Environmental Engineering Reference
In-Depth Information
levels of intensity. Greens and tees are always the most intensively
maintained, followed by fairways, and then roughs, which are often
maintained as utility turfs.
Regardless of the particular use to which turfs are subjected and the
intensity of culture applied, they are incredibly complex systems. In these
ecosystems, turf-grass communities exist in close association with cli-
mate, soil and biotic environments. The quality and persistence of turfs
reflect how well all of the components interact to form a sustainable and
efficient association.
Climate Adaptation
Grasses are divided into two major groups of species: (i) those suitable
for warm; and (ii) those suitable for cool climates. The first, called warm-
season grasses, are best adapted to temperatures around 30
C and differ
from the second, called cool-season grasses, not only in climatic require-
ments but also in the way they carry out photosynthesis. Most of the
warm-season species belong to a classification called C4 plants, in which
photosynthesis is much more efficient than that in C3, or temperate-
climate, plants. In addition, they use only one-third to one-half as much
water to produce the same amount of dry matter, and overall they thrive
in hot weather. Another unique characteristic of warm-season grasses
is that they undergo dormancy when soil temperature drops below 10
8
C.
They lose their chlorophyll and remain yellow or brown until the
temperature rises above 10
8
C again. Tropical grasses are essentially
warm-season grasses that never become dormant and often manifest little
tolerance for cold stress. This volume will discuss only warm-season
species grown in the climates where temperature is relatively uniform
and warm year-round.
Turf-grasses, like all other plants, undergo physiological processes
that govern their growth and development. Turf physiology is very
complex and includes thousands of such processes. The most essential
are photosynthesis, respiration, growth and storage.
8
Physiology
Photosynthesis
Plants have the unique ability to change carbon dioxide from the air and
water from the soil into carbohydrates, such as glucose and oxygen. This
conversion process, called photosynthesis, takes place in the leaves and
green stems and requires energy supplied by the sun. Carbohydrates
