔隙的影响,系统梳理了矿区机械压实作用下土壤孔隙的获取和表征方法,对农业机械压实相关研究进行了简单归纳,在此基础之上阐述了矿区机械压实对土壤孔隙影响的研究进展,总结了当前研究存在的问题,并提出今后在探究矿区机械压实对土壤孔隙特性影响时应创新压实土壤孔隙的定量表征方法,重视机械压实对土壤孔隙特性影响机理的考究,以期为改善矿区土地复垦效果提供理论指导。     

典型薄层黑土区前期坡面水蚀对土壤风蚀的影响

为了探究东北黑土区水力风力叠加作用的多营力复合侵蚀机理,该研究利用直流吹气式风洞对有、无前期降雨的地表进行风蚀试验,对比分析前期坡面水蚀作用对黑土区坡耕地土壤风蚀的影响。结果显示：不同降雨强度下前期坡面水蚀作用使土壤风蚀量明显减小,即前期坡面水蚀作用对地表产生了明显抗风蚀效应。在9、12和15 m/s风速作用下,50和100 mm/h降雨强度的前期坡面水蚀作用产生的抗风蚀效率分别为68.4%～96.2%和77.2%～97.6%,且随降雨强度增加,其抗风蚀效率增大。土壤风蚀强度受前期坡面水蚀作用中降雨强度和风蚀作用风速的综合影响,降雨强度的增加对土壤风蚀的抑制效果明显。前期坡面水蚀作用降低了土壤风蚀输沙量和输沙高度,且风蚀输沙量随前期坡面水蚀作用中降雨强度的增大而减小。前期坡面水蚀作用对地表产生抗风蚀效应的主要原因一方面是前期降雨径流侵蚀作用对土壤的压实过程改变了土壤性质和地表形态,使地表土壤抗剪强度和土壤紧实度增加,从而提高了土壤结构的稳定性和抗风蚀能力;另一方面前期降雨侵蚀作用使地表土壤颗粒分散并随径流流失,减少了后期土壤风蚀的物质来源,抑制了土壤风蚀的发生。该研究结果不仅揭示了前期坡面水蚀作用对黑土区土壤风蚀的影响机制,也为针对性防治黑土坡面复合侵蚀和黑土资源的可持续利用提供了理论依据。     

Effects of compaction on soil surface water repellency

Water repellency can reduce the infiltration capacity of soils over timescales similar to those of precipitation events. Compaction can also reduce infiltration capacity by decreasing soil hydraulic conductivity, but the effect of compaction on soil water repellency is unknown. This study explores the effect of compaction on the wettability of water repellent soil. Three air‐dry (water content ～4 g 100 g^?1) silt loam samples of contrasting wettability (non‐repellent, strongly and severely water repellent) were homogenized and subjected to various pressures in the range 0–1570 kPa in an odeometer for 24 h. Following removal, sample surface water repellency was reassessed using the water drop penetration time method and surface roughness using white light interferometry. An increase in compaction pressure caused a significant reduction in soil surface water repellency, which in turn increases the soil's initial infiltration capacity. The difference in surface roughness of soils compacted at the lowest and highest pressures was significant (at P > 0.2) suggesting an increase in the contact area between sessile water drops and soil surfaces was providing increased opportunities for surface wetting mechanisms to proceed. This suggests that compaction of a water repellent soil may lead to an increased rate of surface wetting, which is a precursor to successful infiltration of water into bulk soil. Although there may be a reduction in soil conductivity upon compaction, the more rapid initiation of infiltration may, in some circumstances, lead to an overall increase in the proportion of rain or irrigation water infiltrating water repellent soil, rather than contributing to surface run‐off or evaporation.     

昆明市城市绿地蓄水滞洪效益研究

城市绿地的蓄水滞洪效益是城市绿地水土保持效益的重要方面。以昆明市建成区城市绿地为研究对象,分析其蓄水滞洪效益,结果表明:绿地表层土壤总孔隙度较大,然而土壤稳渗率普遍较小,尤其是人工绿地,平均值只有0.242mm/min;在一年一遇1 h降雨(36 mm)条件下,除了自然绿地外,人工绿地均有径流产生,人工绿地平均蓄渗率只有15.10%;当前期非毛管孔隙没有水分滞存时,绿地的暂时滞洪效益非常显著,12.35 cm土壤即可蓄存全部降水;土壤稳渗情况下,绿化区平均下凹3.73 cm即可额外蓄渗非绿化区50%的径流;若要绿化区不产流,则绿地平均入渗率至少要达到0.6 mm/min或下凹2.1 cm。从降水特点分析,昆明市城市绿地目前滞洪效益较低,需要提高土壤入渗性能或建下凹式绿地。     

Compaction,hydrological processes and soil erosion on loamy sands in east Shropshire,England

Field investigations on loamy sands in east Shropshire show that compaction by agricultural machinery increases soil bulk density and soil erodibility, and decreases infiltration rates. Structural and hydrological changes, in combination with runoff concentration in cultivation lines, can contribute to serious erosion of arable soils. Compacted soils are also more responsive to rainfall and evidence is presented that intensities as low as approximately 1 mm h^?1 can be erosive. Evidence suggests that compacted subsoils impede infiltration and so contribute to surface runoff and serious topsoil erosion.     

Incidence of soil surface crust types in semi-arid Niger

Soil water availability is most essential in the Sahelian agriculture but is hampered by several factors. Surface crusts or crust-like surfaces, which are characteristic of most Sahelian soils, have been shown to decrease water infiltrability and increase runoff. Their type and structure are influenced by soil texture, vegetation cover, erosion and deposition effects of wind and water. A soil and terrain survey in semi-arid SW-Niger was carried out to explain the patterns of soil surface crusts and the deterioration of the land. The soil surface crusts were shown to depend also on specific terrain factors including land use type and intensity, and terrain type and position. Chemical and physical soil factors such as organic carbon, soil colour and texture occurring with specific crusts indicate soil degradation, especially in sloping terrain, which increases runoff and soil erosion. For sandy soils, surface tillage is required to break up the crusts. Higher surface organic matter is recommended to enhance water infiltration in soils.     

Soil water repellency and infiltration in coarse-textured soils of burned and unburned sagebrush ecosystems

Millions of dollars are spent each year in the United States to mitigate the effects of wildfires and reduce the risk of flash floods and debris flows. Research from forested, chaparral, and rangeland communities indicate that severe wildfires can cause significant increases in soil water repellency resulting in increased runoff and erosion. Few data are available to document the effects of fire on the spatial and temporal variability in soil water repellency and potential impacts on infiltration and runoff on sagebrush-dominated landscapes. Soil water repellency, infiltration and runoff were assessed after two wildfires and one prescribed fire in three steep, sagebrush-dominated watersheds with coarse-textured soils. Water repellency was generally greater on unburned hillslopes and annual variability in water repellency had a greater impact on infiltration capacity than fire effects. The most significant impact of fire was canopy and ground cover removal on coppice microsites. Infiltration rates decreased on coppice microsites after fire even though soil water repellency was reduced. Fire-induced reduction in infiltration resulted from the combined effect of canopy and ground cover removal and the presence of naturally strong water repellent soils. Removal of ground cover likely increased the spatial connectivity of runoff areas from strongly water repellent soils. The results indicate that for coarse-textured sagebrush landscapes with high pre-fire soil water repellency, post-fire increases in runoff are more influenced by fire removal of ground and canopy cover than fire effects on soil water repellency and that the degree of these impacts may be significantly influenced by short-term fluctuations in water repellent soil conditions.     

斥水土壤中水热运动模型的应用

作者运用所建立的斥水土壤中水热运动的数值模型，模拟分析了以下因素对沟中时苗床不分散失与温度的影响：（１）不同的沟垄尺寸；（２）湿润剂；（３）镇压；（４）沟垄的走向。以此为当地的耕种工程设计提供了依据。一般认为土壤斥性严重影响产量，但采用沟种后，表层的斥水土壤形成的不透不的垄能促进雨水渗入沟中，又能阻止水分的蒸发，降低沟中的温度，有利于种子发育出苗，从而使不利因素变化成有利条件。     

Soil compaction and soil management – a review

Soil compaction is an important component of the land degradation syndrome which is an issue for soil management throughout the world. It is a long standing phenomenon not only associated with agriculture but also with forest harvesting, amenity land use, pipeline installation, land restoration and wildlife trampling. This review concentrates on the impact of soil compaction on practical soil management issues, an area not previously reviewed. It discusses in the context of the current situation, the causes, identification, effects and alleviation of compaction. The principal causes are when compressive forces derived from wheels, tillage machinery and from the trampling of animals, act on compressible soil. Compact soils can also be found under natural conditions without human or animal involvement. Compaction alters many soil properties and adverse effects are mostly linked to a reduction in permeability to air, water and roots. Many methods can be used to measure the changes. In practical situations, the use of visual and tactile methods directly in the field is recommended. The worst problems tend to occur when root crops and vegetables are harvested from soils at or wetter than field capacity. As discussed by a farmer, the effects on crop uniformity and quality (as well as a reduction in yield) can be marked. By contrast, rendzinas and other calcareous soils growing mainly cereals are comparatively free of compaction problems. The effect of a given level of compaction is related to both weather and climate; where soil moisture deficits are large, a restriction in root depth may have severe effects but the same level of compaction may have a negligible effect where moisture deficits are small. Topsoil compaction in sloping landscapes enhances runoff and may induce erosion particularly along wheeltracks, with consequent off‐farm environmental impacts. Indirect effects of compaction include denitrification which is likely to lead to nitrogen deficiency in crops. The effects of heavy tractors and harvesters can to some extent be compensated for by a reduction in tyre pressures although there is concern that deep‐seated compaction may occur. Techniques for loosening compaction up to depths of 45 cm are well established but to correct deeper problems presents difficulties. Several authors recommend that monitoring of soil physical conditions, including compaction, should be part of routine soil management.     

The implications of spatial variability in surface seal hydraulic resistance for infiltration in a mound and depression microtopography

Soil surface crusting has a major impact on water infiltration and erosion in many soils. Considerable progress has been made in describing crusting processes and in modelling the impact of crusting on infiltration. Most studies, however, have neglected the high spatial variability in crust characteristics observed in the field. The objective of this experiment was to determine the influence of runoff depth on infiltration rate in the presence of a surface seal varying in hydraulic characteristics with microtopography. The Blosseville silt loam has a low aggregate stability and forms crusts readily. The Villamblain silty clay loam has a greater aggregate stability due to its greater clay and organic matter contents, and it is more resistant to aggregate breakdown processes under rainfall. Samples of the soils were sieved to retain aggregates less than 2.0 cm and packed in 50×50×15 cm soil trays. The trays were surrounded by a 10 cm soil border to compensate for splash loss. After molding the surface into a mound and depression microtopography, the samples were subjected to simulated rainfall at an intensity of 22.8 mm h⁻¹. Hourly measurements of surface roughness showed that the original roughness was smoothed out due to the infilling of depressions by sediments detached from the mounds. For the final hour, runon was added to the top of the soil tray to increase the runoff rate and depth. For both soils, infiltration rate increased more than could be attributed to the increased ponding pressure head. The change in infiltration rate was particularly great for Villamblain. The measurements of hydraulic resistance showed that structural crusts had a lower hydraulic resistance than sedimentary crusts. They also showed that the crusts formed on Villamblain were of a lower hydraulic resistance than those of Blosseville. It appears that small changes in runoff depth can significantly increase infiltration rate when structural crusts of lower hydraulic resistance are inundated. The effect was less important in Blosseville which formed seals of relatively high hydraulic resistance everywhere. The results provide a suitable explanation for field observations of increasing infiltration rate with either increasing rainfall intensity or runoff rate. The results also have implications for the relationships between surface roughness, surface water storage, and infiltration.     

土壤翻耕对坡地水分转化与产流产沙特征的影响

坡耕地严重的水土流失是导致黄土高原土壤质量退化与生态环境恶化的重要原因。采用模拟降雨的方法研究了翻耕与压实对休闲黄绵土坡耕地水分转化与产流产沙特征的影响。结果表明，(1)与压实相比，土壤翻耕导致入渗率下降40%～60%，产流强度增加1至3倍，降雨向土壤水分的转化率降低50％以上。(2)翻耕条件下流失径流的平均含沙量增加近70％，坡地产沙量增加3倍，径流流失量增加1倍，因此对坡地实行免耕休闲可以有效减轻水土流失、遏制坡地土壤质量退化的态势。(3)降雨过程中，随着产流时间的延长，坡地产沙量呈加速增加的趋势，而且增加速度显著快于坡面径流，因此采取适当措施延长初始产流时间、减少产流量以及提高降雨向土壤水分的转化率均可有效减少坡地土壤流失量。     

Infiltration in reclaimed mined land ameliorated with deep tillage treatments

Reclamation of mined land with heavy machinery can result in soil compaction. Compaction increases soil bulk density and reduces porosity, water infiltrability, root elongation and crop productivity. Mine operators have used deep tillage equipment to alleviate the compaction problem. The main objectives of this study were to examine (1) the effect on infiltration in reclaimed surface mined land of a deep tillage treatment, and (2) the subsequent changes in infiltration after the amelioration. The experiment was conducted at the Horse Creek Mine near Conant, Perry County, IL, USA. The soil was classified as Schuline series, which is a fine, loamy, mixed, mesic, Typic Udorthents. The treatments included tillage depths of 20 (as a control), 40, 60 and 80 cm. Infiltrometers and runoff plots were installed to evaluate infiltration and rainfall-runoff relationships affected by the treatments. Results indicated that the steady infiltration rates of the 40- and 60-cm tillage treatments were lower than that of the control treatment successively during the experimental period for 3 years. Results also revealed that the 80-cm tillage treatment increased infiltration and reduced surface runoff most. Even though the beneficial effects declined over a 3-year test period, the 80-cm tillage is recommended in the amelioration of soil compaction because tillage depths less than 80 cm did not enhance water infiltration rate much.