Environmental Engineering Reference
In-Depth Information
Further, the reduction of pore diameters is often accompanied by loss of
pore continuity, which reduces even further the diffusion of air and soil
water movement and results in further growth reduction. Compaction
also increases soil strength, especially when the soil is dry. The mechan-
ical resistance of compacted soil significantly limits the growth of deep
roots and therefore reduces turf-grass drought resistance.
Compaction of turf soils typically occurs close to the soil surface, and
can usually be corrected by cultivation devices that penetrate the com-
pacted soil relatively shallowly, not more than 10-15 cm. Several cultiva-
tion techniques can be used to alleviate surface compaction, but
core
aerification
, sometimes simply called
coring
, is the most frequently used.
Besides reducing compaction, coring also controls thatch accumulation,
so one operation offers double benefit.
Cultivation Methods
Coring
is a cultivation method in which small holes are made in the soil,
usually by removal of small cylinders or plugs of soil and turf. These
plugs are extracted by means of devices with hollow tines, spoons or
screws that pull soil to the surface. The most commonly used are vertical,
self-powered hollow-tine aerifiers and tractor-pulled drum surface-
coring units. The vertical-tine type is the most effective on high-mainten-
ance areas such as golf greens. Tractor-pulled, spoon-type aerifiers are
used most often on large areas such as golf course fairways or large
athletic fields (Fig. 8.1). During operation, the cylindrical, hollow tines
are first inserted into the soil, so that small cylinders of soil and turf are
forced in through their open ends. When they are removed, they pull
these cores out of the ground. The tines are then discharged; i.e. the cores
are pushed out of the tines and left behind on the surface of the soil.
These cores or soil plugs are usually 1-2 cm in diameter and 5-10 cm in
length. They must either be removed or be broken up and worked back
into the turf. The density of cores depends upon the type of machine but
generally ranges from 100 to 200 per m
2
. Core aerification can be quite
disruptive to the surface, but within 1 week the turf area usually returns
to its typical appearance.
Hollow-tine aerification is the most effective technique for relieving
compaction. The removal of the core permits nearby soil to slide slowly
down into the opening. Within 1 or 2 weeks, the core holes are filled with
roots growing vigorously in a loosened soil (Fig. 8.2). The cores them-
selves are a valuable by-product; they are considered an excellent source
of vegetative material for turf-grass propagation. When spread on a
newly established seedbed, they require only moderate watering and,
of all establishment techniques, assure the fastest and the most uniform
