Field Science
22 SportsTurf | February 2015 www.sportsturfonline.com
T
here seems to be some confu-
sion in the industry regarding
the proper topdressing practices
for sports fields. The confusion
stems from taking a manage-
ment practice designed for a high-sand
soil and applying it to native silty soils or
vice versa.
Let's review. If you have a soil that is
high in silt and clay, you should be man-
aging the soil to improve soil structure.
Structure is the aggregation or binding
of soil particles together to form larger
particles (Figure 1). These larger par-
ticles can then stack against each other,
almost like sand, and gaps or air spaces
(pores) are formed between the particles.
So when you are managing for
increased soil structure, you are trying to
create/increase soil particle aggregation.
The way you do that is to add glue and stir.
Organic matter is the glue that binds
soil particles together. Thus if you are
adding high quality organic matter to
your soil, you are adding the glue and
working to create stronger aggregates
that in turn provide air to the root sys-
tem. In a previous article I discussed
how to select a quality compost to use
as topdressing just before aeration. That
information can be found at http://
plantscience.psu.edu/research/centers/
turf/extension/factsheets/composts and
composts can be tested for quality at
www.aasl.psu.edu.
I keep running across high schools
that are topdressing with a combination
of sand and compost. I don't understand
why. Adding a small amount of sand
to a soil high in silt and clay (most soils
in Pennsylvania) will not help with soil
structure. In fact it can hurt. Sand does not
aggregate to an appreciable degree and just
takes up space until you add so much sand
that you make the soil into a loamy sand.
Let's look at the textural triangle
(Figure 2). If your soil is a silt loam soil,
Topdressing
sporTs fields
■ By Dr. AnDrew Mcnitt
figure 1. Soil structure is the aggregation or sticking
together of smaller particles to form larger particles.
