Environmental Engineering Reference
In-Depth Information
Tolerance of salt stress
In the dry tropics, salts are brought to the soil surface mainly as a result of
imbalance between evaporation and infiltration of rainwater. Other major
sources of salt accumulation are saltwater flooding, saltwater intrusion
and saltwater (ocean) spray.
Turf-grass species differ considerably in tolerance to salt. The most
resistant varieties of seashore paspalum may tolerate long-term irrigation
with ocean water (over 3% NaCl), whereas centipede grass may be
severely injured by one saltwater spray event (Table 2.3).
Tolerance of soil acidity
High soil acidity (low pH) can be corrected by application of lime (cal-
cium hydroxide), but liming may not be practical along roadsides or on
large turf areas subject to low maintenance. Therefore, species tolerating
high soil acidity are frequently selected for these areas. Of the warm-
season grasses, carpet grass and centipede grass tolerate low pH quite
well. Bahia grass and St Augustine grass do not (Table 2.3).
Heat tolerance
Tropical turf-grasses are more frequently stressed by extreme heat than
by cold. Hot days followed by very cold nights sometimes occur in
tropical desert areas, especially at higher elevations. Zoysia grass and
cynodon tolerate both heat and cold well. St Augustine grass requires
mild conditions (Table 2.3).
Cool-season Turf-grasses
Turf-grasses having a temperature optimum of 15-22
C are referred as
cool-season turf-grasses. These species are widely distributed in cool
climates but can be also found in some tropical locations, for example
at high elevations. The most important cool-season grass species are
members of the four genera
Poa
(the blue grasses),
Festuca
(the fescues),
Agrostis
(the bent-grasses) and
Lolium
(the rye-grasses).
8
The genus Poa (Festucoideae)
The highly diverse genus
Poa
comprises more than 500 annual and peren-
nial species, including bunch-grasses (species that tend to grow in clumps),
rhizomatous grasses and stoloniferous grasses. Only seven
Poa
species are
used as turf-grasses, and only three are of significant importance.
