From the September issue of SportsTurf, Dr. Grady Miller’s “Q and A”
Q: What are my options to
reduce my field’s compaction so it is not so hard?
A: My July issue column on
measuring field hardness encouraged several folks to send me a message. Most of
you had questions related to alleviation of compaction/hardness. So I thought I
would follow up my previous “Q and A” to address those questions related to
alleviating soil compaction.
First, I should mention that
my co-columnist, Pamela Sherratt from Ohio State, wrote a great spring aeration
“Q and A” as recently as April 2018. Go back and review that article online if
you get a chance. Most of your follow-up questions were about either
aerification frequency or new equipment technology for aerification, a little
different than the subject Pam addressed back then.
Let me briefly address the
issue on aerification frequency. If a regular reader, you may know that I
encourage frequent aerification. There are few things that can turn around a
high-use, compacted field like aggressive aerification. While using the
techniques I mentioned in July’s article may be valuable for monitoring field
hardness and determining the best time to aerify, it is not a requirement. Most
fields will benefit from aerification regardless of their compaction status.
So, if you are thinking about aerification then you field is probably ready for
its next aerification.
more common follow-up question was how should I aerify given the new technology
currently available? It is interesting to consider that one can now aerify a
sports field with steel, water, or air. I know, it sort of sounds like an 80’s
rock band. But even before big-hair bands, aerification was accomplished by
pushing either steel solid spikes or hollow tines into the soil. The resulting
hole diameter, depth, and spacing varied based on the equipment used. The solid
spike pushed impacted soil away from the spike toward the bottom and sides of
the hole. A hollow tine allowed the impacted soil to be removed from the
profile and then deposited on the soil surface. Another take on solid tine
aeration is the oscillating, solid-tine aerators. This uses an oscillating
motion of a solid spike to fracture the soil. For this reason the process is
often called shatter tining or the more commercial label, aeravating.
Using water and air for
aerification, while not new, has continued to be refined over the last 25
years. Pulsing a stream of water or air are like solid tines when it enters the
soil surface, but as it impacts soil particles it disperses within the profile
to provide some lateral shattering. The benefit is there is less surface
disruption while one may still get a pretty substantial void below the surface.
A University of Tennessee study found that air injection reduced surface
hardness by 19% immediately after treatment. Long-term effects were not
reported, but the positive to using air injection is that with minimal surface
disruption, they could be used during the playing season with minimal surface
I am also increasingly
hearing the term decompaction to describe a way to remove compaction that is
different from aerification. From an equipment perspective what is usually used
to decompact a soil is some type of vertical linear aerator. These are
sometimes called rotary decompactors. One commercial name that is used today is
the Shockwave. The Shockwave uses slowly rotating thick steel knives to
vertically slice through a soil profile. With a roller following the knives,
there is minimal surface disruption. In some respects, “shockwave” is a bit
like a deep verticutting of the soil profile. In a recent Iowa State study,
hollow tine aeration increased water infiltration by 148% and shockwave
aerification increased it by about 70%. Old-fashion solid tine aerification
increased infiltration by only 17%.
Longevity of these treatments
is a common question. Several researchers are presently looking to answer this
question with the new technology, so stay tuned for more of that information.
We do have some longevity data on more traditional core aerification. In an
Auburn University study they evaluated deep-tine aeration on compacted native
soils growing Tifway bermudagrass over time. Aerations were applied either once
(July), twice (April and July), or four times a year (January, April, July, and
October) with 0.75-inch solid tines that penetrated 8 inches on 4-inch spacing.
Despite the total area impacted by those big tines going down deep, the effects
only lasted about 1 month on heavily trafficked turfgrass. This study proved
that turf managers should aerate more than just once or twice a year.
While not normally considered
an aerification method, fraze mowing could be used to alleviate soil compaction
since the zone of greatest compaction is often near the surface. By removing the
top surface layer with a fraze mowing, compaction can be carted off the field.
Obviously this is a pretty drastic technique to use to reduce compaction since
the entire turfgrass surface is removed. At least fraze mowing results in a
smooth surface unlike the ultimate remover of compacted soil—a chisel plow and