Publication Number 426-720, Posted July 1997
Introduction
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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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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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)
| Acceptable Quality | Sept | Oct | Nov | May 15-June 15 |
| Low | 0 | 1 | 0 | 0 - 1/2 |
| Med | 1 | 1 | 0 | 0 - 1/2 |
| High | 1 | 1 | 1 | 0 - 1/2 |
PROGRAM 2. Nitrogen fertilization of cool-season grasses using slowly available fertilizers (50%) or more slowly available nitrogen or WIN)
| Acceptable Quality | Aug 15 to Sept 15 | Oct 1 to Nov 1 | May 15 to June 15 |
| Low | 1.5 | 0 | 0 |
| Med | 1.5 | 1.5 | 0 |
| High | 1.5 to 2 | 1.5 | 0 to 1.5 |
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)
| Acceptable Quality | April | May | June | July/Aug |
| Low | 1 | 1 | 0 | 0 |
| Med | 1 | 1 | 1 | 0 |
| High | 1 | 1 | 1 | 1 |
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
| Acceptable Quality | April/May | June/July |
| Low | 2.0 | 0 |
| Med | 1.5 | 1.5 |
| High | 2.0 | 2.0 |
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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.
| Fertilizer analysis |
lbs of nitrogen desired per 1000 sq. ft. | |||
| 1/2 | 1 | 1.5* | 2.0* | |
| lbs fertilizer per 1000 sq. ft. | ||||
| 6-2-0 | 8.3 | 16.6 | 25.0 | 33.0 |
| 10-10-10 | 5.0 | 10.0 | 15.0 | 20.0 |
| 12-4-8 | 4.1 | 8.3 | 12.5 | 17.0 |
| 16-8-8 | 3.1 | 6.2 | 9.4 | 12.0 |
| 20-0-16 | 2.5 | 5.0 | 7.5 | 10.0 |
| 23-3-7 | 2.1 | 4.3 | 6.5 | 8.6 |
| 28-0-12 | 1.8 | 3.6 | 5.3 | 7.2 |
| 31-0-0 | 1.6 | 3.2 | 4.8 | 6.4 |
| 33.5-0-0 | 1.5 | 3.0 | 4.5 | 6.0 |
| 38-0-0 | 1.3 | 2.6 | 3.9 | 5.2 |
| 46-0-0 | 1.1 | 2.2 | 3.2 | 4.4 |
For more information on selection, planting, cultural practices, and environmental quality, contact your local Virginia Cooperative Extension Office. If you want to learn more about horticulture through training and volunteer work, ask your Extension agent about becoming an Extension Master Gardener. For monthly gardening information, subscribe to The Virginia Gardener Newsletter by sending your name and address and a check for $5.00 made out to "Treasurer, Va. Tech" to The Virginia Gardener, Department of Horticulture, Virginia Tech, Blacksburg, VA 24061-0349. Horticultural information is also now available on the Internet by connecting with Virginia Cooperative Extension's server at www.ext.vt.edu.
The original development of this series was funded by ESUSDA Smith Lever 3(d) National Water Quality Initiative Funds and the Virginia Department of Conservation and Recreation, Division of Soil and Water Conservation.
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