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Watering Your Florida Lawn
J. L. Cisar, L. B.
McCarty and R. J. Black
Water is an essential element in all living plants:
It combines with carbon dioxide and sunlight for photosynthesis.
Food manufactured by photosynthesis and nutrients absorbed by the roots
are transported by water to all parts of the plant.
Plant temperatures are maintained by transpiration of water.
Seeds need water to germinate.
Turfgrasses that have been fully watered can withstand more stress and
wear.
Lawn irrigation is often necessary in Florida’s hot climate. Daily
temperatures can be over 90°F (32.2°C) 6 months per year which causes
large water losses from soils and plants. Rainfall averages 60 inches per
year, but half the amount falls from June through September, often in
sporadic large rainstorms. Less rainfall occurs during the winter and
spring. Another reason for lawn irrigation is the fact that Florida’s
sandy soils do not hold much water.
An efficient watering program must include three basic steps:
1.
determining when water is needed.
2.
determining how much should be applied, and
3.
deciding how water is to be applied.
DETERMINING WHEN
TO WATER
The most efficient way to water a lawn is to apply water when it begins to
show signs of stress from lack of water. The following signs are
indications of water needs:
bluish-gray areas in the lawn,
footprints or tire tracks that remain in the grass long after being made,
many leaf blades folded in half, and
soil sample from the root zone feels dry.
Prolonged dry periods of high temperatures, strong winds, and low relative
humidity cause these symptoms. During such times, plants wilt even though
water may be in the soil, because they are losing water faster than it is
absorbed through root systems. However, watering may be needed.
Watering immediately when the lawn first shows signs of stress is the most
economical way to water; delay can cause permanent damage. Add-on devices
are available for some sprinkler systems to automatically determine when
to water. Electronic moisture sensing units or tensiometers allow
automatic sprinkler systems to operate only when soil water is getting
low. These devices eliminate overwatering and have potential for water
savings.
AMOUNT OF WATER TO
APPLY
The amount of water to apply at any one time varies with the amount of
water present in the soil, the water-holding capacity of the soil, and
drainage characteristics. An efficient watering wets only the turfgrass
root zone, does not saturate the soil, and does not allow water to run
off.
Florida soils are typically sandy and hold 1 inch of water in the top 12
inches of soil. If the roots are in the top 12 inches of soil and the soil
is dry, then ¾ to 1 inch of water is required to wet the area thoroughly.
This is equivalent to 465 to 620 gallons of water for each 1000 square
feet of lawn.
Generally, Turfgrasses require no more than 0.3 inches of water per day.
Under extreme summer conditions, water use can be as high a 0.4 inches of
water per day.
Figure 1.
Cross section of
grass leaves showing varying degrees of wilting.
Left:
leaf fully expanded.
Center:
leaves wilting and folded.
Right:
leaf rolled up under drought conditions.
During the winter when grasses are not actively growing, water use can be
as little as 0.05 inches of water per day. A simple watering schedule
would be to apply ¾ inch of water when the turfgrasses show water
deficiency symptoms as discussed earlier. Once this ¾ inch of water is
applied,
do not apply any more
until water stress symptoms are again noticeable.
Typically, two to three waterings per week in the summer and once every 10
to 14 days in the winter are required. If rainfall occurs, irrigation
should be suspended according to the rainfall amount.
MANNER OF APPLYING
WATER
Water should never be applied at a rate faster than it can be absorbed by
the soil. If the sprinkler applies too much water, it runs off, and is
wasted. This seldom happens with small sprinklers unless the lawn is thick
or the soil compacted.
Avoid extremes in watering frequency and amount. Light, frequent watering
is inefficient and encourages shallow root systems. Excessive irrigation,
which keeps the root system saturated with water, is harmful to the lawn.
Roots need a balance of water and air to function and grow properly.
The time of watering is important. The best time for lawn irrigation is in
the early morning hours. Watering during the day can waste water by
excessive evaporation and during very hot periods can scald the lawn.
Watering in late afternoon or late morning may be detrimental if it
extends the time the lawn is naturally wet from dew. Lawn irrigation
should be scheduled to avoid peak residential water demand if using
municipal water.
LAWN WATERING
ECOLOGY
To ensure quality turf, Bermuda grass and St. Augustine grass need
supplemental irrigation. Lack of properly timed irrigation can weaken the
turfs and predispose them to weed invasion and other pest problems.
Centipede grass often needs no supplemental irrigation under shaded
conditions where natural rainfall and runoff is often sufficient. However,
in sunny open areas, centipede grass may need supplemental irrigation.
Bahiagrass is the southern turfgrass that when properly established and
maintained requires less irrigation than the others. Improper watering of
bahiagrass lawns is detrimental to turf quality and leads to weed
problems.
Underwatering of turf is obvious by wilting of the leaves, but
overwatering is not so obvious and may show up in numerous ways. Excessive
thatch buildup and constantly wet turf are signs of overwatering. The
presence of dollarweed and sedges indicate too much water is being applied
and turf disease and other pests may invade the lawn under this situation.
An efficient watering program combined with a moderate level of
fertilizing and proper mowing height will produce a superior lawn. Not
only will your lawn look good, but it will also be able to withstand the
stresses it encounters.
INSPECT SPRINKLER
SYSTEM FREQUENTLY
Check sprinkler heads for an even spray pattern and direction of spray.
Check for damaged sprinkler heads, replace these if leaking.
Check that valves open and close properly.
Check for proper time on controller if your system has one.
TIPS FOR TURFGRASS
Follow these tips to reduce leaching, thus saving fertilizer. Remember,
your objective is to keep water and fertilizer in the root zone of the
grass for as long as possible.
Know how much water your system applies over a time period. Simply place
coffee cans in a straight line from your sprinkler to the edge of the
watering pattern. Turn the water on for 15 minutes and calculate the
average depth of water. Multiply this number by four to determine the
irrigation rate in inches per hour.
Make sure your sprinkling system applies water uniformly. Don’t mix head
types or let the reach of two sprinklers overlap excessively.
Apply no more than ¾ to 1 inch of water per irrigation.
Wait until turf stress symptoms are noticeable before applying ¾ inch
of water. Watch the grass for a bluish-gray color, folded leaf blades,
and/or inability to recover from foot or vehicular traffic.
Don’t water when rain is forecasted for your area.
Don’t be fooled by the word “organic.” Some organic fertilizers leach as
quickly as inorganic.
Look for the words “slow release” and “insoluble” on the fertilizer
labels. Nitrogen in this type of fertilizer will not wash away as quickly.
Include potassium (K) in your fertilizer as this element is necessary to
increase the turf’s drought tolerance.
Lime your lawn if your soil is highly acidic (a low pH) to reduce
phosphorus solubility. Have your soil tested every few years to test the
needs of your turf.
Increase mowing height of lawns; this increased height allows the plant to
develop a deep root system.
How to Calibrate
Your Sprinkler System
J. L. Cisar and L. B.
McCarty
Knowing the amount of water your sprinkler system applies to your lawn is
an important step in using water efficiently. Most people irrigate their
turf for a given number of minutes without knowing how much water they are
really applying. This leads either to giving too little water or to wasted
water which runs down sidewalks and streets, or through the root zone and
deep into the ground where turfgrass roots cannot reach it.
Calibrating or determining the rate of water your sprinkler system applies
is an easy job. You can use the following steps, in order, if you have an
in-ground system or a sprinkler at the end of a hose.
1.
Obtain several (5 to
10) coffee cans, tuna fish cans, or other straight-sided containers to
catch the irrigation water. Containers which are 3 to 6 inches diameter
work the best.
2.
If you have an in-the-ground system, place the containers in one zone at a
time. Scatter the cans at random within the zone. Repeat the entire
procedure in every zone because there may be differences in the irrigation
rates.
- OR -
If you use a hose-end sprinkler to water your turf, place the containers
in a straight line from the sprinkler to the edge of the watering pattern.
Space the containers evenly.
3.
Turn on the water for 15 minutes.
4.
Use a ruler to measure the depth of water in each container. Note: The
more precise the measurement, the better your calibration will be. For
most cases, measurements to the nearest 1/8 inch are adequate.
5.
Find the average depth of water collected in the containers (add up the
depths and then divide by the number of containers).
6.
To determine the irrigation rate in inches per hour, multiply the average
depth of water times four.
Now that you know your sprinkler system irrigation rate, you can more
efficiently apply water to your turf.
Use Table 1 as a guide for sprinkler times. For example, if the sprinkler
system applies water at the rate of 2 inches per hour and you wish to
apply ¾ inches of water, then you would need to run your sprinklers for
about 23 minutes.
Table 1. Time required to apply water for a given irrigation rate.
Suggested mowing practices for Florida lawns.
To calculate the time of irrigation for rates not listed
in Table 1, use Equation 1.
Minutes required to
run each zone = Amount of water to be applied x 60 (1)
Your calibrated irrigation rate
CALIBRATION
POINTERS
Try to calibrate the sprinkler system during the same time the system is
normally run, so that water pressures are similar.
Low water pressure can significantly reduce the amount and coverage of
water applied by the sprinkler system.
Application rates normally should not exceed ¾ inch of water per
irrigation.
Most time clocks can be adjusted for accurate time settings. Consult your
local sprinkler company for details.
If you use a hose-end sprinkler, a mechanical timer and shut-off switch
that attaches to the faucet will help make watering more efficient.
Avoid mixing sprinkler head types. Mist heads apply more water than impact
heads. Match sprinkler heads for uniform coverage.
For more specific information on turf irrigation, see the section
“Watering Your Florida Lawn.”
Check the sprinkler system frequently. Replace broken sprinkler heads,
clear clogged nozzles, and adjust the direction of spray.
Use water efficiently: do not waste it.
For more information call 850-469-0588
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