Technically, the term infield skin refers to segments
of the baseball field that contain clay, specifically the areas around
the bases and base paths. The keys to quality infield skin are good
materials, proper moisture and consistent maintenance practices. With
70 percent of the game played on the infield, having a consistently
firm, smooth playing surface is essential.
Infield construction
Infield mixes are made from various combination's and
percentages of sand, silt and clay. People consider the general
standard for an OK infield to be 60 to 70 percent sand, 30 percent clay
and 10 percent silt. Particle size also makes a big difference in these
materials. Infields vary greatly by regional conditions, commercially
available mixes and the preferences of the sports field manager and
their facility and teams.
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| The
nail drag scarifies the surface and digs deeper to further loosen the
infield mix. With any drag, be careful not to drag too close to the
turf edge. |
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| Annual laser-grading is used to check the infield slope and correct any inconsistency. |
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The weight of the infield mix is in the clay and the
silt and that's what retains the moisture. You may be in an area with a
lot of rain, and if you don't have much maintenance help for tarping
you'll want to have a bit sandier infield mix. If you have a heavily
used field or one for university or professional play, you'll probably
want a more stable infield with a heavier mix containing more clay and
silt to withstand the wear and tear of multiple events. For some
infield mixes with lesser percentages of silt and clay, a conditioning
amendment of calcined or vitrified clay is worked into the top 1 to 2
inches of the mix to help bind the clay and stabilize the infield.
When constructing a new field or rebuilding an existing
one, the general depth of the infield material for the baselines is
approximately 5 inches. The depth, the type of material used and the
subbase components are subject to budgetary constraints. There are
fields with the infield mix placed directly on the subbase soil, some
on a sand layer over the subbase soil, some directly on a pea gravel
layer and some on geo cloth covering any of these subbases.
Opinions differ on whether a geo cloth layer will be
detrimental to drainage. While drainage within the infield mix will
vary according to the percentages of clay and silt, it is generally
slow, so many prefer the geo layer for other advantages. It can keep
pea gravel from migrating up into the infield mix and bordering grassed
areas. Geo cloth on the pea gravel does keep the infield mix from
sifting into the gravel, reducing the need for continual addition of
the mix during the first few years of construction and helping
stabilize the surface more quickly.
To counteract slow drainage within the infield mix, many
fields are constructed with a slope to help move the surface water off
the clay and into the grass. A slope of about .5 percent, extending
from the edge of the pitcher's mound out past the 95 arc should provide
sufficient water movement for most fields. Some skinned baseball
infields and some softball fields are constructed with a greater
percentage of slope.
It's critical to achieve consistency of slope across the
entire surface. Use laser-grading equipment and a skilled operator.
Otherwise, once all the material is in place, run string lines from the
infield grass to the outfield grass across the infield and work your
way across the field with shovels and rakes. Keep moving the string
lines every 1 to 2 feet, and check and recheck for accuracy as you move.
Managing moisture
An inground irrigation system with a zone that only
waters the infield clay is one way to deliver volumes of water quickly.
When water patterns are diverted in windy conditions, hand-watering
will be required to reach the places missed.
Quick-connect outlets behind the mound and behind home
plate provide access to hook up a water hose. Some field managers place
quick couplers at the infield corners behind first and third base in
the grass. A 1-inch hose is preferred to deliver a larger volume of
water faster. A retractable hose reel installed in the ground behind
the mound makes pull out and rollback easier and eliminates hauling the
hose out and back for each watering.
Select hoses and hand-nozzle sizes based on the number
of fields you need to maintain and the size of your crew. Ideally, your
nozzle selection should be able to apply enough water to reach the
desired depth for the initial soaking and to lightly mist repeatedly to
maintain the desired moisture level. Some infields drain so well that
you can "puddle" the infield after a night game and it will be perfect
for play by morning.
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| When necessary, crews can level the infield skin using a string line and hand-held tools and hand-pulled drags. |
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Top it off
Using the different calcined or vitrified clay
amendments as the top surface coat can make it a little easier to
manage the skin moisture levels and achieve consistency. You don't want
the players to pick up wet clay on their spikes or have the infield get
too dry during the pregame workouts. With a topping of 1/8 to .25-inch,
you can soak the infield as you would normally and have a good surface
for workouts and sufficient moisture retention for the game.
Consistency of depth is extremely important during the initial
application of the top layer both for accuracy of the slope and footing
for the players. Once in place, use a cocoa mat or the back of a fan
rake so you're just lightly smoothing the top surface and not moving
piles of material.
Dry down
An infield tarp is an important tool in moisture
management. No one likes to use it, but covering the infield when you
have rain issues can be the quickest and easiest way to preserve
playability.
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| Edging
the infield as a weekly maintenance practice will reduce lips and keep
turf edges smooth. This Turfco Edge-R-Rite was used in 2004 during the
Olympics. Along with edging the bermudagrass, it doubled as a small sod
cutter. |
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| Rolling infields is an important practice to stabilize the areas. |
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The worst thing you can do following a heavy rain on an
uncovered field is to work the field too early. Let the sun do its work
on the dry down before you get out there to squeegee, rake and dig. The
dryer subsurface material will try to draw down the moisture from an
undisturbed wet surface. If you must work existing or added material to
dry down the surface, use a roller squeegee rather than a rake to
spread the water so you're not cutting into the wet material and
disrupting that downward movement.
If you have depressions with standing water, fill them
with calcined clay and let it soak up the moisture for 15 to 20
minutes. Then, spread out that moist material to dry further, or borrow
a technique from ground crews in South America to remove excess water
with no surface penetration. They use a supply of 12-by-24-inch
foam-rubber sponges (old padding) and place one in an area of standing
water, step down on it, allow it to absorb water to capacity, pick it
up, wring it out and use it again.
Another technique to combat light rain or drizzle, and
to use between innings when the dirt is starting to look shiny, is to
apply a very thin layer of conditioner using a regular walk-behind or
hand-held spreader set for the largest opening. You'll get a more
consistent layer than pouring conditioner from the bag or putting out
piles to spread.
Working the dirt
The right equipment used properly is critical in
maintaining the infield skin. You'll want a series of different types
of drag mats, rigid and flexible steel mats for breaking up dirt clods
and leveling, and cocoa mats for finishing the surface. You'll need
both a fine nail and heavy nail drag for scarifying the surface and
digging deeper to further loosen the mix and allow better moisture
penetration. You'll need rakes, brooms, edgers and rollers. The 1 or
2-ton roller will become your favorite tool.
The three-wheel field rakes produced by the major
equipment suppliers do an excellent job, and they come with an
assortment of attachments, as well as connection points for other
implements. You also can use a small tractor, lawn mower, utility
vehicle or golf cart to pull the drags.
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| We
bored into the infield to check soil conditions and discovered a
layering of different clays. We had to rototill to remove the barriers
so the clays would not "plate" when the players took the field. |
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Always pull the bases and insert the plugs so you can
drag the entire infield. Pay close attention to the wear areas around
and in front of the bases, such as where the first baseman plants his
foot. Consider incorporating a heavier clay mix 10 feet out from first
base and also at second and third base to make it easier to reduce
divoting and keep indentations from forming. Follow different routes
when driving equipment onto the field to reduce compaction issues.
Transport the drags to the field and drop them at different spots each
day. When working the field, keep attachments, drags and screens 6
inches away from the grass at both edges of the base path to avoid lip
build up. Use a variety of dragging techniques, continually altering
your patterns and incorporating circular spirals and figure eights. Go
slow, especially in the turns, to avoid slinging materials.
Lips
To avoid creating lips when hand-raking, always rake up
and down the base path, not across it. Work the grass edges with a fan
rake or stiff-bristled broom after every practice, workout and game. If
you don't have the staff for that, use the water hose to blast the
infield mix from the grass edges at least once a week.
You'll want to edge the infield grass periodically,
cutting away turf to remove any lip buildup, then backfill with new
infield mix, tamp down firmly and test the edge. There should be no
transition between the grass and the clay. If you can feel even the
slightest difference with your foot, the ball can feel it when it hits,
and that's what causes a bad hop.
This article was published in sports field management magazine
