不同干扰对城市绿化用地土壤物理性质的影响

为了解压实对城市新建绿地土壤物理性质的影响,以西安植物园新园区为研究对象,依据土壤压实程度的不同以及地表植被的差异进行区域划分,对不同区域内的土壤分层采样,并进行土壤容重、孔隙状况、水分常数等物理性质的测定。结果表明：随着压实程度的增加,土壤各层次间的发生规律发生了改变,土壤出现退化现象。研究区域内的土壤容重偏高,平均值为1.52 g/cm³;土壤总孔隙度、通气孔隙度、土壤含水量、田间持水量、土壤饱和导水率明显偏低,平均值分别为44.71%、12.81%、15.46%、20.77%、20.7 mm/h。土壤容重与总孔隙度、通气孔隙度、田间持水量、自然含水量、饱和导水率之间呈极显著的负相关;通气孔隙度与饱和导水率、自然含水量、田间持水量之间均呈现显著的正相关。压实对各层土壤物理性质的影响表现为表层土>浅层土>深层土,人为践踏产生的压实只影响到表层土壤。     

农田机械化耕作与甜菜生长

近年来随着农业机械化水平的快速提高,土壤机械压实问题越来越突出。通过分析土壤机械压实对土壤容重、坚实度、孔隙度、地表水分渗透、土壤含水率等特性的影响,阐述了土壤压实后引起的农业机械机组作业阻力增加、油耗上升,以及对甜菜生长的不利影响,造成甜菜减产。在促进农业机械化发展的同时,应切实考虑其负面影响,采取切实的措施,改善土壤压实情况,确保甜菜可持续生产。     

不同土壤目标含水量对夏玉米光合性能及产量的影响

利用防雨设施研究了不同土壤目标含水量对夏玉米光合性能及产量的影响,结果表明,土壤水分含量与产量密切相关,夏玉米产量形成的土壤水分临界值为田间持水量的４５％左右,最佳产量形成的土壤水分临界值为８０％,５０％左右是夏玉米出苗的土壤水分临界值,７０％左右是最佳出苗率的土壤水分临界值,土壤干旱及过湿均使光合面积,光合势,干物质积累强度及光合速率下降,导致大幅度减产,夏玉米不同生育阶段对水分的需求量有别,有     

Auswirkungen differenzierter Bodenbearbeitung auf das Bodengefüge und die Stickstoffdynamik von Lößböden bei viehloser und viehstarker Bewirtschaftung

Effect of different tillage practices on soil structure and nitrogen dynamic in loess soils with and without longterm application of farmyard manure
Field trials were conducted in 1979 and 1980 on two farms with and without longterm application of farmyard manure respectively, to study the effect of different tillage practices (ploughing at low soil moisture in summer and autumn and ploughing at highsoil moisture in autumn) on soil structure and nitrogen dynamic. Soil structure measurements showed great differences between ploughing at low and high soil moisture contents. Ploughing soil at high moisture contents caused a rise in penetrometer resistance as in bulk density and a decrease of macropors as well as in oxygen concentration in top soil and in tillage pan. But little differences were observed between ploughing in summer and autumn at low soil moisture contents.
Ploughing soil at high moisture contents caused a higher soil compaction on the farm without longterm application of farmyard manure compared to the farm with longterm application of farmyard manure.
The differences in soil nitrate content were strongly correlated with soil compaction. Very large differences in soil nitrate content between ploughing at low and high soil moisture contents were always observed in May, when the soil temperature was higher than 15°C These differences in soil nitrate content are due to reduced nitrogen mineralization and an increase of denitrification activity after ploughing at high soil moisture contents.     

保护性耕作对潮土物理性质的影响

为了研究保护性耕作对土壤物理性质的影响,以黄淮海平原典型潮土区小麦—玉米轮作系统的长期定位试验为基础,探讨不同耕作方式与秸秆还田处理下土壤容重、饱和导水率、紧实度、含水量的变化。结果表明,0~20 cm土层,土壤容重、土壤紧实度随着翻耕频率的减少而增加,每两年翻耕一次(CNTW2T)和每四年翻耕一次(CNTW4T)的土壤紧实度比长期免耕分别降低了40%、17%,土壤紧实度与土层深度呈显著正相关;保护性耕作改变土壤导水性能,随着免耕年限的增加,土壤饱和导水率显著降低;少免耕土壤含水量比传统翻耕高0.77%~3.01%。秸秆覆盖能显著降低土壤紧实度,改良土壤压实状况,提高土壤饱和导水率,减少土壤水分蒸发,从而改善土壤保水能力。免耕有利于土壤蓄水保墒,但长期免耕易导致土壤压实,不利于作物生长,少耕(CNTW2T、CNTW4T)既可改善土壤导水、保水性能,又可减少土壤压实,因此在黄淮海平原实施少耕与秸秆还田相结合的保护性耕作有利于改良土壤物理性质,提高土壤保水能力。     

土壤机械压实与甜菜生长研究进展

土壤机械压实是由于机械化作业引起的土壤结构破坏,导致土壤质量下降,已经成为制约农业可持续发展障碍因子之一。笔者阐述了国内外有关土壤机械压实对土壤容重、坚实度、孔隙度、地表水分渗透、土壤含水率等特性的影响,分析了土壤压实后引起的农业机械机组作业阻力增加、油耗上升,以及对甜菜生长的不利影响,造成甜菜产质量下降。提出了在大力发展甜菜生产机械化发展的同时,应切实考虑其负面影响,采取固定到作业、联合作业等技术措施,改善土壤压实情况,确保甜菜可持续生产。     

机械碾压对新建城市绿地土壤理化性质的影响

为了揭示机械碾压对城市绿地土壤的影响,为城市植被栽植及土壤科学管理提供参考,以在建的西安植物园新园区为例,对机械碾压前后园区土壤理化性质和养分特征进行了研究与分析。结果表明：碾压后土壤容重升高,孔隙度普遍降低,0~30、30~60、60~100 cm土壤容重分别高出碾压前4.20%、14.60%、20.70%;碾压后土壤pH升高;碾压后,土壤表层速效氮含量普遍升高,提高了287%,表层土壤速效磷含量提高了20.30%,表层土壤速效钾含量提高了12.10%,碾压前后表层土壤有机质含量变化不大。碾压破坏了土壤结构,导致土壤容重增加,土壤pH升高,改变了土壤养分分布。针对以上问题及植物园建设的复杂性,须采取精准的土壤改良措施并长期监测碾压对植物生长的影响。     

农田土壤机械压实及改进技术

近年来随着农业机械化水平的快速提高,土壤机械压实问题越来越突出。通过分析机组轴载荷、进地次数、高湿作业等产生土壤机械压实的原因,阐述了机械压实后土壤容重、坚实度、孔隙度、含水率等物理特性的变化以及引起的机组作业阻力的增加、油耗上升、对作物生长的不利影响等负面作用,提出了在农业机械化技术方面采用固定道作业系统、减轻机器质量、采用低压轮胎、避免土壤高湿时机耕作业、采取联合作业等和在农艺技术方面增加土壤有机质、加强作物轮作等减轻土壤压实的农机与农艺技术融合措施,改善土壤压实情况,确保农业生产的可持续性并获得较好的效益。     

Varietal Differences in Development of Maize (Zea mays L.) Seedlings on Compacted Soils

Differences among open-pollinated tropical maize ( Zea mays L.) varieties in seedling development and establishment on compacted soils were studied. Soil dry density was used as an index of compaction. Three soil compaction levels and 12 traits associated with development and establishment of maize seedlings were investigated. A control (without compaction) was also included. Varietal differences were observed for most traits measured. Genetic differences for seedling development on compacted soil were detected. Varietal differences contributed about three times the contribution of compaction to total variability in the traits. Better seedling development and performance were obtained in moderately compacted soil than in the control. Shoot length, shoot dry weight and per cent dry matter in roots were good indicators of the tolerance of maize seedlings to compaction. A physiological strategy for maize seedling establishment on compacted soil was proposed. The implications of the results for seed testing were also highlighted. It was concluded that consideration should be given to the genotype of maize destined for use in ecologies prone to high soil densities. All varieties of maize grown in an agroecological zone could be screened to identify genotypes tolerant of higher soil densities. The seeds could then be multiplied and distributed to farmers.     

Effect of Soil Content on Dynamic Modulus in Filling Sand Subgrade

To analyse the effect of the soil content on dynamic modulus in filling sand subgrade, the portable falling weight deflectometer (PFWD) test and degree of compaction test in field were carried out at first. The relationship of the soil content and the dynamic modulus was analysed as well. Based on the test data, the regression models among the dynamic modulus, degree of compaction, consistency and the soil content were established. Then combining with the out-and-indoor test results, the controlling standard of soil content in filling sand embankment was presented. The results turn out that the soil content in the embankment is 3.0%~5.5%. The dynamic modulus increases with the soil decreasing, and there is a good power function regression between them. There is also a good regression among dynamic modulus, degree of compaction, consistency and soil content. When the soil content is within 10%, the dynamic modulus increases then turn to decrease with the soil content increasing. When soil content is smaller than 3% or larger than 8%, the dynamic modulus are significantly smaller than others. So the controlling standard of soil content in filling sand embankment is recommended at 3%~8%.     

不同肥力水平的土壤紧实度与含水量的相关度分析

为探讨不同肥力条件下土壤紧实度值对含水量的依赖程度,选择质地相同肥力不同的3个田块监测土壤紧实度和实时含水量,分析不同肥力水平土壤的紧实度与含水量的相关程度,揭示不同肥力水平的土壤条件下,土壤紧实度对含水量依赖程度的差异。结果表明：0~25 cm土层范围内,同一田块各土层之间的土壤紧实度对含水量的依赖程度没有显著差异;但在土壤质地相同、肥力条件不同的情况下,土壤含水量对土壤紧实度影响的强弱程度存在明显差异,表现为土壤肥力越低,土壤紧实度对含水量的依赖程度越强。研究表明,在土壤健康评价过程中,当土壤肥力条件较好时,可以适当降低土壤水分对紧实度影响的权重水平,而肥力条件差的土壤,在对土壤紧实度进行拟合时,应充分考虑土壤水分条件的影响。     

Water movement and stability of profiles in drained, clayey and swelling soils: at saturation, the structural stability determines the profile porosity

In clayey, swelling and more or less sodic soils, cultivation and seasonal climatic cycles induce variations in soil moisture which in turn cause variations in the soil structure. In particular, when the soil profile is saturated, some soils become impermeable because the soil porosity value does not remain sufficiently high throughout the drainage period to be effective for water movement. In the marshland soils of the French Atlantic coast, this ability is linked with the soil stability. We showed that soil profile stability and porosity are linked. First, we produced a classification of soil profiles ordered according to their degree of stability. Then, after describing the main features of the soil profile structure at saturation period, we proposed the concept of ‘porosity profile’. This classification and concept were tested on farm fields by measuring two parameters: the water table in winter and the rooting depth of winter wheat. The values assumed by these parameters are indicators of field hydraulic and agronomic behaviour and more precisely of the depth of the soil layers where macroporosity allows water circulation and root colonisation. These results enabled us to validate the concept of ‘porosity profile’.     

土壤机械压实及其对作物生长的影响

在生产中农业机械替代人畜力从事农业生产劳动是必然的趋势。随着农业机械化水平的快速提高,土壤机械压实问题越来越突出。通过分析土壤机械压应力传递模型,以及土壤压实后土壤容重、坚实度增加,孔隙度、含水量降低,土壤的渗透性变差等土壤质量恶化现象,发现土壤压实可导致土壤质量下降,抑制作物的根系生长发育,对作物吸收土壤中的水分、养分产生不利影响。可造成玉米减产9.5%～14.4%,小麦减产4.0%～20.0%,大豆减产3.8%～13.4%,甜菜根产量降低5.81%～24.13%,含糖率降低0.49～0.81oZ。因此,在农业生产中必须要重视土壤压实问题,采取切实可行的技术措施,减轻农业机械化作业对土壤造成的负面影响,促进作物生长,提高农艺综合效益。     

Relations between pore-space and hydraulic properties in compacted beds of silty-loam aggregates

The aim of this study was to better understand features of the hydrodynamics of aggregated soil from experiments conducted on repacked soil samples. In the laboratory, aggregates 2 to 3 mm in diameter were prepared using a silty-loam material. These aggregates were wet to a water content close to their air-entry point value, and compacted to a predetermined bulk density. Two sets of samples were studied, with mean bulk density ranging between 1.0 and 1.6 Mg·m⁻³. Aggregates were extracted from samples of a first set, and their bulk density and water retention curve were determined. Water retention curve and unsaturated hydraulic conductivity of samples of a second set were determined using an instantaneous profile method. Experimental results were interpreted with respect to a functional pore-space classification. The water retention properties of the aggregates extracted from the samples were different, although differences in porosity between such aggregates were sometime too small to be measured. This was explained by a narrowing in the constrictions of intra-aggregate pores induced by compaction, even when this compaction was small. Discontinuities in the shape of the hydraulic properties of a loosely-compacted bed of aggregates were found. This was consistent with an independent desaturation of the inter- and intra-aggregate pores. However, unsaturated hydraulic conductivity of the loosely-compacted sample was affected by a small amount of water, which formed menisci between the aggregates close to the air entry point value of the aggregates. Soil hydraulic conductivity increased with the degree of compaction for a range of massbased water contents dryer than the water content at the air-entry point value of the aggregates. The influence of the contact surface between the aggregates on the unsaturated hydraulic conductivity of the samples was quantified, by assuming that water flows only through the aggregates. These experimental results are related to aspects of soil hydrodynamics, which are difficult to study in situ and difficult to predict with the existing models for the soil hydraulic properties.     

Soil compaction around a small penetrating cylindrical body and its consequences

Penetrometer probes as well as roots and earthworms push soil particles (grains or small aggregates) radially during penetration and/or thickening due to growth. By this, the adjacent soil within a concentric layer is compacted. The degree of compaction depends on soil texture and soil physical properties that are influenced by soil moisture status. In the present study an estimate of the mean but constant increase of the initial bulk density and of the outer radius of this concentrically compacted zone, which are interdependent, is given. For instance, an increase from 1.2 g/cm³ to 1.6 g/cm³ yields a compacted zone of radius 0.5 mm when a body of radius 0.25 mm penetrates into a soil. This estimation is less laborious, but also less exact than that of Dexter (1987: Comparison of soil around roots. Plant Soil, 97: 401–406). This study shows that the distance between adjacent penetrations, when measuring resistance to penetration, should be ⪖ 10 times the probes radius. It is moreover supposed that the compaction produced by roots and earthworms makes it easier for them to anchor within (loose) soil. However, it possibly diminishes infiltration and exchange of soil solution.     

最大承载力状态下全风化花岗岩路基变形特性与控制方法

为了研究南方湿热条件下全风化花岗岩填筑路基的科学方法,以提高路基在运营期的耐久性与稳定性,对全风化花岗岩进行了湿法重型击实与加州承载比试验。结果表明：承载力最大状态下全风化花岗岩的含水率比最佳含水率更接近天然含水率。为进一步了解其湿胀特性,通过改变初始含水率进行了膨胀率试验,得到了全风化花岗岩在不同初始含水率下的干密度衰变规律;通过改进的固结试验对比分析了全风化花岗岩在最大承载力和最大干密度状态时的变形特性。结果显示：与常规的以最大干密度控制方法相比,全风化花岗岩在最大承载力状态下抗变形能力和稳定性更好。按最大承载力状态铺筑了全风化花岗岩路基试验段并进行了现场回弹模量和压实度检测,结果表明：最大承载力状态下全风化花岗岩路基完全能满足下路床94区的压实要求,为了满足路面对路基回弹模量的要求,基于变形等效原理提出刚度补偿设计方法,以确保全风化花岗岩路基整体刚度与耐久性。     

黑土机械压实对土壤结构和甜菜产量的影响

黑土机械压实是由于机械化作业引起的土壤结构破坏,导致土壤质量下降。通过对土壤孔隙比、土壤孔隙度比、土壤透气性、渗透率等指标的分析,明确了土壤压实积累区变化特征总体上表现为,随着机械压实次数的增加,土壤隙比和土壤孔隙度比均减小,通气性变差,土壤雨水入渗率降低,影响区域以5-10cm耕层土壤为最大,拐点在10cm处,对深层土壤的影响减小。土壤压实给甜菜生长造成不利影响,与对照比甜菜块根直径小6.67%-16.08%,甜菜块根长度短1.96%-17.65%,块根产量减产5.81%-24.13%,含糖率降低0.49-0.81度,糖产量降低4.73%-27.03%,碾压次数越多对甜菜产质量的降低作用越显著。     

Transport of Anion Towards Root as Influenced by Soil Compaction

This experiment was conducted in metal container of 2 liters capacity in the glass house to find out the effect of different bulk densities on the movement of non-adsorbed anion (Cl) towards the root. It is inferred from the study that at low moisture content, compaction to a certain degree can increase movement of nutrients to the root due to increase in moisture content per unit volume of soil, further increase in compaction may however affect nutrient availability to the roots. This has a far greater significance in No₃ movement. But from the salinity point of view, plant roots in soil containing salt will be exposed to a much higher salt concentration than that may be obtained from the analysis of the bulk soil.     

Effect of Compaction and Tillage on the Yield and Percolation Loss of Rice in Lateritic Sandy Loam Soil

There is a large area of acid lateritic soils (Acrorthox) around Kharagpur in the state of West Bengal, India, where the top thin layer of soil mostly of detrital material, is underlain by a deep and highly porous lateritic crust (burried). Management of these soils poses a problem for their exceedingly high permeable nature. With the objective of increasing the production of rice in lateritic tract by way of reducing deep percolation, artificially compaction with the help of roller (800 kg) at the surface and subsurface levels were introduced under field conditions. Results indicate that the 6 passes of roller reduced the percolation by more than 3 folds over control. The increase in percolation rate with tillage depth was associated with the change in pore geometry obtained by tillage. The percentage increase in grain yield over the control was about 37 per cent at 4 passes of compaction, the increase was attributed to the reduction of deep percolation losses. The decrease in yield at high level (6 passes) compaction may be attributed to increased mechanical impedence and reduced condition (low Eh) in the compacted soil. Yield of rice has increased significantly with tillage depths at high level (6 passes) compaction probably due to increased root penetration.     

Using a computed tomography miniscanner for studying tillage induced soil compaction

Gamma-ray computed tomography (CT) is used to study thin compacted soil layers, such as millimeter thick “blades” that occur at plowing depth. The technique has the advantage, over the traditional gamma-ray attenuation techniques, of opening the possibility of measuring water contents and bulk-densities of odd-shaped samples. Being a 2-or 3-dimensional technique it is possible to detect small change of bulk-density and soil water content within the sample, even in thin layers of the order of millimeters. Results are reported for thin compacted layers in soil samples collected at the plowing depth from sugar-cane fields in Brazil, which clearly demonstrate the usefulness of this new method for compaction investigations and its quantitative evaluation.