July 14, 2008

Proper Watering, Mowing, Fertilizing for Lawns

By Masterful Gardening

Automatic irrigation systems constitute 50 percent of our water consumption and are probably the worst things for a healthy lawn. They promote shallow roots and invaders, like dollar weed.

St. Johns River Water Management District still permits twice- weekly watering before 10 a.m. or after 4 p.m., but even that may be too much for a healthy lawn. Water as infrequently as possible and only when 30 percent to 50 percent of the blades show signs of wilt: the blades of grass fold, they turn a blue-gray color or when footprints remain after walking on it.

Ideally, irrigation systems should run on manual setting. The exception is a new lawn, which needs daily water for short intervals to become established. Installing a moisture sensor, which measures soil moisture at the root zone would be ideal because, living here, 5 percent to 35 percent of rainfall is intercepted by our canopies, making it difficult to know how much rainwater actually reaches the roots.

Our typically sandy soil holds 1/2 inch of water in the top 4 to 6 inches of soil and because healthy roots are 4 to 6 inches deep, 1/ 2 inch of water should be applied when signs of wilt are present.

Irrigation systems vary greatly in their distribution amounts and patterns. To determine how long to water, mark 1/2 inch on six to eight tuna cans and place around one zone. Run the irrigation system for 15 minutes and then at five-minute intervals until all the cans have between 1/4-inch to 1/2-inch of water in them. More than 1/2 inch of water is a waste. Repeat in other zones.

At least monthly, check the system to be sure that the lawn is being watered and not the roads or sidewalks. The best time to water is early in the day as evening watering has increased potential of disease.

Proper mowing is also necessary for a healthy, drought-tolerant lawn. Setting the mower to the highest position will help to condition the turf because the taller the grass, the deeper and more extensive the root system. For specific information on mowing heights, see the UF/IFAS publication Mowing Your Florida Lawn at edis.ifas.ufl.edu/LH028.

The mower blades should be kept sharp as dull blades shred the edges of the grass causing more water loss. Leave grass clippings on the lawn as you mow; it helps the lawn by releasing nitrogen during decomposition.

Proper fertilization can help drought-condition the turf, but improper fertilization can undo all the benefits of proper watering and mowing. Excess nitrogen promotes blade growth at the expense of the root system, requires more water, and promotes disease and insect infestation. Use a 15-0-15 fertilizer with 25 percent slow- release nitrogen. It should not be applied again until the fall. Iron sulfate can be applied this month to green up the turf without stimulating blade growth or increasing water needs. Excessive fertilizer can seep into our waterways and aquifer causing lakes and springs to turn green from algae overgrowth. The algae blooms use up the oxygen which chokes out plants, fish and marine life.

A thick healthy drought-tolerant turf leaves no room for weed seeds to germinate and grow.Beverly Stormoen has lived on Amelia Island for five years and is an active Master Gardener volunteer.MASTER GARDENERSMaster Gardener volunteers are trained by County Horticultural Extension agents and are required to serve 75 volunteer hours in the first year of their accreditation and 50 volunteer hours annually in all subsequent years, to maintain their certification.Nassau County Master Gardeners serve under the direction of Rebecca L. Jordi, UF/IFAS Nassau County Horticultural Extension Agent. For information on the Master Gardener program and application requirements, contact Jordi at 548-1116 or [email protected]

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