Environmental Engineering Reference
In-Depth Information
7
Irrigation
Precipitation in the tropics ranges from just about zero to over 2000 mm
per year. Warm-season turf-grasses are able to use from 2 to 5 mm of
water per day, depending upon location, species, weather conditions,
type of maintenance and several other factors. Unfortunately the highest
usage of water occurs in arid regions, where rainfall is small, and the
lowest occurs in the humid tropics, where rainfall is highest. Even though
total yearly precipitation in many regions is more than adequate, its
seasonal distribution is usually unsatisfactory to maintain a dense,
green turf of high quality year-round. Except in a few localities in the
tropics, medium- and high-quality turfs require supplemental irrigation.
Irrigation Needs
The water required by growing turf may originate from rainfall, irriga-
tion, or a combination of the two. By far the most important factor that
determines the plant's need for water is
evapotranspiration
. This term
combines the words
evaporation
, meaning water loss from the surface,
and
transpiration
, meaning water loss from the plant. It refers to total loss
of water from soil covered by vegetation. In turf, where the soil is usually
completely covered by growing leaves and stems, most of the water loss
is due to transpiration.
Water enters turf-grass through the roots and exits through small
openings in the leaf cuticle called
stomata
. Stomata can open and close
in response to changing environmental conditions and therefore can
