effects of soil compaction - penn state extension

Effects ofSoil Compaction

College of Agricultural SciencesAgricultural Research and Cooperative Extension

2 EFFECTS OF SOIL COMPACTION

Effects of SoilCompactionINTRODUCTION

Soil compaction is the reduction of soil volume due toexternal factors; this reduction lowers soil productivityand environmental quality. The threat of soil compac-tion is greater today than in the past because of thedramatic increase in the size of farm equipment(Figure 1). Therefore, producers must pay moreattention to soil compaction than they have in the past.In this fact sheet we will discuss the effects of soilcompaction and briefly identify ways to avoid oralleviate it.

Figure 1. Tractor weight incresed dramatically since the 1950s.Soane, B. D. and C. Van Ouwerkerk. 1998. “Soil compaction: A globalthreat to sustainable land use.” Advances in GeoEcology 31:517–525.

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EFFECTS OF SOIL COMPACTION 3

EFFECTS OF COMPACTIONON CROP YIELDS

Soil Compaction Effects on ForagesThe effect of traffic on alfalfa and grass sod is a combi-nation of soil compaction and stand damage. In arecent study in Wisconsin and Iowa, annual alfalfayield losses up to 37 percent due to normal field trafficwere recorded. Based on this work, a multistate projectwas initiated to get a better understanding of yieldlosses due to traffic in alfalfa. Yield losses ranged from1 to 34 percent (Figure 2). The damage to alfalfa standsis much greater 5 days after cutting than 2 days aftercutting, showing the importance of timeliness inremoving silage or hay from the field.

Figure 2. Yield losses due to traffic in alfalfa 2 and 5 days aftercutting. One-hundred percent of the plots were wheeled sixtimes with a 100-hp tractor.Undersander, D. 2003. Personal communication.

Figure 3. Relative crop yield on compacted soil compared tononcompacted soil with moldboard plowing. One-hundredpercent of fields in multiple locations in northern latitudes werewheeled four times with 10-ton axle load, 40-psi inflated tires.Hakansson, I. and R. C. Reeder. 1994. “Subsoil compaction by vehicleswith high axle load—extent, persistence, and crop response.” Soil TillageResearch 29:277–304.

Soil Compaction Effects on Tilled SoilsTillage is often performed to remove ruts, and farmersassume that it takes care of soil compaction. Thus,farmers become careless and disregard soil moistureconditions for traffic and other important principles ofsoil compaction avoidance, assuming that they canalways correct the problem with tillage.

Distinguishing between topsoil and subsoilcompaction is important. Research has shown thattillage can alleviate effects of topsoil compaction onsandy soils in 1 year. However, on heavier soils moretillage passes and repeated freeze-dry cycles arerequired to alleviate effects of surface compaction.Therefore, the effects of topsoil compaction reduceyields on these soils despite tillage. Since most soils inPennsylvania contain significant amounts of clay intheir surface horizons, topsoil compaction is likely toreduce crop yields, even with tillage.

Subsoil compaction is below the depth of normaltillage operations. Research shows that subsoil com-paction is not alleviated by freeze-thaw and wetting-drying cycles on any soil type. In an internationalresearch effort that included tillage after compaction,average first-year yield losses were approximately 15percent, although results varied from year to year andfrom site to site (Figure 3). This first-year loss wasconsidered to be primarily the result of topsoil com-paction residual effects. Without recompaction, yieldlosses decreased to approximately 3 percent 10 yearsafter the compaction event. The final yield loss, whichwas most likely due to subsoil compaction, can beconsidered permanent. The effects of subsoil compac-tion are due to using high axle loads (10 tons andheavier) on wet soil and are observed in all types ofsoils (including sandy soils).

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Tillage can also cause the formation of a tillagepan. The most damaging form of tillage is moldboardplowing with one wheel (or horse) in the furrow,which causes direct subsoil compaction. On-landmoldboard plowing is certainly preferred over thispractice. However, even then the moldboard plow canstill cause compaction just below the plow. The disk isanother implement that can cause the formation ofsuch a pan. In our research in Pennsylvania, we alsoobserved the formation of plow pans on dairy farmsthat used the chisel plow (Figure 4, see next page).


More tillage operations and more power areneeded to prepare a seedbed in compacted soil. Thisleads to increased pulverization of the soil and ageneral deterioration of soil structure, which makesthe soil more sensitive to recompaction. Therefore,compaction can enforce a vicious tillage spiral thatdegrades soil (Figure 5) and results in increasedemissions of the greenhouse gases carbon dioxide,methane, and nitrous oxide due to increased fuelconsumption and slower water percolation. Ammonialosses also increase because of decreased infiltration incompacted soil. More runoff will cause increasederosion and nutrient and pesticide losses to surfacewaters. At the same time, reduced percolation throughthe soil profile restricts the potential for groundwaterrecharge from compacted soils. Thus, this viciouscompaction/tillage spiral is an environmental threatwith impacts beyond the individual field.

Soil Compaction Effects on No-Till CropProductionNo-till has a lot of advantages over tillage—reducedlabor requirements, reduced equipment costs, lessrunoff and erosion, increased drought resistance ofcrops, and higher organic matter content and biologi-cal activity. The higher organic matter content andbiological activity in no-till makes the soil moreresilient to soil compaction. One study illustrates thisvery well (Figure 6). Topsoil from long-term no-till andconventional till fields were subject to a standardcompaction treatment at different moisture contents.The “Proctor Density Test” is used to determine whatthe maximum compactability of soil is. The conven-tional till soil could be compacted to a maximumdensity of 1.65 g/cm3, which is considered rootlimiting for this soil. The no-till soil could only becompacted to 1.40 g/cm3, which is not considered root

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Figure 4. Penetration resistance on a PA dairy farm that used chisel/disking for field preparation.A pan was detected just below the depth of chisel plowing.


This being said, compaction can still have signifi-cant negative effects on the productivity of no-till soils.In our own research we observed a 30-bushel yielddecrease in the dry year of 2002 and a 20-bushel yieldloss in the wet year of 2003 (Figure 7). In research inKentucky, corn yield on extremely compacted no-tillsoil was only 2 percent of that in uncompacted soil inthe first year after compaction (Figure 8). Remarkably,the yields bounced back (without tillage) to 85 percentthe second year after compaction and stabilized atapproximately 93 percent after that. This shows theresilience of no-till soils due to biological factors, but italso shows that compaction can cause very significantshort- and long-term yield losses in no-till.

Figure 5. The dynamics of modern animal husbandry farms caneasily lead to a downward compaction-tillage spiral of soildegradation.

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Figure 6. The surface of long-term, no-till soil cannot becompacted to as great a density as conventionally tilled soil dueto higher organic matter contents.Thomas, G. W., G. R. Haszler, and R. L. Blevins. 1996. “The effects oforganic matter and tillage on maximum compactability of soils using theproctor test.” Soil Science 161:502–508.

Figure 7. Soil compaction can result in significant yield losses inno-till. One-hundred percent of the field was compacted with a30-ton manure truck with 100-psi inflated tires. (Penn StateTrial in Centre County.)

Figure 8. Corn yield reduction due to severe compaction in thetop 12 inches of a long-term no-till soil in Kentucky.Murdock, L. W. 2002. Personal communication.

More dairy cows on farm,more manure, bigger storage,greater time crunch…

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limiting. Thus, topsoil compaction would be less of aconcern in no-till fields. The increased firmness ofno-till soils makes them more accessible, and no-tillfields may become better drained over time.

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EFFECTS OF SOIL COMPACTION ONSOIL AND CROP HEALTH

In this section we will review the effects of soil com-paction on soil physical, chemical, and biologicalproperties, as well as on crop growth and health.

Soil DensityThe most direct effect of soil compaction is an increasein the bulk density of soil. Bulk density is the mass ofoven-dry soil in a standard volume of soil, often givenas grams per cubic centimeter (g/cm3). Optimum bulkdensities for soils depend on the soil texture (Table 1).Whenever the bulk density exceeds a certain level,root growth is restricted. A note of caution must bemade here in respect to the effects of tillage on bulkdensity. No-till soils often have a higher bulk densitythan recently tilled soils. However, because of higherorganic matter content in the topsoil and greaterbiological activity, the structure of a no-till soil may bemore favorable for root growth than that of a culti-vated soil, despite the higher bulk density.

recompaction. In one study, the total porosity andmacroporosity of a pasture was compared to that of aplow pan in arable soil. In one case, the plow pan hadnever been broken up with subsoiling, whereas in theother case the plow pan had been broken up, but thepan had reformed after years of normal field trafficand tillage. The results illustrate the reduction of largepores in the plow pan and the worst condition of therecompacted plow pan (Figure 9). A long-term no-tillsoil that has not been subjected to compaction wouldbe in a similar state as the pasture soil.

PorosityDue to the increase in bulk density, the porosity of soildecreases. Large pores (called macropores), essentialfor water and air movement in soil, are primarilyaffected by soil compaction. Research has suggestedthat most plant roots need more than 10 percent air-filled porosity to thrive. The number of days withadequate percentage of air-filled porosity will bereduced due to compaction, negatively affecting rootgrowth and function. It is important to note that tillingcompacted soils makes them more susceptible to

Table 1. Ideal and root-restricting bulk densities.

Bulk densityIdeal restricts

Soil texture bulk density root growth

g/cm3

Sand, loamy sand < 1.60 > 1.80

Sandy loam, loam < 1.40 > 1.80

Sandy clay loam, clay loam < 1.40 > 1.75

Silt, silt loam < 1.30 > 1.75

Silty clay loam < 1.40 > 1.65

Sandy clay, silty clay < 1.10 > 1.58

Clay < 1.10 > 1.47

USDA. 1999. Soil quality test kit guide. USDA Soil Quality Institute.Washington, D.C.

Penetration ResistanceRoot penetration is limited if roots encounter muchresistance. Research on completely disturbed soilpacked to different densities has shown that rootgrowth decreases linearly with penetration resistancestarting at 100 psi until root growth completely stopsat 300 psi (Figure 10). Penetration resistance is a betterindicator of the effects of soil compaction on root

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Figure 9. Total porosity and macroporosity were greatly reducedin an original and a subsoiled but subsequently recompactedplow pan compared to an uncompacted pastureAdapted from Kooistra, M. J., and O. H. Boersma. 1994. “Subsoilcompaction in Dutch marine sandy loams: Loosening practices andeffects.” Soil Tillage Research 29:237–247.

Figure 10. Relationship between penetration resistance and rootpenetration.Adapted from Taylor, H. M., G. M. Roberson, and J. J. Parker. 1966. “Soilstrength-root penetration relations for medium- to coarse-textured soilmaterials.” Soil Science 102:18–22.

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growth than bulk density because results can beinterpreted independent of soil texture. More informa-tion on penetration resistance can be found inAgronomy Facts 63, Diagnosing Soil Compaction Using aPenetrometer (soil compaction tester), available fromPenn State Cooperative Extension.

Soil StructureSoil compaction destroys soil structure and leads to amore massive soil structure with fewer natural voids(Figure 11). In a pasture soil (similar to a no-till soilthat has not been tilled for a long time), the soilstructure is very well developed due to effects ofincreased organic matter and the fine root systems ofgrasses. Even if exposed to rainfall, such a soil will notwash away because the aggregates are very stable andinfiltration is high. Pores can be seen below the topsoilbecause of the action of soil animals such as earth-worms and roots. In tilled soil with plow pan, how-ever, the structure of the topsoil is much weaker.Raindrops hitting the surface will quickly form a sealthat becomes a crust upon drying. Infiltration willdecrease rapidly on this soil. Below the depth of tillagea pan developed that is very dense, and below the

depth of plowing few pores created by soil animalsand decomposed roots are visible. Subsoiling the plowpan helps, but it does not improve soil structure(Figure 11). To improve soil structure, stimulating soilbiological activity by reducing tillage and increasingthe inputs of organic matter is necessary.

Soil BiotaSoil contains a tremendous number of organisms.They can be classified into micro- , meso- , andmacrofauna (small, medium, and large sized). Bacteriaand fungi are important microfauna in soil that live onorganic matter or on living plants. An acre of grass-land contains 0.5–1 ton of bacteria and 1–2 tons offungi biomass. The same soil contains approximately10 tons of living grass roots and 40 tons of “dead”organic matter. Most bacteria and fungi perform usefulfunctions such as the decomposition of plant residues,release of nutrients, and formation of aggregates.Some bacteria such as rhizobia provide nitrogen toplants. Some fungi live in symbiosis with plant roots,facilitating the uptake of immobile nutrients such asphosphorus and potassium. Only few bacteria andfungi have negative effects (e.g., plant diseases).

Figure 11. Soilcompaction damagessoil structure, andtillage does little toimprove it.Adapted from Kooistra,M. J., and O. H. Boersma.1994. “Subsoil compactionin Dutch marine sandyloams: Loosening practicesand effects.” Soil TillageResearch 29:237–247.

1. Strongly developed structure, crumb2. Weakly developed structure, crumb3. Soil material with many old root and earthworm channels4. Weakly developed structure, cloddy5. Plow pan, compacted, few root or earthworm channels6. Soil material with root channels7. Broken plow pan with some large air pockets8. Weakly developed structure

Plough-Deep Blade-type mounted

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Bacteria and fungi are at the bottom of the soil foodweb (Figure 12). They are fed upon by other organismssuch as protozoa, nematodes, and arthropods (somenematodes feed on plant roots), which are fed on bybigger soil animals. Having a greater diversity of soilorganisms helps keep the “bad” bugs under controlbecause predators may also be numerous.

Soil compaction affects the habitat of soil organismsby reducing pore size and changing the physical soilenvironment. The smallest organisms such as bacteriaand fungi can live in pores that are not easily com-pacted. Even protozoa are very small and are not likelyto be affected directly by compaction. Nematodes, onthe other hand, will most likely be reduced in numberby soil compaction because their pore space might bereduced. This could affect both the “bad” (root-feeding)and the “good” (fungal- and bacterial-feeding) nema-todes. Because compaction can reduce the population offungal- and bacterial-feeding nematodes, it is feasiblethat the bacterial population increases with compactionbecause there are fewer predators.

Another effect of compaction on soil biota isindirect. Due to slower percolation of water in com-pacted soil, prolonged periods of saturated conditionscan occur. Certain soil organisms then start to use

Figure 12. The soil food web. Courtesy USDA Natural Resources Conservation Service.

nitrate instead of oxygen, and denitrification occurs.Certain anaerobic bacteria release hydrogen sulfide(rotten egg–smell typical of swamps). This gas istoxic to many plants. In general, organic matterdecomposition will be slower in compacted soils, andless biological activity will occur.

Larger soil animals (meso- and macrofauna) arealso affected by soil compaction. Nonburrowinganimals such as mites, springtails, and fly larvae willhave an especially difficult time living in compactedsoil. Burrowing animals such as earthworms, termites,ants, and beetles can defend themselves better butwill still suffer negative effects. In a study in Australia,compaction of wet soil with a 10-ton axle loaddecreased total macrofauna numbers. Earthwormsdecreased from 166,000 to 8,000 per acre due to severecompaction (Table 2). Compaction of dry soil with6-ton axle load did not have a negative effect onmacrofauna. Earthworm tunnel creation was reducedin soils with high bulk density, indicating reducedearthworm activity (Figure 13).

Soil organisms are extremely important for soilproductivity and environmental functions, especiallyin no-till. Therefore, the reduction of biological activitydue to compaction is of great concern. Fortunately,

Animals

Organic MatterWaste, residue,and metabolitesfrom plants,animals andmicrobes

PlantsShoots androots

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FungiMycorrhizalfungiSaprophyticfungi

NematodesRoot-feeders

NematodesFungal- andbacterial-feeders

ProtozoaAmoebae, flagellates,and ciliates

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Figure 13. Soil compaction reduces earthworm tunneling.Rushton, S. P. 1986. “The effects of soil compaction on Lumbricus terrestrisand its possible implications for populations on land reclaimed fromopen-cast coal mining.” Pedologie 29:85–90.

Table 2. Effects of soil compaction on earthworm counts inAustralia (average of 5 years).

EarthwormsCompaction treatment (# per acre)

No compaction 166,000

Annual compaction of wet soil @ 10-ton axle load 8,000

Annual compaction of wet soil @ 6-ton axle load 20,000

Annual compaction of dry soil @ 6-ton axle load 220,000

Compaction only in first year 110,000

Deep tillage after compaction in first year 100,000

Adapted from Radford, B. J., A. C. Wilson-Rummenie, G. B. Simpson,K. L. Bell, and M. A. Ferguson. 2001. “Compacted soil affects soilmacrofauna populations in a semi-arid environment in centralQueensland.” Soil Biology & Biochemistry 33:1, 869–1, 872. Table 3. Effects of compaction on macropore volume, air

permeability, and infiltration rate in a grassland study.

Macropore Air InfiltrationCompaction volume permeability ratetreatment (ft3/ft3) (mm2) (inch/hr)

Uncompacted 0.119 55 1.06

Compacted 0.044 1 0.25

Douglas, J. T. and C. E. Crawford. 1993. “The responses of aryegrass sward to wheel traffic and applied nitrogen.” Grass ForageScience 48:91–100.

higher biological activity in no-till soils also helpsthem recover from compaction more quickly thantilled soils. To guarantee high soil productivity,however, avoiding soil compaction is necessary.

Water Infiltration and PercolationSoil compaction causes a decrease in large pores (calledmacropores), resulting in a much lower water infiltra-tion rate into soil, as well as a decrease in saturatedhydraulic conductivity. Saturated hydraulic conductiv-ity is the movement of water through soil when the soilis totally saturated with water. Unsaturated hydraulicconductivity is the movement of water in soil that is notsaturated. Unsaturated hydraulic conductivity some-

times increases due to compaction. Unsaturatedhydraulic conductivity is important when water has tomove to roots. Thus, compacted soils are sometimes notas drought sensitive as uncompacted soils—assumingthe root system is of equal size in both cases, which isusually not the case. Typically, the net effect of compac-tion is that crops become more easily damaged bydrought because of a small root system.

In an experiment on grassland, the macroporevolume of compacted soil was half that ofuncompacted soil (Table 3). The air permeability andinfiltration rate were reduced dramatically. Reducedaeration and increased runoff will be the result.

If a soil is tilled after compaction, the infiltrationrate will be high because the soil is cloddy and rough.Seedbed preparation to shatter clods includes severalpasses with a tractor over the field. This will decreasesurface roughness, but compacted soil that has beentilled has coarser aggregates than the same soil thatwas not compacted. So, the infiltration rate may still berather high in the compacted soil immediately aftertillage. The action of raindrops on the soil surface andsubsequent trips over the field destroy much of thisapparent advantage. This is visible in the field asstagnating water in wheel tracks (Figure 14, see nextpage). It is common for runoff and erosion to start inthese wheel tracks, especially if they run up and downthe slopes.

Root GrowthRoot growth in compacted soils is restricted becauseroots can develop a maximum pressure above whichthey are not able to expand in soils. As mentionedabove, the maximum penetration resistance (measuredwith a standard conepenetrometer) that roots canovercome is 300 psi. In many cases, cracks and fissureswill be available for roots to grow through, so a total


lack of root growth is not likely. Instead, roots willconcentrate in areas above or beside compacted zonesin the soil (Figure 15). Aside from the effect of penetra-tion resistance, roots also suffer from increased anaero-bic conditions in compacted soils. A reduction of rootgrowth will limit root functions such as crop anchor-ing and water and nutrient uptake. In addition, soilcompaction has been found to reduce nodulation ofleguminous crops such as soybean, which may limitnitrogen nutrition of these crops.

Figure 15. Roots occupy a larger soil volume in uncompactedsoil (left) than in compacted soil (right).Adapted from Keisling, T. C., J. T. Batchelor, and O. A. Porter. 1995.“Soybean root morphology in soils with and without tillage pans in thelower Mississippi River valley.” Journal of Plant Nutrition 18:373–384.

Figure 16. Nitrogren response curve of ryegrass on a clay loamsoil in Scotland in compacted and uncompacted soil. To achievethe same yield of 2 tons/acre more than twice the amount ofnitrogen had to be applied.Douglas, J. T., and C. E. Crawford. 1993. “The responses of a ryegrasssward to wheel traffic and applied nitrogen.” Grass Forage Science48:91–100.

Nutrient UptakeSoil compaction affects nutrient uptake. Nitrogen isaffected in a number of ways by compaction: (1)poorer internal drainage of the soil will cause moredentrification losses and less mineralization of organicnitrogen; (2) nitrate losses by leaching will decrease;(3) loss of organic nitrogen (in organic matter) andsurface-applied nitrogen fertilizer may increase; and(4) diffusion of nitrate and ammonium to the plantroots will be slower in compacted soils that are wet,but faster in those that are dry. In humid temperateclimates— as in Pennsylvania—soil compactionprimarily increases denitrification loss and reducesnitrogen mineralization. In one study on a loamy sandin a humid temperate climate, nitrogen mineralizationwas reduced 33 percent and the denitrification rateincreased 20 percent in a wet year. In a study withryegrass, the nitrogen rate had to be more thandoubled on the compacted soil to achieve the same drymatter yield (Figure 16). Thus, compaction results inless-efficient use of nitrogen and the need to applymore for the same yield potential.

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MANAGING SOIL COMPACTION

The primary aim of this fact sheet has been to revieweffects of soil compaction on soil properties and cropgrowth. Soil compaction increases soil density, reducesporosity (especially macroporosity), and leads toincreased penetration resistance and a degradation ofsoil structure. This degradation is enforced whentillage is used to break up compacted soils. Soil biotasuffers from compaction. For example, earthwormnumbers and activity will be reduced in compactedsoils; water infiltration and percolation are slower incompacted soils; root growth will be inhibited due tosoil compaction, leading to reduced uptake of immo-bile nutrients such as phosphorus and potassium; andincreased nitrogen losses can be expected because ofprolonged periods of saturated conditions in com-pacted soils. Thus, limiting soil compaction is neces-sary. Below are some tips to manage compaction. Moreinformation is available in the fact sheet Avoiding SoilCompaction, which is available from Penn State Coop-erative Extension.

• Avoid trafficking wet soil. Only wet soil can becompacted. Fields should not be trafficked if theyare at or wetter than the plastic limit. To check if soilis at the plastic limit, start by taking a handful ofsoil. If you can easily make a ball by kneading thissoil, conditions are suboptimal for field traffic.Artificial drainage can help increase the number oftrafficable days on poorly drained soil.

• Keep axle loads below 10 tons. Subsoil compactionis caused by axle load and is basically permanent.To avoid subsoil compaction, keep axle loads below10 tons per axle—preferably below 6 tons per axle.

• Decrease contact pressure by using flotation tires,doubles, or tracks. Topsoil compaction is caused byhigh contact pressure. To reduce contact pressure, aload needs to be spread out over a larger area. Thiscan be done by reducing inflation pressure. A rule ofthumb is that tire pressure is the same as contactpressure. Tires inflated to 100 psi such as truck roadtires should be kept out of the field. To be able tocarry a load at low inflation pressure, bigger ormultiple tires are needed, hence the need for flota-tion tires and doubles. Large-diameter tires also helpto increase the tire footprint. Tracks help to spreadthe load over a large area, but having multiple axlesunder the tracks is necessary to avoid high spikes ofpressure. Tracks have the advantage over doubles ofreducing contact pressure without increasing thearea of the field trafficked.

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Figure 17. Phosphorus uptake and concentration in grain andstraw are decreased due to soil compaction.Lipiec, J., and W. Stepniewski. 1995. “Effects of soil compaction and tillagesystems on uptake and losses of nutrients.” Soil Tillage Research 35:37–52.

Compaction strongly affects phosphorus uptakebecause phosphorus is very immobile in soil. Exten-sive root systems are necessary to enable phosphorusuptake. Because compaction reduces root growth,phosphorus uptake is inhibited in compacted soil(Figure 17). Potassium uptake will be affected in muchthe same way as phosphorus.


Prepared by Sjoerd W. Duiker, assistant professor of soil management.

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CAT UC188 3M8/04ps4669

• Decrease trafficked area by increasing swath andvehicle width or by decreasing number of trips.Reduce the area of a field that is subject to traffic byincreasing swath width of manure spreaders or thespacing between wheels so individual wheel tracksare more widely spaced. Using larger equipmentand no-tillage can reduce the number of trips acrossthe field. A very promising approach is to usepermanent traffic lanes and never traffic the areabetween the lanes with heavy equipment. Thedisadvantage of such an approach is the need toadjust wheel spacing on all heavy equipment.

• Increase soil organic matter content and soil life.Soil that has high organic matter content and thriveswith soil organisms is more resistant to compactionand can better recuperate from slight compactiondamage. To increase organic matter content, returncrop residue to the soil, grow cover crops in the offseason, and use compost and manure. Manage formaximum productivity to optimize organic matterinput in the soil. Reduce losses of organic matter bypreventing soil erosion and using no-tillage. Thesepractices will also help increase biological activityin soil.

• Use tillage sparingly. Soil tillage should be usedsparingly to alleviate compaction when no othermeans can be used. Growers should avoid falling intothe vicious compaction/tillage spiral as explainedearlier. If any tillage is done, try to leave as much cropresidue as possible at the soil surface to protectagainst erosion and to use as a food source for certainsoil organisms such as earthworms. Noninversiontillage is preferable. If possible, perform tillage onlyin the seed zone. There are two different schools ofthought regarding the usefulness of shattering belowthe soil surface. One school of thought is that maxi-mum shattering is desirable to provide maximumchannels for water infiltration, aeration, and rootpenetration. The disadvantage of this approach is thatthe soil is more susceptible to compaction aftertillage, hence the need to limit traffic after the tillageoperation. The second school of thought promotescreation of widely spaced slots for root penetration,water infiltration, and air exchange in an otherwisefirm soil matrix. The firm soil between the slots willprovide support for field traffic, and the slots willstay intact. However, a smaller soil volume will beavailable for root exploration in this approach asopposed to that of the former. The depth of a compactlayer should dictate the depth of tillage. Tillage depthshould be set an inch or two below a compacted pan,if this is present. If a compacted pan is not present,there is no reason to perform deep tillage.

effects of soil compaction - penn state extension

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