prevention strategies for field traffic-induced subsoil compaction: a review: part 1. machine/soil...

Soil & Tillage Research 73 (2003) 145–160

Prevention strategies for field traffic-inducedsubsoil compaction: a review

Part 1. Machine/soil interactions

L. Alakukkua,∗, P. Weisskopfb, W.C.T. Chamenc, F.G.J. Tijinkd,J.P. van der Lindend, S. Pirese, C. Sommerf, G. Spoorga MTT Agrifood Research Finland, Soils and Environment, FIN-31600 Jokioinen, Finland

b Swiss Federal Research Station for Agroecology and Agriculture (FAL), Reckenholzstrasse 191, CH-8046 Zurich, Switzerlandc 4’C’easons, Church Close Cottage, Maulden, Bedford MK45 2AU, UK

d Institute of Sugar Beet Research (IRS), P.O. Box 32, 4600 AA Bergen op Zoom, The Netherlandse Dept. De Engenharia Rural, Instituto Superior de Agronomia, Universidade Tecnica de Lisboa (ISA/UIL), 1399 Lisbon Cedex, Portugal

f Institute of Production Engineering and Building Research, Federal Research Centre of Agriculture (FAL),Bundensallee 50, 38116 Braunschweig, Germany

g Model Farm, New Road, Maulden, Bedford MK45 2BQ, UK

Abstract

Subsoil compaction is a severe problem mainly because its effects have been found to be long-lasting and difficult to correct.It is better to avoid subsoil compaction than to rely on alleviating the compacted structure afterwards. Before recommendationsto avoid subsoil compaction can be given, the key variables and processes involved in the machinery–subsoil system mustbe known and understood. Field traffic-induced subsoil compaction is discussed to determine the variables important to theprevention of the compaction capability of running gear. Likewise, technical choices to minimise the risk of subsoil compactionare reviewed. According to analytical solutions and experimental results the stress in the soil under a loaded wheel decreaseswith depth. The risk of subsoil compaction is high when the exerted stresses are higher than the bearing capacity of the subsoil.Soil wetness decreases the bearing capacity of soil. The most serious sources of subsoil compaction are ploughing in thefurrow and heavy wheel loads applied at high pressure in soft conditions. To prevent (sub)soil compaction, the machines andequipment used on the field in critical conditions should be adjusted to actual strength of the subsoil by controlling wheel/trackloads and using low tyre inflation pressures. Recommendations based on quantitative guidelines for machine/soil interactionsshould be available for different wheel load/ground pressure combinations and soil conditions.© 2003 Elsevier Science B.V. All rights reserved.

Keywords:Average ground pressure; Axle load; Inflation pressure; Soil moisture content; Subsoil bearing capacity; Wheel load

∗ Corresponding author. Tel.:+358-3-41881;fax: +358-3-41882437.E-mail address:[email protected] (L. Alakukku).

1. Introduction

The changes in agricultural production techniquesin industrialised countries over the past few decadeshave been dramatic. The economic pressure favoursthe continuous increase of machinery power, vehicleweight and implement size. For instance, in Germany,

0167-1987/$ – see front matter © 2003 Elsevier Science B.V. All rights reserved.doi:10.1016/S0167-1987(03)00107-7

146 L. Alakukku et al. / Soil & Tillage Research 73 (2003) 145–160

the proportion of newly registered tractors largerthan 44 kW increased from 33 to 77% between 1976and 1992 (Renius, 1994). In recent years, the num-ber of large tracked tractors which weigh more than10 Mg has increased in western Europe. The heav-iest loaded combine harvesters may be more than25 Mg and slurry tankers may weigh more than 30 Mg(Håkansson and Petelkau, 1994). Likewise, six-rowself-propelled sugar beet harvesters are increasinglyused. Fully loaded the weight of two-axle sugar beetharvesters is about 35–40 Mg and of three-axle har-vesters up to 50 Mg or even more (van der Lindenand Vandergeten, 1999).

The continuous increase in the weight of farmmachinery and the necessity to use heavy machinesin unfavourable soil conditions have increased thepotential for subsoil damage. Subsoil compactionhas been found to have harmful effects on manysoil properties relevant to soil workability, drainage,

Fig. 1. A framework of machinery–soil system in connection with subsoil compaction.

crop growth and environment. For instance, subsoilcompaction has increased surface runoff and top-soil erosion by impeding water infiltration (Fullen,1985). Subsoil compaction is a severe problemmainly because its effects have been found to belong-lasting (more than 5 years) (Blake et al., 1976;Pollard and Webster, 1978; Etana and Håkansson,1994; Alakukku, 1996) and difficult to correct, forinstance, by deep loosening (Kooistra and Boersma,1994).

It is better to avoid subsoil compaction than to relyon alleviating the compacted structure afterwards. Themachinery–subsoil system includes several variablesand processes (Fig. 1). Before recommendations toavoid subsoil compaction can be given, the key vari-ables and processes involved in the system must beknown and understood. In the present paper the pre-vention of field traffic-induced subsoil compaction isdiscussed with the following objectives:

L. Alakukku et al. / Soil & Tillage Research 73 (2003) 145–160 147

(1) to determine the variables controlling the risk forsubsoil compaction induced by field traffic,

(2) to identify those field operations that have a highrisk for subsoil compaction,

(3) to discuss the existing technical recommendationsto avoid subsoil compaction,

(4) to evaluate the need for further development ofmachines to reduce or avoid subsoil compaction.

In the present paper, we concentrate on the run-ning gear/soil interaction and technical solutionsto control the risk of subsoil compaction.Chamenet al. (2003)discuss more detailed equipment andfield practices to avoid subsoil compaction. Like-wise, Jones et al. (2003)examine subsoil vulner-ability and Chamen et al. (2003)assess the bene-fits that might be achieved by topsoil management.This paper is a part of the activities of the Work-ing Group ‘Equipment selection and field practicesfor the control of subsoil compaction’ set up withina European Union Concerted Action ‘Experienceswith the impact of subsoil compaction on soil,crop growth and environment and ways to preventsubsoil compaction’ (contract No. FAIR 5 CT973589).

2. Definition of the subsoil

In the present paper, subsoil is divided into twodistinct layers as defined below:

Pan layer. This is the layer below the annually cul-tivated layer. It will vary in thickness depending onthe type and severity of compaction created by eitherimplements or wheels or both. In some instances it isloosened on a regular basis.

Unloosened subsoil. This is the layer which nor-mally remains undisturbed by tillage operations. Itis also at a depth where tillage operations wouldbe considered to be undesirable and often uneco-nomic, and if carried out, would create the potentialfor damage. This layer may, however, be disturbedduring drainage operations, such as subsurfacedrainage and mole ploughing, and soil improvementoperations.

It should be noted that although these definitionsare universal, the layers will occur at different depthsdepending upon the production system in use.

3. Field traffic-subsoil system

Field traffic-subsoil system may be divided into twomain variables: soil bearing capacity and soil stresscaused by field traffic (Fig. 1). Subsoil bearing capac-ity means the capability of a soil structure to withstandstresses induced by field traffic without changes in thethree-dimensional arrangement of its constituent soilparticles.

3.1. Subsoil bearing capacity

Different parameters have been used to assess soilbearing capacity and the susceptibility of soil forplastic deformation. Constitutive soil properties liketexture, organic matter, structure, bulk density as wellas soil moisture status, which are indirectly related tosoil strength, have been used as classifying parametersto qualitatively predict soil stability (e.g.Anonymous,1997; Jones et al., 2003). To quantify bearing capacityas an indicator for trafficability directly in the field, acone penetrometer technique has been used (Paul andDeVries, 1979). Also soil consistency (the Atterbergparameter “plastic limit” and “liquid limit”) as wellas parameters of the Proctor test (“critical moisturecontent”) have been used to predict the susceptibil-ity of soils to compaction (Mapfumo and Chanasyk,1998). In order to get direct measurements of soilstrength and to model the interactions between ve-hicles and soil quantitatively, parameters have beenadapted from geotechnical engineering. Of specialinterest were parameters of compaction and sheartesting, as pre-consolidation stress, angle of internalfriction, cohesion.

Using pre-consolidation stress as an indicator ofthe bearing capacity of a soil, it was expected toestimate quantitatively the compaction risk in givenvehicle–soil interactions. Pre-consolidation stress canbe determined in the laboratory by means of uniaxialcompaction tests or in the field with plate sinkagetests. The resulting stress–strain curve can be inter-preted by deriving different parameters, one of thembeing the pre-consolidation stress at the point whichseparates elastic from plastic behaviour of a soil. Theassumption is that as long as soil stresses are smallerthan pre-consolidation stress, soil deformation andtherefore changes of soil function remain small be-cause of the elastic behaviour of the soil. On the other


hand, stresses higher than the pre-consolidation stresslead to plastic deformation and permanent damage(Lebert, 1989).

Based on data sets obtained from arable soils withdifferent properties, quantitative prediction of sub-soil bearing capacity became feasible by using pedo-transfer functions for calculating pre-consolidationstress from constitutive soil properties (DVWK,1995). Data sets of field measurements on arable soilsin Central Europe (e.g.Horn et al., 1989b; Nissenand Horn, 1996; Nissen, 1999) showed consider-able differences (factor of 5 and more) between pre-consolidation stresses of different soils. Accordingly,DVWK (1995) divided soils (or soil horizons respec-tively) into six classes from<30 kPa up to >150 kPapre-consolidation stress.

In addition to the effect of soil type and soil con-stituents, soil moisture status influences markedly thepre-consolidation stress. As the moisture content in-creases, the strength of an unsaturated subsoil drops(Lebert, 1989; Salire et al., 1994). Arvidsson (2001)found that the pre-consolidation stress of sandy, sandyloam and loam soils at 0.30 m depth was average85 kPa at 6 kPa water potential and 104 kPa at 30 kPawater potential.Arvidsson et al. (2001)measured thesoil displacement caused by a sugar beet harvester(weight 35 Mg on two axles, tyre inflation pressure170–200 kPa) at different moisture conditions on asandy clay loam. They found that pre-consolidationstress at 0.50 m depth reduced from 165 to 98 kPawhen soil moisture content increased from 11.0 to20.8 g 100 g−1. When pre-consolidation stress reducedfrom 165 to 98 kPa at 0.50 m depth, subsoil displace-ment increased from 0 to 2.1 mm (Arvidsson et al.,2001).

Because the strength of soils as a measure forsoil bearing capacity depends on aggregation andsince development of soil structure is influencedby natural and anthropogenic factors, values forpre-consolidation stress and therefore also for bearingcapacity, are the result of individual stress histories ofsoils. They therefore have to be deduced for clearlydefined situations consisting of site characteristics andcultivation practices. For instance, in a layered soilprofile, compacted layers such as plough pans can,by their high mechanical stability, reduce the stresson the subsoil layers beneath by spreading it over awider area (Poodt et al., 2003; Wiermann et al., 2000).

Likewise, it is expected that the bearing capacity ofsoils will be improved by increasing their structuralstability, such as may be achieved with reduced or notillage systems (Sommer, 2000; Chamen et al., 2003).

3.2. Stresses applied to soil by running gear

3.2.1. Wheel load, contact area and averageground contact pressure

The weight distribution of machines can be de-scribed by axle loads or wheel loads. In most papersstatic axle/wheel loads are discussed. However, dur-ing field operations, the weight distribution may easilyvary between axles and wheels on the same axle, de-pending on the degree of the loading of tank or weighttransfer during ploughing, for example.

The tyre or track contact area is the portion of thetyre or track which is in direct contact with the sup-porting soil surface. Several contact area estimationsbased on wheel parameters have been given. For in-stance,McKyes (1985)proposed to estimate the con-tact area of tyres on a rigid surface by multiplying thetyre section width by overall tyre diameter and divid-ing the product by 4. On a deformable surface, thecontact area of tyres is, however, always larger thanon a rigid surface.

The average ground contact pressure (wheel loaddivided by contact area between tyre and soil surface)estimates the average value of the vertical stress in thecontact area.Burt et al. (1992)andTijink (1994)offera detailed examination of the determination of groundcontact pressure. The pressure is not uniformly dis-tributed over the contact area. Pressure distributionbeneath the wheel is complex because of the tyrelug patterns and of tyre construction (stiffness of thecarcass, etc.). Thus, the maximum ground contactpressure under lugs or stiff tyre walls may be severaltimes (4–10) the estimated average ground contactpressure (Smith, 1985; Burt et al., 1992; Gysi et al.,2002). Likewise, the ground contact pressure under atrack will concentrate under the jockey wheels (Wong,1986). It is shown that the effect of the uneven pres-sure distribution is limited to the upper part of the soilprofile. Measurements byGysi et al. (2002)showedthat at a depth of 0.30 m, the influences of pressuredistribution in the contact area due to the tyre profilehave changed to a standard stress distribution, withhigh pressures concentrated around the vertical axis


of the loaded area. The uneven pressure distributionbelow a tyre running in the furrow during ploughingmay, however, introduce high peak stresses into thesubsoil as calculated byRüdiger (1989). Measure-ments of pressure distribution in the contact area arecomplicated, which is one reason for the need ofsimplistic approaches.

The average ground contact pressure is often evalu-ated from the tyre inflation pressure. The relationshipbetween the average ground contact pressure and theinflation pressure of a tyre depends, however, on tyrestiffness and soil conditions. For stiff agriculturaltyres, tyre walls carry a considerable proportion of thetotal load, and on rigid surfaces stress in the contactarea, especially peak values of profiled tyres are con-sidered higher than the inflation pressure (Plackett,1984). Burt et al. (1992)found that the dynamic av-erage ground contact pressure below an 18.4R-38tractor tyre on rigid soils was closely approximatedby the inflation pressure, whereas on non-compactedsoils the contact pressure was clearly lower than theinflation pressure.

3.2.2. Stress componentsDuring field trafficking, vertical and horizontal

stress components as well as shear forces in the soilare caused by the profiled, moving and deflecting tyre.Under the rolling tyre wheel load and stress distribu-tion in the contact area are permanently changing dueto accelerating/braking of the tyres and the drive as-sembly, respectively, as well as due to changing pay-load and the uneven soil surface. Even the directionof horizontal stresses changes in a given soil element,depending on whether a wheel is approaching or leav-ing (e.g.Bakker et al., 1995; Weisskopf et al., 2000).The resulting stress path is decisive for the effectsof loading on soil structure. Stress paths with strongchanges in the direction of stresses will lead, depend-ing on the stability of soil, to kneading and shearingof soil, as can be shown by tracing the displacementof soil particles (Wiermann et al., 2000). The sheareffect is, however, expected to vanish rapidly withdepth (Koolen et al., 1992). On the other hand, shearstress can damage the subsoil markedly, especiallyduring ploughing, owing to furrow wheel slipping.Davies et al. (1973)suggest a slip maximum of 10%to avoid topsoil damage owing to shear. The samelimit is probably appropriate for subsoils.

Contrary to these dynamic effects, extreme combi-nations of mechanical loading and soil stability mayprovoke shearing even under static loading conditions(Weisskopf et al., 1998). This holds, for instance, forlarge and highly loaded contact areas on the surfaceof weak soils (as for heavy harvesters or transportvehicles on wet soils). Simulations with finite ele-ment models suggest that under these conditions thereexist, apart from regions with volume decrease andsoil compaction, zones with volume increase and soilsoftening as a consequence of shearing effects. De-pending on the geometry of the contact areas of avehicle (as influenced by its construction, e.g. tan-dem vs. pendulum axles) interactions of stresses com-ing from neighbouring contact areas may occur, lead-ing to stress paths specific for certain axle or wheelarrangement.

In addition to these stresses, which may change dur-ing intervals of from one-tenth of a second to one sec-ond, stresses with very short loading/unloading cycles(“vibrations”) can also be transferred to the soil. Thecontribution of vibration effects to soil compactionbelow running gear has seldom been documented forarable soils (Soane et al., 1981). Vibration is, how-ever, evaluated to be unimportant in relation to sub-soil compaction. With the stress distributions normallyoccurring in soil, intense detrimental effects on soilstructure caused by high frequency loading changes,or the reversal of stress direction, seems be restrictedto topsoil layers.

When the velocity of a machine is increased, theduration of the loading is reduced.Bolling (1987)measured the effects of velocity on the maximum soilstress below a wheel centre with two wheel loads(0.82 Mg with a tyre inflation pressure of 160 kPa,and 1.5 Mg with 170 kPa) on sandy loam soil. Re-sults showed that an increase in velocity from 2to 10 km h−1 decreased stress at 0.30 m depth be-low the wheel centre. The effect of velocity wasgreater on loose than on dense soil. Similar resultswere reported byHorn et al. (1989a). An increasein velocity seems to reduce the stress transmittedto upper subsoil layers. This effect can probably beattributed to the water conductivity characteristicsof a soil. The effects of velocity on the stress indeeper layers and the practical importance of veloc-ity to subsoil compaction have seldom been docu-mented, however. The highest velocity tested has been


8–12 km h−1, which is the upper speed range for fieldoperations.

3.2.3. Extent of stressesIn unsaturated soil, stresses are transmitted

three-dimensionally via solid, liquid and gaseousphases. The analytical models for the propagation anddistribution of stresses in the soil still mostly describethe stress distribution under a point load or a loadedarea acting on a homogenous, isotropic, semi-infinite,ideal elastic medium. The theoretical solution wasproposed byBoussinesq (1885)(cited by Söhne,1953). Fröhlich (1934) later modified the originalsolution by introducing an empirical concentrationfactor to account for the increase in Young’s moduluswith soil depth due to overburden stress.Söhne (1953,1958) and Koolen and Kuipers (1983)review theequations of analytical models that describe stresseson a soil element.

By changing the value of concentration coeffi-cient, the stress distribution in the model soil body ischanged from confining stresses to the upper part ofso called “hard soils” (with spherical isobars), to astress distribution concentrated along the stress axisand reaching deeper into “soft soils” (with longish

Fig. 2. Calculated vertical normal stress (σz) as a function of depth (z) beneath the centre of a circular and uniformly loaded contact area.Equation (Söhne, 1953, 1958): σz = p(1− cosγα), wherep is the average ground contact pressure acting on the tyre–soil contact area,γ

the concentration factor (here 5);α the half aperture angle between the point at depthz and the contact area’s edge. Examples of stressdistribution in a homogenous elastic medium caused by different wheel load/ground contact pressure combinations. Legend: Mg, wheelload; kPa, average ground pressure;r, radius of the circular contact area.

isobars).Horn et al. (1987)reported that the con-centration factor depends on the moisture content,density, load history, structure and texture of thesoil. Unfortunately, this coefficient cannot directly berelated to real soil properties; based on direct mea-surements of normal stress in soil it can be calculatedwith the procedure of Newmark (DVWK, 1995).

From the analytical solution and experimental re-sults the following conclusion can be drawn on theeffects of wheel load and contact pressure on the soilstress:

(1) The stress in the soil under a loaded wheel de-creases with depth (Fig. 2). Olsen (1994)con-cluded that the decrease of induced vertical normalstress with depth in the upper subsoil (0.10–0.30to 1 m depth) depends on both ground contactpressure and wheel load, and below 1 m solely onwheel load. Based on the equation used inFig. 2,the wheel load determines the normal stress leveldeep in the soil profile, but this will never exceedthe maximum ground contact pressure level.

(2) Vertical stresses can be reduced by using largertyres (lower inflation pressure, larger contactarea) with constant wheel load; the effect is more


pronounced in the topsoil and decreases withdepth (Fig. 2, Lebert et al., 1989).

(3) When the average contact pressure is kept con-stant by increasing tyre dimensions or the num-ber of tyres (dual, triple), a higher wheel loadincreases the stress transmitted deeper into the soiland a greater soil volume is stressed. In the caseof additional wheels, this is only true if, there isinteraction between the stress distribution belowthe wheels (Fig. 2, Lebert et al., 1989).

(4) A higher moisture content and/or soil tillagewhich by decreasing the strength of a soil in-creases the stress transmitted deeper into the soil(Söhne, 1958; Arvidsson et al., 2001).

(5) A common situation in arable fields is that thestrength of the soil profile is non-uniform. There isoften a hard layer below the plough layer (ploughpan). Hard pans tend to act like an elastic bridge,spreading the stress over a wider area by reducingthe stress transmitted deeper into the subsoil (e.g.Poodt et al., 2003).

In summary it can be stated that the risk of subsoilcompaction exists whenever a moist or weak soil isloaded by a moderate to high ground contact pressureon a large contact area, i.e. with a high wheel load.

3.3. Number of passes and cumulative effectsof stresses

The number of passes affects the number of load-ing events and the coverage, intensity and distributionof wheel traffic. When a vehicle has been convertedto low wheel load and ground pressure by increasingthe number of wheels that follow in the same track(tandem axle-concept), average ground contact pres-sure is lower, but the number of wheel passes in thesame track is higher. Because of the multi-pass effect,tandem axle construction would be less efficient inavoiding high levels of compactness in the topsoil thanwide tyres and dual wheel arrangement. The repeatednumber of wheel passes may also increase the riskof subsoil compaction.Wilde (1998) measured soilstress at 0.10, 0.15, 0.25 and 0.40 m depth in marshysoil. He found that when the number of passes in thesame track was increased, soil stress at 0.40 m depthalso increased. During the first pass the stress was60 kPa and during the fourth pass 200 kPa. Likewise,

the compactness of mineral subsoils (Gameda et al.,1987; Schjønning and Rasmussen, 1994; Alakukkuand Elonen, 1995) and the depth of the compactedlayer (Sommer and Altemüller, 1982; Alakukku, 1996)were found to increase as the number of passes in thesame track increased.

The natural alleviation of the effects of severe sub-soil compaction takes many years, if it occurs at all.The annually repeated traffic may cause cumulativeeffects if the effects of earlier subsoil compaction havenot disappeared before new loading. The area of com-pacted subsoil may increase year by year due to ran-dom field traffic. The effects of subsoil compactionmay thus become more harmful with time, even thoughthe effect of a single pass by a heavy vehicle tends tobe rather small (Håkansson, 1994).

3.4. Stress/strain equations

Boussinesq’s half-space model for homogeneousisotropic elastic media, as well as its extension byFröhlich for elasto-plastic behaviour of a media, doesnot allow for estimations of soil strain. This restricts itsuse to a semi-quantitative assessment of stress distri-bution in soil without the possibility of getting quanti-tative information about effects on soil structure. Withthe coupling of a purely statistical model to predictthe pre-consolidation stress of soils and the model ofBoussinesq/Fröhlich to estimate the stress distributionin soil, DVWK (1995) offered a quantitative decisiontool for assessing the risk of deformation of a given soilstructure as a consequence of field traffic. Later workextended this tool with the potential to assess the ef-fect of soil stress on soil structure. This assumed rela-tionships between predicted plastic deformation in theload range of virgin compression behaviour and asso-ciated changes in physical properties of soils (DVWK,1997). O’Sullivan et al. (1999)presented a simplifiedmodel to explore the stress/strain relations betweenmachinery and soil factors governing compaction pro-cesses. On the stress distribution side they used thesame fundamentals asDVWK (1997), whereas soilstrength was described with the empirical concentra-tion factors, and the consequences for soil structurewere expressed by specific volume as an indicator forthe compactness of soil.

With critical state theory it has become possible tointerconnect stress and strain as a process directly in


both homogenous and layered soils by using finite el-ement models (Horn et al., 1998; Kirby, 1999; Poodtet al., 2003). Based on soil mechanical propertiesfrom compression, shear or triaxial tests respectively(Kirby, 1994; O’Sullivan and Robertson, 1996; Kirbyet al., 1998), these models allow for the calculationof stress distribution and the resulting strain (as voidratio or total porosity) in 2D layered soil profilesor even in 3D-space. In contrast to fully elastic oranalytical elasto-plastic models, critical state the-ory makes it possible to take elasto-plastic reactionsof soils (volume decrease “compaction” or volumeincrease “softening”) into account. Additionally, itallows for calculations of the influence of definedloading events on soils with defined mechanical prop-erties, i.e. quantitative predictions of the risk of dam-age to soil structure as durable, plastic deformations.Although originally developed for saturated soils, ef-forts have been taken to extend its use to unsaturatedsoil conditions (Horn et al., 1998).

With the intention of extending the possibilitiesof describing the three-phase soil medium, completemultiphase models have been developed. These mod-els couple the state and characteristics of the threephases fully, i.e. any change in water content willaffect not only the mechanical, but also the hydraulicproperties of a soil structure, for example,Klubertanz(1999). Considering both dynamic and hydraulic load-ing, soil deformation caused by the pressure on thecontact area as well as by weather-induced changesin soil moisture content can be simulated. In this way,effects such as a strength increase caused by a suc-tion increase, structural collapse as a consequence ofwetting the soil or increasing brittleness of a dryingsoil structure can be considered.

4. Critical field operations

Table 1shows the summary of the critical opera-tions listed byChamen et al. (2000)which could leadto subsoil compaction.Chamen et al. (2000)providethe definitions necessary forTable 1. There are cleardifferences between countries in the high risk opera-tions depending on the main crops grown and the pre-vailing weather conditions. In Finland, for instance,the seedbed preparation of spring sown crops is clas-sified as a moderate to high risk operation since at

the time of sowing the subsoils are often wet after thefrost has thawed in spring.

The risk of subsoil compaction is high when moistto wet (i.e. weak) soils are loaded with high wheelload traffic with moderate to high ground contact pres-sure (Table 1). Up to now the most serious source ofsubsoil compaction has been mostly the tractor wheelrunning in the open furrow during mouldboard plough-ing, because the wheels on one tractor side are run-ning directly on the upper part of the subsoil.Tijinket al. (1995)calculated vertical soil stress under lowground pressure tyres. According to their calculations,the stress caused by a wheel carrying 2 Mg load andhaving an average ground contact pressure of 80 kPa inthe plough furrow, was greater in the 0.30–0.70 m layerthan a tyre on the soil surface with 5 Mg wheel loadand 60 kPa ground pressure. Also, subsoiling is foundto be a critical operation as discussed byChamenet al. (2000). Deep loosening reduces soil strengthclearly, and loosened subsoil may be recompacted eas-ily (Kooistra and Boersma, 1994).

5. Stress and wheel load recommendations

With the aim of avoiding soil compaction, recom-mendations have been given for maximum values ofaverage ground contact pressure (Rusanov, 1994, cf.Table 2). These are combined with soil conditionsby giving separate recommendations for spring (soilmoist and therefore weak) and summer/autumn (soilstrength higher than in spring,Table 2). Petelkau(1984) recommended that on sand, loam and claysoil the ground contact pressure should not exceed50 kPa (80), 80 kPa (150) or 150 kPa (200), respec-tively, in spring (in autumn, soil moisture content<70% of field capacity). For the moisture contentsof mineral soils higher than field capacity, groundcontact pressures not exceeding 40–50 kPa have beenrecommended (Bondarev et al., 1988; cited byLipiecand Simota, 1994).

The ground pressure recommendations above aregiven to avoid soil compaction in the topsoil andprobably in conventional primary tillage systems.Carpenter and Fausey (1983)suggest that the maxi-mum ground contact pressure with high wheel loadsshould not exceed the stress allowed in the subsoil.Rusanov (1994)reported official standard values


Table 1Operations with a medium to high risk of damage to the subsoil categorised under cropsa

Country, critical operation Crop Critical machineryb

United KingdomDeep cultivation after subsoiling All TractorPloughing <cSugar beetd, potatoesd>, cereals> Tractor—in furrowHarvesting Cereals, root crops, fresh peasd, 1st cuts of silage Harvesters/trailersFertilisation

Mineral All Lime spreadersOrganic All Tractors/tankers

Bed forming/cultivation Vegetables Tractor

SwitzerlandPloughing Maized, sugar beet and others Tractor—in furrowHarvesting Grain and silage maize, cereals, sugar beet, peas, potatoes Harvesters/trailersFertilisation

Organic All Tractor/tankers

PortugalDeep cultivation after subsoiling All Tractor/heavy discsPloughing Sugar beet, potatoes> Tractor—in/out of furrowHarvesting Cereals, root crops, fresh peas, 1st cuts of silage Harvesters/trailersHarvesting Olivesd, nuts, citrus TractorsLevelling for flood irrigation Irrigated crops Tractors

The NetherlandsSubsoiling Potatoes, cereals, silage maize> SubsoilerPloughing <All crops except permanent grassland Tractor—in furrowHarvesting Cereals, silage maize, root crops, fresh peas,

1st cut intensive silageHarvesters/trailers

FertilisationOrganic All Tractor/tankers

GermanyPloughing <Winter wheatd, maize, sugar beet, potatoes Tractor—in furrowPloughing Grain maize, sugar beet, potatoes, fodder crops> Tractor—in furrowHarvesting Cereals, grain maize, oilseed, sugar beet, legumes,

potatoes, fodder cropsHarvesters/trailers/tractors

FertilisationOrganic All grain, sugar beet, cover Tractors/tankers

FinlandPloughing in early spring <Spring cereals, sugar beet, potatoes Tractor—in furrowPloughing in late autumn Spring cereals, sugar beet, potatoes, cover crop, grass> Tractor—in furrowSeedbed preparation <Spring cereals, sugar beet TractorHarvesting Cereals, root crops, 1st cuts of silage Harvesters/trailers/tractorsFertilisation

Mineral All Lime spreaderOrganic All Tractor/spreader/tankers

a Summarised for returns from United Kingdom, Switzerland, Portugal, The Netherlands, Germany and Finland.Chamen et al. (2000)provide the definitions necessary for the table.

b In all instances, the risks are increased as soil moisture content rises.c The symbols< and > represent just before crop sowing and just after crop harvesting, respectively.d Sugar beet (Beta vulgaris), potatoe (Solanum tuberosum), pea (Pisum sativum), maize (Zea mays), olive (Olea europaea), winter

wheat (Triticum aestivum).


Table 2USSR official standard for maximum average ground contact pressure and vertical soil stress at 0.50 m depth in different soil conditionsto prevent the soil compaction of fine-grained soils in arable fields, meadows and pasture (USSR State Committee for Standards, 1986;Rusanov, 1994)a

Soil moisture contentof field capacity (%)

Ground contact pressure (kPa) Stress at 0.50 m depth (kPa)

Spring Summer/autumn Spring Summer/autumn

Clay Sand, sandy loam Clay Sand, sandy loam

>90 80 95 100 120 25 3070–90 100 120 120 145 25 3060–70 120 145 140 170 30 3550–60 150 180 180 215 35 45

<50 180 215 210 250 35 50

a For two passes in the same rut the values are 10% lower; for three and more passes in the same rut the values are 20% lower.

of maximum permissible normal stress at a depthof 0.5 m (Table 2). He gave also maximum groundpressure levels which were clearly higher than theallowable stress in subsoil (Table 2). Few data ex-ist, however, to allow assessment of the maximumallowable subsoil stress in different conditions, andthis area should be addressed in future studies. Theallowable subsoil stress may be evaluated by lookingat the stress history of subsoil.

From a practical point of view it is relevant thatthe recommendations for ground contact pressure arewithin the same range of recommended tyre inflationpressures given byDwyer (1983, 50 kPa for moist soil,100 kPa for dry soil)and Perdok and Tijink (1990,50 kPa for moist soil, 250 kPa for dry soil). Relevant tothis,Söhne (1953)had already recommended a maxi-mum inflation pressure of 80 kPa in the early 1950s forthe tilled arable layer in normal field moisture range.

To avoid soil compaction below normal primarytillage depth (0.2–0.3 m), single axle loads not exceed-ing 4–6 Mg have been recommended for moist mineralsoils (Danfors, 1974, 1994; Voorhees and Lindstrom,1983; Petelkau, 1984) even when the tyre inflationpressure is 50 kPa (Danfors, 1994). For tandem axleloads on moist soils,Danfors (1974, 1994)proposeda limit of 8–10 Mg.

The use of axle load recommendations in con-nection with the prevention of subsoil compactionshould be avoided. The weight distribution may varymarkedly between wheels on the same axle. Thus,wheel load is to be preferred (interaction betweenwheels near each other must be noticed) instead ofaxle load and wheel load should be linked with ground

contact pressure recommendations. This linkage innecessary because the wheel load alone does not giveany information about the stress level transferred tothe soil and the corresponding stress distribution inthe soil. Recommendations need to be set with a viewto the most critical conditions prevailing during thenormal use of a machine. Otherwise, the recommen-dations could be too theoretical and not adapted toreal situations.

To prevent subsoil compaction, recommendationsfor wheel load–ground contact pressure combinationsin different soil conditions should be made available.True regulations which account for the interactions be-tween machinery and soil (e.g.DVWK, 1995) would,however, be scientifically more sound than generalrecommendations. For machine designers such regu-lations may provide a means of evaluating the rangeof soil conditions when the stress due to a machineis lower than the bearing capacity of subsoil.Chamenet al. (2003)review the practical equipment and fieldpractices to avoid subsoil compaction.

6. Technical solutions to prevent subsoilcompaction

The fundamental principle of subsoil protection isto prevent structural deformation and not to alleviateroutinely existing compaction. This should be doneonly if soil damages are interfering with subsoil func-tion (Fig. 1). The basic idea of prevention is to avoidirreversible plastic deformation; this is often inter-preted as a conservative attitude against change of the


existing soil structure. Based on the data reviewed weconclude that limitations of the average ground con-tact pressure and wheel load can be considered to bethe major engineering tools for the control of sub-soil compaction. In the following sections we suggestways of choosing machines and of adapting them tolow subsoil strength, as just one part of the process ofthe prevention of subsoil compaction. In addition, thegeneral planning of cultivation practices and the or-ganisation of field operations are important. This couldtake the form of a flow chart showing the preferen-tial sequence of operations, particularly for subsoiling.Chamen et al. (2003)discuss the equipment and fieldpractices to avoid subsoil compaction.

Quantitative models to assess the interaction of tyreand soil over a broad spectrum of different condi-tions are sparse. With the DVWK-model (DVWK,1995) a comparison between soil stability (expressedas pre-compression stress) and soil stress (expressed asvertical stress under the centre line of the contact area)was proposed. A differing approach was chosen byMatthies (1998), who presented a computer-based in-formation system as a decision-making tool for the useof forest harvesters. This system gives values for soilmoisture which allow the use of vehicles with knownspecifications (wheel loads, tyres) on given soils with-out a high risk of soil compaction.

6.1. Wheel/track load

The weight of a tractor is largely associated withthe draught force which it must develop to pull an im-plement. Similarly, the draught load and tractor trac-tion control system will affect the dynamic loading onthe front and rear axles. In theory, the control systemshould maximise the tractive efficiency of the combi-nation of tractor and implement by transferring loadfrom the implement onto the tractor. As this weighttransfer also includes an element of draught load, theloading on the axles will be constantly changing anddifficult to predict. Setting minimum tyre pressuresin this situation cannot therefore be very precise andnew monitoring and control systems that average dy-namic loads and adjust inflation pressures on the moveshould be encouraged.

In critical conditions, wheel loads can be temporar-ily reduced by using only a proportion of the loadingcapacity of a combine harvester or trailer. Load distri-

bution between axles may also be influenced by usingweight transfer facilities (Tijink et al., 1995). Like-wise, wheel load can be reduced by dividing the totalload between two or more axles instead of one. Theaxles/wheels should be spaced apart to avoid any in-teraction between them as described byOlsen (1994).In this case the contact areas of the additional wheelswill act as separate, smaller contact areas with im-proved stress compensation. Multi-pass effects may,however, reduce the advantage of several axles as dis-cussed inSection 3.3.

To control the wheel loads of heavy machinery,weighing axle or wheel load on the move would beuseful. Likewise, the testing procedure of a machineshould include information about dynamic wheel loadsand their fluctuation during the pulling or filling pro-cess. The procedure would also determine the proper-ties of standard tyres used on the machine (e.g. width,inflation pressure with different loads and speeds, tyredeflection on rigid surface with different loads), stan-dard ground pressures and standard soil stresses at de-fined depths.

6.2. Tyre inflation pressure

When the tyres are selected, the technical solutionwill depend on the demands of the given machine, thewheel load and the field operation in which a machineis used. The tyre inflation pressure should always bethe lowest allowable in the prevailing situation (tyreloading capacity, velocity, traction). Pressure distribu-tion in the tyre–soil contact area should be uniform.Thus, the tyre should adapt to soil properties withouthigh peak stresses due to stiff carcass construction.Ground contact pressure prediction based on easilymeasurable parameters should be available. Likewise,tyre manufactures should publish their data sheets forthe use of machinery designers, farmers and advisors.

Low tyre inflation pressure usually provides lowground contact pressure and allows even pressure dis-tribution. These are advantageous to both soil com-paction caused by wheel traffic and to wheel trac-tive efficiency. When wheel load can be measured,the proper tyre inflation pressure can be determinedeasily by using specifications given by tyre manufac-tures. If a weighbridge is not available the proper in-flation pressure can be determined simply by usingthe specifications and measuring procedure described


by Chamen et al. (2003). Tyres have to meet differentrequirements for field and road traffic: driving on theroad requires high inflation pressure but in the field,the inflation pressure should be low. With a central tyreinflation system (Koolen and Kuipers, 1989; Bradley,1996), it is possible to control ground contact pressurein the field and on the move, so this system shouldbe used more extensively, especially on vehicles withhighly loaded large contact areas.

The inflation pressure may be reduced by increasingthe size of a single tyre (width or height or both), orby dividing the load among several tyres (dual, triple)or several axles. Radial tyres, which are now generallyfitted as standard, are flexible and their deflection in-creases the contact area, especially on a firm surface,in that way reducing the average ground contact pres-sure. Low profile tyres with radial carcass constructionare now available. These tyres allow very low infla-tion pressure (below 50 kPa) without high ground con-tact pressure below the tyre side walls. On the otherhand,Koolen (1994)pointed out that the increasinguse of low tyre inflation pressures gives farmers eas-ier access to soft terrain, so that in future plastic flowtype soil behaviour may occur more frequently. Fordetailed discussion of tyre factors see among othersTijink (1994) andTijink et al. (1995).

6.3. Tracks

Tracks can give a large contact area. Rubber-belttracks remove many of the disadvantages of steeltracks (Erbach, 1994; Höfflinger, 1999). However,Marsili and Servadio (1996)reported that steel trackscompacted the soil less in 0–0.40 m layer than rub-ber tracks (tractor weight 3.8 Mg). Below the rubbertracks the distribution of ground contact pressurewas more uneven than below steel tracks. The edgesof the rubber track were flexible and stress concen-trated below the centre of the track (below the jockeywheels). A track system consists of a number ofrigid jockey wheels running over a stationary sur-face. Each jockey axle creates a pronounced stresspulse in the track (Blunden et al., 1994). Without animplement, the pulses are relatively uniform fromfront to rear. When pulling an implement, the stresspulses increase clearly from the front idler to therear driven wheel on the track system due to weighttransfer.

Bashford et al. (1988)and Rusanov (1991)foundthat tracked tractors compacted the soil less than sim-ilar wheel tractors. On the other hand,Brown et al.(1992)found that rubber-belt tractors (average groundcontact pressure 40 kPa) compacted the soil below0.13 m depth as much as wheel tractors with 125 kPaground contact pressure.Blunden et al. (1994)loadedsand soil with a track tractor (weight 15 Mg, averageground contact pressure 58 kPa) and a wheel tractor(18 Mg, 74–81 kPa). They found that even though thetrack tractor exerted less normal stress on the soil thanthe wheel tractor at 0.40 and 0.50 m depth, the pen-etrometer resistance of a sand soil at 0.40 m depth was1.51 and 1.48 MPa when track and wheel tractor wereused, respectively. There were no differences in resis-tance at 0.50 m depth. The reason for small differencesin subsoil compaction between wheeled and trackedtractors is not evident from the reports cited above.According toWolf and Hadas (1984)andWong andPreston-Thomas (1984), the reason for smaller differ-ence in topsoil compaction than expected was basedon longer loading time (longer contact area), unevenpressure distribution or vibration transmitted to soil,all of which are associated with tracks.

Based on the results discussed above, it is difficult todraw clear conclusions about the advantages of trackscompared to tyres to avoid subsoil compaction. Undernormal agricultural conditions, the advantages of us-ing tracks are less slip (improved tractive efficiency),lower rut depth on wet or soft soils and a compactvehicle design.

6.4. Technical and research requirementsfor the future

The machines and equipment used in the fieldshould be adjusted to actual strength of the sub-soil by controlling wheel/track loads and using lowtyre inflation pressures. Relevant to this, the use ofpre-consolidation stress to forecast subsoil vulner-ability and the standardisation of pre-consolidationstress measuring techniques should be investigatedmore intensely. Likewise, models to evaluate sub-soil vulnerability and the risk of harmful effects ofsubsoil compaction in different conditions should bedeveloped further. In much the same way as irrigationscheduling is based on crop and weather data, it maybe possible to determine the local vulnerability of


subsoils. The procedure would involve an element ofmodelling and on-farm records of rainfall, evapotran-spiration and days following cessation of drain-flow,if available.Arvidsson et al. (2000)made a risk as-sessment using a soil water model. They calculatedthe risk of compaction at 0.30 m depth for a wheelload of 8 Mg (ground contact pressure 220 kPa) basedon the soil strength simulated by using a soil watermodel and long-term weather data.

In the future, subsoil damage due to field trafficshould be avoided by modifying the present ma-chines. Technical solutions to reduce loads carriedin the field are now available and the use of theseshould be encouraged. For instance,Weisskopf et al.(2000) found that on-land ploughing reduced therisk of subsoil compaction compared to in-furrowploughing. Likewise, to reduce compaction duringwet conditions, Godwin et al. (1990)distributedslurry with umbilical injection equipment, not requir-ing a heavily laden tanker. Accordingly,Sommer andZach (1992)pointed out, that conservation tillagewith crop rotation-specific non-inverting soil loosen-ing promises to be a potential strategy not only withregard to reducing soil erosion but a program for re-ducing costs and reducing the risk of traffic-inducedsoil compaction.

In the long term, the development of less soilloading field practices should be continued. The au-tomated information and decision aid systems inmachines should be developed further. For instance,the testing data (seeSection 6.1), dynamic weighingand central tyre inflation pressure control systems,slip sensors and rut depth sensors may be integratedin the information and decision aid systems of the ma-chines. Machine weight may be reduced by using new,lighter materials. In Norway, a prototype tractor madeof aluminium was introduced (Melding fra trekkraftog jordpakking til lett basismaskin, 1997). Automa-tion may also allow lighter machines. In Finland, alight, self-navigating tractor for agricultural applica-tions (Nieminen et al., 1994) has been developed.Such a self-guiding system allows a single operatorto control more than one tractor at a time, enablingfield operations to be done with two to three smallunits as fast as with one large unit. Adoption of newsystems to practise will be enhanced if profit on-farmlevel increases or stays at least equal.Chamen et al.(2003) offer a more detailed discussion of visions

to develop machines and practices to avoid subsoilcompaction.

7. Conclusions

According to analytical solution and experimentalresults the stress in the soil under a loaded wheel de-creases with depth. The risk of subsoil compactionis high when the exerted stresses are higher than thebearing capacity of the subsoil. Soil wetness decreasesthe bearing capacity of soil. The most serious sourcesof subsoil compaction are ploughing in the furrowand heavy wheel loads applied at high ground con-tact pressure in soft soil conditions. To prevent subsoilcompaction, the stresses induced by field traffic mustbe less than the subsoil’s bearing capacity. The ma-chines and equipment used on fields in critical condi-tions should be adjusted to the actual strength of thesubsoil by controlling wheel/track loads and using lowtyre inflation pressures. Relevant to this, recommen-dations for wheel load–ground contact pressure com-binations in different soil conditions, or regulationsbased on quantitative guidelines for machinery–soilinteractions, should be established.

References

Alakukku, L., 1996. Persistence of soil compaction due to highaxle load traffic. I. Short-term effects on the properties of clayand organic soils. Soil Till. Res. 37, 211–222.

Alakukku, L., Elonen, P., 1995. Cumulative compaction of a clayloam soil by annually repeated field traffic in autumn. Agric.Sci. Finland 4, 445–461.

Anonymous, 1997. Richtlinien zum Schutze des Bodens beimBau von unterirdischen Rohrleitungen (Bodenschutzrichtlinien).Bundesamt für Energiewirtschaft, 24 pp.

Arvidsson, J., 2001. Subsoil compaction caused by heavy sugarbeetharvesters in southern Sweden. I. Soil physical properties andcrop yield in six field experiments. Soil Till. Res. 60, 67–78.

Arvidsson, J., Trautner, A., Van den Akker, J.J.H., 2000. Subsoilcompaction—risk assessment and economic consequences.In: Horn, R., Van den Akker, J.J.H., Arvidsson, J. (Eds.),Subsoil Compaction: Distribution, Processes and Consequences.Advances in GeoEcology 32. Catena Verlag, Reiskirchen,Germany, pp. 3–12.

Arvidsson, J., Trautner, A., Van den Akker, J.J.H., Schjønning, P.,2001. Subsoil compaction caused by heavy sugarbeet harvestersin southern Sweden. II. Soil displacement during wheeling andmodel computations of compaction. Soil Till. Res. 60, 79–89.


Bakker, D.M., Harris, H.D., Wong, K.Y., 1995. Measurement ofstress paths under agricultural vehicles and their interpretationin critical state space. J. Agric. Eng. Res. 61, 247–260.

Bashford, L.L., Jones, A.J., Mielke, L.N., 1988. Comparison ofbulk density beneath a belt track and tire. Appl. Eng. Agric. 4,122–125.

Blake, G.R., Nelson, W.W., Allmaras, R.R., 1976. Persistence ofsubsoil compaction in a Mollisol. Soil Sci. Soc. Am. J. 40,943–948.

Blunden, B.G., McBride, R.A., Daniel, H., Blackwell, P.S., 1994.Compaction of an earthy sand by rubber tracked and tyredvehicles. Aust. J. Soil Res. 32, 1095–1108.

Bolling, I., 1987. Bodenverdichtung und Triebraftverhalten beiReifen-Neue Mess- und Rechenmethode. ForschungsberichtAgrartechnik des Arbeitskreises Forschung und Lehre derMax-Eyth-Gesellschaft (MEG) 133, 1–274.

Bondarev, A.G., Sapozhnikov, P.M., Utkaieva, V.F., Shepotiev,V.N., 1988. Izmeneniye fizicheskykh svoystv I plodorodyapochv pri ikh uplotnieny dvizhytelamy sielskokhazyaystvennoytyekhniki. (Changes in soil physical properties and productivityas related to compaction by agricultural vehicles, in Russian.)Sbornik Nauchnykh Trudov, vol. 188, VIM, Moscow, USSR,pp. 46–57.

Boussinesq, J., 1885. Application des potentials à l’etude del’equilibre et du mouvement des solides elastiques. Gauthier-Villais, Paris, France, 30 pp.

Bradley, A.H., 1996. Trial of a central tire inflation system onthawing forest roads. Tech. Rep. Forest Eng. Res. Inst. Canada,TR-166, 27 pp.

Brown, H.J., Cruse, R.M., Erbach, D.C., Melvin, S.W., 1992.Tractive device effects on soil physical properties. Soil Till.Res. 22, 41–43.

Burt, E.C., Wood, R.K., Bailey, A.C., 1992. Some comparison ofaverage to peak soil–tire contact pressures. Trans. Am. Soc.Agric. Eng. 35, 401–404.

Carpenter, T.G., Fausey, N.R., 1983. Tire sizing for minimizingsubsoil compaction. Am. Soc. Agric. Eng. Paper No. 83/1058,23 pp.

Chamen, W.C.T., Alakukku, L., Jorge, R., Pires, S., Sommer,C., Spoor, G., Tijink, F., Weisskopf, P., van der Linden, P.,2000. Equipment selection and field practices for the control ofsubsoil compaction—Working Group methodologies and dataacquisition. In: Proceedings of the Third Workshop of theConcerted Action on Subsoil Compaction, Uppsala, Sweden,June 14–16, 2000. Report 100. Department of Soil Sciences,Swedish University of Agricultural Sciences, Uppsala, Sweden,pp. 207–219.

Chamen, W.C.T., Alakukku, L., Pires, S., Sommer, C., Spoor, G.,Tijink, F., Weisskopf, P., 2003. Prevention strategies for fieldtraffic-induced subsoil compaction. Part 2. Equipment and fieldpractices. Soil Till. Res. 73, 161–174.

Danfors, B., 1974. Packning i alven. Swedish Inst. Agric. Eng.Special Report S24, pp. 1–91.

Danfors, B., 1994. Changes in subsoil porosity caused by heavyvehicles. Soil Till. Res. 29, 135–144.

Davies, D.B., Finney, J.B., Richardson, S.J., 1973. Relative effectsof tractor weight and wheel slip in causing soil compaction. J.Soil Sci. 24, 399–409.

DVWK, 1995. Gefügestabilität ackerbaulich genutzter Mineral-böden. Teil I: Mechanische Belastbarkeit. DVWK-Merkblätterzur Wasserwirtschaft, Heft 234. KommissionsvertriebWirtschafts- und Verlagsgesellschaft Gas und Wasser mbH,Bonn, 12 pp. ISBN 3-89554-025-0.

DVWK, 1997. Gefügestabilität ackerbaulich genutzter Mineral-böden. Teil II: Auflastabhängige Veränderung von boden-physikalischen Kennwerten. DVWK-Merkblätter zur Wasser-wirtschaft, vol. 235. Kommissionsvertrieb Wirtschafts- undVerlagsgesellschaft Gas und Wasser mbH, Bonn, 7 pp. ISBN3-89554-025-0.

Dwyer, M.J., 1983. Soil dynamics and the problems of tractionand compaction. Agric. Eng. 38, 62–68.

Erbach, D.C., 1994. Benefits of tracked vehicles in crop production.In: Soane, B.D., Van Ouwerkerk, C. (Eds.), Soil Compactionin Crop Production. Developments in Agricultural Engineering,vol. 11. Elsevier, The Netherlands, pp. 501–520.

Etana, A., Håkansson, I., 1994. Swedish experiments on thepersistence of subsoil compaction caused by vehicles with highaxle load. Soil Till. Res. 29, 167–172.

Fröhlich, O.K., 1934. Druckverteilung im Baugrunde. Verlag vonJulius Springer, Wien, Austria.

Fullen, M.A., 1985. Compaction, hydrological processes anderosion on loamy sands in east Shropshire, England. Soil Till.Res. 6, 17–29.

Gameda, S., Raghavan, G.S.V., McKyes, E., Theriault, R., 1987.Subsoil compaction in a clay soil. I. Cumulative effects. SoilTill. Res. 10, 113–122.

Godwin, R.J., Warner, N.C., Hanh, M.J., 1990. Comparison ofumbilical hose and conventional tanker-mounted slurry injectionsystems. Agric. Eng. 45, 45–50.

Gysi, M., Maeder, V., Weisskopf, P., 2002. Pressure distributionbeneath agricultural tyres, (in preparation).

Håkansson, I., 1994. Soil tillage for crop production and forprotection of soil and environmental quality: a Scandinavianviewpoint. Soil Till. Res. 30, 109–124.

Håkansson, I., Petelkau, H., 1994. Benefits of limited axle load.In: Soane, B.D., Van Ouwerkerk, C. (Eds.), Soil Compactionin Crop Production. Developments in Agricultural Engineering,vol. 11. Elsevier, The Netherlands, pp. 479–500.

Höfflinger, W., 1999. Rubber-belt tracks—a complement to tractortires. Landbauforschung Völkenrode SH 196, 35–48.

Horn, R., Burger, N., Lebert, M., Badewitz, G., 1987. Druckfortpflanzung in Böden unter fahrenden Traktoren. ZeitschriftKulturtechnik Flurbereitung 28, 94–102.

Horn, R., Blackwell, P.S., White, R., 1989a. The effect of speed ofwheeling on soil stresses, rut depth and soil physical propertiesin an ameliorated transitional red-brown earth. Soil Till. Res.13, 353–364.

Horn, R., Lebert, M., Burger, N., 1989b. Die mechanischeBelastbarkeit von Böden als Pflanzenstandort. MaterialbandNr. 73, Bayerisches Staatsministerium für Landwirtschaft undUmwelt.

Horn, R., Richards, B.G., Gräsle, W., Baumgartl, T., Wiermann,C., 1998. Theoretical principles for modelling soil strength andwheeling effects—a review. Zeitschrift für Pflanzenernährungund Bodenkunde 161, 333–346.


Jones, R.J.A., Spoor, G., Thomasson, A.J., 2003. Vulnerability ofsubsoils in Europe to compaction: a preliminary analysis. SoilTill. Res. 73, 131–143.

Kirby, J.M., 1994. Simulating soil deformation using a critical-statemodel. I. Laboratory tests. Eur. J. Soil Sci. 45, 239–248.

Kirby, J.M., 1999. Soil stress measurements. Part I. Transducer ina uniform stress field. J. Agric. Eng. Res. 44, 217–230.

Kirby, J.M., O’Sullivan, M.F.O., Wood, J.T., 1998. Estimatingcritical state soil mechanics parameters from constant cellvolume triaxial tests. Eur. J. Soil Sci. 49, 85–93.

Klubertanz, G., 1999. Zur hydromechanischen Kopplung indreiphasigen porosen Medien. These de doctorat. EcolePolytechnique Federale de Lausanne, Lausanne, Switzerland.

Kooistra, M.J., Boersma, O.H., 1994. Subsoil compaction in Dutchmarine sandy loams: loosening practices and effects. Soil Till.Res. 29, 237–247.

Koolen, A.J., 1994. Mechanics of soil compaction. In: Soane,B.D., Van Ouwerkerk, C. (Eds.), Soil Compaction in CropProduction. Developments in Agricultural Engineering, vol. 11.Elsevier, The Netherlands, pp. 23–44.

Koolen, A.J., Kuipers, H., 1983. Agricultural Soil Mechanics. Adv.Series Agric. Sci. 13. Springer, Berlin.

Koolen, A.J., Kuipers, H., 1989. Soil deformation undercompressive forces. In: Larson, W.E., Blake, G.R., Allmaras,R.R., Voorhees, W.B., Gupta, S.C. (Eds.), Mechanics andRelated Processes in Structured Agricultural Soils, NATO ASISeries E: Applied Science 172, pp. 37–52.

Koolen, A.J., Lerink, P., Kurstjens, D.A.G., Van den Akker,J.J.H., Arts, W.B.M., 1992. Prediction of aspects of soil–wheelsystems. Soil Till. Res. 24, 381–396.

Lebert, M., 1989. Beurteilung und Vorhersage der mechanischenBelastbarkeit von Ackerboden. Dissertation. BayretherBodenkundliche Berichte, vol. 12, 131 pp.

Lebert, M., Burger, N., Horn, R., 1989. Effects of dynamic andstatic loading on compaction of structured soils. In: Larson,W.E., Blake, G.R., Allmaras, R.R., Voorhees, W.B., Gupta,S.C. (Eds.), Mechanics and Related Processes in StructuredAgricultural Soils, NATO ASI Series E: Applied Science 172,pp. 73–80.

Lipiec, J., Simota, C., 1994. Role of soil and climate factors ininfluencing crop responses to soil compaction in central andeastern Europe. In: Soane, B.D., Van Ouwerkerk, C. (Eds.), SoilCompaction in Crop Production. Developments in AgriculturalEngineering, vol. 11. Elsevier, The Netherlands, pp. 365–390.

Mapfumo, E., Chanasyk, D.S., 1998. Guidelines for safe traffickingand cultivation, and resistance–density–moisture relations ofthree disturbed soils from Alberta. Soil Till. Res. 46, 193–202.

Marsili, A., Servadio, P., 1996. Compaction effects of rubber ormetal-tracked tractor passes on agricultural soils. Soil Till. Res.37, 37–45.

Matthies, D., 1998. Ein Informationssystem zum bodenschonendenEinsatz von Holzerntemaschinen in der Forstwirtschaft.Mitteilungen der Deutschen Bodenkundlichen Gesellscheft 88,523–526.

McKyes, E., 1985. Soil Cutting and Tillage. Developments inAgricultural Science, vol. 7. Elsevier, Amsterdam.

Melding fra trekkraft og jordpakking til lett basismaskin, 1997.Norges Landbrukshøgskole. Institutt for Tekniske Fag, NR.12-1997, 22 pp.

Nieminen, T., Mononen, J., Sampo, M., 1994. Unmanned tractorsfor agricultural application. In: Proceedings of the XII CIGRWorld Congress and AgEng’94 Conference on AgriculturalEngineering, vol. 29.8.–1.9., Milan, Italy, 11 pp.

Nissen, B., 1999. Vorhersage der mechanischen Belastbarkeit vonrepräsentativen Ackerböden der Bundesrepublik Deutschland—bodenphysikalischer Ansatz. Schriftenreihe des Institutes fürPflanzenernährung und Bodenkunde der Universität Kiel, vol.50, 159 pp.

Nissen, B., Horn, R., 1996. Bodenmechanische Untersuchungenzur Vorhersage der Bodenfestigkeit. Abschlussbericht DVWK,Materialiensammlung.

Olsen, H.J., 1994. Calculation of subsoil stresses. Soil Till. Res.29, 111–123.

O’Sullivan, M.F.O., Robertson, E.A.G., 1996. Critical stateparameters from intact samples of two agricultural topsoils.Soil Till. Res. 39, 161–173.

O’Sullivan, M.F., Henshall, J.K., Dickson, J.W., 1999. A simplifiedmethod for estimating soil compaction. Soil Till. Res. 49, 325–335.

Paul, C.L., DeVries, J., 1979. Effect of soil water status andstrength on trafficability. Can. J. Soil Sci. 59, 313–324.

Perdok, U.D., Tijink, F.G.J., 1990. Developments in IMAGresearch on mechanization in soil tillage and field traffic. SoilTill. Res. 16, 121–141.

Petelkau, H., 1984. Auswirkungen von Schadverdichtungen aufBodeneigenschaften und Pflanzenertrag sowie Massnahmen zuihrer Minderung. Tag.-Ber. Akad. Landwirtsch.—Wiss. DDR,Berlin, Tagungsbe., vol. 227, pp. 25–34.

Plackett, C.W., 1984. The ground pressure of some agriculturaltyres at low load and with zero sinkage. J. Agric. Eng. Res.29, 159–166.

Pollard, F., Webster, R., 1978. The persistence of the effects ofsimulated tractor wheeling on sandy loam subsoil. J. Agric.Eng. Res. 28, 217–220.

Poodt, M.P., Koolen, A.J., van der Linden, J.P., 2003. FEM analysisof subsoil reaction on heavy wheel loads with emphasis onsoil preconsolidation stress and cohesion. Soil Till. Res. 73,67–76.

Renius, K.Th., 1994. Trends in tractor design with particularreference to Europe. J. Agric. Eng. Res. 57, 3–22.

Rüdiger, A., 1989. Beitrag zur quantitativen Bewertung derBodenbelastung durch Radfahrwerke. Dissertation. RechnicalUniversity of Dresden, Germany, 94 pp.

Rusanov, V.A., 1991. Effects of wheel and track traffic on the soiland crop growth and yield. Soil Till. Res. 19, 131–143.

Rusanov, V.A., 1994. USSR standards for agricultural mobilemachinery: permissible influences on soils and methods toestimate contact pressure and stress at a depth of 0.5 m. SoilTill. Res. 29, 249–252.

Salire, E.V., Hammel, J.E., Hardcastle, J.H., 1994. Compressionof intact subsoils under short-duration loading. Soil Till. Res.31, 235–248.


Schjønning, P., Rasmussen, K., 1994. Danish experiments onsubsoil compaction by vehicles with high axle load. Soil Till.Res. 29, 215–227.

Smith, D.L.O., 1985. Compaction by wheels: a numerical modelfor agricultural soils. J. Soil Sci. 36, 621–632.

Soane, B.D., Blackwell, P.S., Dickson, J.W., Painter, D.J., 1981.Compaction by agricultural vehicles: a review. II. Compactionunder tyres and other running gear. Soil Till. Res. 1, 373–400.

Söhne, W., 1953. Druckverteilung im Boden und Bodenverformungunter Schlepper Reifen. Grundlagen Landtechnik 5, 49–63.

Söhne, W., 1958. Fundamentals of pressure distribution andsoil compaction under tractor tires. Agric. Eng. 39, 276–281,290.

Sommer, C., 2000. Management of the arable layer to avoid subsoilcompaction. In: Proceedings of the Third Workshop of theConcerted Action on Subsoil Compaction, Uppsala, Sweden,June 14–16, 2000. Report 100. Department of Soil Sciences,Swedish University of Agricultural Sciences, Uppsala, Sweden,pp. 173–177.

Sommer, C., Altemüller, H.J., 1982. Direkt- und Nachwirkungenstarker verdichtungen auf das Bodengefüge und den Pflanze-nertrag. Mitteilungen Deutsche Bodenkundliche Gesellschaft34, 187–192.

Sommer, C., Zach, M., 1992. Managing traffic induced soilcompaction by using conservation tillage. Soil Till. Res. 24,319–336.

Tijink, F.G.J., 1994. Quantification of vehicle running gear. In:Soane, B.D., Van Ouwerkerk, C. (Eds.), Soil Compaction inCrop Production. Developments in Agricultural Engineering,vol. 11. Elsevier, The Netherlands, pp. 391–416.

Tijink, F.G.J., Döll, H., Vermeulen, G.D., 1995. Technical andeconomical feasibility of low ground pressure running gear.Soil Till. Res. 35, 99–110.

USSR State Committee for Standards, 1986. Standard 26955:Agricultural mobile machinery; rates of force produced by

propelling agents on soil. USSR State Committee for Standards,Moscow, Russia.

van der Linden, J.P., Vandergeten, J.-P., 1999. Aandachtvoor rooiwerk bespaart tot 200 gulden per hectare. Eenterugblik op de rooidemonstratie in het Belgische Watervliet.CSM-informatie No. 521, December 1999, pp. 10–12.

Voorhees, W.B., Lindstrom, M.J., 1983. Soil compactionconstraints on conservation tillage in the northern corn belt. J.Soil Water Conserv. 38, 307–311.

Weisskopf, P., Zihlmann, U., Diserens, E., Anken, T., 1998.Zuckerrübenernter und Bodenverdichtung—nicht nur eine Fragedes Maschinengewichtes!. Schweizer Landtechnik 10/97, 16–20.

Weisskopf, P., Zihlmann, U., Wiermann, C., Horn, R., Anken,T., Diserens, E., 2000. Influences of conventional andonland-ploughing on soil structure. In: Horn, R., Van den Akker,J.J.H., Arvidsson, J. (Eds.), Subsoil Compaction: Distribution,Processes and Consequences. Advances in GeoEcology 32.Catena Verlag, Reiskirchen, Germany, pp. 73–81.

Wiermann, C., Werner, D., Horn, R., Rostek, J., Werner, B., 2000.Stress/strain processes in a structured unsaturated silty loamLuvisol under different tillage treatments in Germany. Soil Till.Res. 53, 117–128.

Wilde, T., 1998. Rübenernte. Wirkungen der Gross Maschine aufden Boden. Landtechnik 53, 72–73.

Wolf, D., Hadas, A., 1984. Soil compaction effects on cottonemergence. Trans. Am. Soc. Agric. Eng. 27, 655–659.

Wong, J.Y., 1986. Computer aided analysis of the effects ofdesign parameters on the performance of tracked vehicles. J.Terramech. 23, 95–124.

Wong, J.Y., Preston-Thomas, J., 1984. A comparison betweena conventional method and an improved method forpredicting tracked vehicle performance. In: Proceedings ofthe Eighth International Conference on International Societyof Terrain-Vehicles Systems, August 5–11, Cambridge, UK,pp. 361–380.

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