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Chapter 8: Water
Requirements
After Bud
and Scott finished talking about fertilizers, Bud prompted
Scott, "Say, let's go back to watering. I know I should water
my grass, but how much? And how often? Should I use a
sprinkler, or a sprayer, or what?"
"Slow down," Scott
said, "and we'll take it one at a time. Yes, you need to
water. How much will depend on your grass, your soil, and your
climate. How often will depend on how hot it is and if it's
rained recently."
"OK," Bud agreed. "So I'll use a
sprinkler, right?"
"Perhaps, but do you know how many
kinds there are on the market? Dozens! So, let's grab a drink
and talk about watering."
Lawns are like thirsty
joggers on a hot summer's day--always needing water. How much
will depend on the climate in which you live. And you have
several choices to make. One is, does your lawn need for you
to water it, or do you live in a tropical climate where
there's enough rain to handle it? Another choice, do you want
to stand out with a hose and hand-water (some people do--they
feel it connects them to the land), or do you want to use a
sprinkler that you must turn on and remember to turn off, or
do you want to add a timer to the sprinkler, or do you want to
install an underground, automated sprinkler system that you
program seasonally?
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Helpful Hints
If you notice brown spots in the lawn,
dont increase the times in your irrigation system.
Instead, use a single hose to water those spots once
more each day. | As much as
80 percent of the water used around the home during the summer
is for outside uses. Watering the lawn is the main outside
water use. During dry summers, local water authorities may cut
off water for outside use or only allow watering on certain
days. Both measures are necessary and effective means to
reduce water consumption and relieve the strain on city water
supplies.
To avoid severe loss of turf and to
conserve water, homeowners should manage their lawns each year
in anticipation of water restrictions.
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Here are some
cultural practices that will reduce the need for irrigation
while improving the competitiveness and appearance of your
lawn.
Quick facts on lawn
watering
Lawns in temperate
climates may require as much as 2 to 4 cm (0.75 to 1.50 in.)
of water per week from irrigation or rainfall during summer to
remain green and actively growing.
When managed
properly, tall fescue requires 25 percent less water and
zoysiagrass requires 50 percent less water than Kentucky
bluegrass to maintain a green, actively growing
lawn.
Turfgrasses rank as follows in resistance
to leaf wilting and browning during summer dry periods -
bermuda, zoysia, tall fescue, Kentucky bluegrass, perennial
ryegrass.
During extended periods of summer
drought, dormant lawns (browned-out leaves) containing
Kentucky bluegrass, tall fescue, or perennial ryegrass should
receive 4 cm. (1.50 inches) of irrigation every two weeks to
maintain hydrated grass crowns and allow for full lawn
recovery when more favorable moisture and temperature return
in the fall.
Deeper roots draw moisture from a
larger volume of soil and therefore require less supplemental
irrigation.
Taller grass has deeper roots and a
lower tendency to wilt.
Taller grass provides
shading of the soil surface and reduces lethal temperatures
near the base of grass plants.
Lawns mowed
weekly at a taller mowing height are less likely to be
scalped. Scalped lawns lose density and have shallow root
systems.
Learn to read a lawn and know when to
water
Purple-blue wilting leaves,
footprints that stay, and folded or rolled leaves are signs
that lawns should be thoroughly watered if grasses are to
remain green and actively growing.
Turf water-use rates
are high during sunny and windy days with low relative
humidity. In situations where lawns are not watered and
rainfall is limited, grasses first show symptoms of wilt and
later turn completely brown.
When soil lacks moisture,
grass blades first turn bluish-purple, indicating plant
wilt.
Another early sign of insufficient water in the
plant occurs when footprints remain in the lawn for several
hours. Leaves with plenty of water quickly return to their
rigid upright shape, while leaves lacking water will remain
trampled for a period of time.
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Leaves also may be folded or rolled
lengthwise along the blade, indicating a lack of plant
water.
If high temperatures and dry conditions continue
without rain or irrigation, the above-ground portion of
grasses will turn entirely brown and die. Grasses are said to
be dormant during this browned-out stage, since the lower
portion of the plant usually remains alive but not growing.
Thorough watering will bring the lawn out of dormancy and new
growth will resume from the below-ground base of grass
plants.
Even though grasses are dormant, watering
restrictions that result in extended dry periods can cause
large ground cracks, severe soil drying, and excessive loss of
turf cover even when watering is resumed later in the summer
or early fall.
Summer dormancy of grasses is a
mechanism that helps a lawn survive, but it does not guarantee
that a lawn will fully recover from the browned-out
stage.
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Helpful Hints
Live in a dry area and fed up with brown
lawns? Look into xeriscaping, a landscaping technique
that uses as little water as possible while still
allowing you to grow certain types of grasses and
plants.
| Dormant lawns
should receive at least 2 cm. (0.75 in.) of water every two to
three weeks during summer to prevent complete turf loss.
Grasses may not show a noticeable greening, but that amount of
irrigation should be sufficient to hydrate the lower plant
portions and increase the recovery once adequate moisture is
available.
Wet wilt is another type of wilt to look
for. Wet wilt occurs when the soil is obviously wet, but the
root system is not able to keep pace with the water demands
from the atmosphere. The curling of leaves from wet wilt looks
very similar to wilt caused by lack of soil moisture.
Waterlogged lawns that have a shallow root system are
susceptible to wet wilt. Do not add more water when lawns are
wilting and soil moisture appears to be adequate; it will only
aggravate the problem by starving the root zone of
oxygen.
Prepare for a drought
Management practices in the
fall and spring determine the drought tolerance of the lawn in
the summer. To reduce the need for irrigation, your lawn
management program should maximize root volume and depth in
preparation for summer drought. By the time summer rolls
around, there is little you can do to help a lawn except mow
and irrigate properly.
The following lawn care tips
will help reduce the need for irrigation and increase the
chance of surviving summer drought.
Avoid the
temptation to irrigate in spring just to get grass growing.
Allow it to green up naturally. Mow frequently and avoid
scalping. Do not begin to irrigate until dry conditions of
early summer cause obvious turf wilt that lasts for more than
one day.
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In the spring, atmospheric water
demands are low and moderate wilting of turf does not damage
the lawn. If, in the spring, the soil is allowed to dry
slightly and the grass to wilt some, a deeper and more hardy
root system will develop. Such a root system will be necessary
to reduce the need for summer irrigation and to survive
drought conditions or when city water restrictions are
imposed.
Mow grass as tall and as frequently as
possible with a properly sharpened blade to produce a dense
cover with a deep root system. Taller grass has a deeper root
system that draws moisture from a larger volume of soil and
results in less need for irrigation.
Grass
height should never be less than 6 cm (2.375 in.) after
mowing. Mow frequently enough so that clippings are 2 to 3 cm
(0.75 to 1.1875 in.) long. Raise the mower height if grass has
grown too tall since the previous mowing. A lawn mowed at
heights of 7 to 9 cm (2.75 to 3.50 in.) will have a better
chance of surviving prolonged drought and water
restrictions.
Most homeowners mow lawns once a
week regardless of the mowing height. Taller mowing heights
are less likely to cause turf scalping, especially when grass
leaves are rapidly growing in the spring. Dull mower blades
and scalped turf result in an unattractive lawn that too many
homeowners try to correct with excessive
irrigation.
Apply nitrogen fertilizer to
cool-season grasses (Kentucky bluegrass, tall fescue, and
perennial ryegrass) primarily in the fall.
Some
nitrogen may be applied in the spring if the lawn is sparse
and bare soil is visible. Avoid summer application of
nitrogen. Nitrogen fertilizer applied in the spring and summer
causes additional leaf growth, which uses stored plant energy
that normally would be used to produce roots needed for water
uptake during the summer.
Test the soil to
ensure an adequate amount of phosphorus and potassium.
Additional applications of potassium - 0.5 kg of K2O per 92
square meters (1 lb. of K2O per 307 square feet) - in late
spring and twice again in early summer will also improve the
summer performance of lawns.
Core aerify tight
soils and thatched turf in the fall or spring to increase
water and air movement into the soil. This builds better root
systems. Avoid summer coring in the absence of water, since it
may cause excessive drying and drought
stress.
Limit thatch removal by power raking or
verticutting to fall or early spring, since water demands are
low and turf recovery is rapid. Do not severely power-rake
lawns in the late spring or summer or they will require
excessive irrigation to remain alive. When necessary, severe
power raking and seeding should be done in
September.
Select grasses that require less
summertime irrigation to remain attractive. Zoysia is a
warm-season grass and tall fescue is a cool-season grass. Both
are noted for the ability to make an attractive summer lawn
with less irrigation.
How To Build Auto Lawn
Sprinklers
Select a sprinkler that best fits
your needs
Automatic irrigation systems
with pop-up sprinklers are often associated with excessive
irrigation. This is not necessarily true, since properly
designed and operated systems supply water uniformly over an
entire area without wasted runoff.
Missouri soils
generally have low water infiltration rates. Automatic
controllers can be set to supply several short cycles so that
the total amount of water desired is supplied without
runoff.
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Did You Know?
You can convert your sprinkler system to a
drip irrigation system simply by replacing the heads.
This is a great option in certain climates since it
tends to use less water and go straight to the
roots.
| The most common
type of watering occurs with hose-end sprinklers. Some studies
have shown that the average homeowner applies 2.5 times the
amount of water that is required for turf growth when using
hose-end sprinklers.
There are several types of
hose-end sprinklers (see Figure 1). Select one that best fits
your size and shape of lawn and then operate it efficiently.
All hose-end sprinklers can be attached to inexpensive timers
that can be used to shut off unattended sprinklers and avoid
over-irrigation.
How much water to apply
Once you have decided on the
best sprinkler for your size and shape of lawn, you must
decide how long to operate a sprinkler in a certain location.
This is best achieved by knowing how many centimeters (inches)
of water your system puts out in a certain amount of time. To
do this, place shallow, straight-sided containers (tuna cans
work well) or rain gauges in a grid pattern aroun d the sprinkler. Operate the
sprinklers (use overlapping patterns where needed) for a given
amount of time and measure the amount of water captured (see
Figure 2.)
Measure the depth of water in the cans with
a ruler or read directly from the rain gauges. Then use the
following example to determine your water application rate in
cm (in.) per hour. For example, a sprinkler operated for 45
minutes that delivers 0.5 cm (0.1875 in.) of water has a
delivery rate of 0.67 cm (0.25 in.) per hour.
An
alternative approach would be to measure the area that your
sprinkler pattern covers and the length of time it takes to
fill a four-liter container directly from the sprinkler. For
example, a sprinkler that covers 22 square meters (73.33
square feet) and takes 1 minute and 15 seconds to discharge
four liters (1 gallon) of water has a delivery rate of about
0.67 centimeters (0.25 in.) per hour.
In the above
examples, sprinklers should be operated approximately three
hours in each location to supply 2 cm (0.75 in.) of irrigation
water per week.
Most soils in temperate climates will
take in only about 1 cm (0.375 in.) of water per hour. If your
sprinkler system delivers more than that amount, move it to a
different location more frequently, each time after 1 cm
(0.375 in.) of water has been applied. Repeat the process
until the full amount of water desired has been
applied.
Rotary sprinklers that are set to deliver a
half or quarter sprinkler pattern will discharge two or four
times the amount of water on a given area. Operate rotary
sprinklers with half patterns for half the amount of time and
sprinklers with quarter patterns for one-quarter the amount of
time you would use with an ordinary sprinkler.
The
utility water meter connected to your home can also be used to
check how effectively water is being applied. It accurately
measures water in cubic meters. When no other water is being
used in the home, water a known area for a set amount of time
and use these conversion factors to determine your water
application rate. Some helpful facts to have
are:
2,300 liters (605 gallons) of water are
required to apply 2 cm (0.75 in.) of water on 92 square meters
(307 square feet) of lawn.
1 liter (0.25
gallons) = 0.001 cubic meters of water.
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Once the decision has been made that a
lawn has sufficiently wilted and irrigation is needed, supply
enough water to last a week. Depending on the type of
sprinkler and soil water infiltration rate, several sprinkler
changes may be required over a two- or three-day period to
supply the amount of water desired.
If no rainfall occurs,
continue to irrigate on a weekly schedule. If rainfall occurs,
delay the next irrigation until symptoms of wilt are present.
Even though water application is discussed on a weekly basis,
it is not crucial that water be applied every seven days. Keep
the application schedule flexible and irrigate based on the
determination of lawn wilting and soil moisture.
Use
the table that comes on either your grass seed packages or
with your sod to determine the amount of irrigation that will
be needed for your lawn situation.
Once the decision
has been made to irrigate, use the above recommendations to
guide irrigation scheduling and how much water to supply.
Should puddles or runoff occur before the total amount of
water is applied, stop irrigating and resume only after the
ground has absorbed the free moisture. Lawn areas that are
moist, firm, and have no visible water are ready for a repeat
irrigation cycle. Areas that are soft and produce squashy
footprints when walked on are not ready to receive additional
irrigation.
A day after watering, check a few different
locations in the yard to determine how well your irrigation
program is distributing water into the root zone. With a
shovel, cut a slender 5-cm (1.97- in.) wedge 15 to 20 cm
(5.9375 to 7.875 in.) deep. This wedge of soil, roots, and
turf can easily be replaced after inspection without damaging
the lawn.
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Did You Know?
If youre working with the kids in the
yard and you get thirsty, dont let them reach for the
hose! Many hoses are made from recycled PVC,* and the
sun can cause the PVC to leech toxins into the water
youre drinking. Keep a few bottles of water in a cooler
on the patio
instead.
| Estimate the
moisture content at different depths in the soil profile by
pressing together a golf-ball-sized amount of soil. If drops
of water can be squeezed from the soil ball, you may be
irrigating too much or too often. Soils that hold together
without crumbling and appear moist have been irrigated
properly. Soils that appear dry, dusty and do not form a ball
when squeezed have not received enough irrigation or the water
is running off the surface of the lawn and not into the root
zone.
Adequate soil moisture at 15 to 20 cm (5.9375 to
7.875 in.) deep is sufficient to maintain grasses during the
summer. A 30-cm (11.8125-in.) long slender screwdriver pushed
into the ground in several locations can also give a quick
assessment of the moisture condition of the soil. The
screwdriver will easily penetrate to the soil depth that has
received sufficient water. The screwdriver test can also be
used to help determine where and when there is a need for
irrigation.
Conserve water by knowing when to
water
The best time to water a
lawn is from 6 to 8 a.m. During this time, the water pressure
is highest, disruption of the water pattern from wind is low,
and water lost to the atmosphere by evaporation is negligible.
Watering early in the morning also has the advantage of
reducing the chance of turf diseases that require extended
periods of leaf moisture. Avoid irrigation during mid-day and
windy conditions.
Move sprinklers frequently
enough to avoid puddles and runoff. Difficult-to-wet areas
such as slopes, thatched turf, and hard soils may benefit from
the application of a wetting agent to improve the surface
penetration of the water.
Water only when your
lawn tells you to. Become familiar with areas of the lawn that
wilt first (blue/purple leaves, rolled leaves, foot printing).
Water within a day of observing these symptoms.
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Water problem areas by hand
to postpone the need for irrigation of the entire lawn. Some
areas of a lawn usually wilt before others. These areas, or
"hot spots," may be caused by hard soils that take up water
slowly, slopes, southern exposures, and warmer areas next to
drives and walks. Lawns that have unusual shapes also may
require some hand watering to avoid unnecessary watering of
paved surfaces, mulched beds, and buildings. Soaker hoses that
have a narrow pattern and supply water at a slow rate may be
useful in these areas.
Watering new lawns
Newly seeded or sodded lawns
require special irrigation. A newly seeded lawn should be
watered daily and may need as many as four light waterings in
a single day. Keep the seedbed moist, but not saturated, to a
depth of 2 to 4 cm (0.8125 to 1.5625 in.) until germination
occurs (green cast to the lawn and seedlings are 0.50 to 1 cm
[0.1875 to 0.375 in.] tall.)
Seedlings of a new lawn
must not be stressed to the point of wilt. Continue with light
applications of water - 0.25 to 0.50 cm (0.125 to 0.1875 in.)
- one to four times a day.
Apply straw (one bale per 92
square meters [one bale per 307 square feet]) at time of
seeding to help shade the ground and prevent rapid drying of
the soil surface. Straw also will reduce seedling damage from
the force of large sprinkler drops. Watering with a light mist
is best for establishing new lawns. As seedlings reach 5 cm (2
in.) in height, gradually reduce the frequency of watering and
water more deeply. After the new lawn has been mowed two or
three times, deep, infrequent waterings are best.
Newly
sodded lawns require watering one or two times a day. Begin
irrigation immediately after laying sod. Plan your sodding
operation so that a section of laid sod can be watered
immediately, while other areas are being sodded.
|
Did You Know?
If your grass develops a funky white
colour a few days after mowing, the blades on your mower
may be too dull. Take them to a local repair shop for
sharpening and watch that green
grow!
| Sod should be
watered so that the sod strip is wet as well as the top 2.54
centimeters (1 inch) of soil below the sod. The first
irrigation will take about 2 cm (0.75 in.) of water to achieve
complete wetting of the sod. After watering, lift up pieces of
sod at several locations to determine if it has been
adequately irrigated. Continue watering one to two times a day
with light irrigations to prevent wilting and to ensure a
moist soil just below the sod layer.
As sod becomes
established and roots penetrate and grow into the soil,
gradually reduce the frequency of watering but wet the soil
deeper. After sod has been mowed two or three times, deep,
infrequent watering should be practiced. During hot, windy
conditions, establishing sod may require several light
mistings per day to prevent wilt and potentially high lethal
temperatures. In this case, light misting, just to wet the
leaf surface and not to supply water to the soil, cools the
grass plant as water evaporates from the leaves.
Do not
over-irrigate (saturate) the soil because that will inhibit
sod roots from growing into the soil. If the sod cannot be
watered on a daily basis, thoroughly water the sod and soil to
a depth of 15 cm. (5.9375 in.) This will delay the rooting
time of the sod but will reduce the chance of rapid drying and
severe loss of grass.
Summary
Good lawn care practices save
water and harden turf in preparation for dry periods or local
lawn watering restrictions. Taller mowing and fall nitrogen
fertilization develop a hardy and efficient root system that
reduces the need for supplemental
irrigation.
Irrigation schedules should be kept
flexible and associated with identification of lawn wilting.
Choose a sprinkler that best fits your lawn size and shape.
The amount of water a sprinkler applies should be determined
to accurately water lawns. Newly seeded or sodded lawns
require daily irrigation during establishment.
Some sprinkler types
and their applications
Rotary or
impulse
 Rotary head shoots water out in a pulsating action.
Some have an adjustable screw or paddle that breaks up jet
stream and disperses water pattern. Can be set to water
partial circles. Best for large areas. Accurately distributes
water when placed in an overlapping triangular pattern.
Traveling
 Path guided by hose placement.
Traveling action covers a large area without assistance.
Requires level ground and overlapping pattern to evenly
distribute water. Used primarily on large lawns. Can easily be
manipulated for large irregular lawn shapes. Wheel drive types
are not suitable for newly seeded lawns where soft soil
conditions result in stuck sprinklers.
Whirling
head
Deposits largest amount of water closest to spray
head. Uses a 50 percent overlapping pattern. Deposits larger
amount of water in short period of time and requires frequent
movement. Good for watering tight locations.
Stationary
 Water applied in
irregular pattern evenly with overlapping moves. Difficult to
water large areas evenly. Good for spot-watering tight
locations. Deposits a large amount of water in a short period
of time and requires frequent movement.
Oscillating
 Delivers water in a
rectangular pattern. Deposits most of the water near sprinkler
head. Difficult to achieve even water pattern on large areas
that require sprinkler relocation. Can be adjusted to water
smaller rectangular areas and other tight locations.
Soaker
hose
 Flat pin-holed hose sprays fine streams of water.
Requires several moves to water medium-sized lawn. Delivers
water slowly - good for hard-to-wet locations. Can be
manipulated to water irregular areas and long tight areas
along house or walks.
How To Build Auto Lawn
Sprinklers
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