Table of Contents

Introduction

Testing the Soil

Selecting a Fertilizer

Applying at the Proper Time

Choosing Application Equipment

Fertilizers are used to improve or maintain turfgrass quality. A well-planned and environmentally sound turfgrass fertilization program will take into account native soil fertility, nutrient source characteristics, desired turfgrass quality or performance, nutrient application rate, application frequency, season of application, and application method.

The value of a fertilizer depends upon the total amount of nutrients and the source of nitrogen in the fertilizer.

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Testing the Soil

Before beginning a lawn fertilization program, a soil test should be done to determine the fertility of your lawn soil. The results will indicate the amounts of nutrients your soil can provide to the turfgrass. The test will also indicate the acidity (pH) of your soil and whether lime is needed. Your local Extension agent can provide information on how to sample the soil and submit it for analysis.

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Selecting a Fertilizer

Based on the soil test recommendations, choose a fertilizer with the appropriate amounts of nitrogen, phosphate, and potash for your lawn. If a soil test indicates high levels of phosphorus and potassium availability, then a fertilizer supplying only nitrogen is necessary. Fertilizer analysis is described using three numbers (i.e., 12-4-8 or 46-0-0) indicating, respectively, the percent by weight of nitrogen (N), phosphate (P205), and potash (K20). For example, a 12-4-8 fertilizer would contain 12% nitrogen, 4% phosphate, and 8% potash by weight.

The fertilizer ratio is based on the N. P205, K20 numbers; for example, if the fertilizer analysis is 164-8, the fertilizer ratio is 4-1-2; similarly, a 147-14 analysis would have a 2-1-2 ratio. Mature lawns generally require more nitrogen than phosphorus and potassium; therefore, ratios of 41-2 or 4-1-3 are commonly recommended. The nitrogen content in turf maintenance fertilizers is derived from either a quickly available or slowly available source. Quickly available sources are water soluble and can be readily utilized by the plant. They include ammonium nitrate,
urea, ammonium sulfate, and calcium nitrate. Slowly available sources contain water insoluble nitrogen (WIN) from urea formaldehyde (UF), UF based products (methylene ureas), sulfur coated urea, natural organics (bone meal, fish meal, dried blood, and animal manures), and activated sewage sludge. Slowly available nitrogen sources release nitrogen over extended periods of time and are applied less frequently and at somewhat higher rates than the quickly available nitrogen sources. It is less susceptible to leaching and is preferred on sandy soil types which tend to leach.

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Applying at the Proper Time

Proper timing of nitrogen applications is different for warm-season and cool-season turfgrasses because of their different growth cycles. The following four charts show the recommendations for pounds of actual nitrogen per 1000 square feet of lawn area using both quick release and slow release nitrogen sources for both warm- and cool-season grasses. The charts can be used to determine the most effective times of application for different levels of turfgrass quality.

Programs for Cool-season Grasses. The best time to fertilize cool-season grasses, including Kentucky bluegrass, tall fescue, perennial ryegrass, and fine fescue (creeping red fescue, hard fescue, sheep fescue, and chewings fescue), in Virginia is from August 15 through November. Excessive spring application of nitrogen to coolseason grasses in Virginia leads to excessive leaf growth at the expense of stored food reserves and root growth, increasing injury to lawns from summer disease and drought.

PROGRAM 1. Nitrogen fertilization of cool-season grasses using quickly available nitrogen fertilizers (less than 50% slowly available nitrogen)

Nitrogen Application by Month - lbs N/1000 sq ft

PROGRAM 2. Nitrogen fertilization of cool-season grasses using slowly available fertilizers (50%) or more slowly available nitrogen or WIN)

Nitrogen Application by Month - lbs N/1000 sq ft

Fine fescue performs best at 1 to 2 pounds of nitrogen per 1000 square feet. Up to 1 pound of nitrogen in Program 1 and up to 1.5 pounds of nitrogen in Program 2 may be applied per 1000 square feet in the May 15 to June 15 period if nitrogen was not applied the previous fall, or to help a new lawn get better established.

Program for Warm-season Grasses. Warmseason grasses, including bermudagrass, zoysiagrass, and centipedegrass, perform best when fertilized between April 1 and August 15 in Virginia. Centipedegrass and mature zoysiagrass perform best at 1 to 2 pounds of nitrogen per 1000 square feet per year.

PROGRAM 3. Nitrogen fertilization of warmseason grasses using quickly available nitrogen fertilizers (less than 50% slowly available nitrogen)

Nitrogen Application by Month - lbs N/1000 sq ft

PROGRAM 4. Nitrogen fertilization of warmseason grasses using predominantly slowly available nitrogen fertilizers (50% or more slowly available nitrogen or WIN)

Nitrogen Application by Month - lbs N/1000 sq ft

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Choosing Application Equipment

It is important to apply all fertilizers uniformly. This will eliminate streaks of different shades of green turf in the lawn caused by uneven application. Proper application of nitrogen fertilizers by hand is difficult, even for a trained professional.

Drop-type or rotary fertilizer spreaders are most effective. Drop-type spreaders are more difficult to maneuver around trees and shrubs. Rotary spreaders usually give better distribution where sharp turns are encountered because they tend to cover a broader swath and fan the fertilizer out at the edges of the swath.

By applying half the material in one direction and the other half in a perpendicular direction, streaking can be minimized. Avoid application of any fertilizer to nonturfed areas (driveways, roads, or bare soil) since it is then prone to run off which could affect water supplies.

Use the following chart to determine the correct amount of fertilizer when applying nitrogen required per 1000 square feet.

*These amounts are only recommended for predominantly slowly available nitrogen sources