Environmental Engineering Reference
In-Depth Information
Fig. 8.7. Top-dressing, the application of a thin layer of soil over a turf-grass area, is
usually used to cover thatch or to smooth the playing surface.
Even though top-dressing looks quite simple, it is one of the most
difficult management practices performed on high-quality turfs. The
greatest danger of this cultivation technique is soil layering, and selecting
the right top-dressing material is the greatest challenge. When top-dress-
ing is carried out incorrectly over a period of years, the entire turf surface
may have to be removed and an expensive turf reconstruction conducted.
When finer soil is laid over coarser soil, water movement can be seriously
disrupted and turf growth severely impeded. In general, top-dressing
soil should be of the same or slightly coarser texture than the underlying
soil. So long as a detailed record is kept from the time of initial turf
construction and is followed by the turf manager, top-dressing is sound
and usually does not cause any long-term problems. If these records do
not exist, or they are not followed, as often happens when turf managers
change frequently, problems are virtually certain. Often, every new man-
ager implements a new top-dressing programme. After several years, the
result can be a sequence of contrasting layers of top-dressing material,
each correlated with the time of manager's employment. If the textures of
these multiple layers differ substantially, they may cause soil problems so
severe that reconstruction of the entire area is unavoidable.
Top-dressing rates normally range from 0.2 to 0.5 m 3 of soil per
100 m 2 (a soil layer 2-5 mm thick). The applied soil should not cover
the turf-grass leaves completely and should allow the turf-grass plants to
carry out photosynthesis. Top-dressing is often applied by special ma-
chinery, but on small areas it can be distributed with a drop-type fertil-
izer spreader or even applied with a shovel and smoothed with a large
broom.
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