South Florida Landscape Irrigation Adrian Hunsberger UF/Miami-Dade County Extension Dr. Dorota Z. Haman Agricultural and Biological Engineering University of Florida
Rainfall
The average rainfall in South Florida is 60 inches It varies by: – Season (summer 70% of total) – Location
Florida Rainfall & ET (evapotranspiration) 8 7 6 5 4 3 2 1 0 c De v No ct O p Se g Au l Ju
n Ju ay M r Ap ar M b Fe n Ja
Monthly Potential ET
Monthly Rainfall
Principal aquifers in South Florida
A. Ground Level B. Limestone C. Biscayne Aquifer (10-200-feet below ground) D. Marl (more limestone) E. Floridan Aquifer (900-feet below ground)
Why do we need landscape irrigation in South Florida? - sandy soils (in some areas) - low water holding capacity in sandy soils - shallow roots (turf, vegetables, and annuals) - recently planted plants - temporal distribution of rain (hot, dry spring)
Objectives of landscape irrigation Healthy,
beautiful landscape Efficient water use Minimal impact on the environment
Selection of appropriate system or system combination Sprinklers
– Rotary heads – Impact heads – Spray heads Microirrigation Soaker
hoses
Is the exposure full sun, shade, or mixture? A shady or northern exposure will likely require 1/2 the water of a sunny location. What type of plants are being grown? Group plants with similar water requirements together and water appropriately.
Uniformity and efficiency Low uniformity always results in low efficiency of the irrigation
Why Worry About Efficiency? Wasted water Increased water bills Increased demand on limited fresh water resources
Poor system selection
Uniformity of water application Good
design Good management System maintenance
Pop-up spray heads produce a static spray band of a set pattern depending on the type chosen (1/4, 1/2, 3/4, full, or variable circle). Heads rise when water is turned on and retract when not in use.
How to design a uniform “efficient” irrigation system? Uniform pressure distribution Coverage “head to head on the sprinklers” Matching precipitation with the sprinklers Appropriate location of emitters Separate zones
turf landscape beds sprinklers spray heads micro
Uniform pressure distribution Number
of sprinklers, spray heads or emitters per zone (total flow rate) Appropriate sizing of all components (pipes, valves, etc.)
Uniform water application
Separate zones for rotors or spray heads with varying precipitation rates
Rotors precipitation rate 0.1 – 0.75 in/hr Spray head precipitation rate 1.0 – 1.5 in/hr
What to avoid
Microirrigation: Drip Soaker
hose Microsprinkler Bubblers Water bags
Advantages of Microirrigation possible
water savings delivery of water directly to the roots easily automated
Disadvantages high
maintenance difficult to notice damage visually limited wetting in sandy soils Need water filters
Where to put the emitters?
Combination systems Sprinklers
for large grass areas Drip and microsprinklers for annuals, & recently planted shrubs and trees.
Temporary systems – use as needed
When developing an irrigation plan, it is essential to consider the following: - How frequently to water - How much to water - How to uniformly apply water - How your turf irrigation affects your landscape plants - Any micro-environmental effects in the landscape that affect irrigation requirements
Efficiency of irrigation
Plant zoning according to water requirements Well designed, installed and maintained irrigation system Irrigation scheduling (less water needed in winter, no irrigation needed during rainy season) Plants in shade need less water
Maintenance Timely
maintenance of sprinklers Repairs of leaks Maintenance of microirrigation zones
Irrigation scheduling Applying water only when needed and in needed amounts. Need to change schedule due to change in season & plant needs.
Irrigation - when? Plant
appearance Weather conditions Soil moisture (soil moisture sensors ???)
Soil Moisture Control Sensors
Rainbird Irrometer Water Watcher
ECHO
Acclima
Effectiveness of rainfall The
average annual rainfall in humid climates is usually significant.
Water Storage – Rain Barrels
Rain Shut-off devices Prevent
irrigation system from watering when sufficient water is supplied by rainfall. Increase system efficiency and conserve water.
Plant Water Needs
Established trees, shrubs and perennial bedding plants – usually no irrigation needed St. Augustinegrass, vegetables & annual bedding plants – 1/2 – 3/4 inch per irrigation
When to Water? - When plants are wilting due to dry soil
(need to check the soil)
- Water when the top two inches of soil have dried out.
When to Water
The most efficient way is to apply water when turf begins to show signs of stress: – bluish gray color – footprints remain – leaf blades folded in half
How Much to Water • An efficient watering only wets the turfgrass root zone, does not saturate the soil and does not allow water to run off. • Apply ½” to ¾” when turf shows symptoms of wilt and do not apply any more until water stress symptoms are again noticeable.
Catch Can Testing How long to irrigate
3/4 to 1 inch of rain or irrigation will wet soil… A. B. C. D.
3 inches deep 6 inches deep 12 inches deep 20 inches deep
C. One inch of rain or irrigation wets a typical Florida soil 12” deep. WRONG
RIGHT
Wetting the Root Zone
When to Water? - Watering during the day wastes water due to excessive evaporation and can scald plants when temperatures are high. Permanent water restrictions (Miami-Dade County): Up to twice a week. Residential landscapes can NOT be watered between 9 am – 5 pm Exceptions: newly installed plants, hand watering
Water source
Ground water
Rain water
Municipal water
Well water
Lake water
Time of Day To Water Wet
grass & leaves = disease opportunity Dew point should not be extended – grass & leaves must dry out Best time to water is just before or at sunrise (anytime between 2 am – 8 am)
Where to water?
water the soil (root zone), not the plant!
How much? depth
of the root zone soil water holding capacity initial soil moisture level
Root depth
- Deep and infrequent
irrigation tends to cause grass roots to grow deeper into the soil, making the plants more drought tolerant. - Shallow and frequent waterings lead to shallowrooted plants with less drought tolerance.
Good
Not good, watered too often
The majority of people over-irrigate or irrigate incorrectly (water too often, too long, or too lightly). Too much water is damaging to plants and is often the underlying cause of lawn and plant failure.
In 2000, the highest consuming states withdrew: California 51,200 mgd (million gallons per day); Texas 29,600; and Florida 20,100. On average, 50 to 70 percent of home water is used outdoors for watering lawns and gardens.
American Water Works Association
Which of the following does not indicate an over-watered lawn?
A. The presence of dollarweed. B. Excessive thatch C. Disease D. A blue-green cast to the lawn.
D. A blue-green cast
Problems with overwatering include: - A less developed and shorter root system,
which has less capacity to seek out water and nutrients at lower soil depths and has less overall stress resistance - Overly succulent shoots, susceptible to disease and insect infestation. -Buildup of excessive thatch, particularly in St. Augustinegrass.
Overwatering Induces nutritional deficiencies by leaching Leached nutrients – pollutes ground and surface water Reduces soil oxygen – root rots Encourages weed/plant growth Wastes water
620 gallons are required to apply one inch of water over 1000 square feet.
The amount of water it takes to provide a lifetime of drinking water to a person is? 16,000 gallons
How many lawn irrigations are the equivalent to a lifetime of drinking water? ~5 irrigations
Summary Efficient irrigation systems depend on proper design, installation, and maintenance to minimize water losses in landscape irrigation. High efficiency of water use requires high uniformity of water application and good management.
For more information: Check out the University of Florida’s publication resources website: http://edis.ifas.ufl.edu http://miami-dade.ifas.ufl.edu
