TIME TO TUNE UP YOUR LAWN IRRIGATION
SYSTEM
Ed Perry
Farm
advisor
UC, Cooperative
Extension
Stanislaus
County
There is no doubt that water
management is the most important cultural practice in maintaining a lawn. Now that hot weather is here to stay for
a while, it’s a good idea to review some basic lawn watering practices. Remember, you’re doing the best job of
watering your lawn when the amount of water you apply replaces the water used by
the grass with none lost to surface runoff or penetration below the roots.
Lawns
need complete water coverage to maintain their vigor and a healthy
appearance. Brown spots in a lawn
are often due to uneven coverage.
Make sure your sprinkler system provides uniform coverage. Too much water is not only wasteful but
can cause turf to grow faster, which requires more frequent mowing. Saturated soil can cause poor soil
aeration and, as a result, weaken the turf making it vulnerable to diseases and
invasions of weeds. Not enough
water can cause turf to dry out, also making it more susceptible to diseases and
weed invasion.
You can determine when your lawn
needs watering by observing its appearance, and by examining the soil. When your lawn changes from bright green
to dull gray-green, it needs water immediately. Also, when stressed for water, your lawn
will show footprints and will not spring back from normal foot traffic. If you don’t apply water at this time,
the gray-green hue will deteriorate to a tan color which indicates severe water
stress and dead grass.
Light
sprinkling should only be used for newly planted turf when the roots are
developing in the very top portion of the soil. As the lawn becomes established, roots
extend deeper into the soil. Light
sprinkling will encourage shallow root development and stunt deeper root
growth. Shallow root systems
require frequent watering to keep the surface wet, creating an ideal environment
for weeds and diseases. Although
some grasses have less extensive root systems than others, deep, infrequent
watering that allows water to penetrate the top 6 to 8 inches of soil will
promote healthy root growth. It
also maximizes water-use efficiency and turfgrass quality. Allow the soil to partially dry out
between waterings. Water when the
top two inches of soil have dried out.
Use an object such as a screwdriver to probe your soil and measure the
depth of the moisture.
The
frequency of watering depends on your grass species, the weather and your soil
type. Warm-season grasses such as
burmudagrass and St. Augustine grass have extensive root systems that penetrate
deep into the soil and require deep and infrequent watering. Water as few times a week as necessary
to wet the soil to the desired depth without causing excessive runoff. For warm-season grasses, usually one or
two times a week is sufficient.
Cool-season grasses such as fescue and ryegrass require more frequent
watering than warm-season grasses because their root systems are not as
extensive. Usually about three
equally-spaced irrigations a week are necessary to maintain these grasses. Fewer applications are necessary during
cooler months.
When
irrigating, don’t apply water more rapidly than the soil can absorb it. Avoid water runoff. To do so you might have to turn off the
sprinklers for 1 to 2 hours to let the water soak in before continuing
irrigation. Repeat this cycle until
the top 6 to 8 inches of soil are wet.
If you
want to determine the maximum amount of time your sprinklers can be left on at
one time, observe a cycle from the beginning to the time when runoff
begins. That is the maximum amount
of time that you let your sprinklers run in any given watering. Space out the applications evenly during
the week.
In order to get water to penetrate
deeply, you may need to correct such problems as thatch accumulation or soil
compaction. Thatch is undecomposed
organic matter that builds up between the leaf blades and the soil surface. Thatch keeps water, air and nutrients
from moving into the root zone. A
thick thatch layer should be removed in spring or fall by vertical mowing or by
hand raking. Heavy foot traffic on
turfgrass can compact the soil surface.
Like thatch, compacted soil restricts water, air and nutrient movement,
and hinders root development. You
should aerify (core) the compacted areas in your lawn.
The best times to water are between
2 and 8 in the morning. At these
times, water use is most efficient, water loss from evaporation is minimal, and
distribution is usually good because of good water pressure and limited
wind. During the afternoon, water
is wasted due to high evaporation rates.
Do not water during the evening or pre-midnight hours because lawns are
more susceptible to diseases if they are wet during the cool night
hours.
In
summary, how often you need to irrigate your lawn depends on its appearance and
how moist the soil is. Avoid daily, light irrigations. Grasses and soils differ, so irrigation
schedules must be tailored to individual lawns. Remember, it is not uncommon to irrigate
for ½ to 1 hour or longer at each irrigation to do a good
job.