Three Irrigation Cycles Per Week Recommended
(hills and/sloped lawns in full sun) 6/15/2008
(1 irrigation cycle recommended per week, during the
Spring and late Fall)
(2 Irrigation Cycles recommended per week, during the
(3 Irrigation Cycles recommended per week, Late Summer
or when drought conditions exist)
Check the index once a week on the first of your assigned watering
days. The weekly watering amount shown is the amount needed over the
next 7 days for your lawn. If you're watering only once weekly, apply
all of the amount to your lawn then. If you prefer to water twice a
week, split the total amount over the two days.
What do all these numbers mean?
These numbers show weather data that
help determine how much water your lawn needs. High and low
temperatures are two of the factors used to calculate the potential evapotranspiration
amount, shown as ETo. You can think of ETo
as the amount of water a plant would need if left constantly exposed
to the sun. Since most plants have varying amounts of sunlight through the day, we apply
stress coeffients for an average St. Augustine lawn in Austin to
determine the ET Index.
What is evapotranspiration?
Evapotranspiration is a measurement of
the total amount of water needed to grow plants and crops. This word
is from the word evaporation and
transpiration. The equation
used to determine potential ET (ETo) considers a large number of
weather factors, such as wind, temperature, dew point, humidity and
If we know how much water is lost each day, why don't we water
Allowing your lawn to dry out between waterings
actually encourages a deeper root structure as the grass then has to
for the water it needs. Plants with deeper roots are better able to
withstand drought, harder to uproot, and can be more resistant to
disease. Plus, the daily ET amounts for Austin are usually very small.
Most automatic irrigation systems can't be adjusted to water less
than 1/4" with each operation, so it would be next to impossible to
apply a tenth of an inch daily.
How do I know when I've watered enough? Set
tuna or cat food cans around your lawn and
garden and turn on your sprinkler for 15 minutes to measure the amount of
water in the cans. Now that you know how much water your sprinkler
puts out, you can figure out how long to leave it running when it's
time to water.
Example: After 15 minutes of running your sprinkler, you have an
average of 1/4" in your tuna cans. When the ET Index is 1/2", you should run your sprinkler for 30 minutes.
For an ET of 1/3", you'd run the sprinkler for about 20 minutes.