Fertilization and Irrigation Needs for Florida Lawns and Landscapes

There are approximately four million acres of residential and commercial lawns in Florida. Florida is not only surrounded by surface water, but is also home to many miles of rivers, streams, springs, lakes, and karst areas. In addition, the water table in many parts of the state is close to the soil surface. All of these conditions lead to the potential for environmental impairment of ground and surface waters from agricultural and urban horticultural activities.

This has led to development of Best Management Practices (BMPs) for many agricultural industries, including commercial and residential turf grass and landscapes. How we fertilize and irrigate our lawns and landscapes can have a direct impact on our environment, so it is imperative that the green industry and homeowners alike adopt environmentally friendly landscape maintenance practices.

Establishment of Lawns and Landscapes

Fertility and irrigation needs of recently established lawn and landscape plants differ from those of mature lawn and landscape plants. During establishment, plants are less able to support themselves and generally require more fertilizer and water. The water and fertilizer needed vary according to season and location in the state, but some general guidelines can be followed:

Lawns - Irrigation

Florida lawns are generally established by sod, sprigs, or plugs. These lawns will require frequent, short watering to develop a root system following planting. The objective in watering during establishment is to keep the root system alive until it starts to root down and then to encourage deep rooting. To ensure that roots don't die from lack of water following planting, irrigate a few times during the day until roots have pegged down into the soil. This will generally take five to ten days. Only irrigate enough to wet the top few inches of soil for this period (five to fifteen minutes per zone). After roots are pegged down, reduce irrigation gradually over the next two weeks to two to three times weekly. In the summer months, under drought conditions, daily irrigation may be necessary for this period.

Fertility

Begin fertilizing newly planted lawns about two weeks after planting. Apply a complete (N-P-K) turf-type, slow-release nitrogen fertilizer (e.g., 16-4-8 or 15-4-15) to provide 1/2 pound of actual nitrogen per 1000 square feet. Do this every two to three weeks until the lawn has completely filled in, and then follow fertility regimes as recommended for your grass species. Time for establishment will vary depending on planting method, but most lawns should be considered established two to three months after planting. If you are planting centipede grass, only apply fertilizer once during establishment.

Look for the words slow-release or controlled-release on the fertilizer labels. Nitrogen in this type of fertilizer will not burn or wash away as readily as quick-release nitrogen sources. Don't be fooled by the word organic. Some organic fertilizers are water-soluble and can leach as quickly as inorganic fertilizers.

Landscape - Irrigation

Research shows that, unlike established plants, recently transplanted trees and shrubs survive best and establish most quickly with light, frequent irrigation. Irrigation scheduling depends on the region of the state. To ensure the survival of trees planted in spring or summer, provide two irrigations each week in north Florida or three irrigations each week in south Florida during the first few months after planting (Table 1). Daily irrigation provides the quickest establishment. Following the initial few months of frequent irrigation, provide weekly irrigation until plants are fully established. At each irrigation, apply about two to three gallons of water per inch trunk diameter (e.g. four to six gallons for a two-inch tree) over the root ball. Never add irrigation if the root ball is saturated.

Shrubs planted during the warm part of the year should be watered every day for the first few weeks after planting. Gradually decrease the frequency of irrigation to every other day and then to every third day until shrubs have established (Table 2). Shrubs planted in cooler seasons can be watered less often. Bedding plants should be watered immediately after planting and daily until they have become established.

Fertility

Controlled-release fertilizer can be applied on top of the root ball and backfill soil or on top of the mulch at planting. There is no need to mix it with the backfill soil or place it at the bottom of the planting hole. Under most circumstances, mulch will not prevent fertilizer from reaching the tree roots. Slow release fertilizer at planting has not been associated with improved survival but can increase growth rate in some situations. Adding soluble fertilizer to a newly installed plant could burn roots if too much is applied. This will injure the plant and could kill it.

Bedding plants should be fertilized before planting or at planting time. Incorporate 12-4-12 or a similar analysis fertilizer uniformly throughout the soil at the rate of one pound per 100 square feet of bed area. Controlled fertilizers are ideal for establishing bedding plants.

Established Lawns and Landscapes

Lawns - Irrigation

Lawns should be irrigated when approximately 50% of the lawn shows signs of wilt. These signs include:
• Leaf blades are folded in half lengthwise in an attempt to conserve water.
• The grass takes on a blue-gray tint.
• Footprints or tire tracks remain visible on the grass long after being made.
• The length of time needed between irrigations will vary depending upon grass species, soil characteristics, and your location in the state, time of year, temperatures, and any particular micro-environmental effects such as shade. If rain is forecast in the next two days, delay irrigation.

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