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Turf Care
Soil Compaction
What is Topdressing?
Topdressing Sports Fields: The 3 "W's"
Topdressing with Compost
There is a lot to know about "growing grass."
There is a great deal of helpful information on turfgrass science
and management practices available on the internet.
Of particular interest will be academic sites, which tend to be impartial,
and report results based on solid research. Below is some basic information,
some quite simple, some very detailed. We hope you find something
helpful here.
What is Soil Compaction?
Soil compaction is the process of increasing the density of soil by
packing the particles closer together and reducing the volume of air.
Soil is a mixture of sand, silt and clay surrounded by air-filled
pores and water-filled pores. Ideally, 25% of soil volume should be
solid matter, 25% water, and 50% should be pore space. Compaction
alters the balance of air pores, water pores, and soil particles.
It squeezes the air out of the upper root zone. It destroys the channels
for air and water movement. It leaves no room for:
- Air exchange
- Water absorption
- Fertilizer absorption
- Drainage
Turf roots need water, oxygen, nitrates, phosphorous and potassium
to grow. Soil compaction literally shuts out those nutrients.
What causes soil compaction?
Traffic of all kinds:
- Pedestrian
- Golf carts
- Events held on sports fields
- Mowers and other machinery
- Athletic play
- Flooding
Why should turf professionals worry about it?
Turf - its beauty and its health - suffer when pore space decreases
by even 10%. Soil compaction is a major cause of turf deterioration.
Turf will grow slowly and will grow short. Eventually, it will become
thin, allowing weeds, algae and moss to grow. Unhealthy turf means
less play time and more repair time.
Soil compaction stresses turf grass plants, making them vulnerable
to weed competition and slow to recuperate from injury.
In addition, compacted soil contributes to the accumulation of thatch
because restricted oxygen levels impair the activity of earthworms
and other thatch-decomposing organisms. Left unmanaged, thatch can
lead to serious maintenance and pest problems. Thatch accumulates
faster on compacted soils.
How do you diagnose soil compaction?
Soil compaction is usually easy to spot:
- Areas of heavy traffic or continual play
- Puddles of water remain on level ground
- Water runs off slopes
- Uneven turf growth
- Little or no root growth
- Ground resists spade, shovel or penetrometer
How do you treat soil compaction?
Aeration is usually the easiest and fastest treatment. Until the soil
can breathe, the turf will not grow beautifully or vigorously.
Please note that increased amounts of fertilizer will not fully compensate
for restricted root growth. If the fertilizer can't get to the roots,
putting on more will only waste time and money.
What is aeration?
Aeration is the process of creating more pore space under the turf.
Aeration mechanically removes cores of soil to improve the flow of
air, water and nutrients in dense soil. Once aerated, the soil exchanges
air, water and nutrients with turf roots. Thus, the roots grow deeper
and the turf is healthy, lush and drought-resistant.
Aeration is beneficial to turf because it:
- Loosens the soil
- Increases drought resistance
- Enhances water and fertilizer uptake
- Reduces puddling and water runoff
- Decomposes thatch particles
- Enhances the activity of thatch-decomposing organisms
- Improves germination of reseeded and overseeded turf
In addition, aeration in drier climates can help reduce the effects
of drought and reduce the amount of watering needed to keep turf healthy.
Millcreek Aerators are basic equipment for core aeration of turf,
and can loosen compacted soil in the top three inches of the root
zone, depending on soil conditions and the amount of weight applied
to the Aerator.
Millcreek Aerators
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What is Topdressing; Why is it Done?
To topdress means to spread a layer of sand or sand plus organic
material over the turf surface. The material is then redistributed
by dragging a mat or section of chain link fence to move the sand
from the high spots to the low spots.
Topdressing evens the surface of the field, helps prevent thatch build
up by providing a more favorable environment for microorganisms, and
prolongs the effects of aeration by physically preventing hole closure.
Topdressing is done routinely on golf greens and is used on sports
fields and other fine turf when soil compaction or thatch problems
develop.
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Topdressing Sports Fields: The Three W's
Dr. John N. Rogers,
III
Department of Crop and Soil Sciences
Michigan State University
Players, coaches and fans all appreciate athletic fields that
look good and play well. Most realize the practices of mowing, irrigation,
and fertilization are responsible for keeping these fields in playing
condition. Maybe a few would even know core cultivation is an important
practice. What about the practice of topdressing? It is likely this
would be very foreign to most people. Yet, it is just as vital as
the four practices listed above.
Failure to topdress will lead to an uneven, unsafe playing surface
very quickly. Timing of topdressing is essential. Apply topdressing
at the wrong time, and you can be the proud owner of a skating rink;
too bad it is supposed to be a football field. Use of the wrong material
may convert your field to either a parking lot or a quagmire (or a
combination of both) for years to come.
Topdressing is a science whose importance cannot be overstated, and
is a valuable tool to the knowledgeable professional. The logical
question for implementing or strengthening your topdressing program
now is Why, When, and What? The Three W's.
Why Topdress?
We topdress turfgrass to improve both agronomic and playing conditions.
The term is self-describing, in that material is applied to the turfgrass
surface from above. This is currently the only way to apply material
and minimize disruption to your field. There are five major reasons
to topdress. Each topdressing application can address one or all of
the following reasons.
1. Smooth the playing surface
A smooth playing surface is critical and unquestionable for ball and
player performance. However, this same topdressing is used to provide
an uninterrupted slope for surface drainage. If this surface drainage
is disrupted, then the formation of duck ponds is imminent.
2. Modify the thatch layer
Thatch is our friend, but too much can be our enemy. We do not see
thatch on high traffic portions of our sports fields, but there can
be excessive thatch accumulation on low use areas. Topdressing modifies
the thatch layer, maintaining adequate soil macroporosity and providing
a better growing environment for the plant by aiding the microbial
community for thatch decomposition.
3. Change the soil texture
If the soil of your sports field is unsuitable and a wholesale change
is not possible, a gradual change could be the answer. This is accomplished
through core cultivation and harvesting to remove unwanted soil and
subsequent topdressing to incorporate back favorable material. Over
time, soil texture changes, and surface and soil conditions improve.
4. Provide resilient surface
Topdressing a new material can change the surface characteristics
and provide a more resilient surface that retains macroporosity. This
objective often plays hand-in-hand with modifying soil texture, however
it can be a single objective after efforts to change soil texture
through core cultivation techniques are complete.
5. Provide favorable environment for germination
Sports turf managers know one thing: they lose grass to activities
on the fields they manage and they must overseed. Topdressing provides
a favorable environment for germination by enhancing seed to soil
contact and reducing soil water evaporation.
When to Topdress?
Simply stated, the best time to topdress sports fields is during periods
of active growth and little, or no, play. This may be impractical,
but it is the ideal to strive toward. In order for topdressing to
be effective, it must be at the soil/plant interface.
Following topdressing, there is a time period where the particles
are migrating to this interface. The speed in which they can migrate
is critical. Irrigation will help in this process, but the best aid
is simply actively growing grass. Therefore, the best time to work
topdressing into the profile is the spring and summer for both cool
and warm season grasses.
We can learn a little from the golf course regarding topdressing and
timing.
Putting greens are topdressed, but typically only during periods of
active growth. The amount applied matches the growth of the grass
and is done to minimize disruption to the putting surface because
golf courses receive their heaviest traffic during the growing season.
We can take this approach as well, but our amounts in the spring and
summer can be greater if there is low play. The higher cutting heights
(as compared to a putting green) will also lend themselves to greater
amounts of topdressing.
Topdressings during periods of heavy traffic, i.e. during the season,
should be done with caution. Fall topdressings during the season should
be done early and with caution, if at all. If there is low growth,
then it will be difficult for the material to migrate and the topdressing
will be unstable, thus creating footing problems on the field.
Another issue is the abrasiveness of the material. Topdressing material
(like sand) damage leaf tissues. During active growth times this abrasion
is not an issue. However, during low growth periods the plant cannot
recover as quickly and this abrasion can accelerate deterioration
of the turfgrass plant.
In summary, remember timing is everything! Plan topdressings around
periods of active growth and low play. This may mean topdressing in
the spring and then late fall after the season.
Cool season grasses should be topdressed heavily (6-16 mm) once per
year in combination with core cultivation in late spring after spring
football and soccer. This will provide topdressing to smooth the surface,
modify thatch, and help with surface resiliency. If there are no games
until late summer, the heavy topdressing will have time to migrate
and not affect play.
What to Topdress?
The choice of topdressing materials is extremely important, with the
range of materials available wide and varying. There are a couple
of rules of soil physics to keep in mind. These center around soil
macropore space.
If your macropore space is the same throughout the root zone then
drainage will proceed at the rate allowed by the size of the macropores.
If the pore space of the top layer is finer than the pore space of
the soil below, then water will not flow until the top layer becomes
very wet.
This has caused many problems on fields over the years, particularly
with poor choices of turfgrass sod and/or topdressing. The key is
to remember to topdress with a material that is at least equal to
or coarser than the root zone material or the material at the surface.
This will ensure that the macropore space on top is greater and water
will drain at the rate of the root zone profile.
There are numerous materials from which to choose, both organic and
inorganic. The potential for success with these materials can be just
as great as the potential for disaster.
Never use a topdressing product without a thorough understanding and
testing of the particle size of the material. Sand is a good example.
It is a long-time excellent choice for topdressing, as it is readily
available and relatively inexpensive. However, you must perform a
particle size analysis for the material, and never assume that a named
sand will always be suitable for your needs. Numbers and names of
sands can have tremendous variation, as their original purpose was
usually for road building or construction, not sports fields.
Several products on the market today have proven themselves as very
effective topdressing materials. These are heat-treated materials
like calcined clay, diatomaceous earth, and porous ceramics. One key
to porous ceramics is the particle size of the product. The product
helps to maintain adequate macroporosity in the soil profile.
Another inorganic product used is crumb rubber from used tires. Although
expensive in comparison to sand, one benefit is its lack of abrasiveness
on leaf tissue. This can be an advantage during periods of low growth.
Again, you must monitor product particle sizes to prevent any soil
layering problems.
Conclusion
Topdressing is as essential to quality sports fields as any other
cultural practice, and must be included as part of the management
plan. Applications should revolve around periods of low play and good
growing conditions. Materials should be chosen with an understanding
of the particle size and its relation with the existing root zone.
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Considering Using a Compost Topdressing Application On Your Fairways
This Fall?
By Mike Boehm and Joe Rimelspach
The Ohio State University
Department of Plant Pathology
OTF TurfNews * Vol 63 * No. 5 * 2001
Overview of the Composting Process
Although there are several different types of composting processes,
most of the compost used by the turf grass industry is produced via
a process in which fresh organic matter such as yard wastes, de-watered
sewage sludge or poultry manure is either piled, stacked or otherwise
arranged to facilitate it decomposition by microorganisms such as
bacteria, actinomycetes (a unique type of bacteria) and fungi.
As these microbes degrade the organic material, they generate a great
deal of heat which inactivates or kills weed seeds, plant, animal
and human pathogens and many beneficial microbes such as nitrogen
fixing bacteria and biological control organisms. As these microbes
use the freely available carbon and nitrogen sources, their metabolism
and subsequently, the composting process slows resulting in a cooling
of the pile.
As the compost cools, other microorganisms, some wind-borne and yet
others rain-borne, are introduced into and colonize the pile. This
final phase of the composting process is referred to as the curing
stage. It is during the curing stage that microbes capable of suppressing
plant pathogens such as those that cause Pythium root rot, proliferate.
The type of composting system used (i.e. windrow versus static pile
versus in vessel) and the characteristics of the parent organic material
being composted are two major factors which influence both the rate
of the composting process and the quality and consistency of the finished
product.
For example, grass clippings degrade much more rapidly than tree bark
or wood chips. Once adequately cured, the compost is typically screened
to 1/4 to 1/2 inch and used as a topdressing material. Although numerous
methods of assessing whether a composted material has been adequately
cured or is "mature" enough for use in plant production,
no single method provides all the answers and quite often one must
rely upon a collection of such assays stressing the need for the development
of practical standards and guidelines and future work in this area.
Step 1: Goal Setting
Deciding to use compost topdressings on your fairways is no different
than implementing other turf health or pest management practices.
Although the reasons for using compost topdressings are many, often
times the decision revolves around one of the following:
1) Compost topdressings are perceived to be an environmentally sound
practice;
2) Composts may serve as an excellent source of plant-available nutrients;
3) Composts have been shown to provide valued sources of organic matter
and may improve soil fertility; and,
4) Some composts have been reported as being able to suppress turf
diseases such as dollar spot and Pythium root rot.
Knowing one's rationale for implementing compost topdressings is critically
important because it will not only allow you to make informed decisions
as to product selection and application and timing strategies, but
may ultimately allow you to determine how best to modify your existing
management practices to maximize overall turf quality and vigor.
Compost
The use of composts to improve turfgrass health or soil tilth is not
a new concept. Indeed, one might consider it a "lost art"
as compost applications were common until the advent of the agro-chemical
revolution of the 1940's and 50's.
After nearly 60 years of heavy reliance on chemical inputs, we find
ourselves in the midst of a resurgence in the use of organic matter
amendments and topdressings. The specific aims of this article are
to present an overview of the composting process and to provide a
four step approach for implementing the use of compost topdressings
based on our experiences and the experiences of those superintendents
with whom we have worked.
Step 2: Product Selection
Once you have figured out your goals for implementing a compost topdressing
program, the next step is selecting the right compost for the job.
This might be a case of "easier said than done" as one of
the major historical reasons for a reduced reliance on the use of
composts early in the 20th century in part revolved around the reality
that not all composts are created equal.
In other words, composts can and typically do vary tremendously in
their chemical, physical and microbiological characteristics. Such
variation typically exists even though our knowledge and understanding
of the complex nature of the composting process and the parameters
which influence this process are perhaps better understood and controlled
now than ever before.
As a potential user of composts, it is important to realize that some
composts vary more than others and that variability in the parent
organic material being composted typically corresponds to inconsistencies
in the final product.
As mentioned previously and underscored here, the composting process
used and the consistency and chemical characteristics of the organic
material being composted are two key factors that greatly influence
the consistency and quality of the final composted product.
Additional factors such as the type of bulking agent (materials such
as wood chips, sawdust or crumb rubber that are added to some types
of compost to increase and maintain adequate air-filled pore space
during the composting process) used, the frequency of turning or mixing,
and the moisture content of the compost all significantly impact the
consistency of the final product.
Other factors such as seasonal variations in the waste stream flow
and the weather also have the potential to adversely effect the quality
of the finished product. Consider for example the differences that
exist in the yard waste stream between Spring and Fall in which grass
clippings predominate in the Spring and leaves dominate in the Fall.
The experience level of those managing the composting facility also
may significantly influence the quality and consistency of the final
product. Even with the potential for such variations, however, there
are numerous clues that might be useful in determining which compost
is right for your course.
Just as in selecting the right wine for that special occasion, so
too can selecting the right compost be rather subjective. For example,
often times you will read or hear that a "good" compost
is said to be dark in color with a crumbly texture, a moisture content
of around 40-45% and an "earthy" aroma similar to that of
a fertile soil.
Such descriptions are extremely subjective. Yet, there is great value
in this type of sensory-based assessment as many working in the green
industry have an intuitive sense for what a rich fertile soil feels,
smells, and looks like. Luckily, however, for those short in the intuition
department or eager to base their decisions on more quantifiable characteristics,
there are numerous physical and chemical qualities to consider.
In terms of physical properties, particle size and texture are perhaps
two of the most important factors one can use to assess a compost's
physical characteristics.
These properties are important to consider because repeated applications
of composts with excessive amounts of bulking agent or other foreign
materials might lead to an undesired accumulation of unwanted materials
in the thatch or soil.
A quick glance and a handful of the candidate compost should provide
a rapid assessment as to whether a particular compost's texture is
suitable for use on your fairways. In regards to particle size, we
typically use and recommend that composts used on fairway turf be
screened to 1/8 to 1/4 inch to remove excessive bulking agent. Even
then, however, it is often difficult to completely remove unwanted
or excessive bulking agent as thin slivers or splinters typically
have the ability to pass through the screening process.
In addition to the physical nature of the compost, there also are
numerous key chemical properties and processing information that may
provide important clues about the suitability of a particular compost.
In all cases, the compost producer should be willing to provide you
with the following information for each batch of compost prior to
or at the time of delivery.
Hesitation on the part of the producer to divulge this information
may speak volumes about whether or not you should be considering their
product and brings to light the importance of developing a good working
relationship with local compost producers and distributors. Ideally
a supplier should provide the following information:
- Compost type and age;
- The composting process used (i.e. static pile, windrow, forced-air
static pile or in-vessel);
- A complete elemental analysis including heavy metals (especially
if working with a biosolids or municipal solid waste compost);
- Total ammonium and nitrate N concentrations, respectively; pH; CEC,
organic matter and ash content;
- Soluble salts (especially for animal manure composts); and,
- The C/N ratio.
Additional information regarding nutrient release characteristics
and bulk density of the compost might be also valuable pieces of information
and will facilitate your ability to determine nutrient loading and
mineralization rates of the compost. Both of the latter will be extremely
valuable in your attempts to determine the magnitude and duration
of the compost.
Just exactly what all this data means and how it should be evaluated
is the topic of several additional articles. In a nutshell, however,
you can develop a fairly rapid assessment of a compost's fertilizer
potentially concentrating your attention on the:
1) pH;
2) heavy metal and N and P concentrations, respectively; and,
3) C:N ratio.
In general, and taking into account the wide variety of composted
materials available, the pH should range ideally between 5.7 to 7.5.
In regards to heavy metals, concentrations should be below standards
allowed by the US Environmental Protection Agency Rule 503.
The N, P, and K analyses in tandem with the bulk density of the compost
should help provide insights regarding the amount of potentially plant
available nutrients supplied by the compost topdressing application.
In general, the greater the concentration of plant available N (ammonium
and nitrate), the greater the color enhancing and growth stimulatory
effects that may be anticipated assuming the compost topdressings
are applied during a period of active turf growth.
In general, high C:N ratios (above 20:1) may be an indication that
the compost is not fully composted and is not ready for use as a topdressing
material. Immature composts pose the threat of causing a phenomenon
called nitrogen immobilization that is brought about when composts
with excessive C and limited N are applied.
When this occurs, the compost microbes attempt to further breakdown
the excessive C and because they, like all organisms, require a balanced
diet of C and N, they essentially out compete or steal N from the
turf. The result is that the turf goes off color and will require
the addition of additional N fertilizer to bring the system back into
balance.
In general, a good target range for the C:N ratio would be somewhere
around 15:1. Biological or microbiological indicators of compost maturity
and turf enhancing properties also exist, however, they are expensive
and labor intensive to measure.
Besides, these drawbacks, interpretation of the results from such
tests are often difficult and ambiguous as our understanding of the
microbiology and microbial ecology of composts and turfgrass soils
is still in its infancy.
Bottom line, put most of your decision-making eggs in the physical
and chemical property baskets, respectively.
Step 3: Timing and Application Strategies
Once a compost has been selected, the application of the material
should proceed fairly easily. The most frequently used application
method of topdressing fairways with compost is in conjunction with
the normal fairway core cultivation process (hollow tines are recommended)
that takes place in the Spring and Fall during periods of maximum
turf growth and recuperative ability.
These are also times when average daytime temperatures do not exceed
65-70°F thereby reducing the possibility of either burning the
turf through the use of "hot" compost (compost containing
excessive amounts of ammonia or which are warm or hot to the touch)
or otherwise suffocating the turf with a blanket of compost topdressing
and cores on a hot summer day.
Whether you decide to core first and topdress second or topdress first
and core second is ultimately up to you. One advantage to coring first
and then subsequently applying your topdressing is that you significantly
minimize the time the compost sits on the turf. Any device that has
the ability to distribute the compost over distances without compacting
the soil can be used.
The rate used will depend on numerous factors such as time of year,
member's expectations, particle size, turf species and height of cut,
the nutrient loading rate of the compost being applied and on the
ability of the turf to assimilate the provided nutrients.
Members may be more demanding of impeccable turfgrass earlier in the
season, than towards the end, allowing for a more aggressive topdressing
program in the Fall. Similarly, a product that has been screened to
a smaller diameter will moved off of the turf and into the soil profile
quicker than poorly screened product.
Once the compost has been applied, the fairways should be dragged
to blend the compost with the pulled soil cores. The remaining tufts
of turf and thatch can then be blown into the roughs where they can
be picked up with rotary mower fitted with a bagging attachment. The
final step in the application process is to irrigate the fairways
as soon as possible to reduce turf stress and the potential for any
ammonia or thermal burn or heat induced stress.
Step 4: Record Keeping
As with any practice, solid documentation is critical for future reference
and decision making processes. In the case of compost topdressings,
the following records may be useful to maintain:
1) Product records such as any physical, chemical or biological
properties you may have considered and important contact information;
2) Economic records such that you can ultimately run a cost-benefit
analysis comparing your standard and compost topdressing enhanced
programs, respectively;
3) Application records such as timing, steps carried out in
the actual application process, weather data, soil temperatures and
moisture levels, etc.;
4) Follow-up observations such as any effects observed and
the magnitude and duration of these effects; and,
5) Membership comments and concerns that might be useful in
later years regarding this practice. The better your record keeping,
the greater the possibility that you will be able to assess the pros
and cons of this practice in relation to your standard management
practices.
Summary and Conclusions
The use of compost topdressings can be a useful tool for managing
fairway turf. As with any initial attempt at implementing a new management
practice, use common sense and take a somewhat conservative approach
when just getting started. In other words, make certain to try your
hand on a small scale and evaluate the effects of compost topdressings
before attempting to tackle every fairway. The following keys to success
might be useful when attempting to maximize the implementation of
compost topdressings while minimizing any potential detrimental effects
associated with this practice.
Determine your goals for implementing a compost topdressing program.
Are you interested in composts as organic fertilizers, soil conditioners
or to introduce a form of disease suppression? Determine what your
goals and expectations early in the process.
Get to know your local compost producers,
distributors, other superintendents that have tried using composts,
university staff working in the area, and state and local solid waste
authority personnel and regulations.
Remember that not all composts are created equal.
Some positively-, others negatively-, and some have no impact on turf
health and that the more you know about the compost you are considering,
the greater the chances of a successful outcome.
Pay close attention to the consistency or variability of product's
quality.
The amount of bulking agent present, the degree of maturity and the
particle size and texture of the compost are four important things
for which to look.
Make it your business to know WHAT you are applying (elemental
analysis, pH, CEC, parent material of compost, process by which it
was generated, nutrient release characteristics, organic matter and
ash content, soluble, ammonia, organic acids, etc).
Combine compost topdressing applications
with Spring and Fall core cultivation events via blending with cores
and dragging. Avoid applying compost topdressings to fairways when
air temperatures are greater than or equal to 65-70°F.
Modify your application rates to meet your target fertility goals.
Maximize the potential benefits of the compost topdressings by making
applications when the turf is actively growing.
Develop an effective application strategy that can be completed
in a relatively short period of time from the time the compost is
applied to the time irrigation is applied to the turf
Always include an appropriate set of internal control plots
so that you can truly gage the effects of a newly implemented management
practice. Specifically in the case of evaluating the effects of a
compost topdressing program for your fairways, you might consider
including both a non-treated area (no coring or compost) and a cored
but not topdressed area to assess the effects of your coring and topdressing
programs. Without such internal control areas, it is impossible to
accurately assess any practice.
Consider modifying your standard fertility program to account
for the additional nutrients being applied or incorporated.
Keep good records of what worked and did not work for you and
remember there are no silver bullets.
Walk before you run! As with any new practice, take it slow
at first until you get the hang of it.
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