Cooperative Extension Service 
Institute of Food and Agricultural Sciences
Hendry County Extension    P. O. Box 68    LaBelle, Florida 33975-0068    Phone (863) 674-4092

Hendry County Horticulture News

Irrigation - An Essential Part of Good Turf Management

Turf requires water to maintain a healthy and uniform appearance. The drought that has persisted over the past few months has made this fact painfully evident to many homeowners.  Proper watering is an essential part of good turf management.  Water is involved in all aspects of plant growth and development.  It is required photosynthesis and other biological processes and forms a major fraction of all plants. Most of the water used  by turf is transpired through the leaves into the atmosphere. This water moves nutrients from the soil into the plant, and eliminates heat buildup from solar radiation.

An irrigation system is a simply a collection of hydraulic devices that deliver water to the turf. An irrigation system may consist of a single sprinkler with a hose that is moved from location to location or it may consist of an elaborate pipe network with pop-up sprinklers.  Both of these systems can be equally efficient if used properly. To use an irrigation system properly it is necessary to understand how sprinklers operate and where they should be placed.

The water supplied by irrigation and rainfall evaporates from the soil and or is transpired from plant surfaces. Evaporation and transpiration (evapotranspiration) depends mostly on the environment around the plant, thus, the amount of water used by turf changes with the seasons. Because of this, irrigation frequency should change with the time of year.

Only water that is in contact with the roots can be absorbed by the plant. The volume of soil where water can be stored is as deep as the roots are. Root depth is affected by mowing, fertilizing and irrigation practices. Well managed turf will develop most of its roots in the first 10 - 12 inches of the soil.

Another important aspect of the soil reservoir is the fact that soils have a limited ability to store water. The larger the pores in the soil the less water the soil will hold.  Our sandy soils typically hold between 1/4 inch and 1 inch of water per foot of soil. The quantity of water applied to turf should not exceed the required to refill the soil occupied by the root system.

Irrigate by demand. Apply water only when the soil reservoir has been depleted. Always apply only the amount of water that is required to refill the soil. Change the frequency with which you irrigate and not the amount of water applied.

Water should be applied to turf only when the soil water in the root zone has been depleted to an unacceptable level, usually one half  to 2/3 of the stored soil water. There are several ways to determine when the soil water reservoir has been depleted beyond an acceptable level. These include becoming familiar with the way that turf reacts when water is becoming limited in the soil. Common symptoms of water stress include leaf color changes to a bluish gray tint, footprints that linger long after being made, and curled or folded leaf blades.

Past history of climate can be used to estimate how often irrigation should be applied to turf.  Evapotranspiration rates will may range from zero to over 0.20 inches of water per day.  If the soil reservoir represented by the root zone has an average water holding capacity of 0.50 inches of water, and evapotranspiration is 0.20 inches per day, you will need to water ever other day.  A good rule of thumb for evapotranspiration is 0.10 inch per day during the cooler months and 0.20 inches per day.

Keep track of the time since the last rain or irrigation, to determine when the next irrigation is due.  Do not apply daily light irrigation (less than 1/4" depth of water). It has been shown that deep irrigation (more than 2/3" of water) applied less frequently provides better turf quality.

Regardless of the time of year, for an established turf the quantity of water applied at each irrigation should always be the same. Irrigation will not be required as often during low demand periods- cooler, wetter months. Our typical sandy soils normally hold between ½ to 3/4 inch of water per foot of soil. The amount of water to apply to a one foot deep soil water reservoir, which has been depleted to 50 percent and has a water holding capacity of 3/4 inch per foot is about half an inch of water.

In order for irrigation to be successful and efficient, the volume of water applied must be measured.  A simple method is merely to measure the depth of water applied.  If possible, carry out the test in the early morning hours and under no-wind conditions. Place several wide- mouth, flat-bottomed cans spaced equally across the area covered by your sprinklers. After 20 minutes of irrigation, turn the system off and use a ruler to measure the depth of the water is in each can. Average the measurements and use the average to determine the time required to apply 2/3 of an inch of water. For example, if a 20 minute can test resulted in an average water depth of 1/2 of an inch, the time that irrigation system should be turned on in order to apply 2/3 of an inch of water is 27 minutes. Any water applied after 27 minutes will be wasted as deep percolation.

If possible, apply water during the early hours of the morning. The most efficient time to irrigate is from about 4:00 a.m. to 6:00 a.m. Also, avoid peak water use hours to insure that sufficient pressure is available to operate the system.  To reduce watering, use turf areas only where required in the landscape. Make use of mulched areas, especially in hard-to-reach places. Consider using drought tolerant plants.

Detailed information and recommendations for turf management in Florida are available from The Hendry County Extension Office.  Better understanding will help lead the way to a more beautiful and satisfactory lawn.  Good luck and good gardening.

Gene McAvoy is the horticulture agent with the Hendry County Extension Service.  Direct your horticulture questions to PO Box 68, LaBelle, FL 33975,  e-mail - or phone 863-674-4092 or  863-983-1598.  You are also welcome to visit the Hendry County Extension Office at 225 Pratt Blvd., LaBelle.   Office hours are from 8:00 - 5:00.

The Institute of Food and Agricultural Sciences is an Equal Employment Opportunity - Affirmative Action Employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap or national origin.

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