splll1sTIJRf ~. Soil aeration (above) not only reduces compaction but also helps turf stand up to stress, including heavy use. Hollow tines or spoons remove a "core" of soil (below) that is deposited on the soil surface and becomes topdressing over the turf. Shallow aeration equipment (left) may use solid spikes that punch holes in the soil, creating openings without removing soil. Aeration Strategies to Reduce Compaction By Dr. Gil Landry C ompaction is one of turfs hidden enemies. As soil particles are pushed closer together, pore space diminishes, increasing soil density. Air, water and nutrient movement are decreased by the lack of pore space. Percolation and infiltration are reduced. Turf roots struggle in the restrictive soil environment. Compaction reduces turf quality and athletic-field playing conditions. Top growth slows, resulting in less cush- ioning for players. Weeds like goosegrass and annual bluegrass become a problem. The compacted soil itself forms a hard- er surface due to the increased density of soil particles. Soil aeration is an important tool in a turf-maintenance program. It not only reduces compaction, but also helps turf stand up to stress, including heavy use. Aeration opens channels in the soil through which air, water and nutrients can move more freely. Percolation and 24 sports TURF infiltration are improved. Deep rooting is encouraged. Aeration also "softens" hard soil by increasing pore space, enabling the soil to "give" in response to impact, an excellent benefit for sports turf fields. The most effective aeration strategies meet the needs of the turf without dis- rupting its aesthetic appeal or the field- use requirements. Assess Current Conditions Unlike soil pH or fertility, soil com- paction is not easy to quantify. Inspect turf for such signs of stress as thinning, lack of vigor or fading color. Note sections that react most quickly to high tem- peratures or lack of moisture. Check spots where turf shows weed invasion, insect or disease damage or less response to fertilization. Look for factors other than com- paction that can contribute to turf stress. Such situations might include high spots that receive inadequate moisture and dry out quickly, low spots where drainage is poor and excess moisture puddles, areas of heavy thatch buildup, or sections with buried rocks or debris. Where no other contributing factors are discovered, compare stressed turf with areas of thriving turf. Are the grass varieties and soil types the same? Do both areas receive the same maintenance, including fertilization and irrigation? Compare turf-use patterns. Sections subjected to the most activity will be the most susceptible to compaction - for example, between the hash marks on a football field or the goal mouths of a soccer field. Degree and Depth of Compaction Use a soil probe, shovel or pentame- ter to check the degree and depth of compaction. Soil should be moist during this process. The greater the degree of compaction at a specific point, the more difficult it will be to sink the probe into the soil. Foot traffic and sports activity normally will cause the greatest compaction in the top two or three inches of soil. Con-
Transcript
splll1sTIJRf ~.
Soil aeration (above) not only reduces compaction butalso helps turf stand up to stress, including heavy use.Hollow tines or spoons remove a "core" of soil (below)that is deposited on the soil surface and becomestopdressing over the turf. Shallow aeration equipment(left) may use solid spikes that punch holes in the soil,creating openings without removing soil.
Aeration Strategiesto Reduce
CompactionBy Dr. Gil Landry
Compaction is one of turfs hiddenenemies. As soil particles arepushed closer together, pore
space diminishes, increasing soil density.Air, water and nutrient movement aredecreased by the lack of pore space.Percolation and infiltration are reduced.Turf roots struggle in the restrictivesoil environment.
Compaction reduces turf quality andathletic-field playing conditions. Topgrowth slows, resulting in less cush-ioning for players. Weeds like goosegrassand annual bluegrass become a problem.The compacted soil itself forms a hard-er surface due to the increased densityof soil particles.
Soil aeration is an important tool ina turf-maintenance program. It not onlyreduces compaction, but also helps turfstand up to stress, including heavy use.Aeration opens channels in the soilthrough which air, water and nutrientscan move more freely. Percolation and
24 sports TURF
infiltration are improved. Deep rootingis encouraged. Aeration also "softens" hardsoil by increasing pore space, enablingthe soil to "give" in response to impact,an excellent benefit for sports turf fields.The most effective aeration strategiesmeet the needs of the turf without dis-rupting its aesthetic appeal or the field-use requirements.
Assess Current ConditionsUnlike soil pH or fertility, soil com-
paction is not easy to quantify. Inspectturf for such signs of stress as thinning,lack of vigor or fading color. Note sectionsthat react most quickly to high tem-peratures or lack of moisture. Checkspots where turf shows weed invasion,insect or disease damage or less responseto fertilization.
Look for factors other than com-paction that can contribute to turf stress.Such situations might include high spotsthat receive inadequate moisture and dryout quickly, low spots where drainage ispoor and excess moisture puddles, areas
of heavy thatch buildup, or sectionswith buried rocks or debris.
Where no other contributing factorsare discovered, compare stressed turf withareas of thriving turf. Are the grassvarieties and soil types the same? Do bothareas receive the same maintenance,including fertilization and irrigation?
Compare turf-use patterns. Sectionssubjected to the most activity will be themost susceptible to compaction - forexample, between the hash marks on afootball field or the goal mouths of asoccer field.
Degree and Depth of CompactionUse a soil probe, shovel or pentame-
ter to check the degree and depth ofcompaction. Soil should be moist duringthis process. The greater the degree ofcompaction at a specific point, the moredifficult it will be to sink the probe intothe soil.
Foot traffic and sports activity normallywill cause the greatest compaction in thetop two or three inches of soil. Con-
struction equipment or frequent trafficby maintenance equipment can causedeeper compaction. Core aeration, repeat-ed to the same depth, may cause a layerof compaction at the penetration depth.
Examine the core of soil removed forchanges in texture or color. Clay soils andother fine-textured silt soils are more eas-ily compacted than those with a highersand content.
Different soil textures and/or colorswithin the soil-probe sample could sig-nal a layering condition. When layeringoccurs, soil moisture movement, airmovement and rooting may be disrupt-ed. Aeration and topdressing can help alle-viate this condition.
Check turf root growth. Shallow rootsor poor root development can indicate thedepth of compaction or a change in soiltexture.
Cultivation may not be the answer.Improved drainage or soil modificationmay be necessary, or perhaps bettertraffic and irrigation control are sufficient.In most cases, a combination of cultivationand these practices will be needed.
Explore Aeration Options
Shallow aeration is provided by equip-ment that reaches into the top three orfour inches of soil. Deep aeration is pro-vided by equipment that reaches deep-er than four inches.
Shallow aeration equipment may usesolid spikes or hollow tines or spoons. Solidspikes punch holes in the soil, creatingopenings without removing soil. Hollowtines or spoons remove a "core" of soil thatis deposited on the soil surface and thenbecomes topdressing over the turf. Deepaeration equipment may move the soilwith a vibrating or lifting action, or it mayspike or slice into the soil with littlemovement.
Any tool used to penetrate the soil willcause some compaction. The questionshould be whether it relieves more com-paction than it causes. Hollow tines orspoons that remove soil cause less com-paction around and below the tine thando solid tines. Also, cultivating withdifferent types of equipment and to dif-ferent depths should minimize com-paction from cultivation. Normal coringwill not increase weed problems after apre emergence herbicide is applied.
Another consideration is the depth towhich the aeration method is effective.
Obviously, even in shallow aeration,the procedure must work deeply enoughin the soil to reach the level of com-paction. With deep compaction a hard-pan layer can form, stopping the move-ment of air, water and nutrients belowthat depth. Though temporary reliefcan be achieved with frequent, shallowaeration, eventually that hardpan bar-rier must be penetrated for proper turfgrowth. With subsurface aeration, deter-mine whether loosening or vibration of
the soil will be needed, rather than pen-etration alone, to break the compactionbarrier effectively.
The greater the degree of change inexisting conditions, the greater andlonger lasting the effect. Core aerationis more effective than spike aerationand has longer-lasting benefits; deepshatter aeration has a greater andlonger-lasting effect than deep slicing orspiking, which causes little soil movement.
continued on page 26
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Soil Aerationcontinued from page 25
Consider the extent of the problem.How much effect is compaction havingon turf growth and recovery?
If turf on a field is severely thinnedor has worn away completely, players maybe exposed to potential injury. In that caseimmediate action, such as resodding,may be required. Ifdamage is minor, lessdisruptive practices can be used.
Match Method to Turf Conditions
No one cultivation option is right forall conditions or time periods. Matchingthe method to turf growth cycles, weath-er conditions and scheduled use willmean using different types of cultivationat different times during the year.Ideally, an annual deep cultivationshould be combined with a shallow aer-ation program to achieve the best results.
Turf use and aesthetics must be con-sidered. The more disruptive a procedureis, the longer the turf will take to recov-er. The heavy schedule of sports-field usedictates that procedures that causeextensive surface damage will be used
less frequently than procedures thatcause minimal surface damage.
The length of the positive effectsresulting from each alternative proceduremust be weighed. More damage can betolerated when the benefits of treat-ment are long lasting.
Procedures that bring soil to the sur-face must be scheduled when they willnot disrupt play. Turf takes time torecover from the disruption caused by coreaeration. Even when the cores aredragged back into the soil and any tuftsof thatch or grass are removed, the turfwill require' a recovery period. Grassroots need time to regenerate and spreaddeeper into the soil before top growth Winreflect the benefits of the process.
Shallow spiking will make less of animmediate impact on turf aestheticsand can be used when some relief ofcompaction is essential during heavy-useperiods. Spiking also is less disruptiveto turf growth and can be used more fre-quently than core aeration.
Increasing Aeration Effectiveness
Soil moisture levels are critical dur-
ing cultivation. Soil that is too dry is hardto penetrate, and procedures are less effec-tive. Soil that is too dry also puts morestress on cultivation equipment. If soilis too wet, there will be little movementin response to cultivation.
Aeration methods that loosen thesoil should be timed when moisture lev-els are slightly below field capacity,such as 24 hours after rainfall or irri-gation. Aeration methods that causelittle loosening, such as spoon-type tines,should be timed when moisture levels arenear field capacity.
Hot, dry weather and strong winds cancause the turf-bordering aeration holesto dry out. Avoid aeration during thoseperiods or arrange irrigation to com-pensate for moisture loss.
Inmost cases once holes are made, thelonger they remain open to the surface,the longer the effect lasts. Once a holeis sealed, even if only at the surface, thebenefits of air and water movement aresignificantly, if not totally, eliminated.Topdressing with a porous materialkeeps the holes open. If topdressing is notpractical, more frequent cultivation will
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be needed to overcome surface sealing.Timing shallow aeration to periods of
active turf growth will enable the turf torecover more quickly. Aeration in con-junction with oversee ding and fertil-ization will increase their effectiveness.
Since significant root growth occursat lower temperatures than leaf growth,fields that are heavily used going into win-ter probably should be core-aeratedafter use, unless winter desiccation is acommon problem. Core aeration willimprove the water/air relationships dur-ing this period and result in healthier turfthe following year.
To increase the effectiveness of aer-ation throughout the soil profile, use adeep-aeration procedure within twoweeks following shallow core aeration.
Consider Budget ConstraintsWith ever-tightening budgets, the
ideal aeration program may not be prac-tical. When lack of equipment, person-nel or funding limit aeration options, con-centrate resources where they willprovide the greatest benefits. For exam-ple, schedule a complete aeration program
for the football field only or for just thearea between the hash marks with lessfrequent aeration of the entire field andsurrounding grounds. Schedule regu-lar aeration of park -system playgroundareas and sports fields, and use aerationas required to avoid turf decline inlesser-used areas.
Develop a reciprocal relationshipwith other turf professionals, arrangingjoint purchases of equipment or swappingexisting equipment use. Though golfcourses, school systems, park systems,municipalities and large commercialproperties will have similar needs, dif-ferent timing of equipment use maymake such arrangements workable.
As with all sports turf maintenancepractices, constant monitoring is necessaryto evaluate the success of the programthroughout the year and from year to year.Because quantifying aeration resultsis difficult, detailed record-keeping willbe needed. Record the type and timingof aeration procedures. Since wet soilscompact more quickly than dry ones,note irrigation and rainfall in relation tofield use. Also keep records of daily tem-
perature ranges, the frequency of gamesand practices on each field and the timesthey take place, fertilization schedules,oversee ding and topdressing procedures,and any other pertinent activities.
Note the effect of procedures on turfhealth, including any reductions in irri-gation, fertilization, weed, insect anddisease control. Budgeting entities aremore willing to consider funding forequipment and procedures when they cansee documented results.
Be FlexibleDevelop a workable cultivation program
that meets field needs and your budget,but remember that even the best-preparedplans must be modified at times. Knowwhat options are available and be flexi-ble enough to adjust the plan to meetchanging conditions and turf needs. 0
As extension turfgrass specialist withthe University of Georgia, Dr. Gil Landryprovides leadership in the developmentof statewide educational programs inturfgrass management. He is immediatepast president of the STMA.
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